[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: What is Tag Soup?
[Tim Bray] >Certain people in the schema-enthusiast camp tend to condemn as "tag soup" anything that hasn't been >validated by a schema that is the result of 5 years of committee deliberation, and I have little sympathy. I think its important to remember that you can have tag soup that it completely schema valid which is probably worse than tag-soup in the sense of malformed tagging. I say it is worse because the presence of a schema and the proud pronouncements of "100% validity" can mask a multitude of tag soup problems. This is what I was complaining about in this article: "The real cost of XML tags": http://www.itworld.com/nl/xml_prac/04042002/. Schemas have entropy - a tendancy towards disorder - disorder the grows over time as the schema is modified. The disorder grows rather than increases becuase modifications are made that loosen content models to accomodate new requirements whilst guraranteeing that existing documents will remain valid against the looser model. I have seen much evidence in industry of schemas tending towards a collection of foo :== (a|b|c...)* models as modifications are made to account for changed requirements in the simplest possible way that is guaranteed not to break existing documents. The result of a tag soup. 100% XML, even 100% valid, but tag soup nonetheless owing to the weakness of the ordering constraints imposed by the content models. Management wave their schema and congratulate themselves on their XML smarts, little realising that with every self-important exhalation, the key constraints on the ordering of data, that should be in the schema, are migrating further and further into incomprehensible imperative code and (gasp!) XSLT transformations in the bowels of the business process from whence deep surgery will one day be required to remove them. Sean http://seanmcgrath.blogspot.com
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