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XML and Query Languages

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Recent XML Query Specifications

[July 12, 2004] W3C Releases Public Working Draft for Full-Text Searching of XML Text and Documents. W3C has published an initial Public Working Draft for XQuery 1.0 and XPath 2.0 Full-Text. Created as a joint specification by the W3C XML Query Working Group and the XSL Working Group as part of the XML Activity, this new draft specification defines a language that extends XQuery 1.0 and XPath 2.0 with full-text search capabilities. As defined by the draft, "full-text queries are performed on text which has been tokenized, i.e., broken into a sequence of words, units of punctuation, and spaces." New full-text search facility is implemented by extending the XQuery and XPath languages to support a new "FTContainsExpr" expression and a new "ft:score" function. Expressions of the type FTSelection are composed of:(1) words or combinations of words that are the search strings to be found as matches; (2) Match options such as case sensitivity or an indication to use stop words; (3) Boolean operators that allow composition of an FTSelection from simpler FTSelections; (4) Positional constraints such as indication of match distance or window. The new Full-Text Working Draft endeavors to meet search requirements specified in an updated companion draft XQuery 1.0 and XPath 2.0 Full-Text Use Cases. This document provides use cases designed to "illustrate important applications of full-text querying within an XML query language. Each use case exercises a specific functionality relevant to full-text querying. An XML Schema and sample input data are provided; each use case specifies a query applied to the input data, a solution in XQuery, a solution in XPath (when possible), and the expected results." Full-text query designed as an extension of XQuery and XPath will support several kinds of searches not possible using simple substring matching. It allows precision querying of XML documents containing "highly-structured data (numbers, dates), unstructured data (untagged free-flowing text), and semi-structured data (text with embedded tags). Language-based query and token-based searches are also supported; for example, find all the news items that contain a word with the same linguistic stem as the English word "mouse" — which finds occurrences of both "mouse" and "mice" together with possessive forms.

[May 06, 2003] W3C Releases Ten Working Drafts for XQuery, XSLT, and XPath. Through collaborative and coordinated effort between W3C's XML Query Working Group and XSL Working Group, a collection of ten updated working draft specifications has been issued for public review and comment. XQuery 1.0 and XPath 2.0 Data Model and XQuery 1.0 and XPath 2.0 Functions and Operators are in Last Call WD status through June 30, 2003. XPath 2.0, XSLT 2.0, XQuery 1.0, and other specifications are dependent upon the data model, functions, and operators defined in these two WDs. Other working drafts include XQuery 1.0 and XPath 2.0 Formal Semantics, XML Path Language (XPath) 2.0, XSL Transformations (XSLT) Version 2.0, XQuery 1.0: An XML Query Language, XML Query Use Cases, XML Query (XQuery) Requirements, XSLT 2.0 and XQuery 1.0 Serialization, and XQuery and XPath Full-Text Requirements. The W3C XSL Working Group "develops and maintains three main specifications: XSL Transformations (XSLT) for transforming XML documents, XSL Formatting Objects (XSL/FO) for formatting XML documents, and, jointly with the XML Query Working Group, XPath 2.0 and associated documents. XPath is used to address, point into, or match portions of XML documents. Since November 2002, the XSL Working Group has been working closely with the XML Query Working Group on XPath 2, the corresponding Data Model, and on XSLT 2.0. The W3C XML Query working group was chartered "to provide flexible query facilities to extract data from real and virtual documents on the Web; the XML Query language should encompass selecting whole documents or components of documents based on specified selection criteria as well as constructing XML documents from selected components. The WG's goal is to produce a formal data model for XML documents with Namespaces (based on the XML Infoset), a set of query operators on that data model (a so-called algebra), and a query language with a concrete canonical syntax based on the proposed operators." Both working groups are part of the W3C XML Activity.

