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| News: Cover Stories |  |  |
| W3C Publishes SPARQL Protocol and RDF Query Language Semantic Web Standard. |
Contents
SPARQL (a recursive acronym for "SPARQL Protocol and RDF Query Language," pronounced "sparkle") has been released as a standard by W3C. The three-part specification was produced by members of the RDF Data Access Working Group, which is part of the W3C Semantic Web Activity. It defines a standardized query language for RDF enabling the 'joining' of decentralized collections of RDF data.
RDF (Resource Description Framework) is a directed, labeled graph data format for representing information in the Web. RDF "integrates a variety of applications from library catalogs and world-wide directories to syndication and aggregation of news, software, and content to personal collections of music, photos, and events using XML as an interchange syntax. The RDF specifications provide a lightweight ontology system to support the exchange of knowledge on the Web."
As explained in the W3C announcement, SPARQL allows people to "focus on what they want to know rather than on the database technology or data format used behind the scenes to store the data. Because SPARQL queries express high-level goals, it is easier to extend them to unanticipated data sources, or even to port them to new applications." Tim Berners-Lee, W3C Director: "Trying to use the Semantic Web without SPARQL is like trying to use a relational database without SQL. SPARQL makes it possible to query information from databases and other diverse sources in the wild, across the Web."
"Many successful query languages exist, including standards such as SQL and XQuery. These were primarily designed for queries limited to a single product, format, type of information, or local data store. Traditionally, it has been necessary to formulate the same high-level query differently depending on application or the specific arrangement chosen for the relational database. And when querying multiple data sources it has been necessary to write logic to merge the results. These limitations have imposed higher developer costs and created barriers to incorporating new data sources."
"The goal of the Semantic Web is to enable people to share, merge, and reuse data globally. SPARQL is designed for use at the scale of the Web, and thus enables queries over distributed data sources, independent of format. Creating a single query across diverse data stores is easier than having to create multiple queries; it also costs less and provides richer results."
"Because SPARQL has no tie to a specific database format, it can be used to take advantage of the tidal wave of Web 2.0 data and mash it up with other Semantic Web resources. Furthermore, because disparate data sources may not have the same 'shape' or share the same properties, SPARQL is designed to query non-uniform data."
SPARQL "can be used to express queries across diverse data sources, whether the data is stored natively as RDF or viewed as RDF via middleware. SPARQL contains capabilities for querying required and optional graph patterns along with their conjunctions and disjunctions. SPARQL also supports extensible value testing and constraining queries by source RDF graph. The results of SPARQL queries can be results sets or RDF graphs."
SPARQL Query Language for RDF defines the syntax and semantics of the SPARQL query language for RDF. It uses the Turtle data format to show each triple explicitly, where Turtle allows IRIs to be abbreviated with prefixes (Turtle: Terse RDF Triple Language). SPARQL Protocol for RDF uses WSDL 2.0 to describe a means for conveying SPARQL queries to an SPARQL query processing service and returning the query results to the entity that requested them. SPARQL Query Results XML Format defines a SPARQL Results Document that encodes the variable binding query results from SELECT queries and boolean query results from ASK queries in XML format.
Three SPARQL implementation reports accompany the prose specifications. W3C reports that fourteen implementations of SPARQL are already documented, many of which are available as open source software.
A SPARQL Query Language Implementation Report accompanies the published SPARQL Query Language for RDF specification. The implementation report summarizes results from fourteen implementations of the SPARQL Query Language for RDF against the RDF Data Access Working Group's query language test suite. Test results were received in Evaluation and Report Language (EARL) 1.0 Schema format. Each test in the test suite was assigned to one or more facets, representing low-level details of the query language. These facets were matched into eleven high-level features of the query language for the purposes of determining interoperability. The working group examined the coverage of the test suite vis a vis these facets in order to assure that no elements of the SPARQL language were omitted in the test suite."
