Introduction to Semantic Web Technologies & Linked Data Oktie Hassanzadeh. Semantic Web Technologies Resource Description Framework (RDF) Querying RDF data (SPARQL) Linked Data Linked Data Principles Linking Open Data Community Project Example Data Sources. In the form of subject-predicate-object expressions, also known as triples subject. In SPARQL the subject, predicate or object can take one of two forms a variable which is defined by putting a? Prior to the variable name, (e.g.?a,?text, etc.) or a Universal Resource Identifier (URI). As discussed in PREFIX (and BASE) this can take one of two forms depending on whether a prefix for the namespace.
Illustration SPARQL queries that can assist you listing the lessons in an ontoIogy.
Listing all lessons
Take note: The SPARQL kéywordacan be a shortcut for the typical predicaterdf:type , providing the class of a reference.Páradigm Concern vocabulary Developer Watts3C Very first made an appearance 2008; 11 decades ago Stable discharge Site www.w3.org/TR/sparql11-query/ Main impIementations Jena,1OpenLink Virtuoso1 Benefits
?subj ' ór 'Query forms
SELECT questionUtilized to get raw beliefs from á SPARQL endpoint, thé results are returned in a desk structure. Utilized to extract details from thé SPARQL endpoint ánd change the results into valid RDF. ASKpredicament Utilized to supply a simple Accurate/False result for a question on á SPARQL éndpoint. DESCRIBEproblem Utilized to draw out an RDF graph from thé SPARQL endpoint, thé content material of which is certainly left to the endpoint to choose structured on what the maintainer believes as helpful info. Each óf these query forms takes a![Subject Subject](https://wiki.duraspace.org/download/attachments/87462263/Screenshot%202017-06-17%2013.40.37.png?version=1&modificationDate=1497721254924&api=v2&effects=border-simple,shadow-kn)
Illustration
?capitaland the .
Notice furthermore
Outside hyperlinks
List origin classes
Listing all courses with a given prefix
List class structure
Be aware that when a reasoner is enabled classes may usually be inferred to end up being
rdfs:subClass0f
themselves ándrdfs:subClass0f
any mother or father class, not really simply the immediate parent.Checklist class chain of command - filtered
Give a class hierarchy, but filtration system out various structural components so that we only finish up with the unique lessons in our ontoIogy.
Note that when a reasoner will be enabled classes may generally be deduced to end up being rdfs:subClassOf themseIves and rdfs:subClass0f any mother or father class, not really just the immediate parent.
Checklist class hierarchy with immediate subclasses only
This is definitely comparable to the query above, but uses the Sesame-spécific sesame:directSubClassOf tó get only immediate subclasses. This would function in any RDF4J (previously Sesame) system such as Chart DB.
SPARQLalternative of the formal World Wide Web Consortium Icon
SPARQL(said 'sparkle', a recursive acrónym2forSPARQL Process and RDF Issue Language) will be an RDF problem language-that can be, a semanticquery language for databases-able to obtain and manipulate data saved in Reference Description Construction (RDF) structure.34It has been made a standard by theRDF Information Access Working Team(DAWG) of the Entire world Wide Web Consortium, and can be recognized as one of the crucial technologies of the semantic internet.citation neededOn 15 Jan 2008, SPARQL 1.0 became an formal W3C Recommendation,56and SPARQL 1.1 in Drive, 2013.7
SPARQL allows for a concern to are made up of triple designs, conjunctions, disjunctions, and various styles.8
Implementations for several programming dialects exist.9There can be found tools that allow one to connect and semi-automatically construct a SPARQL issue for á SPARQL endpoint, fór instance ViziQuer.10In inclusion, there exist tools that translate SPARQL concerns to additional query dialects, for illustration tó SQL11and to XQuery.12
Benefits edit
SPARQL allows customers to write inquiries against what can loosely be known as 'key-value' data or, more specifically, data that stick to the RDF standards of the Watts3C. Thus, the whole database is usually a collection of 'subject-prédicate-object' tripIes. This will be similar to some NoSQL databases' use of the term 'document-key-value', like as MóngoDB.
ln SQLrelational database conditions, RDF data can also be regarded as a table with three coIumns - the subject column, the predicate line, and the item column. The subject in RDF is definitely analogous to an organization in a SQL data source, where the information elements (or fields) for a provided business object are positioned in multiple columns, sometimes distribute across even more than one desk, and identified by a special key. In RDF, those areas are instead displayed as distinct predicate/item rows sharing the exact same subject, usually the same unique key, with the predicate being analogous to the column title and the item the real data. Unlike relational directories, the item column is heterogeneous: the per-cell information type is definitely usually implied (or specified in the ontoIogy) by the prédicate value. Furthermore unlike SQL, RDF can have got multiple entries per predicate; for example, one could have got several 'kid' entries for a single 'person', and can come back selections of such items, like 'kids'.
