- From: Xan Gregg <Xan.Gregg@jmp.com>
- Date: Thu, 4 Dec 2003 13:14:56 -0500
- To: <www-xml-schema-comments@w3.org>
- Cc: "Ashok Malhotra" <ashokma@microsoft.com>
Also known as "numeric exponents", when applied to model groups these cause inordinate complexity for subsumption testing on state machines generated from content models. Numeric exponents refer to occurrence constraints besides 0, 1, and unbounded (the values supported natively by regular expressions). When asked, the WG members have been unable to point to a good use of such occurrence values. Henry Thomspon has noted in [1] that of the 700 schemas contributed by XSV users, there was only one non-trivial use of numeric exponents on a model group: <seq min=1 max=3> <elt min=0/> <elt min=0/> <elt min=0/> </seq> For completeness, I have also noted one contrived case [2] that was found in a tutorial: sandwich ::= lower_slice [ mustard | mayonnaise ] lettuce? tomato? [ bologna | salami | ham ] {2,4} cheese+ top_slice xan [1] http://lists.w3.org/Archives/Member/w3c-xml-schema-ig/2001Nov/0042.html [2] http://lists.w3.org/Archives/Member/w3c-xml-schema-ig/2002Feb/0079.html
Received on Thursday, 4 December 2003 13:17:59 UTC