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The Schema Component Constraint: Simple Type Definition Properties Correct in section 3.14.6 of Structures reads in part: All of the following must be true: 2 All simple type definitions are derived ultimately from the ·simple ur-type definition (so· circular definitions are disallowed). That is, it is possible to reach a built-in primitive datatype or the ·simple ur-type definition· by repeatedly following the {base type type definition}. Since 'derived' is not defined in Datatypes so as to be a reflexive relation, this wording is problematic. Possible recastings include: Take I 2 All simple type definitions are, or are derived ultimately from, the ·simple ur-type definition (so· circular definitions are disallowed). That is, it is possible to reach a built-in primitive datatype or the ·simple ur-type definition· by following the {base type type definition} zero or more times. Take II 2 All simple type definitions are, or are derived ultimately from, the ·simple ur-type definition (so· circular definitions are disallowed). That is, from any ordinary simple type definition it is possible to reach a built-in primitive datatype or the ·simple ur-type definition· by following the {base type type definition} zero or more times.
At its call of today, the WG agreed to adopt the Take I wording given in comment #1 and close the issue.