[February 17, 2003] W3C Publishes Working Draft Specifications for Full-Text Search. Members of the W3C XML Query Working Group and XSL Working Group have released two initial public working drafts for Full-Text Search. XQuery and XPath Full-Text Requirements and XQuery and XPath Full-Text Use Cases have been produced as part of the W3C XML Activity. "Full-Text Search" in this context involves "an extension to the XQuery/XPath language. It provides a way to query text which has been tokenized, i.e., broken into a sequence of words, units of punctuation, and spaces. Tokenization enables functions and operators which work with the relative positioning of words (e.g., proximity operators). Tokenization also enables functions and operators which operate on a part or the root of the word (e.g., wildcards, stemming)." The Requirements document specifies (initially) that: XQuery/XPath Full-Text functions must operate on instances of the XQuery/XPath Data Model; Full Text need not be designed as an end-user UI language; while XQuery/XPath Full-Text may have more than one syntax binding, one query language syntax must be convenient for humans to read and write while XQuery/XPath Full-Text may have more than one syntax binding, one query language syntax must be expressed in XML in a way that reflects the underlying structure of the query; if XQuery/XPath Full-Text supports search within names of elements and attributes, then it must distinguish between element content and attribute values and names of elements and attributes in any search. The Use Cases document "illustrates important applications of full-text querying within an XML query language. Each use case exercises a specific functionality relevant to full-text querying; a Schema and sample input data are provided. The full-text queries in these use cases are performed on text which has been tokenized." The W3C working groups welcome public comments on the draft documents and open issues.

[August 20, 2002] W3C Working Groups Update Specifications for XSLT, XML Query, and XPath. Seven revised working draft specifications have been published by the W3C Working Groups for XML Query, XSL, and XML Schema. Several working drafts represent collaborative work by the XSL and XML Query Working Groups, which are jointly responsible for XPath 2.0, a language derived from both XPath 1.0 and XQuery; the XPath 2.0 and XQuery 1.0 Working Drafts are generated from a common source. The updated working drafts include: XSL Transformations (XSLT) Version 2.0; XML Path Language (XPath) 2.0; XML Query Use Cases; XQuery 1.0: An XML Query Language; XQuery 1.0 and XPath 2.0 Formal Semantics; XQuery 1.0 and XPath 2.0 Data Model; XQuery 1.0 and XPath 2.0 Functions and Operators. Comments on these drafts may be sent to the W3C Query and Transform mailing list ('public-qt-comments') set up for public feedback on W3C specifications published by the XML Query and XSL Working Groups. [Full context]

[March 26, 2002] W3C Working Draft for XQuery 1.0 Formal Semantics. A public review W3C Working Draft has been published for XQuery 1.0 Formal Semantics, providing the formal semantics of W3C XQuery as specified in XQuery 1.0: A Query Language for XML. "XQuery is a computer language designed to return information to users or their agents. It is applicable to XML data sources from documents to databases, search engines, and object repositories. Much of the WD document is the result of joint work by the W3C XML Query and XSL Working Groups, which are jointly responsible for XPath 2.0, a language derived from both XPath 1.0 and XQuery. The new document defines the formal semantics for XQuery 1.0, and a future version of the document will also define the formal semantics for XPath 2.0. XQuery is a powerful language, capable of selecting and extracting complex patterns from XML documents and of reformulating them into results in arbitrary ways. This document defines the semantics of XQuery by giving a precise formal meaning to each of the constructions of the XQuery specification in terms of the XQuery data model. The document assumes that the reader is already familiar with the XQuery language. Two important design aspects of XQuery are that it is functional (built from expressions, called queries, rather than statements) and typed. 'Types' can be imported from one or several XML Schemas (typically describing the documents that will be processed), and the XQuery language can then perform operations based on these types. In addition, XQuery also supports a level of static type analysis. This means that the system can perform some inference on the type of a query, based of the type of its inputs... These two aspects play an important role in the XQuery Formal Semantics." [Full context]

[August 27, 2001] New W3C Working Draft: XQuery 1.0 and XPath 2.0 Functions and Operators Version 1.0. W3C has published a new working draft document which describes constructors, operators, and functions that are used in XQuery 1.0 and XPath 2.0. The draft "was produced through the efforts of a joint task force of the W3C XML Query Working Group and the W3C XML Schema Working Group and a second joint task force of the W3C XML Query Working Group and the W3C XSL Working Group. The specification defines basic operators and functions on the datatypes defined in XML Schema Part 2: Datatypes for use in XQuery, XPath, and other related XML standards. It also discusses operators and functions on nodes and node sequences as defined in the XQuery 1.0 and XPath 2.0 Data Model for use in XQuery, XPath, and other related XML standards. Where XML Schema Part 2 defines a number of primitive and derived datatypes, collectively known as built-in datatypes, the new working draft defines operations on those datatypes. The document defines a number of constructors and other functions that apply to one or more data types; each constructor and function is defined by specifying its signature, a description of each of its arguments, and its semantics. In addition, examples are given of many constructors and functions to illustrate their use. The WD is generally unconcerned with the specific syntax with which the constructors, operators, and functions will be used, and focuses instead on defining the semantics of them as precisely as feasible." [Full context]

