W3C

SOAP Version 1.2 Part 2: Adjuncts

W3C Working Draft 2 October 2001

This version:
http://www.w3.org/TR/2001/WD-soap12-part2-20011002/
Latest version:
http://www.w3.org/TR/soap12-part2/
Previous versions:
http://www.w3.org/TR/2001/WD-soap12-20010709/
Editors:
Martin Gudgin, DevelopMentor
Marc Hadley, Sun Microsystems
Jean-Jacques Moreau, Canon
Henrik Frystyk Nielsen, Microsoft

Abstract

SOAP version 1.2 is a lightweight protocol for exchange of information in a decentralized, distributed environment. It is an XML based protocol that consists of four parts: an envelope that defines a framework for describing what is in a message and how to process it, a transport binding framework for exchanging messages using an underlying protocol, a set of encoding rules for expressing instances of application-defined data types and a convention for representing remote procedure calls and responses. Part 2 (this document) describes the RPC convention and encoding rules along with a concrete HTTP binding specification; the SOAP envelope and transport binding framework are described in Part 1[1].

Status of this Document

This section describes the status of this document at the time of its publication. Other documents may supersede this document. The latest status of this document series is maintained at the W3C.

This is the second W3C Working Draft of the SOAP Version 1.2 specification for review by W3C members and other interested parties. It has been produced by the XML Protocol Working Group (WG), which is part of the XML Protocol Activity.

The specification has been split into two documents: SOAP Version 1.2 Part 1: Messaging Framework which describes the SOAP envelope and the SOAP transport binding framework, and SOAP Version 1.2 Part 2: Adjuncts, which describes the SOAP encoding rules the SOAP RPC convention and a concrete HTTP binding specification.

For a detailed list of changes since the last publication of this document, refer to appendix C Part 2 Change Log. A list of open issues against this document can be found at http://www.w3.org/2000/xp/Group/xmlp-issues.

Comments on this document should be sent to xmlp-comments@w3.org (public archive[12]). It is inappropriate to send discussion emails to this address.

Discussion of this document takes place on the public xml-dist-app@w3.org mailing list[13] per the email communication rules in the XML Protocol Working Group Charter[14].

This is a public W3C Working Draft. It is a draft document and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use W3C Working Drafts as reference material or to cite them as other than "work in progress". A list of all W3C technical reports can be found at http://www.w3.org/TR/.

Table of Contents

1 Introduction
    1.1 Notational Conventions
    1.2 Examples of SOAP Messages
    1.3 SOAP Terminology
        1.3.1 Data Encoding Concepts
2 Relation to XML
3 The SOAP Data Model
4 SOAP Encoding
    4.1 Rules for Encoding Types in XML
    4.2 Simple Types
        4.2.1 Strings
        4.2.2 Enumerations
        4.2.3 Array of Bytes
    4.3 Polymorphic Accessor
    4.4 Compound Types
        4.4.1 Compound Values and References to Values
        4.4.2 Arrays
            4.4.2.1 PartiallyTransmitted Arrays
            4.4.2.2 SparseArrays
        4.4.3 Generic Compound Types
    4.5 Default Values
    4.6 SOAP root Attribute
5 Using SOAP for RPC
    5.1 RPC and SOAP Body
    5.2 RPC and SOAP Header
    5.3 RPC Faults
6 Using SOAP in HTTP
    6.1 SOAP HTTP Request
        6.1.1 The SOAPAction HTTP Header Field
    6.2 SOAP HTTP Response
    6.3 The HTTP Extension Framework
    6.4 Security Considerations
    6.5 SOAP HTTP Examples
7 References
    7.1 Normative References
    7.2 Informative References

Appendices

A SOAP Envelope Examples (Non-Normative)
    A.1 Sample Encoding of Call Requests
    A.2 Sample Encoding of Response
B Acknowledgements (Non-Normative)
C Part 2 Change Log (Non-Normative)
    C.1 SOAP Specification Changes
    C.2 XML Schema Changes


1 Introduction

SOAP version 1.2 provides a simple and lightweight mechanism for exchanging structured and typed information between peers in a decentralized, distributed environment using XML. SOAP does not itself define any application semantics such as a programming model or implementation specific semantics; rather it defines a simple mechanism for expressing application semantics by providing a modular packaging model and encoding mechanisms for encoding application defined data. This allows SOAP to be used in a large variety of systems ranging from messaging systems to remote procedure calls (RPC).

SOAP consists of four parts:

  1. The SOAP envelope [1](SOAP Envelope) construct defines an overall framework for expressing what is in a message, who should deal with it, and whether it is optional or mandatory.

  2. The SOAP binding framework [1](SOAP Transport Binding Framework) defines an abstract framework for exchanging SOAP envelopes between peers using an underlying protocol for transport. The SOAP HTTP binding 6 Using SOAP in HTTP) defines a concrete instance of a binding to the HTTP protocol[2].

  3. The SOAP encoding rules (4 SOAP Encoding) define a serialization mechanism that can be used to exchange instances of application-defined datatypes.

  4. The SOAP RPC representation (5 Using SOAP for RPC) defines a convention that can be used to represent remote procedure calls and responses.

These four parts are functionally orthogonal. In recognition of this, the envelope and the encoding rules are defined in different namespaces.

1.1 Notational Conventions

The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [3].

The namespace prefixes "env" and "enc" used in the prose sections of this document are associated with the SOAP namespace names "http://www.w3.org/2001/09/soap-envelope" and "http://www.w3.org/2001/09/soap-encoding" respectively.

The namespace prefixes "xs" and "xsi" used in the prose sections of this document are associated with the namespace names "http://www.w3.org/2001/XMLSchema" and "http://www.w3.org/2001/XMLSchema-instance" respectively, both of which are defined in the XML Schemas specification[4],[5].

Note that the choice of any namespace prefix is arbitrary and not semantically significant.

Namespace URIs of the general form "http://example.org/..." and "http://example.com/..." represent an application-dependent or context-dependent URI[6].

This specification uses the augmented Backus-Naur Form (BNF) as described in [2].

1.2 Examples of SOAP Messages

SOAP messages may be bound to different underlying protocols and used in a variety of message exchange patterns. The following two examples show SOAP used in connection with HTTP as the underlying protocol taking advantage of the request/response mechanism provided by HTTP (6 Using SOAP in HTTP).

The following example shows a sample SOAP/HTTP request. The SOAP/HTTP request contains a block called GetLastTradePrice which takes a single parameter, the ticker symbol for a stock. Note that the GetLastTradePrice element is not defined by SOAP itself. The service's response to this request contains a single parameter, the price of the stock. The SOAP Envelope element is the top element of the XML document representing the SOAP message. XML namespaces are used to disambiguate SOAP identifiers from application specific identifiers.

Example: Sample SOAP Message embedded in an HTTP Request
POST /StockQuote HTTP/1.1
Host: www.example.org
Content-Type: text/xml; charset="utf-8"
Content-Length: nnnn
SOAPAction: "http://example.org/2001/06/quotes"

<env:Envelope xmlns:env="http://www.w3.org/2001/09/soap-envelope" >
 <env:Body>
  <m:GetLastTradePrice
        env:encodingStyle="http://www.w3.org/2001/09/soap-encoding"
        xmlns:m="http://example.org/2001/06/quotes">
    <symbol>DIS</symbol>
  </m:GetLastTradePrice>
 </env:Body>
</env:Envelope>

The following example shows the SOAP message sent by the StockQuote service in response to the request shown in the preceeding example.

Example: Sample SOAP Message embedded in an HTTP Response
HTTP/1.1 200 OK
Content-Type: text/xml; charset="utf-8"
Content-Length: nnnn

<env:Envelope xmlns:env="http://www.w3.org/2001/09/soap-envelope" >
 <env:Body>
  <m:GetLastTradePriceResponse
        env:encodingStyle="http://www.w3.org/2001/09/soap-encoding"
        xmlns:m="http://example.org/2001/06/quotes">
   <Price>34.5</Price>
  </m:GetLastTradePriceResponse>
 </env:Body>
</env:Envelope>

More examples are available in A SOAP Envelope Examples.

1.3 SOAP Terminology

1.3.1 Data Encoding Concepts

SOAP data model

A set of abstract constructs that can be used to describe common data types and link relationships in data.

SOAP data encoding

The syntactic representation of data described by the SOAP data model within one or more SOAP blocks in a SOAP message.

2 Relation to XML

All SOAP messages have an XML Information Set[10]

A SOAP node MUST ensure that all element information items and attribute information items in messages that it generates are correctly namespace qualified. A SOAP node MUST be able to process SOAP namespace information in messages that it receives. It MUST discard messages that have incorrect namespace information (see [1]SOAP Fault)

This document defines the following namespaces[7]:

A schema document for these namespace can be found by dereferencing the relevant namespace identifier.

A SOAP message MUST NOT contain a Document Type Declaration. A SOAP message MUST NOT contain processing instruction information items[8].

SOAP uses unqualified attribute information items with a local name of id and a type of ID in the http://www.w3.org/2001/XMLSchema namespace to specify the unique identifier of an encoded element. SOAP uses unqualified attribute information items with a local name of href and a type of anyURI in the http://www.w3.org/2001/XMLSchema namespace to specify a reference to such a value, in a manner conforming to the XML Specification[8], XML Schema Specification[5], and XML Linking Language Specification[9].

A SOAP message MUST NOT impose any XML schema processing (assessment and validation) requirement on the part of any receiving SOAP node. Therefore, SOAP REQUIRES that all attribute information items, whether specified in this specification or whether they belong to a foreign namespace be carried in the serialized SOAP envelope.

3 The SOAP Data Model

Editorial note: JJM20010914
Section 4 currently defines a data model in the form of a directed graph. Elements of the data model include struct, array, and id/href. In addition to the data model, section 4 includes a particular encoding of that model without clearly separating the two. The WG would like to clarify the relationship between the data model and the particular encoding by saying that the SOAP encoding is one of several potential encodings of the SOAP data model. This section is the placeholder for the description of the SOAP data model (see also section 3.5 in the XML Protocol WG Draft Requirements)

4 SOAP Encoding

Editorial note: JJM20010920
The Working Group is aware that the following section does not use the XML Infoset terminology used elsewhere in this specification, and most notably in Part 1. The WG expects to rewrite this section using the XML Infoset terminalogy at a later date.

The SOAP encoding style is based on a simple type system that is a generalization of the common features found in type systems in programming languages, databases and semi-structured data. A type either is a simple (scalar) type or is a compound type constructed as a composite of several parts, each with a type. This is described in more detail below.

This section defines rules for serialization of a graph of typed objects. It operates on two levels. First, given a schema in any notation consistent with the type system described, a schema for an XML grammar may be constructed. Second, given a type-system schema and a particular graph of values conforming to that schema, an XML instance may be constructed. In reverse, given an XML instance produced in accordance with these rules, and given also the original schema, a copy of the original value graph may be constructed.

