XSchema: ease of use (design goal 5)
>I have posted a proposed draft XSchema document at >http://www.ccil.org/~cowan/XSchema-draft-19980601.txt . I think the most important point this paper states (and demonstrates) is: >human beings will find them [XSchemas] painful to write by hand, due to their great redundancy compared to DTDs. This conflicts directly with design goal 5, which states: >XSchema documents shall be easy to create, read, and modify, and shall provide authoring support. When I first looked at the idea of encoding DTDs in XML a couple of months ago, one of my motivations was that I find the current DTD syntax very ugly, and I came to the same conclusion: whatever the merits of an XML encoding, it would not be user-friendly. (My feelings about XSL are the same). XML works well as a markup language for text; it also works well as a markup language for data; but it is very poor as a human-readable lexical encoding of a language with rich syntax. Trying to solve this problem my imagination started running away with me: * one of the limitations of XML is that we cannot constrain the content of character strings (in attributes or PCDATA) in a DTD * the ideal way to define such constraints would be with regular expressions or BNF production rules * let's call "XML with constrained character strings" Rich XML or RXML. Of course an RXML document is an XML document; it just has some "content validity" rules in addition to the XML well-formedness and validation rules. * we can imagine a "pre-parser" which takes an RXML document and automatically generates additional XML markup so that all the syntax is now fully accessible as elements and attributes. This pre-parsed document would no longer be easily readable, but it would be easily processable using standard XML tools * We could encode both the current DTD information and the additional constraints in RXML * if we use RXML rather than plain XML to encode our DTD, we can continue to use BNF-like production rules written as text, while still being able to process the thing using general-purpose XML machinery. In other words, I think we have here not only a solution to the usability dilemma posed at the beginning of this posting, but a generally useful extension to the capabilities of XML. But sorry, I don't intend to devote my life to it! Mike Kay M.H.Kay@e... 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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