The SPARQL Protocol for RDF specification is supported by the SPARQL Protocol Implementation Report. This report by the RDF Data Access Working Group (DAWG) it fulfills the Candidate Recommendation exit criteria set forth in the 6-April-2006 CR publication of the specification, viz., that "Each identified SPARQL feature has at least two implementations." The SPARQL Protocol for RDF defines a WSDL 2.0 interface, SparqlQuery, as well as bindings of that interface for HTTP and SOAP. The SparqlQuery interface consists of one operation with one required in parameter, query and two optional, repeating parameters, default-graph-uri and named-graph-uri. The protocol also interacts with the SPARQL Query Language for RDF in several ways, including the definition of a query's dataset and the form (MIME type) of a query's results...
The SPARQL Query Results XML Format specification was published with the SPARQL Query Results XML Format Implementation Report. The SPARQL Query Results XML Format defines an XML format for the variable binding and boolean results formats provided by the SPARQL Query Language for RDF. To demonstrate multiple implementations of the query results XML format, the Working Group has shown two implementations that produce the format as well as two implementations that consume the format. The Working Group examined producers and consumers of the query results XML format in conjunction with producing an implementation report for the SPARQL Protocol for RDF. Several of the tests of the protocol require the protocol implementation to return the query results XML format, both for the variable binding format and boolean format. In addition, the Python code that serves as the protocol test harness is a consumer of the XML results format, as it parses the format into an internal graph to check for correctness. Finally, we ran each of the result format instances through a second consumer, an XSL transform that consumes the query results XML format and generates HTML. We pairwise tested two producers of the results format with two consumers, and were successful in all tests...
Excerpted from the text of the W3C announcement 2008-01-15: "W3C Opens Data on the Web with SPARQL. Powerful Technology for Querying Distributed and Diverse Data."
SPARQL Turns Data Access into a Web Service
The combination of the SPARQL query language and protocol creates a Web service in its purest sense; running on top of HTTP or SOAP, it provides a standard Web service for anything which asks a question.
"SPARQL's focus on querying the data models saves time for developers; there's no need for a host of little Web services to retrieve different aspects of the state of a system," explained Lee Feigenbaum, Chair of the RDF Data Access Working Group. "This allows the user of the SPARQL endpoint to ask any question — it is as though they could design their own interface instead of having to work with a limited set of fixed services."
The SPARQL specification defines a query language and a protocol and works with the other core Semantic Web technologies from W3C: Resource Description Framework (RDF) for representing data; RDF Schema; Web Ontology Language (OWL) for building vocabularies; and Gleaning Resource Descriptions from Dialects of Languages (GRDDL), for automatically extracting Semantic Web data from documents. SPARQL also makes use of other W3C standards found in Web services implementations, such as Web Services Description Language (WSDL).
W3C's Data Access Working Group Includes Industry Leaders in Database Technology, Web Applications
W3C RDF Data Access Working Group produced the three SPARQL Recommendations issued today: the SPARQL Query Language for RDF, the SPARQL Protocol for RDF, and the SPARQL Query Results XML Format. The Working Group includes invited experts and participants from Agfa-Gevaert N. V.; Asemantics S.R.L.; Clark & Parsia LLC; Cleveland Clinic; Eindhoven University of Technology; Free University of Bozen-Bolzano; Garlik; HP; IBM Corporation; Matsushita Electric Industrial Co., Ltd. (MEI); Nippon Telegraph & Telephone Corp. (NTT); OpenLink Software; Oracle; and Profium, Ltd. The SPARQL Testimonials page contains statements of support and commitments to implement the new Recommendations.
W3C continues to enhance the relationship between the Semantic Web and traditional databases; see the report from the W3C Workshop on RDF Access to Relational Databases from October 2007.
Testimonials for "W3C Opens Data on the Web with SPARQL" Press Release
These testimonials accompany the press release W3C Opens Data on the Web with SPARQL.
Asemantics | Clark & Parsia | Computas AS | CWI | Eli Lilly | Garlik | Hewlett-Packard | INRIA | OpenLink Software | Oracle | Profium | Talis
Asemantics
Asemantics S.r.l., the European Semantic Web company has been actively contributing to the W3C DAWG standardization process and successfully deploying W3C's SPARQL query language and protocol based real-world solutions inside public and private sector; for the European Space Agency (ESA/ESRIN) we successfully built ad-hoc dynamic satellite image galleries and an EO interoperability catalog search engine using the SPARQL. We worked together with Rijkswaterstaat (the Dutch Water Authority) to create an RDF based library of national water measurement data about more than four centuries of different physical and biological measurements related to sea, coastal and inland water; catalog and detailed search are internally being performed using SPARQL. Inside the Joost venture we successfully used RDF related technologies including the SPARQL query and language and protocol to build dynamic and flexible digital asset management tools to bridge content owners, metadata engineering and management related workflows. We are working together with the British Broadcasting Corporation (BBC) to build a next generation feed aggregator inside the Memoryshare initiative which internally stores information in RDF in order to preserve all richness of the original information and all relations among the data; which is then being queried dynamically using the SPARQL query language.
