[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: SGML default attributes.
By "standoff grammars" I mean grammar definitions that are physically separate from the documents they govern. DTDs are syntactically part of the documents they govern (that is, even though you may have an external DTD subset, it is still syntactically part of the document that references it). Consider JATS as an example of a document type. JATS defines many variants of JATS: authoring, publication, archiving. All are part of the JATS abstract document type but each has different specific rules. In addition, the JATS specification explicitly allows anyone to modify the base JATS grammars to modify what is allowed, either by adding constraints or allowing new element types. Thus there are an *infinite number* of grammar instances that can govern JATS documents. There cannot be a single grammar definition instance that encompasses the full set of possible conforming JATS documents (because in fact that set is unbounded). Or consider DITA, which has a more controlled extension mechanism then JATS but is no less unbounded: there is an infinity of possible document instances that are all provably conforming DITA documents. A DITA document's "document type" is defined not by the grammar that is (or isn't) used to validate the document but by the set of vocabulary and constraint modules the document declares it (may) use. In DITA the document type is well defined (in the sense that it is a finite set of invariant modules) but there could be any number of equivalent and equally-conforming grammar files that validate the (abstract) DITA document type. We tend to think of a given grammar as being exactly equal to an abstract document type, but this not true. A given grammar file is simply an implementation expression of a more abstract concept. Because of the limitations of declarative grammars it is never possible for an XSD or RELAX NG or DTD alone to validate all the rules of non-trivial document types. And of course a given document could conform to many different document types--there's no rule that a given document instance can be interpreted in only one way (consider an RELAX NG document with embedded Schematron rules, for example, or the many applications of literate programming). Cheers, Eliot ---- Eliot Kimber, Owner Contrext, LLC http://contrext.com On 5/4/16, 10:52 AM, "Costello, Roger L." <costello@mitre.org> wrote: >Eliot Kimber wrote: > >> Standoff grammars like XSD and RELAX NG > >What is a "standoff grammar"? > >> XSD and RELAX NG at least avoid the problem of >> internal DTD subsets but they still fail to serve as >> reliable definitions of document types in abstract >> because they are still only defining the grammar >> rules for a subset of all possible conforming >> documents in a document document type. > >This sounds interesting (and very important). I am uncertain what it >means. Would you mind explaining this further, in terms that people (such >as myself) without a background in SGML can understand? For example, what >does it mean that an XSD only defines the grammar rules for a subset of >all possible conforming documents? That doesn't jive with my experience >with or understanding of XSDs. > >/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@lists.xml.org >subscribe: xml-dev-subscribe@lists.xml.org >List archive: http://lists.xml.org/archives/xml-dev/ >List Guidelines: http://www.oasis-open.org/maillists/guidelines.php >
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