[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: XML-LINK and IDREF
At 12:58 PM 6/2/97 GMT, Peter Murray-Rust wrote: >In message <0Zm96CAybpkzEwi6@l...> Richard Light writes: >> While we're on the subject of linking, I'm intrigued about the status of >> the IDREF attribute type in XML. > >Agreed. I had thought about this as well. It's not easy to see how >both might be used fruitfully at the same time without confusion. > >Formally, my understanding of ID/IDREF is that it is part of XML-LANG and >must be supported by XML-LANG processors ([50] Validity checks). The IDREF >can only point to an ID in the same document (at least how I read it). >Therefore one option is for implementers not to use XML-LINK and to use >ID/IDREF for whatever purposes they wish (structural, annotation, and >with whatever behaviour.) Although I'm not an SGML expert I imagine this >is frequently done already. There are two problem with IDREFS and XML: 1. Without DTDs, it may not be possible to know what attributes are IDs and which are references. 2. IDREFs provide no direct way to address elements in other documents. Therefore, if you want to enable IDREFs, you have to provide some indirection mechanism that can transform an IDREF to an address into other documents. This is what HyTime and the TEI do by providing various location address element forms. If you don't do this, then you require documents to have different element types for elements that use IDREFs and elements that don't. This has the effect of necessarily binding element types to the forms of address they use, which should not normally be necessary (because addressing is distinct from the semantics of reference and therefore shouldn't necessarily influence the element type). Unless I've misunderstood the current spec, XML Link doesn't provide any ID-based indirection method, so that pretty much elimitates direct ID reference in the general case. [However, using the pointer syntax, you can address elements with IDs, but only through the use of an XML Link URL.] Indirect addressing certainly complicates the processing--it requires you to build recursive processes and may impose significant processing overhead. On the other hand, indirect addressing is very powerful and lets you do things that are difficult or impossible otherwise, especially in terms of managing links and addresses automatically, largely because you can isolate initial references from the details of the addresses of the things referenced. Cheers, E. -- <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 Archived as: http://www.lists.ic.ac.uk/hypermail/xml-dev/ To unsubscribe, send to majordomo@i... the following message; unsubscribe xml-dev List coordinator, Henry Rzepa (rzepa@i...)
|
PURCHASE STYLUS STUDIO ONLINE TODAY!Purchasing Stylus Studio from our online shop is Easy, Secure and Value Priced! Download The World's Best XML IDE!Accelerate XML development with our award-winning XML IDE - Download a free trial today! Subscribe in XML format
|