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[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] RE: NOTATION FPIs (was: <XML:SCRIPT>)
 > From: Michael Kay > > Perhaps I'm being pedantic, but I think it's worth pointing > out that there's no such thing as an FPI in XML. The closest > there is is a "Public Identifier", and the only things that > the spec says about it are (a) that certain spaces within it > are insignificant, and (b) that the processor can try and > convert it to a URI (but it doesn't say how). There are various kinds of public identifiers. The thing that makes an identifier public is generally that it relies on registration with a body, which is why there is an owner part. (If the document is private or limited circulation, this registration can be in-house or by arrangement between the parties involved rather than some external convention. SGML FPIs and MIME media-types have the simplification by having "registered" and "unregisted" owners, where registered ownership guarantees unique naming.) The kinds of public identifiers around are: * ISO 9070: uses "::" to delimit a hierachy of names * URNs: starts with urn: * URIs: you know * SGML FPIs: formal public identifiers start with "-//" (unregistered=private), "+//" (registered: ISBN, or IDN for internet, or a name registered with the designated registration authority") or "ISO" (or "IEC" or "ISO/IEC") * MIME media types. There are moves to extend urn syntax to encompass MIME types--I dont know the status, perhaps they already do. It may be surprising that MIME media types are actually public identifiers currently. But the RFCs define a mechanism for allowing other "registration trees" apart from IETF. One thing this may allow is for an ISO registration tree: e.g. text/iso-8601 (the "-" is a significant delimiter). Anyway there is a general expectation in XML that system identifiers should be URIs and that public identifiers should be SGML FPIs. However, until this is defined, there is no choice but to use MIME media types for SYSTEM identifiers. Even though MIME media types are, strictly speaking, public identifiers, they belong in the "WWW" slot not the "ISO" slot (i.e. the SYSTEM identifier not the PUBLIC identifier). I guess there might be differing views on this as a policy, but there should be an agreed approach. But for future proofing, can I suggest that it might be best if software which interprets the system identifier would also accept whatever the likely future urn syntax for MIME media types might be: e.g. "(urn:.*:)?.*/(.*-)?.*" such as "urn:mime:text/x-iso8601" If you write your software so that it accepts the following notation declaration <!NOTATION ISO8601 PUBLIC "ISO 8601:1998//NOTATION Text elements and interchange formats - Information interchange - Representation of dates and time//EN"> then you would have to make sure it accepted all syntaxes for dates which that standard defines. If your software only accepted a subset, you would have let it accept some other public identifier <!NOTATION my-date PUBLIC "+//IDN mycorp.com//NOTATION simple date (subset of ISO 8601:1998)//EN" > I am not sure if ISO8601 has made it into the current version of ISO/IEC TR 9573-9:1997 "Standardized Data Notation". In ISO 10744 (HyTime) there are also FPIs for time and distance. (If you are interested in notations, I give several chapters on them, with lots of listings for useful and common notations, in my book. I certainly think that XML-DEV should get behind (Tim Bray's) collection of database notations which is in XML-data.) Rick Jelliffe ========================================================== The XML & SGML Cookbook, by Rick Jelliffe Charles F. Goldfarb Series on Open Information Management 656 pages + CD-ROM, Prentice Hall 1998, ISBN 0-13-614223-0 http://www.sil.org/sgml/jelliffeXMLAnn.html http://www.phptr.com/ > Book Search > "Jelliffe" http://www.amazon.com/exec/obidos/ASIN/0136142230/002-4102466-3352420 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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