Architecture Patterns for Semantic Web Applications

NONOSQLArchitecture Patterns for Semantic Web Applications Brian Panulla Penn State Web 2011 Conference

Three things the Semantic Web is not(mostly)

2. Warmed-over AI http://www.movieprop.com/tvandmovie/terminator/t3endoskeletons1.jpg

3. Magic http://bostonist.com/attachments/Anna%20Edwards/109-gob-magic2.jpg

Semantic Web http://xkcd.com/773/

Linked Data - 2008 http://richard.cyganiak.de/2007/10/lod/

Linked Data - 2008 http://richard.cyganiak.de/2007/10/lod/ Last updated: 2010-09-22

RDF: Framework for knowledge representation Declares resources Specifies properties of resources W3C standard since 1999 http://www.w3.org/RDF/

What is a Resource? Everything on the web (or not) is a resource. Uniform Resource Locator

RDF is not XML ...but occasionally dresses up like it XML N-Triples N3 Turtle JSON RDFa in HTML ...

URIs Resources are identified by a Uniform Resource Identifier (URI) Can be found in your XHTML DTD and html tag’s xmlns attribute:

URIs ... Are not necessarily URLs http://webconference.psu.edu http://brian.panul.la http://alumni.psu.edu/brian.panulla

Triples RDF is expressed as triples of URIs: subject (“Penn State”) - resource predicate (”is a") - property object (”University”) - resource Is a Penn State University

Triples Another example: subject (“Brian Panulla”) predicate (”presented at") object (”psuweb11”) presented At Brian Panulla psuweb11

Triples to Graphs United States of America City of Portland State of Oregon North America State of Washington State of California Canada NATO Is a borders Is in Held At Is in Member of presented At Is in borders Member of attended Is in Is in Is a Is located in Is in PSUWEB11 Penn State Brian Panulla Portland State University

RDF Schemas RDFS provides limited Set Theory features subClassOf subPropertyOf Domain Range Think of classes in RDFS as sets rather than OOP classes

Ontologies Ontology is the study of being or reality. A Formal Ontology is a specification of a conceptualization (Gruber, 1995) Aristotle

Defining an ontology Web Ontology Language (OWL) Version 2.0 (October 2009) http://www.w3.org/TR/owl2-overview/ Yes, rly.

Some RDFS/OWL Features Classes Sub-class Equivalent Classes Disjoint Classes Cardinality constraints (max/min) Individuals Same Individual Properties Sub-property Equivalent Inverse Symmetric Transitive

Protégéhttp://protege.stanford.edu/

Triple Stores Graph database that knows RDF Quad Stores: triple store that includes provenance “where did the data come from?” Various stores provide Transactional / non-Transactional In-Memory / File system / RDBMS storage

Popular Triple Stores HP/Apache Jena Pellet Reasoner Storage In memory RDBMS (transactions) Filesystem storage (high performance) Open Source

Popular Triple Stores Franz AllegroGraph (server) Virtuoso Universal Server (server) Mulgara (RESTful service, OSS) Redland (C, Obj-C) New Stardog - Integrated reasoning database RDFa API - https://github.com/webr3/rdf.js

Basic Requirements Information People Bookmarks Tags Functionality Create an account Add a bookmark Delete a bookmark Browse other users’ bookmarks

Relational DB - Physical Schema

Modeling in RDF Minimize artificial entities Re-use existing schemas or ontologies

Useful Schemas Dublin CORE METADATA INITIATIVE (DCMI) FrienD-of-a-friend (FOAF)

FOAF Well-defined ontology for people, organizations, and social networks

RDF Data Model - Member foaf:Person foaf:fullname foaf:nickname foaf:mbox foaf:openid Literal (“datataype”)properties Resource (“object”) property

RDF Data Model - Bookmark foaf:Document dct:title dct:description dct:created dct:modified foaf:page foaf:topic Literal (“datataype”)properties Resource (“object”) properties

Topics from DBPedia SemantifiedWikipedia

Custom properties and classes omnom:bookmarked http://omnomino.us/ontology/om.n3#bookmarked omnom: bookmarked foaf: Document foaf: Person

Custom properties and classes rdfs: subClassOf rdfs: subClassOf foaf: Document foaf: Person omnom: Member omnom: Resource

SPARQL Graph query language Read-only (1.0) Safe to expose endpoint to Web SPARQL 1.1 adds updates

A Simple SPARQL Example SELECT ?subj ?pred ?obj WHERE { ?subj ?pred ?obj. } Demo

SPARQL Query Types SELECT – Returns tuples matching specified pattern ASK – yes or no (tests for existence) CONSTRUCT – Returns a graph DESCRIBE – Returns a graph determined by the query engine

SPARQL Examples: ASK ASK { ?urifoaf:openid <http://brian.panul.la>. }

SPARQL Examples: Member SELECT DISTINCT ?uri ?fullname ?nickname ?email WHERE { ?uri a omnom:Member. OPTIONAL { ?urifoaf:name ?fullname; foaf:nick ?nickname; foaf:mbox ?email. } FILTER (?uri = <http://omnomino.us/member/24601>)

The Good: Domains where schemas/models change rapidly or data is sparse Semantics of relational model inadequate (e.g. inferencing, inheritance) Domains emphasizing relationships Social networks Taxonomies

The Bad: Weaknesses Bad for opaque objects with few relationshps Large sets of homogenous objects Alternatives RDBMS NoSQL Document DBs Key/Value Stores Graph databases

Linked Data Publish/Syndicate complete information sets Embedded explicit semantics, unique identifiers Have minimal impact to other Web information publishing May be static or dynamically generated

Resources Semantic Web Programming - John Hebeler, Matthew Fisher, Ryan Blace, and Andrew Perez-Lopez Semantic Web for the Working Ontologist: Effective Modeling in RDFS and OWL -Dean Allemang and James Hendler Programming the Semantic Web by Toby Segaran, Colin Evans, and Jamie Taylor

Architecture Patterns for Semantic Web Applications

Recommended

Recommended

More Related Content

What's hot

What's hot (16)

Viewers also liked

Viewers also liked (7)

Similar to Architecture Patterns for Semantic Web Applications

Similar to Architecture Patterns for Semantic Web Applications (20)

Architecture Patterns for Semantic Web Applications

Editor's Notes