The data serialized according to the rules defined in this section MAY contain references to data outside the serialization. When present, these references MUST be Uniform Resource Identifiers (see [6]).

The namespace identifier for the elements and attributes defined in this section is "http://www.w3.org/2001/09/soap-encoding". The encoding samples shown assume all namespace declarations are at a higher element level.

Use of the data model and encoding style described in this section is encouraged but not required; other data models and encodings can be used in conjunction with SOAP (see [1]SOAP Encoding Attribute).

4.1 Rules for Encoding Types in XML

XML allows very flexible encoding of data. SOAP defines a narrower set of rules for encoding. This section defines the encoding rules at a high level, and the next section describes the encoding rules for specific types when they require more detail. The encodings described in this section can be used in conjunction with the mapping of RPC calls and responses specified in 5 Using SOAP for RPC.

To describe encoding, the following terminology is used:

  1. A "value" is a string, the name of a measurement (number, date, enumeration, etc.) or a composite of several such primitive values. All values are of specific types.

  2. A "simple value" is one without named parts. Examples of simple values are particular strings, integers, enumerated values etc.

  3. A "compound value" is an aggregate of relations to other values. Examples of Compound Values are particular purchase orders, stock reports, street addresses, etc.

  4. Within a compound value, each related value is potentially distinguished by a role name, ordinal or both. This is called its "accessor." Examples of compound values include particular Purchase Orders, Stock Reports etc. Arrays are also compound values. It is possible to have compound values with several accessors each named the same, as for example, RDF does.

  5. An "array" is a compound value in which ordinal position serves as the only distinction among member values.

  6. A "struct" is a compound value in which accessor name is the only distinction among member values, and no accessor has the same name as any other.

  7. A "simple type" is a class of simple values. Examples of simple types are the classes called "string," "integer," enumeration classes, etc.

  8. A "compound type" is a class of compound values. An example of a compound type is the class of purchase order values sharing the same accessors (shipTo, totalCost, etc.) though with potentially different values (and perhaps further constrained by limits on certain values).

  9. Within a compound type, if an accessor has a name that is distinct within that type but is not distinct with respect to other types, that is, the name plus the type together are needed to make a unique identification, the name is called "locally scoped." If however the name is based in part on a Uniform Resource Identifier, directly or indirectly, such that the name alone is sufficient to uniquely identify the accessor irrespective of the type within which it appears, the name is called "universally scoped."

  10. Given the information in the schema relative to which a graph of values is serialized, it is possible to determine that some values can only be related by a single instance of an accessor. For others, it is not possible to make this determination. If only one accessor can reference it, a value is considered "single-reference". If referenced by more than one, actually or potentially, it is "multi-reference." Note that it is possible for a certain value to be considered "single-reference" relative to one schema and "multi-reference" relative to another.

  11. Syntactically, an element may be "independent" or "embedded." An independent element is any element appearing at the top level of a serialization. All others are embedded elements.

Although it is possible to use the xsi:type attribute such that a graph of values is self-describing both in its structure and the types of its values, the serialization rules permit that the types of values MAY be determinate only by reference to a schema. Such schemas MAY be in the notation described by "XML Schema Part 1: Structures" [4] and "XML Schema Part 2: Datatypes" [5] or MAY be in any other notation. Note also that, while the serialization rules apply to compound types other than arrays and structs, many schemas will contain only struct and array types.

The rules for serialization are as follows:

  1. All values are represented as element content. A multi-reference value MUST be represented as the content of an independent element. A single-reference value SHOULD NOT be (but MAY be).

  2. For each element containing a value, the type of the value MUST be represented by at least one of the following conditions: (a) the containing element instance contains an xsi:type attribute, (b) the containing element instance is itself contained within an element containing a (possibly defaulted) enc:arrayType attribute or (c) or the name of the element bears a definite relation to the type, that type then determinable from a schema.

  3. A simple value is represented as character data, that is, without any subelements. Every simple value must have a type that is either listed in the XML Schemas Specification, part 2[5] or whose source type is listed therein (see also 4.2 Simple Types).

  4. A Compound Value is encoded as a sequence of elements, each accessor represented by an embedded element whose name corresponds to the name of the accessor. Accessors whose names are local to their containing types have unqualified element names; all others have qualified names (see also 4.4 Compound Types).

  5. A multi-reference simple or compound value is encoded as an independent element containing a local, unqualified attribute named id and of type "ID" per the XML Specification [8]. Each accessor to this value is an empty element having a local, unqualified attribute named href and of type "uri-reference" per the XML Schema Specification[5], with a href attribute value of a URI fragment identifier referencing the corresponding independent element.

  6. Strings and byte arrays are represented as multi-reference simple types, but special rules allow them to be represented efficiently for common cases (see also 4.2.1 Strings and 4.2.3 Array of Bytes ). An accessor to a string or byte-array value MAY have an attribute named id and of type "ID" per the XML Specification[8]. If so, all other accessors to the same value are encoded as empty elements having a local, unqualified attribute named href and of type "uri-reference" per the XML Schema Specification[5], with a href attribute value of a URI fragment identifier referencing the single element containing the value.

  7. It is permissible to encode several references to a value as though these were references to several distinct values, but only when from context it is known that the meaning of the XML instance is unaltered.

  8. Arrays are compound values (see also 4.4.2 Arrays). SOAP arrays are defined as having a type of "enc:Array" or a type derived there from.

    SOAP arrays have one or more dimensions (rank) whose members are distinguished by ordinal position. An array value is represented as a series of elements reflecting the array, with members appearing in ascending ordinal sequence. For multi-dimensional arrays the dimension on the right side varies most rapidly. Each member element is named as an independent element (see rule 2/>).

    SOAP arrays can be single-reference or multi-reference values, and consequently may be represented as the content of either an embedded or independent element.

    SOAP arrays MUST contain a enc:arrayType attribute whose value specifies the type of the contained elements as well as the dimension(s) of the array. The value of the enc:arrayType attribute is defined as follows:

    Value of enc:arrayType
    [1]   arrayTypeValue   =   atype asize
    [2]   atype   =   QName *( rank )
    [3]   rank   =   "[" *( "," ) "]"
    [4]   asize   =   "[" #length "]"
    [5]   length   =   1*DIGIT

    The "atype" construct is the type name of the contained elements expressed as a QName as would appear in the type attribute of an XML Schema element declaration and acts as a type constraint (meaning that all values of contained elements are asserted to conform to the indicated type; that is, the type cited in enc:arrayType must be the type or a supertype of every array member). In the case of arrays of arrays or "jagged arrays", the type component is encoded as the "innermost" type name followed by a rank construct for each level of nested arrays starting from 1. Multi-dimensional arrays are encoded using a comma for each dimension starting from 1.

    The "asize" construct contains a comma separated list of zero, one, or more integers indicating the lengths of each dimension of the array. A value of zero integers indicates that no particular quantity is asserted but that the size may be determined by inspection of the actual members.

    For example, an array with 5 members of type array of integers would have an arrayTypeValue value of "int[][5]" of which the atype value is "int[]" and the asize value is "[5]". Likewise, an array with 3 members of type two-dimensional arrays of integers would have an arrayTypeValue value of "int[,][3]" of which the atype value is "int[,]" and the asize value is "[3]".

    A SOAP array member MAY contain a enc:offset attribute indicating the offset position of that item in the enclosing array. This can be used to indicate the offset position of a partially represented array (see 4.4.2.1 PartiallyTransmitted Arrays). Likewise, an array member MAY contain a enc:position attribute indicating the position of that item in the enclosing array. This can be used to describe members of sparse arrays (see 4.4.2.2 SparseArrays). The value of the enc:offset and the enc:position attribute is defined as follows:

    Value of enc:offset and enc:position
    [6]   arrayPoint   =   "[" #length "]"

    with offsets and positions based at 0.

  9. A NULL value or a default value MAY be represented by omission of the accessor element. A NULL value MAY also be indicated by an accessor element containing the attribute xsi:nil with value "1 or true" or possibly other application-dependent attributes and values.

Note that rule 2 allows independent elements and also elements representing the members of arrays to have names which are not identical to the type of the contained value.

4.2 Simple Types

For simple types, SOAP adopts all the types found in the section "Built-in datatypes" of the "XML Schema Part 2: Datatypes" Specification[5], both the value and lexical spaces. Examples include:

Type Example
int 58502
float 314159265358979E+1
negativeInteger -32768
string Louis "Satchmo" Armstrong

The datatypes declared in the XML Schema specification may be used directly in element schemas. Types derived from these may also be used. For example, for the following schema:

Example: Schema with simple types
<!-- schema document -->
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" >

  <xs:element name="age" type="xs:int" />
  <xs:element name="height" type="xs:float" />
  <xs:element name="displacement" type="xs:negativeInteger" />
  <xs:element name="color" >
    <xs:simpleType base="xsd:string">
      <xs:restriction base="xs:string">
        <xs:enumeration value="Green"/>
        <xs:enumeration value="Blue"/>
      </xs:restriction>
    </xs:simpleType>
  </xs:element>

</xs:schema>

the following elements would be valid instances:

Example: Message fragment corresponding to the preceding schema
<!-- Example instance elements -->
<age>45</age>
<height>5.9</height>
<displacement>-450</displacement>
<color>Blue</color>

All simple values MUST be encoded as the content of elements whose type is either defined in "XML Schema Part 2: Datatypes" Specification[5], or is based on a type found there by using the mechanisms provided in the XML Schema specification.

If a simple value is encoded as an independent element or member of a heterogenous array it is convenient to have an element declaration corresponding to the datatype. Because the "XML Schema Part 2: Datatypes" Specification[5] includes type definitions but does not include corresponding element declarations, the enc schema and namespace declares an element for every simple datatype. These MAY be used.

Example: Using elements declared in SOAP encoding schema
<enc:int xmlns:enc="http://www.w3.org/2001/09/soap-encoding" id="int1">45</enc:int>

4.2.1 Strings

The datatype "string" is defined in "XML Schema Part 2: Datatypes" Specification[5]. Note that this is not identical to the type called "string" in many database or programming languages, and in particular may forbid some characters those languages would permit. (Those values must be represented by using some datatype other than xsd:string.)

A string MAY be encoded as a single-reference or a multi-reference value.

The containing element of the string value MAY have an id attribute. Additional accessor elements MAY then have matching href attributes.

For example, two accessors to the same string could appear, as follows:

Example: Two accessors for the same string
<greeting id="String-0">Hello</greeting>
<salutation href="#String-0"/>

However, if the fact that both accessors reference the same instance of the string (or subtype of string) is immaterial, they may be encoded as two single-reference values as follows:

Example: Two accessors for the same string
<greeting>Hello</greeting>
<salutation>Hello</salutation>

Schema fragments for these examples could appear similar to the following:

Example: Schema for preceding example
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
           xmlns:enc="http://www.w3.org/2001/09/soap-encoding" >

  <xs:import namespace="http://www.w3.org/2001/09/soap-encoding" />

  <xs:element name="greeting" type="enc:string" />
  <xs:element name="salutation" type="enc:string" />

</xs:schema>

(In this example, the type enc:string is used as the element's type as a convenient way to declare an element whose datatype is "xsd:string" and which also allows id and href attributes. See the SOAP Encoding schema for the exact definition. Schemas MAY use these declarations from the SOAP Encoding schema but are not required to.)

