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From: Frank Manola <fmanola@o...> >At 1:46 PM -0700 4/23/98, Lisa Rein wrote: >>> >>> What are two properties? Type and class >Whether there's a distinction between "type" and "class" depends on the >context. Loosely speaking, as well as in many contexts, they're generally >considered synonymous I think there is another consideration too. The word "type" has a specialized meaning in markup languages. The way it is typically used is to mean "a notation defined using some other notation". In other words, when I say "this entity is a GIF file" then I am giving its notation, but when I say "this entity is a string with described by the regular expression (abc)* " then I am giving its type. When OO programmers see "document type" or "element type" perhaps they expect there to be some type-system in place (whether inheritance, classes, mixins, or even basic typedef aliasing). But they are, to some extent, being mislead by the word "type". I don't think the SGML/XML literature makes this point explicit, unfortunately, but I think the usage is consistent. Similarly, people get confused between "notation" and "encoding". For example, if I take the ISO 8601 date 1998-05-31 and encode it in Base64 and put it in my XML document, then there are four notations. The date is in ISO 8601 notation, the 8601 notation is in Base64 notation, and the Base64 is in XML notation, and the XML is in the notation of whichever character set (i.e. the charset "encoding") is used. These are not "types" because each notation is not being defined using the previous notation: it is the instance which is being encoded through successive notations (notionallY). Rick Jelliffe 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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