[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Why XML data typing is hard (was Re: Internal subset equivalent in n
<david@m...> writes: > The real question, though, is how constraints could be enforced. > Let's start with an extremely simple example: > <value xml:type="float"></value> Now you're adding type information to the content, what I suggested was to constrain *form*. For one thing, I would not specify this in the document (this is just a gut feeling, but why would you?), I would specify it in the DTD, e.g. like so: <!element value #REGEXP:"-?[0-9]*.[0-9][0-9]"> (or some such, you get the point). > What are the allowed contents? Then the document could contain <value>4.50</value> <value>-0.01</value> or <value>.00</value> but not <value>1.0</value> or <value>4,50</value> > <value xml:type="float">1,5</value> > <value xml:type="float">1.5</value> This won't be a problem, if the DTD specifies what can the processing software should expect. You could even validate processing software to some extent. > This is a very simple example; after you've worked this out, you can > start worrying about how to count combining characters with > field-length restrictions, etc. I think trying to define some set of types to be used in *all* XML documents is taking the wrong approach. I don't really see this as either workable or desirable. What would the point of using xml:type be? As I said, I haven't given this a lot of thought, but to me, it seems like having elements which take multiple types that need to be identified in attributes would be an indication of an ill designed document type. (What would, in the example above, the semantics be if you supplied an xml:type="string" in a value field?) Specifying subsets of #PCDATA as allowable content, however, should be relatively simple and occasionally useful. But hey, I'm in telecommunications these days, not document processing :-) ~kzm -- If I haven't seen further, it is by standing in the footprints of giants 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...)
|
PURCHASE STYLUS STUDIO ONLINE TODAY!Purchasing Stylus Studio from our online shop is Easy, Secure and Value Priced! Download The World's Best XML IDE!Accelerate XML development with our award-winning XML IDE - Download a free trial today! Subscribe in XML format
|