4.2.2 Enumerations

The "XML Schema Part 2: Datatypes" Specification[5] defines a mechanism called "enumeration." The SOAP data model adopts this mechanism directly. However, because programming and other languages often define enumeration somewhat differently, the specification further describes how a value that is a member of an enumerated list of possible values is to be encoded. Specifically, it is encoded as the name of the value.

"Enumeration" as a concept indicates a set of distinct names. A specific enumeration is a specific list of distinct values appropriate to the base type. For example the set of color names ("Green", "Blue", "Brown") could be defined as an enumeration based on the string built-in type. The values ("1", "3", "5") are a possible enumeration based on integer, and so on. "XML Schema Part 2: Datatypes"[5] supports enumerations for all of the simple types except for boolean. The language of "XML Schema Part 1: Structures" Specification[4] can be used to define enumeration types. If a schema is generated from another notation in which no specific base type is applicable, use "string". In the following schema example "EyeColor" is defined as a string with the possible values of "Green", "Blue", or "Brown" enumerated, and instance data is shown accordingly.

Example: Schema with enumeration
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
                   xmlns:tns="http://example.org/2001/06/samples"
                   targetNamespace="http://example.org/2001/06/samples" >

  <xs:element name="EyeColor" type="tns:EyeColor" />
  <xs:simpleType name="EyeColor" >
    <xs:restriction base="xs:string" >
      <xs:enumeration value="Green" />
      <xs:enumeration value="Blue" />
      <xs:enumeration value="Brown" />
    </xs:restriction>
  </xs:simpleType>

</xs:schema>
Example: Message fragment corresponding to the preceding schema
<p:EyeColor xmlns:p="http://example.org/2001/06/samples" >Brown</p:EyeColor>

4.2.3 Array of Bytes

An array of bytes MAY be encoded as a single-reference or a multi-reference value. The rules for an array of bytes are similar to those for a string.

In particular, the containing element of the array of bytes value MAY have an id attribute. Additional accessor elements MAY then have matching href attributes.

The recommended representation of an opaque array of bytes is the 'base64' encoding defined in XML Schemas[4][5], which uses the base64 encoding algorithm defined in MIME[15]. However, the line length restrictions that normally apply to base64 data in MIME do not apply in SOAP. A "enc:base64" subtype is supplied for use with SOAP.

Example: Image with base64 encoding
<picture xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns:enc="http://www.w3.org/2001/09/soap-encoding"
         xsi:type="enc:base64" >
   aG93IG5vDyBicm73biBjb3cNCg==
</picture>

4.3 Polymorphic Accessor

Many languages allow accessors that can polymorphically access values of several types, each type being available at run time. A polymorphic accessor instance MUST contain an xsi:type attribute that describes the type of the actual value.

For example, a polymorphic accessor named "cost" with a value of type "xsd:float" would be encoded as follows:

Example: Polymorphic accessor
<cost xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xmlns:xs="http://www.w3.org/2001/XMLSchema"
          xsi:type="xs:float">29.95</cost>

as contrasted with a cost accessor whose value's type is invariant, as follows:

Example: Accessor whose value type is invariant
<cost>29.95</cost>

4.4 Compound Types

SOAP defines types corresponding to the following structural patterns often found in programming languages:

Struct

A "struct" is a compound value in which accessor name is the only distinction among member values, and no accessor has the same name as any other.

Array

An "array" is a compound value in which ordinal position serves as the only distinction among member values.

SOAP also permits serialization of data that is neither a Struct nor an Array, for example data such as is found in a Directed-Labeled-Graph Data Model in which a single node has many distinct accessors, some of which occur more than once. SOAP serialization does not require that the underlying data model make an ordering distinction among accessors, but if such an order exists, the accessors MUST be encoded in that sequence.

4.4.1 Compound Values and References to Values

The members of a Compound Value are encoded as accessor elements. When accessors are distinguished by their name (as for example in a struct), the accessor name is used as the element name. Accessors whose names are local to their containing types have unqualified element names; all others have qualified names.

The following is an example of a struct of type "Book":

Example: Book structure
<e:Book xmlns:e="http://example.org/2001/06/books" >
   <author>Henry Ford</author>
   <preface>Prefactory text</preface>
   <intro>This is a book.</intro>
</e:Book>

And this is a schema fragment describing the above structure:

Example: Schema for Book structure
<xs:element name="Book"
            xmlns:xs='http://www.w3.org/2001/XMLSchema' >
  <xs:complexType>
    <xs:sequence>
      <xs:element name="author" type="xs:string" />
      <xs:element name="preface" type="xs:string" />
      <xs:element name="intro" type="xs:string" />
    </xs:sequence>
  </xs:complexType>
</xs:element>

Below is an example of a type with both simple and complex members. It shows two levels of referencing. Note that the href attribute of the Author accessor element is a reference to the value whose id attribute matches. A similar construction appears for the Address accessor element.

Example: Book with muli-reference addresses
<e:Book xmlns:e="http://example.org/2001/06/books" >
  <title>My Life and Work</title>
  <author href="#Person-1"/>
</e:Book>
<e:Person xmlns:e="http://example.org/2001/06/books"
          id="Person-1" >
  <name>Henry Ford</name>
  <address href="#Address-2"/>
</e:Person>
<e:Address xmlns:e="http://example.org/2001/06/books"
           id="Address-2" >
  <email>mailto:henryford@hotmail.com</email>
  <web>http://www.henryford.com</web>
</e:Address>

The form above is appropriate when the "Person" value and the "Address" value are multi-reference. If these were instead both single-reference, they SHOULD be embedded, as follows:

Example: Book with single-reference addresses
<e:Book xmlns:e="http://example.org/2001/06/books" >
   <title>My Life and Work</title>
   <author>
       <name>Henry Ford</name>
       <address>
          <email>mailto:henryford@hotmail.com</email>
          <web>http://www.henryford.com</web>
       </address>
   </author>
</e:Book>

If instead there existed a restriction that no two persons can have the same address in a given instance and that an address can be either a Street-address or an Electronic-address, a Book with two authors would be encoded as follows:

Example: Book with two authors having different addresses
<e:Book xmlns:e="http://example.org/2001/06/books" >
   <title>My Life and Work</title>
   <firstauthor href="#Person-1"/>
   <secondauthor href="#Person-2"/>
</e:Book>
<e:Person xmlns:e="http://example.org/2001/06/books"
          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          id="Person-1" >
   <name>Henry Ford</name>
   <address xsi:type="e:ElectronicAddressType">
       <email>mailto:henryford@hotmail.com</email>
       <web>http://www.henryford.com</web>
   </address>
</e:Person>
<e:Person xmlns:e="http://example.org/2001/06/books"
          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          id="Person-2">
   <name>Samuel Crowther</name>
   <address xsi:type="e:StreetAddressType">
       <street>Martin Luther King Rd</street>
       <city>Raleigh</city>
       <state>North Carolina</state>
   </address>
</e:Person>

Serializations can contain references to values not in the same resource:

Example: Book with external references
<e:Book xmlns:e="http://example.org/2001/06/books" >
   <title>Paradise Lost</title>
   <firstAuthor href="http://www.dartmouth.edu/~milton/" />
</e:Book>

And this is a schema fragment describing the above structures:

Example: Schema for preceding example
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
           xmlns:tns="http://example.org/2001/06/books"
                   targetNamespace="http://example.org/2001/06/books" >

  <xs:element name="Book" type="tns:BookType" />
  <xs:complexType name="BookType" >
    <xs:annotation>
          <xs:documentation>
            <info>
        Either the following group must occur or else the
        href attribute must appear, but not both.
                </info>
          </xs:documentation>
    </xs:annotation>
    <xs:sequence minOccurs="0" maxOccurs="1" >
      <xs:element name="title" type="xs:string" />
      <xs:element name="firstAuthor" type="tns:PersonType" />
      <xs:element name="secondAuthor" type="tns:PersonType" />
    </xs:sequence>
    <xs:attribute name="href" type="xs:anyURI" />
    <xs:attribute name="id" type="xs:ID" />
    <xs:anyAttribute namespace="##other" />
  </xs:complexType>

  <xs:element name="Person" type="tns:PersonType" />
  <xs:complexType name="PersonType" >
    <xs:annotation>
          <xs:documentation>
            <info>
        Either the following group must occur or else the
        href attribute must appear, but not both.
                </info>
          </xs:documentation>
        </xs:annotation>
    <xs:sequence minOccurs="0" maxOccurs="1" >
      <xs:element name="name" type="xs:string" />
      <xs:element name="address" type="tns:AddressType" />
    </xs:sequence>
    <xs:attribute name="href" type="xs:anyURI" />
    <xs:attribute name="id" type="xs:ID" />
    <xs:anyAttribute namespace="##other" />
  </xs:complexType>

  <xs:element name="Address" base="tns:AddressType" />
  <xs:complexType name="AddressType" abstract="true" >
    <xs:annotation>
          <xs:documentation>
            <info>
        Either one of the following sequences must occur or
                else the href attribute must appear, but not both.
                </info>
          </xs:documentation>
        </xs:annotation>
    <xs:choice>
          <xs:sequence minOccurs="0" maxOccurs="1" >
            <xs:element name="email" type="xs:string" />
                <xs:element name="web" type="xs:anyURI" />
          </xs:sequence>
          <xs:sequence minOccurs='0' maxOccurs='1' >
        <xs:element name="street" type="xs:string" />
        <xs:element name="city" type="xs:string" />
        <xs:element name="state" type="xs:string"/>
          </xs:sequence>
        </xs:choice>
    <xs:attribute name="href" type="xs:anyURI"/>
    <xs:attribute name="id" type="xs:ID"/>
    <xs:anyAttribute namespace="##other"/>
  </xs:complexType>

  <xs:complexType name="StreetAddressType">
    <xs:annotation>
          <xs:documentation>
            <info>
        Either the second sequence in the following group
                must occur or else the href attribute must appear,
                but not both.
                </info>
          </xs:documentation>
        </xs:annotation>
        <xs:complexContent>
          <xs:restriction base="tns:AddressType" >
            <xs:sequence>
              <xs:sequence minOccurs="0" maxOccurs="0" >
                <xs:element name="email" type="xs:string" />
                    <xs:element name="web" type="xs:anyURI" />
              </xs:sequence>
          <xs:sequence minOccurs="0" maxOccurs="1">
            <xs:element name="street" type="xs:string" />
            <xs:element name="city" type="xs:string" />
            <xs:element name="state" type="xs:string"/>
          </xs:sequence>
                </xs:sequence>
        <xs:attribute name="href" type="xs:anyURI"/>
        <xs:attribute name="id" type="xs:ID"/>
        <xs:anyAttribute namespace="##other"/>
          </xs:restriction>
        </xs:complexContent>
  </xs:complexType>

