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[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: overrun with bohemians?
 Rick Jelliffe wrote, > I think we need to draw the line between different kinds of > "typelessness". > > There is > * late binding (where the information needed for typing is only > available at the last minute) Available to what? Concrete instances are always precisely typed even when access to them is mediated via a supertype reference. > * reflection (where the object carries its type information > around) As above ... if it's there to be reflected, it's there. > * casting (where the language or some context forces a thing > to be treated a certain type) Ditto. > * generic operations (where, rather than a thing having no type, > it is deemed to have some very generic operations, such as > equality testing only) This is just _sub_typing. > * dynamic typing, where a value is looked at, and the type is > selected from it according to lexical hints OK, this is a better example ... and presumably the value can be looked at in other ways? Or are you assuming that the lexical hints imply or constrain the type (in which case this is pretty much the same as reflection). > * typelessness, at an extreme where an operation occurs without > any checking on some kind of memory location or a pointer. No argument here. > The occurrences of these in XML might be > * late binding, such as in XML Schemas when you may access base > types very late In what way is this typeless? Given WXS type annotations, elements in document instances are precisely typed (for all that their type might have more derived/restricted subtypes). > * reflection, such as using xsi:type to figure out the type Huh? xsi:type _tells_ you the WXS type ... there's no figuring out to do. > * casting, such as where a query treats some text as a particular > type Don't follow ... this sounds more like what you called "dynamic typing" above. > * generic operations, pretty much what XML is without XML > Schemas, wander around trees and look a strings. Well, no. The basic lexical structure of an XML document instance isn't a type _in_ XML ... in a sense it's the type _of_ XML. I don't think that anyone's complaining that not all character sequences count as well-formed XML. > * dynamic typing, such as the = operation in XSLT Pretty clearly typed. > I don't really see any typelessness at work in XML: it seems to be a > property of languages rather than data. Now I'm confused. You started with what you claimed were different kinds of typelessness (for all that I mostly disagree), then showed how they're applied them to XML, and now you're claiming there's no evidence of typelessness at work in XML? What am I missing? Cheers, Miles 
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