[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Notations
>> From: W. Eliot Kimber >> Remember that notations do not affect the *parsing* of the data, only its >> semantic interpretation. > >If that is so, I am back to square zero in my understanding of notations! > >For example, I thought that if I wanted to put MIDI data in an XML document, >I would use notations to the indicate the fact. But I can't semantically >interpret MIDI data (or even hear the music) before I've parsed it. The >notation is surely there to tell me that it's MIDI, not that it's Vivaldi. By "not affect[ing] the *parsing of the data", I think Eliot means the parsing by an XML processor. The point is that NOTATIONs say nothing about how an XML processor is to treat the character data. They are about helping an application interpret the syntax of the character data. As I've discovered before on this list, there can be a lot of confusion in the use of the term "semantic[s]". I think this is partly because you need to know what layer you are talking about. At the token level, XML specifies both a syntax and a semantics. (eg it tells you where '<' can occur and tells you want it means when it does). But the semantics at this level are purely to provide the syntax for the next. At the element level, XML optionally specifies a syntax (via a DTD) but *not* a semantics. (eg it tells you where 'Price' can occur but not what it means). At the application layer, it's different again. At one level, element types could be viewed as providing semantic labelling of data and notations as providing syntactic labelling, eg <song format="MIDI">...</song> (where format is a notation attribute) Elements, with their name, generally express an isa relationship between element type and content. Attributes, generally express a hasa relationship between properties and content. Notations, say something about how the syntax of the content is to be interpreted by some separate application. But even though notations are about syntax, they aren't about XML token syntax, or XML element syntax. In as much as notations help an application *INTERPRET*, they are providing a form of semantics. It is semantics leading to how to subsequently parse the syntax of the character data. Remember: One application's semantics is another's syntax. :-) James -- James Tauber / jtauber@j... / www.jtauber.com Associate Researcher, Electronic Commerce Network Curtin University of Technology, Perth, Western Australia Maintainer of : www.xmlinfo.com, www.xmlsoftware.com and www.schema.net 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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