Subject: XSL more than stylesheet From: "Didier PH Martin" <martind@xxxxxxxxxxxxx> Date: Mon, 8 Feb 1999 17:24:03 -0500 |
Hi, This time I looked at XSL or at an improved DSSSL more as a transformation language than to simply a reduced role as a style sheet language. I went, as usual to OASIS to look at what's new and saw that more and more announcements are made about new declarative languages based on XML. Some are simply knowledge bases serialized for exchange, others are more like imperative languages. OK now let's bring together two concepts: a) Domain specific languages b) XML documents Because XML is in fact a standardized syntax (I mean here syntax construction rules) and do not touch semantics, XML could be a good candidate for domain specific languages and this is a trend that we see evolving each days. This means that XML will induce a plethora of interpreters that will "know what to" do with a declarative program or XML document. There will be also a need for transformation tools not only from XML to formatting object but also from XML to imperative instructions and XML to declarative instructions. As a good example of a declarative program (document would be more appropriate but a paradigm shift is not easy :-), is a CDF document. A CDF interpreter could be, in fact, a software installation program. You do not say in the CDF document what to do, you just specify what is contained in the package. The interpreter figure what to do. Actually, within the Mozilla development process, a newborn: XUL is an application specification document. You simply state the application parts and the interpreter figure out what to do with it and the result is an application. Idem for BML (IBM stuff), you specify a Bean whole-part compound and the interpreter figure what to do with it: an application (especially when BML will have the capability to include scripts or event handlers). Of course, this plethora of DSLs (Domain Specific Languages) will have their associated interpreters and wont have necessarily the same vocabulary. In fact, as we already see, XML development do not force everything to be in the same melting pot but, a highly diverse universe is emerging with several vocabularies emerging for a same domain. Thus, these vocabularies could be semantically close enough to be translated from one to the other. This means that XSL or any other transformation language could be used to transform from one DSL to an other one as long as both are for the same domain. Thus, a DSL based document that could be interpreted with a particular interpreter could be also interpreted on an other one after being transformed by a transformation language. Let's say for example that "XUL" is used for Mozilla and that "Ghostbusters" is used by an other user agent or interpreter (movies fans will recognize why these two names fits together). XSL could be used to translate from Ghostbusters to XUL and vise versa. Then a XUL compliant interpreter could use a Ghostbusters program (XML document based DSL) and vise versa. This implies that a transformation language could be at the heart of inter-operability and this gives also more weight to consider the transformation part of XSL as more than to be simply in the style sheet category. If we forget, for a moment all political factors, we should also keep in mind that transformation languages play major role with DSL interoperability. We do not have this problem yet in our daily lives, but more and more as we will move from imperative to declarative languages, transformation languages will become centerpiece to portability or adaptation to diversity of interpreters. For more info on DSL you can read some proceedings from a conference on the subject: http://www-sal.cs.uiuc.edu/~kamin/dsl/index.html For major manufacturers, a certain level of control won't be on the underlying document syntax (XML) but more on the voabulary and interpreters that "knows waht to do" with these vocabularies. Of course, we cannot expect that they would unify under a single vocabulary (are we all talking the same language on earth?). So expect that the next level of control for these manufacturers will be on interpreters and vocabularies. Transformations languages are clients path to freedom of choice. Regards Didier PH Martin mailto:martind@xxxxxxxxxxxxx http://www.netfolder.com XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list
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