  <xs:complexType name="ElectronicAddressType">
    <xs:annotation>
          <xs:documentation>
            <info>
        Either the first sequence in the following group
                must occur or else the href attribute must appear,
                but not both.
                </info>
          </xs:documentation>
        </xs:annotation>
        <xs:complexContent>
          <xs:restriction base="tns:AddressType" >
            <xs:sequence>
          <xs:sequence minOccurs="0" maxOccurs="1">
            <xs:element name="email" type="xs:string" />
            <xs:element name="web" type="xs:anyURI" />
          </xs:sequence>
                  <xs:sequence minOccurs="0" maxOccurs="0">
            <xs:element name="street" type="xs:string" />
            <xs:element name="city" type="xs:string" />
            <xs:element name="state" type="xs:string"/>
          </xs:sequence>
                </xs:sequence>
            <xs:attribute name="href" type="xs:anyURI"/>
        <xs:attribute name="id" type="xs:ID"/>
        <xs:anyAttribute namespace="##other"/>
          </xs:restriction>
        </xs:complexContent>
  </xs:complexType>

</xs:schema>

4.4.2 Arrays

SOAP arrays are defined as having a type of enc:Array or a derived type having that type in its derivation hierarchy (see also rule 8 in 4.1 Rules for Encoding Types in XML). Such derived types would be restrictions of the enc:Array type and could be used to represent, for example, arrays limited to integers or arrays of some user-defined enumeration. Arrays are represented as element values, with no specific constraint on the name of the containing element (just as values generally do not constrain the name of their containing element). The elements which make up the array can themselves can be of any type, including nested arrays.

The representation of the value of an array is an ordered sequence of elements constituting the items of the array. Within an array value, element names are not significant for distinguishing accessors. Elements may have any name. In practice, elements will frequently be named so that their declaration in a schema suggests or determines their type. As with compound types generally, if the value of an item in the array is a single-reference value, the item contains its value. Otherwise, the item references its value via an href attribute.

The following example is a schema fragment and an array containing integer array members:

Example: Schema declaring an array of integers
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
           xmlns:enc="http://www.w3.org/2001/09/soap-encoding" >
  <xs:import namespace="http://www.w3.org/2001/09/soap-encoding" />
  <xs:element name="myFavoriteNumbers" type="enc:Array" />
</xs:schema>
Example: Array conforming to the preceding schema
<myFavoriteNumbers xmlns:xs="http://www.w3.org/2001/XMLSchema"
                   xmlns:enc="http://www.w3.org/2001/09/soap-encoding"
                   enc:arrayType="xs:int[2]" >
  <number>3</number>
  <number>4</number>
</myFavoriteNumbers>

In the preceding example, the array myFavoriteNumbers contains several members each of which is a value of type xs:int. This can be determined by inspection of the enc:arrayType attribute. Note that the enc:Array type allows both unqualified element names and qualified element names from any namespace. These convey no type information, so when used they must either have an xsi:type attribute or the containing element must have a enc:arrayType attribute. Naturally, types derived from enc:Array may declare local elements, with type information.

As previously noted, the enc schema contains declarations of elements with names corresponding to each simple type in the "XML Schema Part 2: Datatypes" Specification[5]. It also contains a declaration for Array. They are used in the following example:

Example: Using the enc:Array element
<enc:Array xmlns:enc="http://www.w3.org/2001/09/soap-encoding"
           xmlns:xs="http://www.w3.org/2001/XMLSchema"
           enc:ArrayType="xs:int[2]" >
  <enc:int>3</enc:int>
  <enc:int>4</enc:int>
</enc:Array>

Arrays can contain instances of any subtype of the specified arrayType. That is, the members may be of any type that is substitutable for the type specified in the arrayType attribute, according to whatever substitutability rules are expressed in the schema. So, for example, an array of integers can contain any type derived from integer (for example "int" or any user-defined derivation of integer). Similarly, an array of "address" might contain a restricted or extended type such as "internationalAddress". Because the supplied enc:Array type admits members of any type, arbitrary mixtures of types can be contained unless specifically limited by use of the arrayType attribute.

Types of member elements can be specified using the xsi:type attribute in the instance, or by declarations in the schema of the member elements, as the following two arrays demonstrate respectively:

Example: Array with elements of varying types
<enc:Array xmlns:enc="http://www.w3.org/2001/09/soap-encoding"
           xmlns:xs="http://www.w3.org/2001/XMLSchema"
                   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           enc:arrayType="xs:anyType[4]">
   <thing xsi:type="xs:int">12345</thing>
   <thing xsi:type="xs:decimal">6.789</thing>
   <thing xsi:type="xs:string">
      Of Mans First Disobedience, and the Fruit
      Of that Forbidden Tree, whose mortal tast
      Brought Death into the World, and all our woe,
   </thing>
   <thing xsi:type="xs:anyURI">
      http://www.dartmouth.edu/~milton/reading_room/
   </thing>
</enc:Array>
Example: Array with elements of varying types
<enc:Array xmlns:xs="http://www.w3.org/2001/XMLSchema"
           xmlns:enc="http://www.w3.org/2001/09/soap-encoding"
           enc:arrayType="xs:anyType[4]" >
   <enc:int>12345</enc:int>
   <enc:decimal>6.789</enc:decimal>
   <enc:string>
      Of Mans First Disobedience, and the Fruit
      Of that Forbidden Tree, whose mortal tast
      Brought Death into the World, and all our woe,
   </enc:string>
   <enc:anyURI>
      http://www.dartmouth.edu/~milton/reading_room/
   </enc:anyURI >
</enc:Array>

Array values may be structs or other compound values. For example an array of "xyz:Order" structs :

Example: Arrays containing structs and other compound values
<enc:Array xmlns:enc="http://www.w3.org/2001/09/soap-encoding"
           xmlns:xyz="http://example.org/2001/06/Orders"
           enc:arrayType="xyz:Order[2]">
   <Order>
       <Product>Apple</Product>
       <Price>1.56</Price>
   </Order>
   <Order>
       <Product>Peach</Product>
       <Price>1.48</Price>
   </Order>
</enc:Array>

Arrays may have other arrays as member values. The following is an example of an array of two arrays, each of which is an array of strings.

Example: Array containing other arrays
<enc:Array xmlns:xs="http://www.w3.org/2001/XMLSchema"
           xmlns:enc="http://www.w3.org/2001/09/soap-encoding"
           enc:arrayType="xs:string[][2]" >
   <item href="#array-1"/>
   <item href="#array-2"/>
</enc:Array>
<enc:Array xmlns:xs="http://www.w3.org/2001/XMLSchema"
           xmlns:enc="http://www.w3.org/2001/09/soap-encoding"
           id="array-1"
           enc:arrayType="xs:string[3]">
   <item>r1c1</item>
   <item>r1c2</item>
   <item>r1c3</item>
</enc:Array>
<enc:Array xmlns:xs="http://www.w3.org/2001/XMLSchema"
           xmlns:enc="http://www.w3.org/2001/09/soap-encoding"
           id="array-2"
           enc:arrayType="xs:string[2]">
   <item>r2c1</item>
   <item>r2c2</item>
</enc:Array>

The element containing an array value does not need to be named "enc:Array". It may have any name, provided that the type of the element is either enc:Array or is derived from enc:Array by restriction. For example, the following is a fragment of a schema and a conforming instance array:

Example: Schema for an array
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
           xmlns:enc="http://www.w3.org/2001/09/soap-encoding"
           xmlns:tns="http://example.org/2001/06/numbers"
           targetNamespace="http://example.org/2001/06/numbers" >

  <xs:simpleType name="phoneNumberType" >
    <xs:restriction base="xs:string" />
  </xs:simpleType>

  <xs:element name="ArrayOfPhoneNumbers" type="tns:ArrayOfPhoneNumbersType" />

  <xs:complexType name="ArrayOfPhoneNumbersType" >
    <xs:complexContent>
      <xs:restriction base="enc:Array" >
            <xs:sequence>
          <xs:element name="phoneNumber" type="tns:phoneNumberType" maxOccurs="unbounded" />
            </xs:sequence>
        <xs:attributeGroup ref="enc:arrayAttributes" />
        <xs:attributeGroup ref="enc:commonAttributes" />
      </xs:restriction>
    </xs:complexContent>
  </xs:complexType>

</xs:schema>
Example: Array conforming to the preceding schema
<abc:ArrayOfPhoneNumbers xmlns:abc="http://example.org/2001/06/numbers"
                         xmlns:enc="http://www.w3.org/2001/09/soap-encoding"
                         enc:arrayType="abc:phoneNumberType[2]" >
   <phoneNumber>206-555-1212</phoneNumber>
   <phoneNumber>1-888-123-4567</phoneNumber>
</abc:ArrayOfPhoneNumbers>

Arrays may be multi-dimensional. In this case, more than one size will appear within the asize part of the arrayType attribute:

Example: Multi-dimensonal array
<enc:Array xmlns:xs="http://www.w3.org/2001/XMLSchema"
           xmlns:enc="http://www.w3.org/2001/09/soap-encoding"
           enc:arrayType="xs:string[2,3]" >
   <item>r1c1</item>
   <item>r1c2</item>
   <item>r1c3</item>
   <item>r2c1</item>
   <item>r2c2</item>
   <item>r2c3</item>
</enc:Array>

While the examples above have shown arrays encoded as independent elements, array values MAY also appear embedded and SHOULD do so when they are known to be single reference.

