<HTML>Strangely Noel's reply was the first I saw of MJR's message, though I have not read his original post as well, via the list's archive. In a message dated 7/26/2002 10:06:51 AM Central Daylight Time, noelwelsh@yahoo.com writes: <BLOCKQUOTE TYPE=CITE style="BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px">--- MJ Ray <markj@cloaked.freeserve.co.uk> wrote: > > The WebIt! collection supports the creation and > processing of XML, HTML, and > > CSS using Scheme. The core of WebIt! is RS-XML, an > abstract datatype for XML. I'm interested in WebIt! as a replacement for the hacky syntax-case transformation system I have put into SchemeDoc (yes MJ, I'm still working (slowly) on it!)</BLOCKQUOTE> Great! <BLOCKQUOTE TYPE=CITE style="BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px">Some docs on the schema definition part of the library would be nice.  I have no intention of writing an XML Schema for SchemeDoc just to translate it into Scheme!</BLOCKQUOTE> That is one big hole right now in the library's documentation. I will fix that this weekend. <BLOCKQUOTE TYPE=CITE style="BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px">> I sent you some queries about this, especially > asking how it compares to > SSAX-SXML and the match.ss currently in PLT-Scheme. </BLOCKQUOTE> Noel is dead on with both comments. I'll add a few other points: re: match-- A difference between my matcher and match.ss is that I specify the pattern in terms of the data constructors, match.ss specifies the pattern in terms of the data. With s-exprs, you would write an xml-rules pattern for a list as (cons ,v1 (cons ,v2 '()), rather than (,v1 ,v2). Now obviously you would never want to write patterns for lists this way (in terms of cons calls), but for XML, you would never want to have to write the pattern in terms of the underlying data structure. First, it would be less natural looking-- the underlying data is actually a tree of structures. Second, you would expose really ugly things, like namespace urls. I had originally thought to extend either PLT's match or the Indiana match to use WebIt!'s constructor's as pattern for matching XML, but in the end I liked the syntax-rules style of patterns better. Noel, I think, stated what is really the big philosophic difference between SXML and WebIt!- the generated constructors versus the more dynamic s-expr representation of SXML. But a few other comments: SXML and WebIt! are very similar ADT's for XML- though with very different concrete types. One thing I do not have is an equivalent of SXML's auxillary nodes, though I have not had a need for them yet. I could probably have used SXML as the underlying data type beneath WebIt! constructor's. But I really prefer working with structures instead. It bothers me that once (href "something") has been extracted from a (@ ...) node, there is no way to tell whether it is an attribute or an element. In WebIt!, there are separate structures: xml-attribute and xml-element. On the other hand, SXML can be a much more compact representation- which could matter a lot when you are dealing with megabytes (or gigabytes?) of XML. As a "surface API" one of the benefits of WebIt! is it's treatment of XML namespaces. Elements and attributes are always constructed to include their expanded names (e.g. {http://w3c.org/schemas/html}:a), but these inconvenient namespace uri are hidden away behind a constructor like h4:a. Working with expanded names in an s-expression-based SXML is nasty, and yet so is using namespace prefixes: depending on the mapping of prefixes to uri's (somewhere else in the SXML tree), a:tag and b:tag could in fact be the same element type. In WebIt!, comparisons and matching are always in terms of the expanded names. namespace prefixes are significant only in *output* of XML. SSAX is another matter. It is *the* XML parser. WebIt! currently does not have a parser- though a parser was the first thing I wrote (a year and a half ago). The plan is that I will create a WebIt! instantiation of SSAX, along the lines of the SSAX->SXML parser, but producing WebIt! structures. (By the way- if you are interested in using WebIt! but need an XML parser, write to me. You might get this moved up my to-do list!) Jim </HTML>