- From: C. M. Sperberg-McQueen <cmsmcq@blackmesatech.com>
- Date: Mon, 14 Mar 2011 16:25:29 -0600
- To: ht@inf.ed.ac.uk (Henry S. Thompson)
- Cc: "C. M. Sperberg-McQueen" <cmsmcq@blackmesatech.com>, www-xml-schema-comments@w3.org
On Mar 14, 2011, at 9:39 AM, Henry S. Thompson wrote: > > ht writes: > >> A third example follows in the next message. > > Consider the following set of 4 schema documents. > ... > > Algorithm O classifies this as OK starting from A, but not if starting > - From B, C or D. I agree that if one starts from B, C, or D one definitely end up with contradictory declarations and thus with a non-conforming schema. I'm not entirely convinced that it's plausible to require that the schema be accepted if one starts from schema document A. It depends, I think, on how aggressive the processor wishes to be about detecting component identity. A step by step derivation of the meaning of schema(A) in this case, working with the same notation introduced in the phase-1 discussion of bug 6021, is at http://lists.w3.org/Archives/Member/w3c-archive/2011Mar/0151.html The commentary points out a few points in the calculation at which different processors might reach different conclusions. The algebraic derivation of schema(A) goes on for a long long time and involves several inclusions of overridden versions of B, C, and D with different sets of children in the override. Requiring that a processor recognize that override(E1,B) and override(E1>E2, B) are the effectively the same resource (where 'E1>E2' denotes the overlay of E2 by E1) probably requires more intelligence than I think the rest of the spec has been inclined to require of a processor. So I think the status of the example is indeterminate in the status quo and probably should remain so: we cannot provide a firmer footing here without a complete revision of the foundations of the spec. Unfortunately, I don't think we are in a position to do that now. -- **************************************************************** * C. M. Sperberg-McQueen, Black Mesa Technologies LLC * http://www.blackmesatech.com * http://cmsmcq.com/mib * http://balisage.net ****************************************************************
Received on Monday, 14 March 2011 22:25:59 UTC