The following is an example of a schema fragment and an array of phone numbers embedded in a struct of type "Person" and accessed through the accessor "phoneNumbers":

Example: Schema fragment for array of phone numbers embedded in a struct
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
           xmlns:enc="http://www.w3.org/2001/09/soap-encoding"
           xmlns:tns="http://example.org/2001/06/numbers"
                   targetNamespace="http://example.org/2001/06/numbers" >

  <xs:import namespace="http://www.w3.org/2001/09/soap-encoding" />

  <xs:simpleType name="phoneNumberType" >
    <xs:restriction base="xs:string" />
  </xs:simpleType>


  <xs:element name="ArrayOfPhoneNumbers" type="tns:ArrayOfPhoneNumbersType" />

  <xs:complexType name="ArrayOfPhoneNumbersType" >
    <xs:complexContent>
      <xs:restriction base="enc:Array" >
            <xs:sequence>
          <xs:element name="phoneNumber" type="tns:phoneNumberType" maxOccurs="unbounded" />
            </xs:sequence>
        <xs:attributeGroup ref="enc:arrayAttributes" />
        <xs:attributeGroup ref="enc:commonAttributes" />
      </xs:restriction>
    </xs:complexContent>
  </xs:complexType>

  <xs:element name="Person">
    <xs:complexType>
          <xs:sequence>
        <xs:element name="name" type="xs:string" />
        <xs:element name="phoneNumbers" type="tns:ArrayOfPhoneNumbersType" />
      </xs:sequence>
    </xs:complexType>
  </xs:element>

</xs:schema>
Example: Array of phone numbers embedded in a struct conforming to the preceding schema
<def:Person xmlns:def="http://example.org/2001/06/numbers"
            xmlns:enc="http://www.w3.org/2001/09/soap-encoding" >
   <name>John Hancock</name>
   <phoneNumbers enc:arrayType="def:phoneNumber[2]">
       <phoneNumber>206-555-1212</phoneNumber>
       <phoneNumber>1-888-123-4567</phoneNumber>
   </phoneNumbers>
</def:Person>

Here is another example of a single-reference array value encoded as an embedded element whose containing element name is the accessor name:

Example: Single-reference array encoded as en embedded element
<xyz:PurchaseOrder xmlns:xyz="http://example.org/2001/06/Orders" >
   <CustomerName>Henry Ford</CustomerName>
   <ShipTo>
       <Street>5th Ave</Street>
       <City>New York</City>
       <State>NY</State>
       <Zip>10010</Zip>
   </ShipTo>
   <PurchaseLineItems xmlns:enc="http://www.w3.org/2001/09/soap-encoding"
                      enc:arrayType="xyz:Order[2]">
       <Order>
           <Product>Apple</Product>
           <Price>1.56</Price>
       </Order>
       <Order>
           <Product>Peach</Product>
           <Price>1.48</Price>
       </Order>
   </PurchaseLineItems>
</xyz:PurchaseOrder>
4.4.2.1 PartiallyTransmitted Arrays

SOAP provides support for partially transmitted arrays, known as "varying" arrays in some contexts[5]. A partially transmitted array indicates in an enc:offset attribute the zero-origin offset of the first element transmitted. If omitted, the offset is taken as zero.

The following is an example of an array of size five that transmits only the third and fourth element counting from zero:

Example: Array of size five that transmits only the third and fourth element
<enc:Array xmlns:enc="http://www.w3.org/2001/09/soap-encoding"
           xmlns:xs="http://www.w3.org/2001/XMLSchema"
           enc:arrayType="xs:string[6]"
           enc:offset="[3]" >
  <item>The fourth element</item>
  <item>The fifth element</item>
</enc:Array>
4.4.2.2 SparseArrays

SOAP provides support for sparse arrays. Each element representing a member value contains a enc:position attribute that indicates its position within the array. The following is an example of a sparse array of two-dimensional arrays of strings. The size is 4 but only position 2 is used:

Example: Sparse array
<enc:Array xmlns:enc="http://www.w3.org/2001/09/soap-encoding"
           xmlns:xs="http://www.w3.org/2001/XMLSchema"
           enc:arrayType="xs:string[,][4]" >
   <enc:Array href="#array-1" enc:position="[2]" />
</enc:Array>
<enc:Array id="array-1"
           enc:arrayType="xs:string[10,10]" >
   <item enc:position="[2,2]">Third row, third col</item>
   <item enc:position="[7,2]">Eighth row, third col</item>
</enc:Array>

If the only reference to "array-1" occurs in the enclosing array, this example could also have been encoded as follows:

Example: Alternative serialisation
<enc:Array xmlns:enc="http://www.w3.org/2001/09/soap-encoding"
           xmlns:xs="http://www.w3.org/2001/XMLSchema"
           enc:arrayType="xs:string[,][4]" >
  <enc:Array enc:position="[2]" enc:arrayType="xs:string[10,10]" >    <item enc:position="[2,2]">Third row, third col</item>
    <item enc:position="[7,2]">Eighth row, third col</item>
  </enc:Array>
</enc:Array>

4.4.3 Generic Compound Types

The encoding rules just cited are not limited to those cases where the accessor names are known in advance. If accessor names are known only by inspection of the immediate values to be encoded, the same rules apply, namely that the accessor is encoded as an element whose name matches the name of the accessor, and the accessor either contains or references its value. Accessors containing values whose types cannot be determined in advance MUST always contain an appropriate xsi:type attribute giving the type of the value.

Similarly, the rules cited are sufficient to allow serialization of compound types having a mixture of accessors distinguished by name and accessors distinguished by both name and ordinal position. (That is, having some accessors repeated.) This does not require that any schema actually contain such types, but rather says that if a type-model schema does have such types, a corresponding XML syntactic schema and instance may be generated.

Example: Generic compound types
<xyz:PurchaseOrder xmlns:xyz="http://example.org/2001/06/Orders" >
  <CustomerName>Henry Ford</CustomerName>
  <ShipTo>
    <Street>5th Ave</Street>
    <City>New York</City>
    <State>NY</State>
    <Zip>10010</Zip>
  </ShipTo>
  <PurchaseLineItems>
    <Order>
      <Product>Apple</Product>
      <Price>1.56</Price>
    </Order>
    <Order>
      <Product>Peach</Product>
      <Price>1.48</Price>
    </Order>
  </PurchaseLineItems>
</xyz:PurchaseOrder>

Similarly, it is valid to serialize a compound value that structurally resembles an array but is not of type (or subtype) enc:Array. For example:

Example: Compound value
<PurchaseLineItems>
    <Order>
        <Product>Apple</Product>
        <Price>1.56</Price>
    </Order>
    <Order>
        <Product>Peach</Product>
        <Price>1.48</Price>
    </Order>
</PurchaseLineItems>

4.5 Default Values

An omitted accessor element implies either a default value or that no value is known. The specifics depend on the accessor, method, and its context. For example, an omitted accessor typically implies a Null value for polymorphic accessors (with the exact meaning of Null accessor-dependent). Likewise, an omitted Boolean accessor typically implies either a False value or that no value is known, and an omitted numeric accessor typically implies either that the value is zero or that no value is known.

4.6 SOAP root Attribute

The SOAP root attribute can be used to label serialization roots that are not true roots of an object graph so that the object graph can be deserialized. The attribute can have one of two values, either "true" or "false". True roots of an object graph have the implied attribute value of "true". Serialization roots that are not true roots can be labeled as serialization roots with an attribute value of "true". An element can explicitly be labeled as not being a serialization root with a value of "false".

The SOAP root attribute MAY appear on any subelement within the SOAP Header and SOAP Body elements. The attribute does not have a default value.

The SOAP root attribute information item is of type boolean from the namespace "http://www.w3.org/2001/XMLSchema".

5 Using SOAP for RPC

Editorial note: JJM20010920
The Working Group is aware that the following section does not use the XML Infoset terminology used elsewhere in this specification, and most notably in Part 1. The WG expects to rewrite this section using the XML Infoset terminalogy at a later date.

One of the design goals of SOAP is to encapsulate remote procedure call functionality using the extensibility and flexibility of XML. This section defines a uniform representation of RPC invocations and responses.

Although it is anticipated that this representation is likely to be used in combination with the encoding style defined in 4 SOAP Encoding, other representations are possible. The SOAP encodingStyle attribute (see [1]SOAP Encoding Attribute) can be used to indicate the encoding style of the RPC invocation and/or the response using the representation described in this section.

Using SOAP for RPC is orthogonal to the SOAP protocol binding (see 6 Using SOAP in HTTP). In the case of using HTTP as the protocol binding, an RPC invocation maps naturally to an HTTP request and an RPC response maps to an HTTP response. However, using SOAP for RPC is not limited to the HTTP protocol binding.

To invoke an RPC, the following information is needed:

SOAP relies on the protocol binding to provide a mechanism for carrying the URI. For example, for HTTP the request URI indicates the resource that the invocation is being made against. Other than it be a valid URI, SOAP places no restriction on the form of an address (see RFC2396[6] for more information on URIs).

5.1 RPC and SOAP Body

RPC invocations and responses are both carried in the SOAP Body element (see [1]SOAP Body) using the following representation:

  • An RPC invocation is modeled as a struct.

  • The invocation is viewed as a single struct containing an accessor for each [in] or [in/out] parameter. The struct is both named and typed identically to the procedure or method name.

  • Each [in] or [in/out] parameter is viewed as an accessor, with a name corresponding to the name of the parameter and type corresponding to the type of the parameter. These appear in the same order as in the procedure or method signature.

  • An RPC response is modeled as a struct.

  • The response is viewed as a single struct containing an accessor for the return value and each [out] or [in/out] parameter. The return value accessor SHOULD be first, followed by the accessors for the parameters which SHOULD be in the same order as they appear in the procedure or method signature.

  • Each parameter accessor has a name corresponding to the name of the parameter and type corresponding to the type of the parameter. The name of the return value accessor is "result" and it is namespace-qualified with the namespace identifier "http://www.w3.org/2001/09/soap-rpc" The return value accessor MUST be present if the return value of the procedure is non-void. The return value accessor MUST NOT be present if the return value of the procedure is void.

  • Invocation faults are handled according to the rules in 5.3 RPC Faults. If a protocol binding adds additional rules for fault expression, those MUST also be followed.

As noted above, RPC invocation and response structs can be encoded according to the rules in 4 SOAP Encoding, or other encodings can be specified using the encodingStyle attribute (see [1]Encoding Attribute).

Applications MAY process invocations with missing parameters but also MAY return a fault.

Because a result indicates success and a fault indicates failure, it is an error for an RPC response to contain both a result and a fault.

5.2 RPC and SOAP Header

Additional information relevant to the encoding of an RPC invocation but not part of the formal procedure or method signature MAY be expressed in the RPC encoding. If so, it MUST be expressed as a header block.

An example of the use of a header block is the passing of a transaction ID along with a message. Since the transaction ID is not part of the signature and is typically held in an infrastructure component rather than application code, there is no direct way to pass the necessary information with the invocation. By adding a header block with a fixed name, the transaction manager on the receiving side can extract the transaction ID and use it without affecting the coding of remote procedure calls.

5.3 RPC Faults

The RPC representation introduces additional SOAP fault codes to those described in [1]Fault Codes. The namespace identifier for these SOAP faultcode element information item values is "http://www.w3.org/2001/09/soap-rpc" and the namespace prefix rpc: is used in this section to indicate association with this namespace.

Errors arising during RPC invocations are reported according to the following rules (in decreasing order of precedence):

  1. A soap-env:Server fault SHOULD be generated when the server cannot handle the message because of some temporary condition, e.g. when it is out of memory.

  2. A soap-env:DataEncodingUnknown fault SHOULD be generated when the arguments are encoded in a data encoding unknown to the server.

  3. An rpc:ProcedureNotPresent fault MUST be generated when the server cannot find the procedure specified.

  4. An rpc:BadArguments fault MUST be generated when the server cannot parse the arguments or when there is a mismatch between what the server expects and what the client has sent.

