Subject: Re: 2.6 patterns: let's try variations on the XML syntax From: "Liam R. E. Quin" <liamquin@xxxxxxxxxxxx> Date: Tue, 25 Aug 1998 01:16:55 -0400 (EDT) |
I heard a number of people at the metastructures conference last week and at Jon's excellent XML Developer's Conference that followed it echo the thought that the XSL query language that (indirectly) links elements in an instance with styles or behaviour should be using something compatible with RDF and XPointer and XLink and namespaces. Or Perhaps I only thought I heard it because I believe it so strongly myself. The XML:XQL submission from AT&T may provide an interesting alternative way of expressing queries. If it goes anywhere, and if the obvious incompatibilities with XML are removed [1], I can imagine us implementing it in our products and using it for both queries and for styles. CSS is too hard for most people. XSL has at the very least to have a clearly defined subset that is very simple, much much simpler than the current draft -- maybe a separate spec that's a subset and thus less utterly overwhelming. But as it stands, I can easily see our customers coping with and even liking it. [if this is too long a message, skip to the line marked XXX near the end] In this spirit, Scott Lawton's idea of <xsl:match> <para></para> </xsl:match> is interesting, although I think that, like most query-by-example languages, it may not scale easily or elegantly to more complex situations -- For each SubSection S: Let e be the first block-formatted element directly contained within S; if the type of e is not Title then if S has an attribute "use-content-of-as-title", and there is an element e2 whose id attribute has the same value as <S>.use-content-of-as-title, then insert <Title> before e, with the contents of e2 else if S has an attribute "title" then insert <Title> before e, with the contents of <S>.title else insert <Title> with the contents "[no title given]" end if end if might be hard to express that way, for example. Is this style or transformation? As I have written it, it looks like a transformation, but if you change insert <Title> with the contents "[no title given]" to make-paragraph size=18 weight=bold content="[no title given]" then it's style -- I'm inserting <Title> so I can reuse the style of the Title element, so I could also say apply the style for a <Title> before e to the content "...", I suppose. This is the sort of thing SGML people have been doing for years, and you can do it declaratively (vide DSSSL) or procedurally (vide monde!), and it makes no difference. ** XXX ** XXX ** The difficult challenge is this, then: Make a style language, a link language, a locator language, a transformation language and a resource description language [2] that all feel as if they belong together, that are simple enough that they can be used by relatively non-technical people in an afternoon, and yet that are powerful enough to meet very advanced needs. It may be that XSL is there, but I don't think so. It's a draft, and I think the wind blowing back is saying, make it simpler. Make it the same as other parts of XML. Make it more accessible. A lot of work has gone into it, and no-one said specs should be easy to read by the intended user base of software conforming to a spec! Many car drivers have little understanding of the chemical reactions used to create motor oil, and nor should they have to. The XSL query syntax needs to be integrated with XPointer and XLink, or maybe a revised form of these, and XSchema, RDF and namespaces should be built on that infrastructure. I hope this doesn't sound too negative -- there is a lot of good work in all of these specifications, but they really _do need to work together, and to be seen to work together. Lee Notes: [1] Using "." as an operator in a way that breaks if "." occurs in a name, using </> as if it were a legal construct; I've only had a chance to read it very quickly, over someone's shoulder, and will send comments back to the authors separately; it's very interesting. [2] Actually I think RDF and XLink ought to be the same specification. RDF is really just a fancy (and important!) way of annotating links. -- Liam Quin, GroveWare Inc., Toronto; The barefoot agitator l i a m q u i n at i n t e r l o g dot c o m [no web page, Interlog deleted it by mistake] XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list
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