W3C XML Query Language WG

Mark Needleman

DRA

ZIG Tutorial

January 19, 2000

QL Workshop 98

• W3C sponsored event - Boston Dec 2-3

• 98 participants - 66 position papers

• W3C members, database vendors, invited experts

• See:– http://www.w3.org/Tands/QL/QL98

W3C QL WG History and Status

• Proposed July 1999 as part of XML Phase 3 Activity

• September 99 - Call for Participants and group chartered

• 1st Face to Face meeting - Sept 15-16• 2nd Face to Face December 2-3• 3rd Face to Face scheduled for early

February

QL Status (2)

• Currently about 55 members - largest W3C Working Group

• Weekly teleconference calls• Requirements document being finalized -

will be submitted as a W3C Note• Public working drafts every 3 months• One or more proposed recommendations is

the goal

Potential QL Requirements

• Possible multiple syntaxes - at least one expressed using XML - one must be human friendly

• Defined independently of any protocol with which it is used

• must not preclude possibility of Updates

• must support real and “virtual “ XML documents

• must support collections of documents

Requirements (2)

• Must support XML namespaces• must support datatypes from XML Schema• able to combine related elements from a single or

multiple documents• Extensibility mechanism • provide access to document DTD or schema if

available• operations on text must be applicable to text that

spans element boundaries

Requirements (3)

• Support Internationalization

• traverse inter and intra document references

• preserve hierarchy and sequence of document structure in query results

• have ability to transform XML structures and create new ones

• Must not enforce any particular evaluation strategy

• must be able to provide access to information derived from the environment in which the query was executed (I.e current time, date or user information)

Potential Usage Scenarios

• XML Document search and management

• XML processing of DBMS data

• Integration of Multiple XML Sources

• Filtering Streams of XML data

Current Mention of Z39.50

• Usage Scenario Section- Following Text:– Queries may be used in many environments.

For example a query might be embedded in a URL, an XML page, or a JSP or ASP page; represented by a string in a program written in a general purpose programming language; provided as an argument on the command-line or standard input; or supported by a protocol such as DASL or Z39.50

Liaison Section• Several Other W3C Working Groups

– DOM, XNL Schema, XSL, XPointer, XML Fragment, Internationalization Working Group, XML Fragment

• IETF DASL - Language Reads:– XML Query must strive for smooth interaction

with the IETF DASL (DAV Searching and Locating) Working Group, in such a way that the XML Query Language can be easily incorporated into the DASL Protocol

QL Liaison with Z39.50• Proposed language similar to that for DASL• Decision made not to do this - DASL

language was their because they had deferred their query language to QL WG - For Z39.50 (and other communities like SQL) it was felt the way to go was to make sure those communities were kept informed and their input was solicited -Chair agreed to work me on this for the ZIG

Relationship to Z39.50

• Conservative: Possible new Query Type in Existing Z39.50 protocol

• Radical: Basis for a total restructuring of Z39.50 functionality with XML Query Language as the core - what this would look like would need to be defined