  5. Other faults arising in an extension or from the application SHOULD be generated as described in [1](SOAP Faults).

In all cases the values of the detail and faultstring element information items are implementation defined. They MAY be specified by some external document.

6 Using SOAP in HTTP

This section describes how to use SOAP within HTTP. Binding SOAP to HTTP provides the advantage of being able to use the formalism and decentralized flexibility of SOAP with the rich feature set of HTTP. Carrying SOAP in HTTP does not mean that SOAP overrides existing semantics of HTTP but rather that SOAP over HTTP inherits HTTP semantics.

SOAP naturally follows the HTTP request/response message model by providing a SOAP request message in a HTTP request and SOAP response message in a HTTP response. Note, however, that SOAP intermediaries are NOT the same as HTTP intermediaries. That is, an HTTP intermediary addressed with the HTTP Connection header field cannot be expected to inspect or process the SOAP entity body carried in the HTTP request.

HTTP applications MUST use the media type "text/xml" according to RFC 2376[11] when including SOAP messages in HTTP exchanges.

6.1 SOAP HTTP Request

Although SOAP might be used in combination with a variety of HTTP request methods, this binding only defines SOAP within HTTP POST requests (see 5 Using SOAP for RPC for how to use SOAP for RPC).

6.1.1 The SOAPAction HTTP Header Field

Editorial note: JJM20010821
SOAPAction is an optional feature of SOAP. The Working Group is considering a formal definition of the general characteristics of such "optional features" for inclusion in a future revision of this specification. At such time, the above description of SOAPAction would be revised, if necessary, to make clear its status as such a feature.

Some SOAP Receivers using this binding might need certain information to be readily available within the underlying protocol. This binding uses the SOAPAction HTTP request header field to supply this information.

SOAP Action HTTP Header
[7]   soapaction   =   "SOAPAction" ":" <"> URI-reference <">
[8]   URI-reference   =   <as defined in RFC2396>

The value of this request header field can be any URI reference, including absolute URIs and relative URIs, in which case it is interpreted relative to the Request-URI.

SOAPAction's presence in this binding's request messages is OPTIONAL. SOAP Receivers MAY use it as a hint to optimise processing, but SHOULD NOT require its presence in order to operate.

Editorial note: JJM20010818
A specific HTTP Status Code (427 proposed) shall be registered with IANA for the purpose of providing a means by which a SOAP Receiver can indicate to a SOAP client that the SOAPAction Header Field is required.

If a SOAP Receiver does require SOAPAction's presence in order to operate, it MUST respond to requests which either contain an unrecognised SOAPAction header value or do not contain a SOAPAction header with a 427 "SOAPAction Required" HTTP response status code. Such response messages MAY contain a 'Required-SOAPAction' HTTP response header field, whose value is the URI which can be used in the SOAPAction request header field to re-submit the request.

Required SOAP Action HTTP Header
[9]   req-soapaction   =   "required-SOAPAction" ":" <"> URI-reference <">

Support for SOAPAction is OPTIONAL in implementations. Implementations SHOULD NOT generate or require SOAPAction UNLESS they have a particular purpose for doing so (e.g., a SOAP Receivers specifies its use).

6.2 SOAP HTTP Response

SOAP over HTTP follows the semantics of the HTTP Status codes for communicating status information in HTTP. For example, a 2xx status code indicates that the client's request including the SOAP component was successfully received, understood, and accepted etc.

If an error occurs while processing the request, the SOAP HTTP server MUST issue an HTTP 500 "Internal Server Error" response and include a SOAP message in the response containing a SOAP fault (see [1]SOAP Faults) indicating the SOAP processing error.

6.3 The HTTP Extension Framework

Editorial note: MJH20010809
Due to it's status as an experimental RFC[17], all normative references to the HTTP extension framework[16] have been removed from this specification. Unless feedback to the contrary is received, the remains of this subsection, including this note, will be removed from the next working draft.

6.4 Security Considerations

Editorial note: MJG20010926
This section will in a future revision provide some guidelines for the security considerations that should be taken into account when using the HTTP binding defined in this document.

6.5 SOAP HTTP Examples

Example: SOAP HTTP Request Using POST
POST /StockQuote HTTP/1.1
Content-Type: text/xml; charset="utf-8"
Content-Length: nnnn
SOAPAction: "http://www.example.org/abc#MyMessage"

<env:Envelope xmlns:env="http://www.w3.org/2001/09/soap-envelope" >
 . . .
</env:Envelope>
Example: SOAP HTTP Response to preceding request
HTTP/1.1 200 OK
Content-Type: text/xml; charset="utf-8"
Content-Length: nnnn

<env:Envelope xmlns:env="http://www.w3.org/2001/09/soap-envelope" >
 . . .
</env:Envelope>

7 References

7.1 Normative References

1
W3C Working Draft "SOAP Version 1.2 Part 1: Messaging Framework", Martin Gudgin, Marc Hadley, Jean-Jacques Moreau, Henrik Frystyk Nielsen, 2 October 2001 (See http://www.w3.org/TR/2001/WD-soap12-part1-20011002/.)
2
IETF "RFC 2616: Hypertext Transfer Protocol -- HTTP/1.1", R. Fielding, J. Gettys, J. C. Mogul, H. Frystyk, T. Berners-Lee, January 1997. (See http://www.ietf.org/rfc/rfc2616.txt.)
3
IETF "RFC 2119: Key words for use in RFCs to Indicate Requirement Levels", S. Bradner, March 1997. (See http://www.ietf.org/rfc/rfc2119.txt.)
4
W3C Recommendation "XML Schema Part 1: Structures", Henry S. Thompson, David Beech, Murray Maloney, Noah Mendelsohn, 2 May 2001. (See http://www.w3.org/TR/2001/REC-xmlschema-1-20010502/.)
5
W3C Recommendation "XML Schema Part 2: Datatypes", Paul V. Biron, Ashok Malhotra, 2 May 2001. (See http://www.w3.org/TR/2001/REC-xmlschema-2-20010502/.)
6
IETF "RFC 2396: Uniform Resource Identifiers (URI): Generic Syntax", T. Berners-Lee, R. Fielding, L. Masinter, August 1998. (See http://www.ietf.org/rfc/rfc2396.txt.)
7
W3C Recommendation "Namespaces in XML", Tim Bray, Dave Hollander, Andrew Layman, 14 January 1999. (See http://www.w3.org/TR/1999/REC-xml-names-19990114/.)
8
W3C Recommendation "Extensible Markup Language (XML) 1.0 (Second Edition)", Tim Bray, Jean Paoli, C. M. Sperberg-McQueen, Eve Maler, 6 October 2000. (See http://www.w3.org/TR/2000/REC-xml-20001006.)
9
W3C Proposed Recommendation "XML Linking Language (XLink) Version 1.0", Steve DeRose, Eve Maler, David Orchard, 20 December 2000. (See http://www.w3.org/TR/2000/PR-xlink-20001220/.)
10
W3C Proposed Recommendation "XML Information Set", John Cowan, Richard Tobin, 10 August 2001. (See http://www.w3.org/TR/2001/PR-xml-infoset-20010810/.)
11
IETF "RFC 2376: XML Media Types", E. Whitehead, M. Murata, July 1998. (See http://www.ietf.org/rfc/rfc2376.txt.)

7.2 Informative References

12
XML Protocol Comments Archive (See http://lists.w3.org/Archives/Public/xmlp-comments/.)
13
XML Protocol Discussion Archive (See http://lists.w3.org/Archives/Public/xml-dist-app/.)
14
XML Protocol Charter (See http://www.w3.org/2000/09/XML-Protocol-Charter.)
15
IETF "RFC2045: Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies", N. Freed, N. Borenstein, November 1996. (See http://www.ietf.org/rfc/rfc2045.txt.)
16
IETF "RFC 2774: An HTTP Extension Framework", H. Nielsen, P. Leach, S. Lawrence, February 2000. (See http://www.ietf.org/rfc/rfc2774.txt.)
17
IETF "RFC 2026: The Internet Standards Process -- Revision 3", section 4.2.3, S. Bradner, October 1996. (See http://www.ietf.org/rfc/rfc2026.txt.)

A SOAP Envelope Examples (Non-Normative)

A.1 Sample Encoding of Call Requests

Example: SOAP message using SOAP encoding in HTTP POST with a mandatory header
POST /StockQuote HTTP/1.1
Host: www.example.org
Content-Type: text/xml; charset="utf-8"
Content-Length: nnnn
SOAPAction: "http://example.org/2001/06/quotes"

<env:Envelope
  xmlns:env="http://www.w3.org/2001/09/soap-envelope" >
   <env:Header>
       <t:Transaction
           xmlns:t="http://example.org/2001/06/tx"
           env:encodingStyle="http://www.w3.org/2001/09/soap-encoding"
           env:mustUnderstand="1" >
               5
       </t:Transaction>
   </env:Header>
   <env:Body >
       <m:GetLastTradePrice
             env:encodingStyle="http://www.w3.org/2001/09/soap-encoding"
             xmlns:m="http://example.org/2001/06/quotes" >
           <m:symbol>DEF</m:symbol>
       </m:GetLastTradePrice>
   </env:Body>
</env:Envelope>
Example: SOAP message using SOAP encoding in HTTP POST with multiple request parameters
POST /StockQuote HTTP/1.1
Host: www.example.org
Content-Type: text/xml; charset="utf-8"
Content-Length: nnnn
SOAPAction: "http://example.org/2001/06/quotes"

<env:Envelope xmlns:env="http://www.w3.org/2001/09/soap-envelope" >
   <env:Body>
       <m:GetLastTradePriceDetailed
             env:encodingStyle="http://www.w3.org/2001/09/soap-encoding"
             xmlns:m="http://example.org/2001/06/quotes" >
           <Symbol>DEF</Symbol>
           <Company>DEF Corp</Company>
           <Price>34.1</Price>
       </m:GetLastTradePriceDetailed>
   </env:Body>
</env:Envelope>

A.2 Sample Encoding of Response

Example: SOAP message using SOAP encoding in HTTP response including a mandatory header
HTTP/1.1 200 OK
Content-Type: text/xml; charset="utf-8"
Content-Length: nnnn

<env:Envelope xmlns:env="http://www.w3.org/2001/09/soap-envelope" >
   <env:Header>
       <t:Transaction xmlns:t="http://example.org/2001/06/tx"
                      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                      xmlns:xs="http://www.w3.org/2001/XMLSchema"
                      xsi:type="xs:int"
                      env:encodingStyle="http://www.w3.org/2001/09/soap-encoding"
                      env:mustUnderstand="1" >
           5
       </t:Transaction>
   </env:Header>
   <env:Body>
       <m:GetLastTradePriceResponse
             env:encodingStyle="http://www.w3.org/2001/09/soap-encoding"
             xmlns:m="http://example.org/2001/06/quotes" >
           <Price>34.5</Price>
       </m:GetLastTradePriceResponse>
   </env:Body>
</env:Envelope>
Example: Similar to previous example but using a struct for the body and ommitting the mandatory header
HTTP/1.1 200 OK
Content-Type: text/xml; charset="utf-8"
Content-Length: nnnn

