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Maybe it's fine to have IDs as long as you never reference them? :) -Gareth On 4/02/2014 8:23 am, "Michael Sokolov" <msokolov@s...> wrote: >I thought ID/IDREF was about expressing the integrity of links (IDREF >must have a matching ID), not about context-sensitivity, but then again >I never used it since my links were always to different documents, and >it seemed useless (rather than evil) so I could be wrong. > > >-Mike > >On 02/03/2014 05:05 PM, Costello, Roger L. wrote: >> Hi Folks, >> >> In this message I will attempt to persuade you: >> >> 1. Do not use the ID/IDREF capability. >> >> 2. Use a layering approach: >> >> (a) Layer 1: express your XML as a context-free grammar. >> >> (b) Layer 2: express context-sensitive rules using Schematron. >> >> 3. The ID/IDREF capability is a context-sensitive rule. >> >> Now for my argument: >> >> First, let me persuade you that by using ID/IDREF you have introduced >>context-sensitive rules into your XML. Consider this XML, which does not >>use ID/IDREF: >> >> <Book> >> <Title>Principles of Programming</Title> >> <Author>M. A. Jackson</Author> >> </Book> >> >> To show XML's rule nature, let's express it like so: >> >> Book --> Title Author >> Title --> string >> Author --> string >> >> That's a context-free grammar. >> >> Now let's add an ID/IDREF: >> >> <Book seller="Amazon"> >> <Title>Principles of Programming</Title> >> <Author>M. A. Jackson</Author> >> </Book> >> >> Assume that @seller is of type IDREF. I don't show the corresponding ID >>attribute. >> >> Let's express that XML using grammar rules. The rule for the Book >>element depends on the existence of a corresponding ID attribute; if >>there is none, the Book rule is invalid. So we may express Book's rule >>like so: >> >> Book Amazon --> Title Author >> >> Read that as: >> >> In the context of an Amazon symbol >> the Book element may be replaced >> by Title and Author. >> >> In other words, our grammar tells us that this a valid string >> >> Principles of Programming M. A. Jackson >> >> only if the symbol "Amazon" exists. >> >> See the context-sensitivity? Book is context-sensitive due to the >>ID/IDREF. >> >> Any time you use ID/IDREF in your XML document you have introduced a >>context-sensitive rule into your XML document. >> >> "So what?" you ask. >> >> Well, here's so what: >> >> All known parsing algorithms for context-sensitive >> grammars are either very inefficient or very complex. >> >> Reasoning about context-sensitive grammars is difficult. >> >> Proofs about context-sensitive grammars is difficult. >> >> Take cue from compiler developers: they separate >> context-sensitive processing into a separate pass. >> >> So don't use ID/IDREF. >> >> Of course, that doesn't mean you will never have data that has >>intra-data dependencies. What it means is that you should modularize >>your grammar rules: express your context-free rules in your XML document >>and express your context-sensitive rules (intra-data dependencies) in >>Schematron. That's a nice, clean separation-of-concerns. That's a >>modular data design. >> >> Let's recap: >> >> 1. ID/IDREF introduces context-sensitive rules into your XML grammar >>wherever there is an ID attribute and wherever there is an IDREF >>attribute. >> >> 2. Don't use ID/IDREF. >> >> 3. Modularize your rules: express context-free rules in XML and express >>context-sensitive rules in Schematron. >> >> Comments? >> >> /Roger >> >> _______________________________________________________________________ >> >> XML-DEV is a publicly archived, unmoderated list hosted by OASIS >> to support XML implementation and development. To minimize >> spam in the archives, you must subscribe before posting. >> >> [Un]Subscribe/change address: http://www.oasis-open.org/mlmanage/ >> Or unsubscribe: xml-dev-unsubscribe@l... >> subscribe: xml-dev-subscribe@l... >> List archive: http://lists.xml.org/archives/xml-dev/ >> List Guidelines: http://www.oasis-open.org/maillists/guidelines.php > > >_______________________________________________________________________ > >XML-DEV is a publicly archived, unmoderated list hosted by OASIS >to support XML implementation and development. To minimize >spam in the archives, you must subscribe before posting. > >[Un]Subscribe/change address: http://www.oasis-open.org/mlmanage/ >Or unsubscribe: xml-dev-unsubscribe@l... >subscribe: xml-dev-subscribe@l... >List archive: http://lists.xml.org/archives/xml-dev/ >List Guidelines: http://www.oasis-open.org/maillists/guidelines.php
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