[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] IDs considered harmful or why keys might be better than IDs...
Hi, I have mixed feelings about this long discussion about XML IDs. On one hand, the concept of ID seems to be very useful and we obviously need unique IDs to avoid ambiguity. OTH, can an ID for application X be exactly the same than an ID for application Y? Can we be sure that their needs will be close enough to guarantee that they will refer to the same "object" with the same scope? In real world, giving unique IDs to concepts which seem as universal as a "company" has proven to be quite a challenge. Why would it be different if the "company" is enclosed in a XML document? RDBMs have been able to break through because in a sense, they've thrown IDs away... Or should I say, they've allowed (or imposed) to every query to specify the "IDs" to use in its where clause. That's a big constraint for SQL: there is no equivalent to foo.xml#bar for SQL and you need to know the name of the column to use as the ID (if there is one) and write "select * from foo where myid=bar" but that's also a major strength. To deal with the compexity and with the performance issues, RDBMS have invented indexes which are "out of band information" and XSLT has already dealt with this issue through keys: http://www.w3.org/TR/xslt#key A way to deal with this issue would be to find a way to associate both concepts and be able to express that you want foo.xml#bar using a specific key definition. A default key definition could be provided within the document or linked from the document, but you could also find a way to specify your own key during the query. My 0,02 Euros, Eric -- Rendez-vous à Paris pour le Forum XML. http://www.technoforum.fr/Pages/forumXML01/index.html ------------------------------------------------------------------------ Eric van der Vlist http://xmlfr.org http://dyomedea.com http://xsltunit.org http://4xt.org http://examplotron.org ------------------------------------------------------------------------
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