<env:Envelope xmlns:env="http://www.w3.org/2001/09/soap-envelope" >
   <env:Body>
       <m:GetLastTradePriceResponse
             env:encodingStyle="http://www.w3.org/2001/09/soap-encoding"
             xmlns:m="http://example.org/2001/06/quotes" >
           <PriceAndVolume>
               <LastTradePrice>34.5</LastTradePrice>
               <DayVolume>10000</DayVolume>
           </PriceAndVolume>
       </m:GetLastTradePriceResponse>
   </env:Body>
</env:Envelope>
Example: Must understand fault in HTTP response
HTTP/1.1 500 Internal Server Error
Content-Type: text/xml; charset="utf-8"
Content-Length: nnnn

<env:Envelope xmlns:env="http://www.w3.org/2001/09/soap-envelope">
   <env:Body>
       <env:Fault>
           <faultcode>env:MustUnderstand</faultcode>
           <faultstring>SOAP Must Understand Error</faultstring>
       </env:Fault>
   </env:Body>
</env:Envelope>
Example: SOAP fault, resulting from failure to handle the SOAP body, in HTTP response
HTTP/1.1 500 Internal Server Error
Content-Type: text/xml; charset="utf-8"
Content-Length: nnnn

<env:Envelope xmlns:env="http://www.w3.org/2001/09/soap-envelope" >
  <env:Body>
    <env:Fault>
      <faultcode>env:Server</faultcode>
      <faultstring>Server Error</faultstring>
      <detail>
        <e:myfaultdetails xmlns:e="http://example.org/2001/06/faults" >
          <message>My application didn't work</message>
          <errorcode>1001</errorcode>
        </e:myfaultdetails>
      </detail>
    </env:Fault>
 </env:Body>
</env:Envelope>

B Acknowledgements (Non-Normative)

This document is the work of the W3C XML Protocol Working Group.

Members of the Working Group are (at the time of writing, and by alphabetical order): Yasser al Safadi (Philips Research), Vidur Apparao (Netscape), Don Box (DevelopMentor), Charles Campbell (Informix Software), Michael Champion (Software AG), Dave Cleary (webMethods), Ugo Corda (Xerox), Paul Cotton (Microsoft Corporation), Ron Daniel (Interwoven), Glen Daniels (Allaire), Doug Davis (IBM), Ray Denenberg (Library of Congress), Paul Denning (MITRE Corporation), Frank DeRose (TIBCO Software, Inc.), James Falek (TIBCO Software, Inc.), David Fallside (IBM), Chris Ferris (Sun Microsystems), Daniela Florescu (Propel), Dietmar Gaertner (Software AG), Rich Greenfield (Library of Congress), Martin Gudgin (DevelopMentor), Hugo Haas (W3C), Marc Hadley (Sun Microsystems), Mark Hale (Interwoven), Randy Hall (Intel), Gerd Hoelzing (SAP AG), Oisin Hurley (IONA Technologies), Yin-Leng Husband (Compaq), John Ibbotson (IBM), Ryuji Inoue (Matsushita Electric Industrial Co., Ltd.), Scott Isaacson (Novell, Inc.), Kazunori Iwasa (Fujitsu Software Corporation), Murali Janakiraman (Rogue Wave), Mario Jeckle (Daimler-Chrysler Research and Technology), Eric Jenkins (Engenia Software), Mark Jones (AT&T), Anish Karmarkar (Oracle), Jeffrey Kay (Engenia Software), Richard Koo (Vitria Technology Inc.), Jacek Kopecky (IDOOX s.r.o.), Yves Lafon (W3C), Tony Lee (Vitria Technology Inc.), Michah Lerner (AT&T), Henry Lowe (OMG), Richard Martin (Active Data Exchange), Noah Mendelsohn (Lotus Development), Jeff Mischinsky (Oracle), Nilo Mitra (Ericsson Research Canada), Jean-Jacques Moreau (Canon), Highland Mary Mountain (Intel), Masahiko Narita (Fujitsu Software Corporation), Mark Needleman (Data Research Associates), Eric Newcomer (IONA Technologies), Henrik Frystyk Nielsen (Microsoft Corporation), Mark Nottingham (Akamai Technologies), David Orchard (BEA Systems), Kevin Perkins (Compaq), Jags Ramnaryan (BEA Systems), Andreas Riegg (Daimler-Chrysler Research and Technology), Herve Ruellan (Canon), Marwan Sabbouh (MITRE Corporation), Shane Sesta (Active Data Exchange), Miroslav Simek (IDOOX s.r.o.), Simeon Simeonov (Allaire), Nick Smilonich (Unisys), Soumitro Tagore (Informix Software), Lynne Thompson (Unisys), Patrick Thompson (Rogue Wave), Asir Vedamuthu (webMethods) Ray Whitmer (Netscape), Volker Wiechers (SAP AG), Stuart Williams (Hewlett-Packard), Amr Yassin (Philips Research) and Jin Yu (Martsoft Corp.).

Previous members were: Eric Fedok (Active Data Exchange), Susan Yee (Active Data Exchange), Dan Frantz (BEA Systems), Alex Ceponkus (Bowstreet), James Tauber (Bowstreet), Rekha Nagarajan (Calico Commerce), Mary Holstege (Calico Commerce), Krishna Sankar (Cisco Systems), David Burdett (Commerce One), Murray Maloney (Commerce One), Jay Kasi (Commerce One), Yan Xu (DataChannel), Brian Eisenberg (DataChannel), Mike Dierken (DataChannel), Michael Freeman (Engenia Software), Bjoern Heckel (Epicentric), Dean Moses (Epicentric), Julian Kumar (Epicentric), Miles Chaston (Epicentric), Alan Kropp (Epicentric), Scott Golubock (Epicentric), Michael Freeman (Engenia Software), Jim Hughes (Fujitsu Limited), Dick Brooks (Group 8760), David Ezell (Hewlett Packard), Fransisco Cubera (IBM), David Orchard (Jamcracker), Alex Milowski (Lexica), Steve Hole (MessagingDirect Ltd.), John-Paul Sicotte (MessagingDirect Ltd.), Vilhelm Rosenqvist (NCR), Lew Shannon (NCR), Art Nevarez (Novell, Inc.), David Clay (Oracle), Jim Trezzo (Oracle), David Cleary (Progress Software), Andrew Eisenberg (Progress Software), Peter Lecuyer (Progress Software), Ed Mooney (Sun Microsystems), Mark Baker (Sun Microsystems), Anne Thomas Manes (Sun Microsystems), George Scott (Tradia Inc.), Erin Hoffmann (Tradia Inc.), Conleth O'Connell (Vignette), Waqar Sadiq (Vitria Technology Inc.), Randy Waldrop (WebMethods), Bill Anderson (Xerox), Tom Breuel (Xerox), Matthew MacKenzie (XMLGlobal Technologies), David Webber (XMLGlobal Technologies), John Evdemon (XMLSolutions) and Kevin Mitchell (XMLSolutions).

The people who have contributed to discussions on xml-dist-app@w3.org are also gratefully acknowledged.

C Part 2 Change Log (Non-Normative)

