![]() ^ "XML and Semantic Web W3C Standards Timeline" (PDF).Archived from the original on 20 January 2008. ^ "W3C Semantic Web Activity News – SPARQL is a Recommendation".O’Reilly Media, Inc., 1005 Gravenstein Highway North, Sebastopol, CA 95472. ^ Segaran, Toby Evans, Colin Taylor, Jamie (2009).Indianapolis, Indiana: John Wiley & Sons. ^ a b Hebeler, John Fisher, Matthew Blace, Ryan Perez-Lopez, Andrew (2009).XSPARQL is an integrated query language combining XQuery with SPARQL to query both XML and RDF data sources at once. It enables the RDF store to be updated with this declarative query language, by adding INSERT and DELETE methods. GeoSPARQL defines filter functions for geographic information system (GIS) queries using well-understood OGC standards ( GML, WKT, etc.). In this query, the prefix " ex" stands for “”. To make queries concise, SPARQL allows the definition of prefixes and base URIs in a fashion similar to Turtle. Important to note here is the "property orientation" (class matches can be conducted solely through class-attributes or properties – see Duck typing) The SPARQL query processor will search for sets of triples that match these four triple patterns, binding the variables in the query to the corresponding parts of each triple. So for example ex:isCapitalOf ?y is short for ?x ex:isCapitalOf ?y. ![]() When a triple ends with a semicolon, the subject from this triple will implicitly complete the following pair to an entire triple. Bindings for ?capital and the ?country will be returned. Variables are indicated by a ? or $ prefix. Specifically, the following query returns names and emails of every person in the dataset: The example below demonstrates a simple query that leverages the ontology definition foaf ("friend of a friend"). In addition, SPARQL provides specific graph traversal syntax for data that can be thought of as a graph. However, schema information (the ontology) is often provided externally, to allow joining of different datasets unambiguously. Thus, SPARQL provides a full set of analytic query operations such as JOIN, SORT, AGGREGATE for data whose schema is intrinsically part of the data rather than requiring a separate schema definition. Also unlike SQL, RDF can have multiple entries per predicate for instance, one could have multiple "child" entries for a single "person", and can return collections of such objects, like "children". Unlike relational databases, the object column is heterogeneous: the per-cell data type is usually implied (or specified in the ontology) by the predicate value. In RDF, those fields are instead represented as separate predicate/object rows sharing the same subject, often the same unique key, with the predicate being analogous to the column name and the object the actual data. The subject in RDF is analogous to an entity in a SQL database, where the data elements (or fields) for a given business object are placed in multiple columns, sometimes spread across more than one table, and identified by a unique key. In SQL relational database terms, RDF data can also be considered a table with three columns – the subject column, the predicate column, and the object column. This is analogous to some NoSQL databases' usage of the term "document-key-value", such as MongoDB. Thus, the entire database is a set of "subject-predicate-object" triples. SPARQL allows users to write queries against what can loosely be called "key-value" data or, more specifically, data that follow the RDF specification of the W3C. In addition, tools exist to translate SPARQL queries to other query languages, for example to SQL and to XQuery. There exist tools that allow one to connect and semi-automatically construct a SPARQL query for a SPARQL endpoint, for example ViziQuer. Implementations for multiple programming languages exist. SPARQL allows for a query to consist of triple patterns, conjunctions, disjunctions, and optional patterns. On 15 January 2008, SPARQL 1.0 was acknowledged by W3C as an official recommendation, and SPARQL 1.1 in March, 2013. It was made a standard by the RDF Data Access Working Group (DAWG) of the World Wide Web Consortium, and is recognized as one of the key technologies of the semantic web. SPARQL (pronounced " sparkle" / ˈ s p ɑː k ə l/, a recursive acronym for SPARQL Protocol and RDF Query Language) is an RDF query language-that is, a semantic query language for databases-able to retrieve and manipulate data stored in Resource Description Framework (RDF) format.
0 Comments
Leave a Reply. |