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"delegate" and "GI" (was RE: Do we need link-catalogs for schemas?)
Date: 10/14/1998 5:50:00 AM
> Peter Murray-Rust wrote: > > > Question in return, what exactly is delegation and can > > you give an example. [It's been mentioned both in the > > context of Java classes and link-catalogs] James Tauber, who graces this list sometimes, devised an extension to the (OASIS) SOCAT catalogs called "delegation". This is one of the main things markup people often have in mind when they use the term "delegation", as far as concrete technologies, though of course, it is a ubiquitous idea. A delegation is a link (i.e. to another catalog) and a policy (i.e. "use these catalog entries by preferene"). SOCAT catalogs is a (non-XML) format which basically allows you to remap or override identifiers in a document. This helps resolve public identifiers and notation identifiers, or correct system identifiers. The online version is at http://www.sgmlopen.org/html/a401.htm. The SOCAT delegation system has a nice wrinkle--delegates are declared using a kind of simple pattern-matching, to exploit the regularities in FPIs: "The DELEGATE keyword indicates that external identifiers with a public identifier that has partial public identifier as a prefix should be resolved using a catalog is specified by the associated storage object identifier." There was another question "what is a GI". Generic Identifier was the term used in the SGML standard for the name of an element type; you can see that the concept of "generic markup" came first, and SGML was developed to support it. One reason it was also chosen was that, strictly, it was felt that the "name" of an element was its ID; people find even the basic distinction between an element and an element type difficult, so it there was a feeling that it might be better to keep the term GI, which avoided mention of elements let alone types. As things progressed it became clearer that the "GI" was really a special attribute, and that it mainly functioned as a content model and attribute selector, rather than identifying the genus which processing might be interested in per se (other attributes might have more useful information, hence the architecture movement). Furthermore that element type was much more than could be usefully expressed in just one DTD (hence the architecture movement again, where you can have multiple parallel DTDs or schemas, but which take other attributes as the "Element Type Name"). Rick Jelliffe xml-dev: A list for W3C XML Developers. To post, mailto:xml-dev@i... Archived as: http://www.lists.ic.ac.uk/hypermail/xml-dev/ To (un)subscribe, mailto:majordomo@i... the following message; (un)subscribe xml-dev To subscribe to the digests, mailto:majordomo@i... the following message; subscribe xml-dev-digest List coordinator, Henry Rzepa (mailto:rzepa@i...)