Asemantics see SPARQL as a major W3C contribution which will enable next generation Internet semantic applications in the mainstream.
— Alberto Reggiori, CTO Asemantics S.r.l.
Clark & Parsia
Clark & Parsia LLC recognizes SPARQL as an important development in the evolution of the Semantic Web. By providing a standard query language for RDF, SPARQL offers developers a "universal query language" that can be used to access information stored in a wide range of systems, including metadata repositories, web services, and legacy information systems. Clark & Parsia supports SPARQL query answering in its OWL DL reasoner Pellet and is readying the first Pellet release with SPARQL extensions for OWL DL.
— Michael Smith, Senior Engineer and W3C AC Representative, Clark & Parsia LLC
Computas AS
Computas AS is currently building systems for its customers where SPARQL is a fundamental core component. When conducting feasibility studies, we found that there are allready many high quality off-the-shelf components that puts the vision of the data web within reach, also for smaller enterprises.
We are pleased to see SPARQL promoted to a W3C Recommendation, as it provides a stable platform for further work. We are allready experimenting with extensions to SPARQL, and will work with the W3C and its membership in the work that lies ahead.
— Kjetil Kjernsmo, Senior Knowledge Engineer, Computas AS
CWI
CWI is a strong supporter of the W3C activities in general and of the steps taken towards a standardization of SPARQL in particular. Use of SPARQL significantly improves the bridge between data- and document-oriented information. CWI's contribution will bear fruit in its ongoing activities on the open source database management system MonetDB/{SQL,XQuery}, which will soon evolve into MonetDB/SPARQL.
— Prof. Dr. J.K. Lenstra, Director, CWI
Eli Lilly
Eli Lilly and Company is a world leader in innovative applications of technology to discover and develop pharmaceutical products to better people's lives. Accordingly, Lilly is using W3C Semantic Web technologies to help scientists gather information about drug targets, and maintain knowledge about experiments. In particular, we use the SPARQL query language in conjunction with an OWL ontology to find out information about experiments that have been undertaken. We are pleased to see SPARQL become a W3C Recommendation.
— Susie Stephens, Principal Research Scientist for Open Innovation, Eli Lilly
Garlik
Garlik make extensive use of the W3C's SPARQL query language andprotocol. Two of our Products, DataPatrol and QDOS use SPARQLcompliant RDF stores as their core data store.DataPatrol uses SPARQL as an access point to a large, complex andrapidly changing data structure, while building on top of HTTP hasallowed us to provide high levels of security in a standards complaintway.QDOS uses SPARQL to provide a standards compliant, web accessiblebackend for a Web 2.0 platform. SPARQL provides a ready-made HTTP-basedquery interface which is capable of providing third party developers withaccess to public data.
— Tom Ilube, Founder & CEO, Garlik
Hewlett-Packard
Hewlett-Packard is pleased to support the SPARQL Recommendations.
SPARQL is a key element for integrated information access across information silos and across business boundaries. HP customers can benefit from better information utilization by employing semantic web technologies.
HP's Jena Semantic Web framework has a complete implementation of query language, protocol and result set processing. Jena is open-source, freely available, with a large and active developer community.
HP is pleased to announce the first full release of SDB, a new SPARQL database system for Jena that leverages existing database installations to give enterprise-grade storage and query of RDF.
— Jean-Luc Chatelain, CTO HP Software Information Management
INRIA
The SPARQL Recommendation sets the standard for querying RDF data. INRIA is very pleased with the W3C efforts converging towards a robust query language that will offer a common way to extract RDF data from the Semantic Web. INRIA teams have invested efforts in implementing the Recommendation and deliver right away SPARQL-compliant tools. The CORESE search engine for the semantic web can evaluate SPARQL queries against RDF, OWL and rule content. We also developed PSPARQL: a query language which can express all SPARQL queries as well as extensions with path expressions allowing more general queries. A PSPARQL query engine is also available.
