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The following is copied with permission of the author: W3C is pleased to announce the advancement of the XML Schema Language to Candidate Recommendation status. XML Schema Part 0: Primer, ed. David C. Fallside <fallside@u...>, 24 October 2000 http://www.w3.org/TR/2000/CR-xmlschema-0-20001024 XML Schema Part 1: Structures, ed. Henry S. Thompson <ht@c...> David Beech <dbeech@u...> Murray Maloney <murray@m...> Noah Mendelsohn <Noah_Mendelsohn@l...> 24 October 2000 http://www.w3.org/TR/2000/CR-xmlschema-1-20001024 XML Schema Part 2: Datatypes, ed. Paul V. Biron <Paul.V.Biron@k...> and Ashok Malhotra <petsa@u...> 24 October 2000 http://www.w3.org/TR/2000/CR-xmlschema-2-20001024 1 Abstracts Part 0: XML Schema Part 0: Primer is a non-normative document intended to provide an easily readable description of the XML Schema facilities and is oriented towards quickly understanding how to create schemas using the XML Schema language. XML Schema Part 1: Structures and XML Schema Part 2: Datatypes provide the complete normative description of the XML Schema language -- this primer describes the language features through numerous examples which are complemented by extensive references to the normative texts. Part 1: XML Schema: Structures specifies the XML Schema definition language, which offers facilities for describing the structure and constraining the contents of XML 1.0 documents, including those which exploit the XML Namespace facility. The schema language, which is itself represented in XML 1.0 and uses namespaces, substantially reconstructs and considerably extends the capabilities found in XML 1.0 document type definitions (DTDs). This specification depends on XML Schema Part 2: Datatypes. Part 2: XML Schema: Datatypes is part 2 of the specification of the XML Schema language. It defines facilities for defining datatypes to be used in XML Schemas and other XML specifications. The datatype language, which is itself represented in XML 1.0, provides a superset of the capabilities found in XML 1.0 document type definitions (DTDs) for specifying datatypes on elements and attributes. 2 Request for publication and outstanding issues The publication is in response to the Working Group Co-Chair's request. The last-call issues on which there was outstanding dissent are listed (along with the other issues raised during last call) in the Working Group chairs' summary of last-call issues. In particular, the W3C Internationalization (I18N) WG dissented from the specification's treatment of dates and times on several grounds: - The type for time durations uses years and months from the Gregorian calendar, and does not allow for other calendar systems, such as the Hebrew calendar and the Islamic calendar. - To avoid comparison problems (one month vs. 30 days), comparison between different time units has been made completely indeterminate. This is unfortunate, as most duration comparisons (such as 1 hour to 30 minutes) are in fact well-defined. - The recurring Duration type, as well as month, year, century, recurringDate, and recurringDay are of limited use. On the first objection, the director judged that for better or worse the international community makes extensive use of the Gregorian calendar, and there are no obvious alternatives to its use. On the other two objections, the director judged that the concerns raised by the I18N WG are indeed valid, but observed that a complete reformulation of the date and time types would be a major undertaking outside the scope of XML Schema itself at this stage. It was decided that the best way to address these questions was through further and wider review and testing through implementation experience, which is what the Candidate Recommendation review is designed to provide. Notes have been included in the specification asking for feedback from software developers and schema authors on various aspects of the design. 3 Exit criteria The Candidate Recommendation period ends when the milestones below are achieved. Currently, input from implementors is accepted at least through 15 December 2000. * Sufficient reports of implementation experience will have been gathered to demonstrate that schema processors as described by the specification are implementable and have compatible behavior. Several partial implementations and ongoing implementation efforts are underway; implementors include the University of Edinburgh and W3C (XSV), IBM and the Apache project (Xerces), TIBCO Extensibility (XML Authority), XML Spy (XML Schema editor), and Oracle (XML Schema Processor). * Sufficient reports of implementation experience will have been gathered to reasonably address concerns that the datetime types interwork with other existing date time systems such as database systems. * Sufficient reports of use will have been gathered to demonstrate that the schema language defined by the spec can usefully be applied in the definition of markup vocabularies and their applications. In particular, it is our goal to have XML Schema documents defining the markup language or markup vocabulary of any W3C specification which currently has a DTD and which is currently a Candidate Recommendation, a Proposed Recommendation, or a Recommendation. (N.B. it is not anticipated that these schema documents will in all cases mimic every feature of the corresponding DTDs -- in particular, the ability of a hostile user to modify or subvert the DTD by suitable redefinition of parameter entities will not necessarily be preserved.) Some W3C specs already have schemas (mostly non-normative at this point), among them XML 1.0, XLink, SMIL, P3P, and XML Digital Signatures. * A formalization of XML Schema will be complete and ready for publication as a normative or non-normative part of the specification. Implementors are invited to contact the Working Group chairs to participate in the final report. 4 Description of what Candidate Recommendation status means The W3C Process Document describes the Candidate Recommendation status of a specification in Section 6.2.3: http://www.w3.org/Consortium/Process/Process-19991111/tr.html#RecsCR Requirements for Entrance The Director must be satisfied that the Working Draft has successfully completed the Last Call with all comments resolved and that the Working Group has prepared an adequate implementation report. Associated activities The Working Group requests implementation experience and uses this to refine the specification as necessary. Duration The duration is specified as part of the request for advancement. The duration may range from zero delay (skipped) to one year. Next State A Candidate Recommendation can be updated, or upon Director approval, advanced to Proposed Recommendation. Otherwise it returns to Working Draft for further work. A Candidate Recommendation has received significant review from its immediate technical community (resulting from the Last Call). Advancement of a document to Candidate Recommendation is an explicit call to those outside of the related Working Groups or the W3C itself for implementation and technical feedback. There is no requirement that a Working Draft have two independent and interoperable implementations to become a Candidate Recommendation. Instead, this is the phase at which the Working Group is responsible for formally acquiring that experience or at least defining the expectations of implementation. 5 Status of This Document The "status of this document" section for the Candidate Recommendation reads: This specification of the XML Schema language is a Candidate Recommendation of the World Wide Web Consortium. This means that the XML Schema Working Groupconsiders the specification to be stable and encourages implementation and comment on the specification during this period. The Candidate Recommendation review period ends on 15 December 2000. Please send review comments before the review period ends to www-xml-schema-comments@w... (public mailing list archive). Readers may find Description of changes (non-normative) (§J) helpful in identifying the major changes since the Last Call Public Working Draft. During the Candidate Recommendation phase, although feedback based on any aspect of implementation experience is welcome, there are certain aspects of the design presented herein for which the Working Group is particularly interested in feedback. These are designated priority feedback aspects of the design, and identified as such in editorial notes throughout this draft. Should this specification prove very difficult or impossible to implement, the Working Group will return the document to Working Draft status and make necessary changes. Otherwise, the Working Group anticipates asking the W3C Director to advance this document to Proposed Recommendation. This document has been produced as part of the W3C XML Activity. The authors of this document are the XML Schema WG members. Different parts of this specification have different editors. A list of current W3C working drafts can be found at http://www.w3.org/TR/. They may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use W3C Working Drafts as reference material or to cite them as other than "work in progress". -- World Wide Web Consortium (W3C) Janet Daly, Head of Communications MIT/LCS NE43-363 200 Technology Square Cambridge, MA USA 02139 voice: +1.617.253.5884 fax: +1.617.258.5999 http://www.w3.org/ janet@w... -- Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh W3C Fellow 1999--2001, part-time member of W3C Team 2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440 Fax: (44) 131 650-4587, e-mail: ht@c... URL: http://www.ltg.ed.ac.uk/~ht/
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