[June 12, 2001] XML Syntax for XQuery 1.0 (XQueryX) Published as W3C Working Draft. The W3C XML Query Working Group has released a first public working draft specifying an XML syntax for the W3C XML Query language (XQuery). The draft supplies a W3C XML Schema for the XQuery XML Syntax as well as an XML DTD. The working group intends that the XQueryX DTD and XML Schema "will track the XQuery 1.0 syntax and will be changed as often as the XQuery 1.0 syntax is changed in future Working Drafts." The syntax specification in 'XQueryX' "is a close representation of the abstract syntax found in Appendix B of the XQuery Working Draft; for each production in the abstract syntax, the authors created an equivalent XML representation. XQueryX is thus an XML representation of an XQuery. [Because] it was created by mapping the productions of the XQuery abstract syntax directly into XML productions, the result is not particularly convenient for humans to read and write; however, it is easy for programs to parse, and because XQueryX is represented in XML, standard XML tools can be used to create, interpret, or modify queries." Concurrent with the release of the new XQueryX draft, the XML Query Working Group has published updated four related working drafts: XQuery 1.0, the XML Query Use Cases, XQuery 1.0 and XPath 2.0 Data Model, and XQuery 1.0 Formal Semantics. W3C XQuery "is designed to be a small, easily implementable language in which queries are concise and easily understood. It is also flexible enough to query a broad spectrum of XML information sources, including both databases and documents." [Full context]

[February 15, 2001] W3C XML Query Working Group Releases XQuery Working Draft and Related Documents. Provisional update. The W3C XML Query Working Group has published an initial public working draft specification for XQuery: A Query Language for XML . XQuery "is designed to be broadly applicable across all types of XML data sources. XQuery is a functional language in which a query is represented as an expression; it is derived from an XML query language called Quilt, which in turn borrowed features from several other languages." Supporting specifications also released include: (1) XML Query Data Model "which is the foundation of XML Query Algebra; together, these two documents will provide a precise semantics for the XML Query Language. (2) The XML Query Algebra defines a a formal algebraic model for an XML query language. (3) XML Query Use Cases "specifies usage scenarios for the W3C XML Query data model, algebra, and query language." XML Query Requirements articulates "goals, requirements, and usage scenarios for the W3C XML Query data model, algebra, and query language." See further details.

[February 04, 2000] The W3C XML Query Working Group published a working draft document XML Query Requirements on January 31, 2000.

[September 14, 1999] Preliminary information on the W3C XML Query Working Group is available from the W3C XML Activity Page.

The W3C QL'98 - Query Languages Workshop represents one of several efforts to coordinate design activities that focus upon "querying" XML documents, document collections, and document webs. Features already designed within XSL, XPointer, XLink, DOM, DSSSL, and related specifications provide mechanisms for specifying locations/addresses, for tree traversal, and so forth. A current challenge, arguably, is to unify some of these expression/querying sub-languages as a basis for building generalized query facilities that are applicable to a broad range of requirements within different user communities. No formal XML 'query language activity' was established by the W3C when the W3C XML Working Groups were re-chartered in late 1998, but several have predicted that the W3C will eventually charter a new (XML) Query Language activity and/or working group.

[May 06, 1999] In connection with the publication of a working draft version of the XSL Transformations (XSLT) Specification (W3C Working Draft 21-April-1999) it was formally announced that the W3C XSL WG and the XML Linking WG "have agreed to unify XSLT expressions and XPointers. A common core semantic model for querying has been agreed upon, and this draft follows this model (see 6.1 Location Paths). However, further changes particularily in the syntax will probably be necessary. . ."

[April 14, 1999] Sharon Adler, as XSL Co-chair, posted a message to the xsl-list indicating that W3C working groups are indeed moving toward 'XPointer and XSL pattern unification'. "To all of you who wish to see this unification work go forward, I am writing this to let you all know that the work is underway. Last month both working groups voted to pursue this effort even if there was an impact to the schedule. Therefore, we will take a delay to our PR schedule. . ."

