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RDF is a directed, labeled graph data format for representing information in the Web. 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. 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.

The Sematic Web Client Library represents the complete Semantic Web as a single RDF graph. The library enables applications to query this global graph using SPARQL- and find(SPO) queries. To answer queries, the library dynamically retrieves information from the Semantic Web by dereferencing HTTP URIs, by following rdfs:seeAlso links, and by querying the Sindice search engine. The library is written in Java and is based on the Jena framework.

This Java Library provides a simple interface for querying the Semantic Web Index Sindice.com. It supports both term queries and advanced queries with the possibility to set different query parameters like : page number, sorting of results by date.

The Virtuoso SPARQL query service implements the SPARQL Protocol for RDF (W3C Working Draft 25 January 2006) providing SPARQL query-processing for RDF data available on the open internet. The query service implementation extends the standard protocol by providing multiple output-formats alongside the standard XML results serialization. At present this uses additional query parameters, although content-negotiation will be supported soon.

The Sematic Web Client Library represents the complete Semantic Web as a single RDF graph. The library enables applications to query this global graph using SPARQL- and find(SPO) queries. To answer queries, the library dynamically retrieves information from the Semantic Web by dereferencing HTTP URIs, by following rdfs:seeAlso links, and by querying the Sindice search engine. The library is written in Java and is based on the Jena framework. Contents

"The W3C standard query language SPARQL is letting people access a growing collection of public and private data. Whether this data is part of a semantic web project or a combination of data from two relational databases on different platforms, SPARQL is making it easier to access this data using both open source and commercial software. "Learning SPARQL" teaches you how to use SPARQL 1.1 by starting you off with simple queries that demonstrate the language's query-by-example approach and then taking you through all the key features of the SPARQL 1.1 query and update languages. All example "

SPARQL (pronounced "sparkle", a recursive acronym for SPARQL Protocol and RDF Query Language) is an RDF query language, that is, a query language for databases, able to retrieve and manipulate data stored in Resource Description Framework format.[1][2] It was made a standard by the RDF Data Access Working Group (DAWG) of the World Wide Web Consortium, and is considered as one of the key technologies of the semantic web.

A semantic wiki is a wiki that stores some portion of its data in a way that can be queried elsewhere. Typical uses of such data include querying it within the wiki (sometimes using standard query languages like SPARQL), aggregating it in displays like tables, maps and calendars; exporting it via formats like RDF, OWL or CSV; and reasoning with it, to calculate new facts from the given facts. Semantic wikis do not necessarily need to include standards or technologies considered part of the Semantic Web, although they usually do, to some extent.

BigQuery is a large-scale, interactive query environment that can handle billions of records in seconds. This project provides support to use Linked Open Data in BigQuery with the goal to interactively query the entire LOD cloud (currently some 25 billion records).

This query page is designed to help you test OpenLink Virtuoso SPARQL protocol endpoint. Consult the Virtuoso Wiki page describing the service or the Online Virtuoso Documentation section RDF Database and SPARQL. There is also a rich Web based user interface with sample queries. You can access it at: /isparql.

Twinkle: A SPARQL Query Tool

Treo: Schema-agnostic queries over databases Treo is a Semantic Search and Question Answering System for Databases. Treo is designed to cope with the Big Data vision of handling very heterogeneous (schemaless) databases, a scenario where it becomes unfeasible for data consumers to understand the representation of the data in order to query the database.

"The Apache Hive ™ data warehouse software facilitates querying and managing large datasets residing in distributed storage. Hive provides a mechanism to project structure onto this data and query the data using a SQL-like language called HiveQL. At the same time this language also allows traditional map/reduce programmers to plug in their custom mappers and reducers when it is inconvenient or inefficient to express this logic in HiveQL."

Faceted Wikipedia Search allows users to ask complex queries against Wikipedia. The answers to these queries are not generated using key word matching as the answers of search engines like Google or Yahoo, but are generated based on structured information that has been extracted from many different Wikipedia articles.

"The Web is full of high-quality Linked Data. But we can't reliably query it. Public SPARQL endpoints are often unavailable, because they need to answer many unique queries."

"Querying Wikipedia like a Semantic Database DBpedia is a community effort to extract structured information from Wikipedia and make this information available on the Web. DBpedia allows you to ask sophisticated queries against Wikipedia and to link other datasets on the Web to Wikipedia data."

"Virtuoso SPARQL Query Editor"

Yebol's mission is to build human-like world's knowledge base and provide knowledge based search (semantics) and services. Yebol utilizes a combination of patented algorithms paired with human knowledge to build a Web directory for each query and each user. Instead of the common "listing" of Web search queries, Yebol automatically clusters and categorizes search terms, Web sites, pages and contents. Yebol allows for a multi-dimensional search result instead of the normal one-dimensional search seen by most web search engines today. This provides a more accurate summary of top sites and categories; a wider array of related search terms; a longer and richer expansion for query results; and a deeper base of links and keywords in search result pages.

Intelligent Network of Querying and Learning Engines

OSS Insight: GPT-powered querying tool for GitHub live data exploration (ossinsight.io).