Experiencia de Implementación de la Web Semántica con Annotea e Amaya

note with text Semantic web advanced development

Jose Kahan

W3C

Introducción

thumbnail images of presentation

Proyecto W3C Sematic Web Advanced Development (SWAD)
Proporciona un marco para communicación rica sobre paginas webs, a traves de metadatos RDF compartidos
Metadatos RDF se pueden guardar en el ordenador o en uno o más servidores RDF elegidos por el usuario
Dos applicaciones:
1. anotaciones compartidas
2. Favoritos compartidos

anotaciones: introducción

Una anotación es una declaración sobre algo

concept: 2 annotations attached

anotaciones: arquitectura básica

annotations from Annotea server

anotaciones: modelo RDF

schema for annotations

anotaciones: una anotación

<?xml version="1.0" ?>
<r:RDF xmlns:r="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:a="http://www.w3.org/2000/10/annotation-ns#"
xmlns:http="http://www.w3.org/1999/xx/http#"
xmlns:d="http://purl.org/dc/elements/1.1/">
<r:Description>
<r:type resource="http://www.w3.org/2000/10/annotation-ns#Annotation" />
<r:type resource="http://www.w3.org/2000/10/annotationType#Comment" />
<a:annotates r:resource="http://example.org/XDoc.html" />
<a:context>#xpointer(/html[1]/body[1]/ul[5]/li[4]/a[1])</a:context>
<d:creator>Ralph</d:creator>
<a:created>2000-01-10T17:20Z</a:created>
<d:date>2000-01-10T17:20Z</d:date>
<a:body r:resource="file:///home/swick/.amaya/annotations/postit.html" />
</r:Description>
</r:RDF>
<?xml version="1.0" ?>

anotaciones: modelo RDF de una anotación respuesto

schema for a reply

anotaciones: interacting with the Annotea RDF store

If time, go thru the protocol document, otherwise, use the following content

Standard HTTP methods for publishing (PUT), updating (PUT, POST), deleteting (DELETE)
Problem: Cómo publicar una declaración RDF sin saber su URI?
--> solución: have the server assign it an URI and discard the previous one

Retrieval done thru a customized HTTP GET Query

GET /Annotation?w3c_annotates=http://serv1.example.com/some/page.html HTTP/1.1
GET /Annotation?w3c_reply_tree=http://annotea.example.org/Annotation/3ACF6D754 HTTP/1.1

--> works, but this is not a generic RDF store query (see Algae)

Retrieval of anotaciones metadata is separate from the retrieval of the anotaciones body
--> download the body only if you need to see it

anotaciones: interacting with the Annotea RDF store (cont)

Algae: Specific RDF store query language (predates the DAWG WG)
Example: query for getting anotaciones with their properties and values:

(namespace (a http://www.w3.org/2000/10/annotation-ns#)

ask '(
    (a::annotates ?annot http://example.com/page.html)
    (?property ?annot ?value))
:collect ?(?annot ?property ?value))

anotaciones: clientes

Amaya <-- supports all the features
Annozilla (Mozilla)
Snufkin (IE)
bookmarklet (javascript, mayoría de los navegadores)

anotaciones: current issues

anotación de documentos HTML
->XPointers funciona solo con XML
anotación de documents en desarollo
-> evitar anotaciones misledaing
-> supporting the revision process

Contribuciones al campo

Problems, !MVC, keeping all the RDF data

favoritos: introducción

Annotea favoritos : helping share favoritos between different browsers and users
RDF schema
- Supports all of the XBEL features, while introducing better semantics
  --> Topics instead of folders
  
  --> Each topic has a URL (simplifies sharing)
```
<rdf:Description rdf:about="ambookmark1">
```
```
     <bm:hasTopic rdf:resource="amtopic1" / >
```
```
</rdf:Description>
    
```
Other features: a bookmark can belong to multiple topics, rdf:seeAlso, multiple views of the same bookmark file

favoritos: RDF model for favoritos

n.b.: b:lastVisited property is missing in the diagram

an instance of a bookmark object

favoritos: RDF model for topics

Topic schema

favoritos: a topic hierarchy

an instance of a topic hierarchy

favoritos: organizing bookmark items with RDF collecciones

Each topic is associated with an RDF collección

 <rdf:Description rdf:about="file:///home/kahan/.amaya/bookmarks.rdf#Topic1">

  <b:collection rdf:parseType="Collection">     <rdf:Description
         rdf:about="file:///home/kahan/.amaya/bookmarks.rdf#bookmark2" /> 
    <b:Separator /> 
   <rdf:Description
         rdf:about="file:///home/kahan/.amaya/bookmarks.rdf#Topic4" /> 
    <rdf:Description 
         rdf:about="file:///home/kahan/.amaya/bookmarks.rdf#bookmark1" />
  </b:collection>

</rdf:Description>

favoritos: exercise

Question: how can we assing a dc:title to a seealso?