— Pierre Paradinas, Head of Technological Development, INRIA
OpenLink Software
SPARQL bridges the gap between the vision and the manifestation of a Web of semantically interlinked data (Linked Data). This powerful mechanism helps expose and explain the data integration prowess of our Virtuoso Universal Server and OpenLink Data Spaces products, across all levels of the Internet, Intranet, and Extranet.
By leveraging Web architecture in devising this standard — comprised of an open query language, communications protocol, and results serialization format — the W3C has ingeniously delivered an unobtrusive bridge between the current Web of Documents and the emerging Web of Linked Data. SPARQL will ultimately enhance the value of the Web for everyone.
— Kingsley Idehen, President & CEO, OpenLink Software
Oracle
Oracle congratulates the W3C on achieving 'Recommendation' status for SPARQL. As an active participant in this working group, Oracle believes the standardization of SPARQL will play an instrumental role in achieving the vision of the Semantic Web. The community's work is intended to help organizations more effectively discover, automate, integrate and re-use data across various applications.
Oracle Database 11g Semantic Store provides native support for efficient and scalable storage, bulk loading, inferencing, and graph-pattern based querying of semantic data represented using W3C's RDF, RDFS, and OWL languages. The Oracle Jena adaptor allows querying of semantic data stored in Oracle using the SPARQL query language while leveraging the performance and scalability of Oracle's Semantic Store.
— Don Deutsch, vice president Standards Strategy and Architecture, Oracle
Profium
Profium provides software solutions for rich digital content management by leveraging the latest Semantic Web technologies. Our software solutions provide for multimedia archiving, centralized metadata management and real-time routing of content for cross-media publishing. Profium's Metadata Server product uses RDF data model and SPARQL as query language and for us, a standardized query language has been a most welcome addition to the Semantic Web technology stack and we foresee great interoperability possibilities in the future.
— Jari Harjula, Product manager, Profium Ltd.
Talis
Talis is delighted to see the publication of the SPARQL Recommendations. We believe that this is an important milestone in making the Semantic Web usable for a broad class of applications in the enterprise. The Talis Semantic Web Platform provides its users with services using the SPARQL query language and protocol to allow searching of their data. We look forward to SPARQL being incorporated in many more applications enabling Web-scale integration of data between and within organisations.
— Ian Davis, CTO, Talis Group Ltd
About the World Wide Web Consortium (W3C)
The World Wide Web Consortium (W3C) is an international consortium where Member organizations, a full-time staff, and the public work together to develop Web standards. W3C primarily pursues its mission through the creation of Web standards and guidelines designed to ensure long-term growth for the Web. Over 400 organizations are Members of the Consortium. W3C is jointly run by the MIT Computer Science and Artificial Intelligence Laboratory (MIT CSAIL) in the USA, the European Research Consortium for Informatics and Mathematics (ERCIM) headquartered in France and Keio University in Japan, and has additional Offices worldwide. For more information see http://www.w3.org/.
Abstracts and extracts from the SPARQL specifications:
This specification defines the syntax and semantics of the SPARQL query language for RDF. SPARQL can be used to express queries across diverse data sources, whether the data is stored natively as RDF or viewed as RDF via middleware.
The SPARQL query language for RDF is designed to meet the use cases and requirements identified by the RDF Data Access Working Group in RDF Data Access Use Cases and Requirements.
The SPARQL query language is closely related to the following specifications:
- The SPARQL Protocol for RDF specification, which defines the remote protocol for issuing SPARQL queries and receiving the results
- The SPARQL Query Results XML Format specification, which defines an XML document format for representing the results of SPARQL SELECT and ASK queries.
SPARQL Query Language for RDF Document Outline:
- Section 1, introduces the SPARQL query language specification. It presents the organization of this specification document and the conventions used throughout the specification.
- Section 2 of the specification introduces the SPARQL query language itself via a series of example queries and query results.
- Section 3 continues the introduction of the SPARQL query language with more examples that demonstrate SPARQL's ability to express constraints on the RDF terms that appear in a query's results.
