[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Goals: XML Event Interface
At 07:32 18/12/97 -0500, David Megginson wrote: >I think that the time has come to deal with a question that we have >postponed so far: the goal of a simple XML event-driven interface. Good thinking. One of the really great aspects of XML was/is the 10 goals. >Right now, there are two completely different ideas: > >1. The interface will provide standardised low-level, pre-DOM > functionality for parsers to implement, for programmers who do not > want to incur the overhead of using the DOM; perhaps a DOM tree > could be built using only these interfaces. Yes. This is needed. It will be needed after the DOM is finalised. (It might then be built on top of the DOM - I don't know). It is needed now (== Jan 12). > >2. The interface will provide standardised high-level, post-DOM > functionality for parsers to implement, for programmers who do not > want to take the time to learn the XML concepts in the DOM; perhaps > the events could be generated from a DOM tree. I understand and agree with the concept. I am not qualified to comment on whether it is needed or is different from the API to the DOM. > >These two are actually quite incompatible: the first is an attempt to >create a less abstract user model, while the second is an attempt to >create a more abstract user model. It's only a (happy) co-incidence >that we have managed a broad agreement so far. Yup. In my limited vision it is *possible* that (1) might be a subset of (2), but not necessarily. > > >LOW-LEVEL INTERFACE >------------------- > >If we decided on (1), then I would consider making the interface the >core interface for lfred, and I would probably want to expand it >slightly to include enough functionality to build a basic level-1 DOM >tree, by adding some or all of the following information: > >- an event for the doctype declaration Essential IMO >- an isSpecified flag for attributes Not quite clear what this is. I assume it is NOT the value of the Default in the ATTLIST (i.e. "#IMPLIED"). BUT this concept is required in some XLL applications. Is it the question of the return value of a non-existent attribute. IOW what does <!ATTLIST FOO PLUGH CDATA #IMPLIED> <FOO BAR="baz" XYZZY="" BLORT="six spaces"/> return for String s = element.getAttval("BAR"); // answer: "baz" String s = element.getAttval("BLORT");// answer "six spaces" String s = element.getAttval("XYZZY");// answer "" String s = element.getAttval("PLUGH");// could be "", or null String s = element.getAttval("Y2");// could be "", or null This is an area where I think we MUST spell out in graphic detail what is returned. If nothing else, this is a prime reason for this API. I have got this hopelessly muddled throughout JUMBO simply because there was no API. I didn't want to hardcode in anything until the semantics of all this was clear. At present JUMBO does not distinguish between a null String and "". If this is going to be important (and I suspect it might) we need to know NOW. It will be almost impossible to reprogram an application that gets it "wrong". Note for newcomers. If I add the declaration: <!ATTLIST FOO BLORT NMTOKENS #IMPLIED> and wave it over the document, the value of BLORT changes to "six spaces" This is always good for a laugh at XML parties, and you can probably make money out of carefully placed bets. >- ignorable whitespace (lfred should return this anyway) >- comments (yech -- _WHY_ is that in the DOM???) > >This interface could use only JDK 1.0.2 features, since I have no >intention of making lfred incompatible with existing browsers. Agreed. 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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