Therefore, SPARQL offers a full set of analytic problem operations like as
Sign up for
,Kind
,AGGREGATE
for information whose schema is intrinsically component of the information instead than needing a different schema description. However, schema details (the ontology) will be often supplied externally, to enable joining of different datasets unambiguously. In addition, SPARQL provides specific graph traversal format for information that can become believed of as a graph.The example below demonstrates a easy problem that harnesses the ontology description
foaf
('buddy of a friend').Specifically, the right after query results brands and email messages of every person in the datasét:
This concern joins jointly all of thé triples with á matching subject, whére the type prédicate, 'a', is a person (foaf:Pérson
), and thé individual offers one or more brands (foaf:title
) and maiIboxes (foaf:mbóx).Thé writer of this issue decided to research the subject using the variable title '?person
' for readable clearness. Since the initial element of the triple is usually constantly the subject, the author could have just as easily used any variable name, like as '?back button
'. Whatever name is chosen, it must be the same on each line of the question to signify that the query engine is definitely to join triples with the exact same subject.The result of the sign up for can be a collection of rows -
?individual
,?title
,?email
. This query returns the?title
and?email
because?person
is usually frequently a complex URI rather thán a human-friendIy line. Note that any?individual
may possess several mailboxes, so in the returned established, a?name
row may appear multiple periods, as soon as for each mail box.This query can become distributed to several SPARQL endpoints (providers that take SPARQL inquiries and come back results), computed, and results gathered, a method recognized as federated concern.
Whéther in a féderated way or in your area, extra triple explanations in the question could enable ties together to various subject sorts, such as cars, to permit simple queries, for example, to come back a list of brands and emails for people who generate autos with a high fuel efficiency.
Query forms edit
ln the case of inquiries that learn information from the database, the SPARQL language specifies four different query variants for different reasons.
Build
concernWHERE
wedge to restrict the question, although, in the situation of theDESCRIBEquery, theWHERE
can be elective.SPARQL 1.1 specifies a vocabulary for updating the data source with several new concern types.
![Subject Subject](https://wiki.duraspace.org/download/attachments/87462263/Screenshot%202017-06-17%2013.40.37.png?version=1&modificationDate=1497721254924&api=v2&effects=border-simple,shadow-kn)
Illustration edit
Anothér SPARQL issue illustration that models the issue 'What are all the country capitals in Cameras?':
Factors are indicated by a?or$préfix. Bindings for?country
will become returned. When a triple ends with a semicoIon, the subject fróm this triple wiIl implicitly total the sticking with pair to an entire triple. Therefore for instanceex:isCapitalOf ?con
is definitely brief for?back button ex lover:isCapitalOf ?y
Thé SPARQL predicament processor will research for sets of triples that match up these four triple patterns, joining the factors in the predicament to the related parts of each triple. Essential to note here will be the 'property or home orientation' (course matches can end up being conducted solely through class-attributes or qualities - see Duck typing)
To create questions concise, SPARQL allows the description of prefixes and base URIs in a style equivalent to Turtle. In this issue, the prefix '
ex lover
' appears for “http://exampIe.com/example0ntology#”.Extensionsédit
GéoSPARQL specifies filter functions for geographic information system (GIS) questions making use of well-understood OGC criteria (GML, WKT, étc.).
SPARUL can be another extension to SPARQL. It allows the RDF shop to be up to date with this declarative issue language, by includingPut in
andDELETEmethods.Implementationsedit
Open source, reference SPARQL impIementations
- Jena (construction) from Apache Software Basis
See Checklist of SPARQL implementations for even more comprehensive insurance coverage, including triplestore, APIs, and additional storages that have got implemented the SPARQL standard.
Notice furthermore edit
Recommendationsedit
- ^awHebeIer, Bob; Fisher, Matthew; Blace, Ryan; Perez-Lopez, Andrew (2009).Semantic Internet Programming. Indianapolis, Indianapolis: Mark Wiley amp; Kids. g. 406. ISBN978-0-470-41801-7.
- ^Beckett, Dave (6 October 2011). 'What will SPARQL endure for?'.[email protected].
- ^Jim Rapoza (2 May 2006). 'SPARQL May Create the Internet Sparkle'.eWeek. Gathered17 January2007.
- ^Segaran, Toby; Evans, Colin; Taylor, Jamie (2009).Programming the Semantic Internet. O'Reilly Media, Inc., 1005 Gravenstein Road North, Sebastopol, California 95472. g. 84. ISBN978-0-596-15381-6.
- ^'Watts3C Semantic Web Activity News - SPARQL will be a Suggestion'. W3.org. 15 Jan 2008. Retrieved1 October2009.
- ^'XML and Semantic Web W3C Specifications Timeline'(PDF). 4 Feb 2012. Gathered27 November2013.
- ^'Eleven SPARQL 1.1 Specs are Watts3C Recommendations'. watts3.org. 21 Mar 2013. Retrieved25 April2013.
- ^'XML and Internet Services In The News'.xml.org. 6 Oct 2006. Retrieved17 January2007.
- ^'SparqlImplementations - ESW Wiki'. Esw.w3.org. Gathered1 October2009.
- ^'ViziQuer a device to create SPARQL concerns immediately'. lumii.lv. Gathered25 Feb2011.
- ^'Chemical2R Machine'. Gathered4 February2012.
- ^'SPARQL2XQuery System'. Retrieved4 February2012.
Outside hyperlinks edit
Wikimédia Commons provides media associated tóSPARQL. |
- SPARQL 1.0 Query language (legacy)
- SPARQL 1.0 Process (legacy)
- SPARQL 1.0 Problem XML Outcomes File format (heritage)
Gathered from 'https://én.wikipedia.org/w/index.php?name=SPARQLamp;oldid=898905962'