- Section 4 presents details of the SPARQL query language's syntax. It is a companion to the full grammar of the language and defines how grammatical constructs represent IRIs, blank nodes, literals, and variables. Section 4 also defines the meaning of several grammatical constructs that serve as syntactic sugar for more verbose expressions.
- Section 5 introduces basic graph patterns and group graph patterns, the building blocks from which more complex SPARQL query patterns are constructed.
- Sections 6, 7, and 8 present constructs that combine SPARQL graph patterns into larger graph patterns. In particular, Section 6 introduces the ability to make portions of a query optional.
- Section 7 introduces the ability to express the disjunction of alternative graph patterns
- Section 8 introduces the ability to constrain portions of a query to particular source graphs. Section 8 also presents SPARQL's mechanism for defining the source graphs for a query.
- Section 9 defines the constructs that affect the solutions of a query by ordering, slicing, projecting, limiting, and removing duplicates from a sequence of solutions.
- Section 10 defines the four types of SPARQL queries that produce results in different forms.
- Section 11 defines SPARQL's extensible value testing framework. It also presents the functions and operators that can be used to constrain the values that appear in a query's results.
- Section 12 is a formal definition of the evaluation of SPARQL graph patterns and solution modifiers.
- Appendix A contains the normative definition of the SPARQL query language's syntax, as given by a grammar expressed in EBNF notation.
The "SPARQL Protocol" specification is defined by a set of three documents:
The SPARQL Protocol contains one interface, SparqlQuery, which in turn contains one operation, query. SPARQL Protocol is described abstractly with WSDL 2.0 in terms of a web service that implements its interface, types, faults, and operations, as well as by HTTP and SOAP bindings. Note that while this [SPARQL Protocol for RDF] document uses WSDL 2.0 to describe SPARQL Protocol, there is no obligation on the part of any implementation to use any particular implementation strategy, including the use of any WSDL library or programming language framework.
The SPARQL Query Language for RDF specification itself defines several "Query Result Forms." These result forms use the solutions from pattern matching to form result sets or RDF graphs. The query forms are:
- SELECT: Returns all, or a subset of, the variables bound in a query pattern match
- CONSTRUCT: Returns an RDF graph constructed by substituting variables in a set of triple templates
- DESCRIBE: Returns an RDF graph that describes the resources found
- ASK: Returns a boolean indicating whether a query pattern matches or not
The SPARQL Query Results XML Format document defines a SPARQL Results Document that encodes the variable binding query results from SELECT queries and boolean query results from ASK queries in XML notation. Applications can use the ASK form to test whether or not a query pattern has a solution; no information is returned about the possible query solutions, just whether the server can find one or not.
The SPARQL specification defines a query language and a protocol and works with the other core Semantic Web technologies from W3C, including:
RDF/XML Syntax Specification. "Resource Description Framework (RDF) is a general-purpose language for representing information in the Web. This document defines an XML syntax for RDF called RDF/XML in terms of Namespaces in XML, the XML Information Set and XML Base. The formal grammar for the syntax is annotated with actions generating triples of the RDF graph as defined in RDF Concepts and Abstract Syntax. The triples are written using the N-Triples RDF graph serializing format which enables more precise recording of the mapping in a machine processable form. The mappings are recorded as tests cases, gathered and published in RDF Test Cases." RDF Vocabulary Description Language 1.0: RDF Schema. "This specification introduces RDF's vocabulary description language, RDF Schema. It is complemented by several companion documents which describe RDF's XML encoding, mathematical foundations, and Resource Description Framework (RDF): Concepts and Abstract Syntax. The RDF Primer provides an informal introduction and examples of the use of the concepts specified in this document. This document is intended to provide a clear specification of the RDF vocabulary description language to those who find the formal semantics specification, RDF Semantics daunting. Thus, this document duplicates material also specified in the RDF Semantics specification . Where there is disagreement between this document and the RDF Semantics specification, the RDF Semantics specification should be taken to be correct. RDF properties may be thought of as attributes of resources and in this sense correspond to traditional attribute-value pairs. RDF properties also represent relationships between resources." OWL Web Ontology Language. The OWL Web Ontology Language is designed for use by applications that need to process the content of information instead of just presenting information to humans. OWL facilitates greater machine interpretability of Web content than that supported by XML, RDF, and RDF Schema (RDF-S) by providing additional vocabulary along with a formal semantics. Gleaning Resource Descriptions from Dialects of Languages (GRDDL). "GRDDL is a mechanism for 'Gleaning Resource Descriptions from Dialects of Languages'. The GRDDL specification introduces markup based on existing standards for declaring that an XML document includes data compatible with the Resource Description Framework (RDF) and for linking to algorithms (typically represented in XSLT), for extracting this data from the document. The markup includes a namespace-qualified attribute for use in general-purpose XML documents and a profile-qualified link relationship for use in valid XHTML documents. The GRDDL mechanism also allows an XML namespace document (or XHTML profile document) to declare that every document associated with that namespace (or profile) includes gleanable data and for linking to an algorithm for gleaning the data."