XML/XSL/TEI Framework

W3C XML Query Working Group

[December 04, 2000] W3C XML Query Working Group Publishes XML Query Algebra Working Draft. The first W3C public working draft for The XML Query Algebra has been released for review. Reference: W3C Working Draft 04-December-2000, latest draft http://www.w3.org/TR/query-algebra/, edited by Peter Fankhauser (GMD-IPSI), Mary Fernández (AT&T Labs - Research), Ashok Malhotra (IBM), Michael Rys (Microsoft), Jérôme Siméon (Bell Labs, Lucent Technologies), and Philip Wadler (Avaya Communication). The document "introduces the XML Query Algebra as a formal basis for an XML query language." The development work "builds on long standing traditions in the database community. In particular, we have been inspired by systems such as SQL, OQL, and nested relational algebra (NRA). We have also been inspired by systems such as Quilt, UnQL, XDuce, XML-QL, XPath, XQL, and YaTL. We give citations for all these systems below. In the database world, it is common to translate a query language into an algebra; this happens in SQL, OQL, and NRA, among others. The purpose of the algebra is twofold. First, the algebra is used to give a semantics for the query language, so the operations of the algebra should be well-defined. Second, the algebra is used to support query optimization, so the algebra should possess a rich set of laws. Our algebra is powerful enough to capture the semantics of many XML query languages, and the laws we give include analogues of most of the laws of relational algebra. It is also common for a query language to exploit schemas or types; this happens in SQL, OQL, and NRA, among others. The purpose of types is twofold. Types can be used to detect certain kinds of errors at compile time and to support query optimization. DTDs and XML Schema can be thought of as providing something like types for XML. The XML Query algebra uses a simple type system that captures the essence of XML Schema Structures. The type system is close to that used in XDuce. On this basis, the XML Query algebra is statically typed. This allows to determine and check the output type of a query on documents conforming to an input type at compile time rather than at runtime. Compare this to the situation with an untyped or dynamically typed query language, where each individual output has to be validated against a schema at runtime, and there is no guarantuee that this check will always succeed..." A tutorial introduction in the WD 'The Algebra by Example' introduces the main features of the algebra, using familiar examples based on accessing a database of books. In Appendix A 'The XML Query Data Model', the authors present a formal mapping relating the algebra to the XML Query Data Model. [cache]

[August 15, 2000] The W3C XML Query Working Group has published a revised working draft specification for XML Query Requirements . Reference: W3C Working Draft 15-August-2000, edited by Don Chamberlin (IBM Almaden Research Center), Peter Fankhauser (GMD-IPSI), Massimo Marchiori (W3C/MIT/UNIVE), and Jonathan Robie (Software AG). The document "specifies goals, requirements, and usage scenarios for the W3C XML Query data model, algebra, and query language." The goal of the XML Query Working Group is "to produce a data model for XML documents, a set of query operators on that data model, and a query language based on these query operators. The data model will be based on the W3C XML Infoset, and will include support for Namespaces. Queries operate on single documents or fixed collections of documents. They can select whole documents or subtrees of documents that match conditions defined on document content and structure, and can construct new documents based on what is selected." The working draft outlines several usage scenarios which are "intended to be used as design cases during the development of XML Query, and should be reviewed when critical decisions are made. These usage scenarios should also prove useful in helping non-members of the XML Query Working Group understand the intent and goals of the project: (1) Human-readable documents: Perform queries on structured documents and collections of documents, such as technical manuals, to retrieve individual documents, to generate tables of contents, to search for information in structures found within a document, or to generate new documents as the result of a query. (2) Data-oriented documents: Perform queries on the XML representation of database data, object data, or other traditional data sources to extract data from these sources, to transform data into new XML representations, or to integrate data from multiple heterogeneous data sources. The XML representation of data sources may be either physical or virtual; that is, data may be physically encoded in XML, or an XML representation of the data may be produced. (3) Mixed-model documents: Perform both document-oriented and data-oriented queries on documents with embedded data, such as catalogs, patient health records, employment records, or business analysis documents. (4) Administrative data: Perform queries on configuration files, user profiles, or administrative logs represented in XML. (5) Filtering streams Perform queries on streams of XML data to process the data in a manner analogous to UNIX filters. This might be used to process logs of email messages, network packets, stock market data, newswire feeds, EDI, or weather data to filter and route messages represented in XML, to extract data from XML streams, or to transform data in XML streams. (6) Document Object Model (DOM) Perform queries on DOM structures to return sets of nodes that meet the specified criteria. (7) Native XML repositories and web servers Perform queries on collections of documents managed by native XML repositories or web servers. (8) Catalog search Perform queries to search catalogs that describe document servers, document types, XML schemas, or documents. Such catalogs may be combined to support search among multiple servers. A document-retrieval system could use queries to allow the user to select server catalogs, represented in XML, by the information provided by the servers, by access cost, or by authorization. (9) Multiple syntactic environments 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."

