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[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] AFs and the DPH (Was Animal Friends, etc.)
 At 07:10 30/09/97 -0400, Jonathan Robie wrote: >At 09:35 AM 9/30/97 BST, Henry S. Thompson wrote: > >So now we have all the players! > Just one more player, please - the DPH (desperate Perl Hacker)... whom I shall try to represent :-) [For those not on xml-sig, this mythical character is assumed to be an eager customer for XML, and ignorant of SGML. Everyone on XML-SIG used to agree that XML must be accessible to the DPH - I hope that's still true. If it's not - and that XML is a commercial-only enterprise - then I'll rethink things.] As a hacker I know very little about AFs, but have been trying to find out more from the SG/XML community. Many people (e.g. Eliot Kimber and James Clark) have been very helpful but I suffer from not having: - a beginner's introduction to AFs on the WWW - simple free working software to see how they work [If I'm wrong in this, I'll be delighted.] It is clear that AFs have passionate supporters in the *ML community, but their message isn't easily spread beyond it. My summary, gleaned over the last year goes something like this: - AFs allow (partial) mapping of one data structure (in SGML) to another. There are restrictions on mapping inconsistent content models, for example. - among the benefits of AFs are that you can manage different 'namespaces' and can alias elements or attributes - AFs are defined in standard SGML and parsers parse them 'without realising what they are' - an AF expert can do very elegant things with AFs. However, all the benefits from AFs have to be realised by having an AF-aware processor (I differentiate parser from processor - an ESIS stream could be input into an AF-aware processor). My understanding is that: - there are no freely available AF processors - generic AF processors are beyond the ability (or at least the time) for a DPH to write from scratch Therefore AFs are only available to largish groups with time and/or money... This rules out the DPH. I have the impression that AFs play the same sort of meta-role as interfaces in Java. They organise things for you but don't actually write any code for you! So a pre-requisite is an AF-engine. These general problems come up with the XLL spec, where there is mapping of attributes and elements. Maybe an AF engine makes implementing XLL easier - certainly there is quite a lot of implied architecture in the spec. I have consistently been asking whether it makes sense to build some generic processing tools for XLL but the feedback that I seem to have got is that this is application-dependent (i.e. different processors need to be written for different DTDs). If so, this is a major deterrent to the use of XLL and AFs. So - is this analysis anywhere near true? And if so, is the XML community going to develop freely available tools for this type of requirement :-)? P. Peter Murray-Rust, Director VSMS, domestic net connection Virtual Hyperglossary specialities 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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