C.1 SOAP Specification Changes

Date Author Description
20010926 MJG Updated member list
20010926 MJG Updated ednote in section 6.4
20010926 MJG Changed rpc namespace to http://www.w3.org/2001/09/soap-rpc
20010921 MJG Added rpc namespace to list in Section 2
20010921 MJG Added new schema for rpc result element as described in section 5.1
20010921 MJG Amended section 5.1 to incorporate description of rpc result element
20010921 MJG Changed targetNamespace attribute of encoding schema to http://www.w3.org/2001/09/soap-encoding
20010921 JJM Used text proposed by Noah for ednote on SOAPAction.
20010920 JJM Make the wording clarification regarding issue 45 (descreasing order of precedence).
20010920 JJM Removed current security section; added new security subsection to HTTP binding section, with a temporary ednote until we get text from Henrik and Chris).
20010920 JJM Change the namespace of the envelope to http://www.w3.org/2001/09/...
20010920 JJM Add an editorial note about why some sections are not written in terms of infoset.
20010920 JJM Add ednote from Jacek regarding SOAPAction.
20010918 JJM Added ednote to the "SOAPAction" section indicating that a HTTP status code needs to be obtained from IANA.
20010918 JJM Removed last electrocommerce.org URL from examples.
20010914 JJM Added text from Henrik to beef-up the "Data Model" section placeholder text.
20010914 JJM Back to "Adjuncts" again.
20010914 JJM Fixed issues 124, 126, 127, 128 and 132.
20010914 JJM Fixed typos and indentation.
20010914 JJM Reference the XML InfoSet Proposed Recommandation instead of the Candidate Recommandation.
20010911 JJM Changed XML Information Set into a normative reference. Changed XML Protocol Comments Archive, Discussion Archive and Charter into non-normative references. Added a reference to RFC2396 in section 4, 3rd paragraph.
20010905 MJH Wordsmithed abstract and introduction to better reflect split into parts 1 and 2. Rationalised list of references so only cited works appear. Removed envelope schema changes. Added bibref entries for cross references to Part 1, fixed links so they target the HTML instead of XML version of the doc.
20010831 JJM Added a close paragraph tag before starting a new olist or ulist.
20010831 JJM Properly declared the language for the spec, so that we can generate valid HTML.
20010831 JJM Added text from Hugo to emphasize the fact that the SOAP root attribute is of type XMLSchema boolean.
20010830 MJG Copied "Relation to XML" section from part 1.
20010830 MJG Removed Design Goals section (design goals listed relevant to Part 1 not Part 2)
20010830 JJM Removed terminology not relevant to part2.
20010830 JJM Added SOAP examples from part 1, introductory sections.
20010830 JJM Added SOAP example appendix from part1.
20010830 JJM Added a paragraph to section 1 pointing to part2 for encoding, rpc and http binding.
20010830 JJM Added a paragraph at the beginning of section 3 to cover serializations containing references to data outside the serialization, as per 20010829 teleconference.
20010830 JJM Remove 2nd sentence, bullet 5, RPC faults section, as per 20010829 teleconference.
20010830 JJM Remove 2nd sentence, bullet 1, RPC faults section, as per 20010822 teleconference.
20010829 JJM Added a placehoder for the forthcoming Data Model section.
20010829 JJM Removed the Envelope Example section, already present in part1.
20010829 JJM Updated the spec's title.
20010829 JJM Replaced specref with xspecref for references to Part1 items.
20010829 JJM Added bibliography entry for SOAP 1.2 Part 1.
20010829 JJM Removed former sections 1, 2, 3 and 4, and the SOAP versioning appendix. Moved the RPC section before the HTTP binding section, as per the 20010815 teleconference call.
20010829 JJM Did split the spec into two parts.
20010829 JJM Refered to the proper DTD and stylesheet.
20010829 JJM Updated the list of WG members: one person per line in the XML file, for easier updating.
20010816 MJH Replaced a mustUnderstand="1" with mustUnderstand="true". Slight rewording in mu description.
20010810 MJH Merged in RPC fault rules text from Jacek. Added new DataEncodingUnknown fault code to SOAP Fault Codes section. Added editorial notes about introduction of new fault code namespace for RPC.
20010809 MJH Merged in "mustHappen" descriptive text from Glen and Noah.
20010809 MJH Fixed language around "default" values of attributes.
20010809 MJH Removed HTTP extension framework, added editorial note to describe why.
20010808 MJH Added Infoset "specified" property text from Chris.
20010808 MJH Removed assumption 4 from version transition appendix.
20010808 MJH Added reference to SOAP 1.1 specification to references section, removed SOAP 1.1 author list from acknowledgments section.
20010807 MJH Converted specification from HTML to XML conforming to W3C XMLSpec DTD. Numerous resulting formatting changes.
20010720 MJG Applied Infoset terminology to sections 1, 2, 3 and 4.
20010629 MJG Amended description of routing and intermediaries in Section 2.1
20010629 JJM Changed "latest version" URI to end with soap12 
20010629 JJM Remove "previous version" URI
20010629 JJM Removed "Editor copy" in <title>
20010629 JJM Removed "Editor copy" in the title.
20010629 JJM Added "Previous version" to either point to SOAP/1.1, or explicitly mention there was no prior draft.
20010629 JJM Pre-filed publication URIs.
20010629 JJM Incorporated David's suggested changes for the examples in section 4.1.1 to 4.4.2
20010629 JJM Fixed some remaining typos.
20010629 MJH Fixed a couple of typos.
20010628 MJG Made various formatting, spelling and grammatical fixes.
20010628 MJG Moved soap:encodingStyle from soap:Envelope to children of soap:Header/soap:Body in examples 1, 2, 47, 48, 49 and 50
20010628 MJG Changed text in Section 2.1 from 'it is both a SOAP sender or a SOAP receiver' to 'it is both a SOAP sender and a SOAP receiver'
20010628 MJG Fixed caption on Example 24
20010628 MJH Fixed a couple of capitalisation errors where the letter A appeared as a capital in the middle of a sentence.
20010628 MJH Updated figure 1, removed ednote to do so.
20010622 HFN Removed the introductory text in terminology section 1.4.3 as it talks about model stuff that is covered in section 2. It was left over from original glossary which also explained the SOAP model.
20010622 HFN Moved the definition of block to encapsulation section in terminology
20010622 HFN Removed introductory section in 1.4.1 as this overlaps with the model description in section 2 and doesn't belong in a terminology section
20010622 HFN Removed reference to "Web Characterization Terminology & Definitions Sheet" in terminology section as this is not an active WD
20010622 HFN Added revised glossary
20010622 HFN Added example 0 to section 1.3 and slightly modified text for example 1 and 2 to make it clear that HTTP is used as a protocol binding
20010622 MJG Added http://example.com/... to list of application/context specific URIs in section 1.2
20010622 MJG Updated examples in section 4.1.1 to be encodingStyle attributes rather than just the values of attributes
20010622 MJG Added table.norm, td.normitem and td.normtext styles to stylesheet. Used said styles for table of fault code values in section 4.4.1
20010622 MJG In Appendix C, changed upgrade element to Upgrade and env to envelope. Made envelope unqualified. Updated schema document to match.
20010622 MJG Moved MisunderstoodHeader from envelope schema into seperate faults schema. Removed entry in envelope schema change table in Appendix D.2 that refered to additon of said element. Modified example in section 4.4.2 to match. Added reference to schema document to section 4.4.2
20010622 MJH Added binding as a component of SOAP in introduction. Fixed a couple of typos and updated a couple of example captions.
20010622 MJG Made BNF in section 6.1.1 into a table.
20010622 MJG Made BNFs in section 5.1 clause 8 into tables. Added associated 'bnf' style for table and td elements to stylesheet
20010622 MJG Amended text regarding namespace prefix mappings in section 1.2
20010622 MJG Added link to schema for the http://www.w3.org/2001/06/soap-upgrade namespace to Appendix C. Updated associated ednote.
20010622 MJG Added reference numbers for XML Schema Recommendation to text prior to schema change tables in Appendix D.2 and linked said numbers to local references in this document
20010622 MJG Reordered entries in schema change classification table in Appendix D.2
20010622 MJG Changed type of mustUnderstand and root attributes to standard boolean and updated schema change tables in Appendix D.2 accordingly
20010622 JJM Manually numbered all the examples (53 in total!)
20010622 JJM Added caption text to all the examples
20010622 JJM Replaced remaining occurrences of SOAP/1.2 with SOAP Version 1.2 (including <title>)
20010621 HFN Added ednote to section 4.2.2 and 4.2.3 that we know they have to be incorporated with section 2
20010621 HFN Added version transition appendix C
20010621 HFN Applied new styles to examples
20010621 HFN Changed term "transport" to "underlying protocol
20010621 HFN Changed example URNs to URLs of the style http://example.org/...
20010621 MJH Updated the Acknowledgements section.
20010621 JJM Added new style sheet definitions (from XML Schema) for examples, and used them for example 1 and 2.
20010621 JJM Incorporated David Fallside's comments on section Status and Intro sections.
20010620 HFN Changed the status section
20010620 HFN Changed title to SOAP Version 1.2 and used that first time in abstract and in body
20010620 HFN Removed question from section 2.4 as this is an issue and is to be listed in the issues list
20010620 HFN Moved change log to appendix
20010615 JJM Renamed default actor to anonymous actor for now (to be consistent)
20010615 JJM Fixed typos in section 2
20010614 JJM Updated section 2 to adopt the terminology used elsewhere in the spec.
20010613 MJH Updated mustUnderstand fault text with additions from Martin Gudgin.
20010613 MJH Added schema changes appendix from Martin Gudgin.
20010613 MJH Added mustUnderstand fault text from Glen Daniels.
20010612 MJH Fixed document <title>.
20010612 MJH Moved terminology subsection from message exchange model section to introduction section.
20010612 MJH Fixed capitalisation errors by replacing "... A SOAP ..." with "... a SOAP ..." where appropriate.
20010612 MJH Removed trailing "/" from encoding namespace URI.
20010612 MJH Fixed links under namespace URIs to point to W3C space instead of schemas.xmlsoap.org.
20010612 MJH Removed some odd additional links with text of "/" pointing to the encoding schema following the text of the encoding namespace URI in several places.
20010611 MJH Incorporated new text for section 2.
20010611 JJM Changed remaining namespaces, in particular next.
20010609 JJM Changed the spec name from XMLP/SOAP to SOAP.
20010609 JJM Changed the version number from 1.1 to 1.2.
20010609 JJM Changed the namespaces from http://schemas.xmlsoap.org/soap/ to http://www.w3.org/2001/06/soap-.
20010609 JJM Replaced the remaining XS and XE prefixes to env and enc, respectively.
20010601 MJH Updated the examples in section 1, 6 and appendix A with text suggested by Martin Gudgin to comply with XML Schema Recommendation.
20010601 JJM Updated the examples in section 4 and 5 with text suggested by Martin Gudgin, to comply with XML Schema Recommendation.
20010531 HFN Removed appendices C and D and added links to live issues list and separate schema files.
20010531 MJH Added this change log and updated schemas in appendix C to comply with XML Schema Recommendation.

C.2 XML Schema Changes

The encoding schema has been updated to be compliant with the XML Schema Recomendation[4][5]. The table below shows the categories of change.

Class Meaning
Addition New constructs have been added to the schema
Clarification The meaning of the schema has been changed to more accurately match the specification
Deletion Constructs have been removed from the schema
Name The schema has been changed due to a datatype name change in the XML Schema specification
Namespace A namespace name has been changed
Semantic The meaning of the schema has been changed
Style Style changes have been made to the schema
Syntax The syntax of the schema has been updated due to changes in the XML Schema specification

The table below lists the changes to the encoding schema.

Class Description
Namespace Updated to use the http://www.w3.org/2001/XMLSchema namespace
Namespace Value of targetNamespace attribute changed to http://www.w3.org/2001/06/soap-encoding
Semantic Changed type of the root attribute from restriction of boolean that only allowed 0 or 1 as lexical values to the standard boolean in the http://www.w3.org/2001/XMLSchema namespace. The lexical forms 0, 1, false, true are now allowed.
Addition Added processContents="lax" to all element and attribute wildcards
Syntax Changed base64 simple type to be a vacuous restriction of the base64Binary type in the http://www.w3.org/2001/XMLSchema namespace
Syntax Updated all complex type definitions with simple base types to new syntax
Syntax Added <xs:sequence> to all complex type definitions derived implicitly from the ur-type
Syntax Added <xs:sequence> to all named model group definitions
Deletion Removed the timeDuration datatype
Addition Added duration datatype derived by extension from the duration datatype in the http://www.w3.org/2001/XMLSchema namespace.
Deletion Removed the timeInstant datatype
Addition Added dateTime datatype derived by extension from the dateTime datatype in the http://www.w3.org/2001/XMLSchema namespace.
Addition Added gYearMonth datatype derived by extension from the gYearMonth datatype in the http://www.w3.org/2001/XMLSchema namespace.
Addition Added gYear datatype derived by extension from the gYear datatype in the http://www.w3.org/2001/XMLSchema namespace.
Addition Added gMonthDay datatype derived by extension from the gMonthDay datatype in the http://www.w3.org/2001/XMLSchema namespace.
Addition Added gDay datatype derived by extension from the gDay datatype in the http://www.w3.org/2001/XMLSchema namespace.
Addition Added gDay datatype derived by extension from the gDay datatype in the http://www.w3.org/2001/XMLSchema namespace.
Deletion Removed the binary datatype
Addition Added hexBinary datatype derived by extension from the hexBinary datatype in the http://www.w3.org/2001/XMLSchema namespace.
Addition Added base64Binary datatype derived by extension from the base64Binary datatype in the http://www.w3.org/2001/XMLSchema namespace.
Deletion Removed the uriReference datatype
Addition Added anyURI datatype derived by extension from the anyURI datatype in the http://www.w3.org/2001/XMLSchema namespace.
Addition Added normalizedString datatype derived by extension from the normalizedString datatype in the http://www.w3.org/2001/XMLSchema namespace.
Addition Added token datatype derived by extension from the token datatype in the http://www.w3.org/2001/XMLSchema namespace.
Clarification Added explicit namespace="##any" to all element and attribute wildcards which did not previously have an explicit namespace attribute
Style Where possible comments have been changed into annotations