Topic schema

favoritos: exercise (cont)

Answer: use reificación: a blank node plus a dc:title

association a dc:title to an rdf:seeAlso property

favoritos: new possibilities

Associating a URL with a bookmark file
Opening more than one bookmark file
Publishing bookmark files to a Web server using HTTP PUT, WebDAV, scp, ...

favoritos: new possiblities (cont)

favoritos: new possibilities (cont)

Possiblity to separate the user browsing properties from the other bookmark properties
--> Different user "browsing preferences" for the same bookmark file

--> Possible to have different views of a same file using this principle and collecciones

separating user browsing preferences in a topic

favoritos: relocación of resources problem

favoritos can be stored locally in files or in a Web server

Refering to a resources inside a file when the file moves around the Web

<rdf:Description rdf:about="amtopic1">

     <dc:creator>Jose</dc:creator>

</rdf:Description>

Relative URLs: change when the file changes locación
URNs: hard to resolve
When publishing statements to an RDF datastore, URIs can be changed

favoritos: chosen solución: URNs + owl:sameAs

Assign a URN to each resource in a local file

<rdf:Description rdf:about="urn:uid:123-4325-53">

     ...
</rdf:Description>

Moving the file around doesn't break references to the resource
However, the client needs to know where a given URN is found
--> keep the resource in the same bookmkark file, assume the clients knows where are those files

Whenver the URI of the resource changes, record its previous URIs using owl:sameAs

<rdf:Description rdf:about="http://annotea.w3.org/ab213450">
 <owl:sameAs rdf:resource="urn:uid:123-4325-53" / >
     ...

</rdf:Description>

Solución depends on robustnees of URN.

favoritos: conclusions

RDF is most appropriate for this kind of applicación
RDF part of the applicación was done very quickly:
--> UI represented most of the work

--> adding new features is very easy (multiple topics and importing a topic hierarchy, a couple of hours)
Possible to process and display the bookmark file with other tools

favoritos: future work

Take into account the SWAD-E Thesaurus work
--> use the thesaurus paradigm to define bookmark topics

--> create (or populate) thesaurus while making favoritos
Finish integrating the URN solución (code written, going thru discussions)
libannotea: move our development from Amaya to Mozilla (see below)

Developing in the Semantic Web: parsing

rdf parsing using raptor and callbacks

Raptor (used in Amaya/anotaciones)
- RDF parser developed by Dave Becket
- Callback programming model: a callback each time a triple is found
- Problems: having to construct an RDF model in memory by hand
- Problems: loosing RDF statements you don't know how to handle
- Possible area of interest: quick parsing (read only, but not updates)

Developing in the Semantic Web: parsing (cont)

rdf parsing using redland and its API

Redland (used in Amaya/favoritos)
- RDF Applicación framework (similar to DOM, but for RDF)
- Builds an RDF model in memory
- Has an API for querying the model
- Can serialize the model as a flat file or in a database
- Possible areas of interest: interacting with an RDF model (parsing, editing)
- Benefits: applicación code only makes queries or adds statements
  --> small code that makes complex things
  
  --> programming using an MVC paradigm

LibAnnotea

Moving our development from Amaya to Mozilla
--> better visiblity

libannotea sketch

Conclusiones: mi experiencia

Learn to expect the unexpected
--> RDF data missing properties or having more than one property... it's valid!
Tenga en cuenta reificación
--> SeeAlso and dc:title
Take into account containers (collecciones, seq, ... ) as much as possible, ignore if not used
--> Se puede usar para rdf:seeAlso en los favoritos
RDF can be serialized in any way and still be legal
--> Don't assume an XML structure order (as RSS does)
RDF permite de combinar propiedades distintas y añadir más como necesite
--> Si no funciona, hay quizas un problema de modelisación
Es complejo mover ficheros o colecciones de RDF