[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] RE: EMBED and validation
At 03:36 PM 12/1/97 UT, Simon St.Laurent wrote: >>From a DOM perspective, EMBEDded material will almost certainly not be >>considered part of the document tree containing the EMBED element. > >I very much look forward to seeing what the DOM does (or doesn't do) with the >EMBEDded material. But is this an issue for the DOM in particular, or should >the XML-Link spec give clearer direction about the nature of EMBEDded >material? Especially as some of the replies so far have said that an >application _could_ include the EMBEDded material in the document tree _if_ >the developer so chose - which opens the door to multiple interpretations in a >large way. XML (or SGML) data can be used in one of two ways: 1. Use by value (you get the data syntactically). This is what text entities are for. A text entity is, by definition, part of the *character string* of the document that references it. That means that the parser parses it at the point of reference and it must be valid or well formed (if the entire document is well formed). A document with a text entity reference is identical, for parsing purposes, to a document with the reference replaced by the entity's replacement text (note that in base SGML ESIS, text entity references are not communicated by the parser). 2. Use by reference (you point to the data but don't get it syntactically). This is what XML Link means by "EMBED" and what HyTime means by "value reference". The referenced data is a separate, self-contained object and the parser does not parse it at the point of reference (if at all, as it may not be XML data). For use-by-reference, it is up to the processing application to make sense of the reference, for example, presenting a referenced image according to the active style settings or presenting a referenced document as though it had occurred in line, or providing an icon you can select to see the referenced thing. As for "document trees" (groves), the initial result is *never* a single tree containing the results of parsing two documents (if the thing used by reference is another document). However, a processing application might choose to construct a *new* tree that combines the two documents in some way that makes sense *to the application*. For example, I've written several instances of a program that takes a tree of subdocuments and creates a single instance from them. Note that making the distinction between use by value and use by reference keeps separate the storage and logical organization of the data, so that data can be organized into storage objects independently of how it might be used logically by reference. For example, I might put all my chapters in a single storage object (document entity) but use individual chapters by reference (using element-level addressing). It's also important to keep in mind that, for XML and SGML, a reference to a document entity is usually taken as shorthand for reference to that document's root element (that is the HyTime default, and I assume, the TEI default). In HyTime's abstract processing model, use by reference is, by default, transparent to processing applications because the HyTime engine redirects the processing application to the data used by reference, making it look to the processor as though there is but a single grove. However, under the covers the groves are distinct and processors can ask to view them that way. This is probably more sophistication than most XML processors (e.g., browsers) need provide, although more sophisticated browsers and hypertext systems need this flexibility. Cheers, Eliot -- <Address HyTime=bibloc> W. Eliot Kimber, Senior Consulting SGML Engineer Highland Consulting, a division of ISOGEN International Corp. 2200 N. Lamar St., Suite 230, Dallas, TX 95202. 214.953.0004 www.isogen.com </Address> 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...)
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