[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: OK, I've read some books, tons of articles, and...
moliphan@f... wrote: > By creating an XML file and a DTD, you have a defined, portable set of > business rules - portable, because if I send you my XML file which contains > a reference to a DTD I have created and which is located on the Internet, > you are presumably unable to alter the contents if I impose a validity > check. Well, that's a little strong. You can't alter the structure, we might say, or at least only in predetermined ways. The content (not just actual #PCDATA content, but the values of attributes) can be altered arbitrarily. > The structure of XML allows parties interested in my data to do searches > with filters specific to the structure of the data. For example, knowing > that a "Grommet" element exists with a "Magical" attribute, interested > parties could search for Grommets with a Magical attribute of "Yes". Just so. > A common storage area for DTDs would possibly allow those unfamiliar with my > data structure to view it. The whole Web serves as the common storage area, since references to DTD are by URL, a local file name being a degenerate case of an URL. > A question I have is, how does my behaviour travel with the data (as > structure does not define behaviour)? I have seen how Java parsers can > traverse document elements, and given elements I can now associate actions > with them using Java, but how does that help you, my interested party > unless you can use my code with the data? It doesn't. That's the meaning of the buzzphrase "XML gives Java something to do/chew on." > Also, is an XML file going to act as a database in some circumstances? > Although I have seen examples of this, I wonder how the heck that is > supposed to work with the portability idea as multiple database instances > would be difficult to reconcile. Depends what you mean by "database". An XML document residing on a server someplace can represent a database, particularly if it has a DTD of the form: top-level element contains zero or more row elements, each of which can contain various column elements. That makes it look like a relational table. Of course, it does not provide the ACID properties that real databases have! > The paradox as I see it is that XML provides an open definition of > structuring data, but there is difficulty then in providing a generic (low > cost) method of using the data. My data will be (and, hopefully act) > different from yours and everybody else's, therefore no generic agent is > going to know what to do with it. XML does not make this problem any worse, though, and moving around behavior is not specifically an XML problem, although behavior-specifying languages could be written as XML applications: the not-yet-fully-defined XSL does this for the behavior of rendering on paper or screen; Java can provide generalized mobile behavior. -- John Cowan http://www.ccil.org/~cowan cowan@c... You tollerday donsk? N. You tolkatiff scowegian? Nn. You spigotty anglease? Nnn. You phonio saxo? Nnnn. Clear all so! 'Tis a Jute.... (Finnegans Wake 16.5) 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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