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Problems with DTDs

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Currently to provide useful information regarding computer science is not all the purpose of this site, though I was in the vein for becoming a webmaster of an attractive site concerning the subjects of computer science. I do not decided what to do next. I may shut this site down permanently to start a new site which is dedicated only to computer. (But not now.)

I’ve found the following reasons of throwing away DTDs:
(1) they are difficult to write and understand
(2) programmatic processing of their metadata is difficult
(3) they are not extensible
(4) they do not provide support for namespaces
(5) there is no support for datatypes
(6) there is no support for inheritance

Did you know that there were another problems except for the namespace in DTDs? I did know. But I forget. So I am posting this article as a memo; I have to explain the reason of using XSD to people sometimes.

Comments

3 responses to “Problems with DTDs”

  1. 복연 Avatar
    복연

    In my case..
    DTD is easier to write and understand than XSD. Many of XSD instances are understandable enough only with a visual displaying application like the XMLSPY. Pure textual representation of XSD documents is too large to understand at a first sight.
    Yes, the XSD document’s structural concept is reasonable, but its realization is not ideal espessialy on its size-related problems. So I heard that some working groups put their heads together to replace it (I don’t think it’s good idea, anyway ^^).

    Ok.. I summarize here.
    When we work with large schema document, XSD instances are easier to write and understand than DTD only if other supporting applications are available. And making supporting application for the XSD is easier than for the DTD. Eventually and practically we can say the XSD is better.

  2. 복연 Avatar
    복연

    And it’s a comprehensive problem.
    DTD is not XML itself. It means XML designers need to learn more than XML. XML tool developers must implement more than XML parser and valid checker. Related problems are number 2 and 4.

  3. 복연 Avatar
    복연

    Hmm..
    I wish I could correct erratas at above my comments, but this site does not allow me to do that. -_-;;
    I’m sorry! ;)

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