[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Semantics
At 03:14 24/04/98 -0400, Paul Prescod wrote: [...] >based on the described abstractions. For example, the DOM couldn't give >two farts about the syntax of a document. It moves seamlessly between HTML ^^^^^ I assume this word is semantically void. >syntax, XML syntax and could easily handle SGML (and probably or VRML, or >even PDF) syntax too. It cares about the abstract structure -- the tree of >attributed-elements described by an XML document. If XML has no semantics, >then how can it describe an abstract tree? If it doesn't describe a tree, >then what the heck is the DOM based on? There seem to me to be at least two types of 'semantics'. One is what meaning is attached to <FOO>, for which the XML community is trying to work out mechanisms. These include: - stylesheets for adding carbon to cellulose for humans. (I hope this is extended in the XSL process to include things other than paper and pseudo-paper rendering, such as interactive processes). - mapping to algorithms (Java classes, ECMAScript, etc.) - linking to human- or machine-readable resources such as glossaries and data dictionaries - architectural forms I think we all agree on the need to develop communal mechanism for this. The other type of semantics is how the words and phrases in the XML specs should be implemented in software or precise documents. The less clearly defined the semantics are, the more variation is possible when humans try to do this implementation. This is one reason why I have constantly raised the problem of implied semantics in the spec and urged that we develop software which implements them. Part of the reason why things like interfaces take so much effort is that it involves semantics as well as many other aspects. Whilst I suspect this has not been a major problem in SAX, it certainly is when we come to what an 'XML processor' and an 'XML application' do. For example, I doubt if we all agree on when a processor is required to validate a document, and what is done with the result. And I expect that we shall see an increasing number of commandline switches or menu items in XML software to allow humans to vary the semantics. For example, JUMBO2 reads and displays all whitespace. If there is no DTD then no whitespace is 'ignorable'. If an element's content consists only of whitespace then it's often 'obvious' to a human that this whitespace is not required for humans. IMO it would be wrong to remove this automatically, so I have a menu switch 'Delete Whitespace', which finds all such occurrences and - deletes them [either locally for elected nodes, or globally]. Wherever we can agree on and make available an algorithm that encodes our semantics (or offers a choice between acceptable views) this is worth highlighting and systematising for else we can descend into semantic incompatibility. P. Peter Murray-Rust, Director Virtual School of Molecular Sciences, domestic net connection VSMS http://www.nottingham.ac.uk/vsms, Virtual Hyperglossary http://www.venus.co.uk/vhg 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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