SPARQL was developed within W3C's RDF Data Access Working Group, chartered to gather requirements and to define an HTTP and/or SOAP-based protocol for selecting instances of subgraphs from an RDF graph.
In its first phase, the WG was asked to evaluate requirements and select a strawman RDF query language, or document why divergent requirements make this impossible. With a strawman RDF query language selected, the WG would enter the second phase in which it will write a formal specification and test cases for this language.
As narrated in the initial RDF Data Access Use Cases and Requirements document:
The W3C's Semantic Web Activity is based on RDF's flexibility as a means of representing data. While there are several standards covering RDF itself, there has not yet been any work done to create standards for querying or accessing RDF data. There is no formal, publicly standardized language for querying RDF information. Likewise, there is no formal, publicly standardized data access protocol for interacting with remote or local RDF storage servers.
Despite the lack of standards, developers in commercial and in open source projects have created many query languages for RDF data. But these languages lack both a common syntax and a common semantics. In fact, the extant query languages cover a significant semantic range: from declarative, SQL-like languages, to path languages, to rule or production-like systems. The existing languages also exhibit a range of extensibility features and built-in capabilities, including inferencing and distributed query.
Further, there may be as many different methods of accessing remote RDF storage servers as there are distinct RDF storage server projects. Even where the basic access protocol is standardized in some sense — HTTP, SOAP, or XML-RPC —there is little common ground upon which to develop generic client support to access a wide variety of such servers..."
The goal of the Semantic Web Initiative is as broad as that of the Web: to create a universal medium for the exchange of data. It is envisaged to smoothly interconnect personal information management, enterprise application integration, and the global sharing of commercial, scientific and cultural data. Facilities to put machine-understandable data on the Web are quickly becoming a high priority for many organizations, individuals and communities.
The Web can reach its full potential only if it becomes a place where data can be shared and processed by automated tools as well as by people. For the Web to scale, tomorrow's programs must be able to share and process data even when these programs have been designed totally independently. The Semantic Web Activity is an initiative of the World Wide Web Consortium (W3C) designed to provide a leadership role in defining this Web. The Activity develops open specifications for those technologies that are ready for large scale deployment, and identifies, through open source advanced development, the infrastructure components that will be necessary to scale in the Web in the future.
The principal technologies of the Semantic Web fit into a set of layered specifications. The current components are the Resource Description Framework (RDF) Core Model, the RDF Schema language, and the Web Ontology language (OWL). Building on these core components is a standardized query language, SPARQL (pronounced "sparkle"), for RDF enabling the 'joining' of decentralized collections of RDF data. The GRDDL Recommendation and the work on RDFa aims at creating bridges between the RDF model and various XML formats, like XHTML..."
- Announcement:
- Announcement 2008-01-15: "W3C Opens Data on the Web with SPARQL. Powerful Technology for Querying Distributed and Diverse Data." [source]
- Testimonials for "W3C Opens Data on the Web with SPARQL" Press Release. From: Asemantics, Clark & Parsia, Computas AS, CWI, Eli Lilly, Garlik, Hewlett-Packard, INRIA, OpenLink Software, Oracle, Profium, and Talis.
- W3C news item
- SPARQL Specifications:
- SPARQL Testing, Implementations, and Requirements:
- Working Group:
- SPARQL Mailing Lists:
- W3C Semantic Web:
- Press, Commentary, Random:
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