For the most part, the answer to this question is the same as the above answer regarding RDFS entailment. However, OWL-DL axioms do not always result in a unique deductive closure, and as such querying OWL-DL entailments requires instantiating the parametrized SPARQL basic graph pattern definition with values appropriate for OWL-DL entailment. The open-source OWL-DL reasoner, Pellet, will answer SPARQL queries while considering OWL-DL entailments.

It is sometimes desirable to use SPARQL to query triples entailed from subclass, subproperty, range, domain, and other relations which can be represented using RDF Schema. The SPARQL specification defines the results of queries based on RDF simple entailment. However, the specification does present a general, parametrized definition of graph pattern matching that can be expanded to other entailments beyond RDF simple entailment.

Several software packages exist which allow SPARQL queries to generate answers from data sources other than RDF, such as relational databases, LDAP servers, or XML data. The community maintains a list of these tools at the W3C ESW Wiki.

While SPARQL does support nested graph patterns, it does not directly support subqueries (for example, the FROM clause of a SPARQL query cannot itself contain a CONSTRUCT query which generates the dataset to be queried against). The Data Access Working Group postponed this issue in early 2005.

A combination of the SPARQL OPTIONAL keyword and the bound(...) filter function can be used to mimic some universally quantified queries. As an example, consider this query which finds the minimum price of every book in the underlying default graph: PREFIX ex: <http://example.org/> SELECT ?book ?minprice WHERE { ?book a ex:book ; ex:price ?minprice . OPTIONAL { ?book ex:price ?otherprice . FILTER( ?otherprice < ?minprice ) . } . FILTER ( !bound(?otherprice) ) .

For the most part, blank nodes in SPARQL queries function exactly as variables which cannot be returned to the user/client. So, the following two queries behave identically: SELECT ?title WHERE { _:book :hasTitle ?title } SELECT ?title WHERE { ?book :hasTitle ?title } However, a SPARQL query may not reuse the same blank node label twice in different basic graph patterns. That is, the following is not a legal SPARQL query: SELECT ?title WHERE { _:book rdfs:seeAlso ?g .

There is no built-in support within SPARQL to query hierarchical structures of an unknown depth (e.g. trees or lists), to query transitive relations, or to query via XPath like paths. The Data Access Working Group postponed this issue in early 2005. Repeated queries. A repeating structure can be queried via a series of queries.

SPARQL is a recursive acronym standing for SPARQL Protocol and RDF Query Language. As the name implies, SPARQL is a general term for both a protocol and a query language. Most uses of the SPARQL acronym refer to the RDF query language. In this usage, SPARQL is a syntactically-SQL-like language for querying RDF graphs via pattern matching. The language's features include basic conjunctive patterns, value filters, optional patterns, and pattern disjunction.

SPARQL provides the function, regex(), which can be used to test whether a literal value contains a certain substring: SELECT ?title WHERE { _:book :title ?title . FILTER (regex(?title, "SPARQL")) . } The regex() function expects its first argument to be either a plain literal without a language tag or else a typed literal with a datatype of xsd:string. Plain literals with a language tag or typed literals of other datatypes will evaluate to a type error which causes the filter to fail.

The current, standardized version of SPARQL deals only with retrieving selected data from RDF graphs. There is no equivalent of the SQL INSERT, UPDATE, or DELETE statements. Most RDF-based applications handle new, changing, and stale data directly via the APIs provided by specific RDF storage systems. Alternatively, RDF data can exist virtually (i.e. created on-demand in response to a SPARQL query).

There are a variety of SPARQL tutorials and introductions scattered around the Web. Some notable ones include:

Around 1960 I came across a book (name and publisher long forgotten), where the writer used the appearance of the Owl/Eye symbol on rocks and pottery to trace an early Neolithic group spreading out by the coastal route from the Mediterranean up the coast of Europe, Ireland, Scotland and Denmark. In 1966, Thames and Hudson published a book by T.G.E. Powell called 'Prehistoric Art', where the 'Ocular' motives were noted, illustrated and its suggested origin to be in the Mediterranean.

The creators of several SPARQL implementations provide online services where SPARQL queries can be input and executed against either canned datasets or arbitrary datasets (identified by URLs). The community maintains a list of SPARQL endpoints on the W3C ESW Wiki.

On January 15, 2008, the W3C published the three SPARQL specifications as Recommendations. This means that the specifications have been endorsed by the W3C membership and should be considered stable documents.

No. Although some specialized commands are used to manage and configure the cluster itself, only standard (My)SQL queries and commands are required for the following operations: Some specialized configuration parameters and files are required to set up a MySQL Cluster - see Section 15.4.4, "Configuration File", for information about these. A few simple commands are used in the MySQL Cluster management client for tasks such as starting and stopping cluster nodes. See Section 15.7.

Yes, just before she went to the Crimean War she had a pet baby owl called Athena who travelled in her pocket. Yes, but only during the war. She ruled her nurses with iron discipline - even locking them up at night! She was doing it to prove to middle-class parents back home that tough discipline and strong female leadership could protect their daughters against sexual harassment.

The SPARQL protocol requires that the results of SPARQL CONSTRUCT and DESCRIBE queries be RDF graphs. SELECT and ASK queries, on the other hand, usually have their results returned as XML (or sometimes as JSON). However, as part of the group's test suite, the DAWG includes an RDF vocabulary which can be used to represent the results of SELECT or ASK queries in RDF.

The DAWG defines an XML serialization format, the SPARQL Query Results XML Format, which is used to return the results of SPARQL SELECT and ASK queries. The SPARQL protocol requires that the results of SPARQL CONSTRUCT and DESCRIBE queries be RDF graphs, which can be represented using the XML-based RDF/XML syntax.

JSON is a lightweight serialization format which is a subset of JavaScript's literal-object notation. It is a useful format to use for SPARQL results when a Web client is issuing the queries and processing the results. The DAWG has published a Note defining a JSON format that closely follows the SPARQL Query Results XML Format, and which can be used to return the results of SPARQL SELECT and ASK queries. public-sparql-dev@w3.

RIF is not yet a W3C Recommendation (or even a Candidate Recommendation), so for now it should only be used on an experimental basis. As it proceeds to Recommendation status, however, it will be accompanied by an answer to this question, which the RIF Working Group is chartered to produce.