[May 11, 2000] The W3C XML Query Working Group has published a first public working draft of the XML Query Data Model . Reference: W3C Working Draft 11-May-2000; edited by Mary Fernandez (AT&T Labs) and Jonathan Robie (Software AG). Document abstract: "This document defines the W3C XML Query Data Model, which is the foundation of the W3C XML Query Algebra; the XML Query Algebra will be specified in a future document. Together, these two documents [will] provide a precise semantics of the XML Query Language." Description: "This document defines the W3C XML Query Data Model, which is the foundation of the W3C XML Query Algebra; the XML Query Algebra will be specified in a future document. Together, these two documents [will] provide a precise semantics of the XML Query Language. . ." [cache]

[February 04, 2000] A public working draft for XML Query Requirements has been published by the W3C XML Query Working Group as part of the W3C XML Activity. References: W3C Working Draft 31-January-2000, edited by Peter Fankhauser (GMD-IPSI), Massimo Marchiori (W3C and MIT), and Jonathan Robie (Software AG). The draft document "specifies goals, usage scenarios, and requirements for the W3C XML Query data model, algebra, and query language." The goal of the XML Query Working Group "is to produce a data model for XML documents, a set of query operators on that data model, and a query language based on these query operators. The data model will be based on the W3C XML Information Set, and will include support for Namespaces. Queries operate on single documents or fixed collections of documents. They can select whole documents or subtrees of documents that match conditions defined on document content and structure, and can construct new documents based on what is selected." Comments on the working draft are invited, and may be sent to the W3C mailing list, where they will publicly archived.

[September 1999] An XML Query Working Group was announced in the Fall of 1999 in connection with W3C's publication of the XML Phase III activity. "Following the W3C Query Languages Workshop (QL'98), the mission of the XML Query working group is to provide flexible query facilities to extract data from real and virtual documents on the Web. The XML Query Working Group plans to develop requirements in 1999 and continue with design work in 2000. Paul Cotton of IBM is the chair of the XML Query Working Group. W3C contact: Massimo Marchiori."

[September 20, 1999] Public W3C mailing list 'www-ql@w3.org' announced by Massimo Marchiori: http://lists.w3.org/Archives/Public/www-ql/.

[March 05, 1999] "The Quest for an XML Query Standard." By Lisa Rein. From XML.com (March 02, 1999). "Is there a need for a query language that speaks XML? Learn what went on when XML experts got together to talk about the need for an XML query standard at QL'98. [This] W3C workshop on query languages for XML produced a number of interesting proposals for extracting information more efficiently from XML documents. In terms of next steps, the W3C must decide whether they will simply incorporate feedback into the existing XML working group activity? Or will a separate Query Language Working Group or XML Query Language Working Group be formed? One of the difficulties is the somewhat delicate placement of the work within the W3C's architecture, since so many different groups will depend heavily on its deliverables. At this point, the W3C is gathering input from its members as to how the query effort should proceed."

QL'98 - W3C Query Languages Workshop

QL'98 - The Query Languages Workshop - W3C Workshop. December 3-4, 1998. DoubleTree Guest Suites Hotel, Boston, Massachussets. The scope of the W3C Workshop on Query Languages is "to begin the discussion of query languages for the Web (with particular emphasis on querying XML and RDF), of the needed requirements for such query language(s), and of proposing solutions." Sample position papers are referenced below. See also: the local Conference Page.

Software

Some sample QL software, much experimental. W3C maintains a list of XQuery implementations.

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