[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: X-Schema
Mark Birbeck wrote: > > I think ultimately it is because it is XML. You now have a document that > can be parsed and processed with the same tools that you use for all > your other documents. This makes a number of things a lot easier. For programmers. But I asked about usability, not programmability. XML instance syntax is certainly easier for programmers. > For example, when we have got a working approach to transclusion > with XLinks, I could include your schema inside my schema. DTDs and W3C XML schemas already do this without any special external standard. A general transclusion mechanism is not good for schemas anyhow -- you want to define custom import and export rules. > For me, though, the main problem with DTDs is not their syntax, but the > difficulty in validating a document that is based on two or more DTDs. I was asking about syntax in particular but I am interested in your other ideas. > With the current XML-Data approach, I can define the schema to be used > on a per-node basis, so including a node also includes the information > needed to validate it. Sorry, I don't understand what you are saying here. What XML data facility allows me to validate XLinks to transcluded "video nodes"? Link validation is a completely separate issue, IMHO. > This means that you > only actually extract the amount of schema you need for the document > being exported, and it makes schema very easy to maintain (you just have > to maintain the database). You've abstracted away the hard parts of the problem and described how easy it is to solve the easy ones. XML's primary goal is interoperability. Company A does not use the same database schema as company B. The primary purpose of the XML interchange is to help them to bridge that gap. The bridging can only be done through haggling, debating and hands-on schema development. If company A and company B used identically-schemed databases then they could have used CSV's, S-Exprs or something similiarly simple a decade ago. Heck, they could have output ten million SQL statements representing the contents of the database. There's no hard problem there. > So, to illustrate the point, I have 'objects' > of type article which can contain objects of type paragraph. When I > export an article I place on the article node a pointer to the article > schema. All the latter does is pull out schema information for the > article and all its children. However, if asked to export just a > paragraph of text from an article, I attach to that node a pointer to > the paragraph schema. Why pass any more? The validater doesn't need it. Piecewise schemas are an orthogonal issue to database generation of schemas. In most cases it will be simplest to send the whole article schema and have it be cached on the other side. But anyhow, from a validation point of view, a schema sent with the data is not any more useful than the schema you could devise by analyzing the data! For a schema to be useful for allowing interchange, it must be sent *in advance*. -- Paul Prescod - ISOGEN Consulting Engineer speaking for only himself http://itrc.uwaterloo.ca/~papresco [Woody Allen on Hollywood in "Annie Hall"] Annie: "It's so clean down here." Woody: "That's because they don't throw their garbage away. They make it into television shows." 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/ and on CD-ROM/ISBN 981-02-3594-1 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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