SuRf – Tapping Into The Web Of Data

SuRF – Tapping into the Web of Data Cosmin Basca Digital Enterprise Research Institute, Galway cosmin.basca@gmail.com Special Thanks to: Benjamin Heitman andUldis Bojars Digital Enterprise Research Institute, Galway firstname.lastname@deri.org

Outline About DERI Why Semantic Web? Linked Open Data (LOD) RDF (Resource Description Framework) SPARQL O-RDF Mapping (ActiveRDF / SuRF) How? Architecture Installation Examples Simple: access DBpedia (Semantic Wikipedia) More complex: create a blog on top of RDF 2

DERI – http://www.deri.ie/ Digital Enterprise Research Institute (DERI): http://www.deri.ie/ main goal: enabling networked knowledge research about the future of the Web biggest Semantic Web research institute in the world 120 people part of the National University of Ireland, Galway 3

Why ? Develop Web applications that allow Data Integration Flexibility Schema definition and modeling Schema evolution Robustness Support for new Data Sources Types 5

There is a Wealth of (RDF) data out there 6

Popular Semantic Web Vocabularies FOAF = for describing people and social network connections between them http://xmlns.com/foaf/spec/ SIOC = for describing Social Web content created by people http://sioc-project.org/ DOAP = for describing software projects http://trac.usefulinc.com/doap used by PyPi 7

The data model Traditional Approach use the Relational model Usually leads to big ugly Schemas 11

The RDF (Graph) Data model Flexible Support for both schema and data evolution during runtime Simple model Relations are represented explicitly Schema is a graph Can integrate data – union of two graphs 12

The RDF (Graph) Data model 13 Subject Object Predicate A triple is a Eric Person

Example RDF graph describing Eric Miller (RDF Primer) – human readable format 14 Person is a Eric has full name Eric Miller has e-mail em@w3.org has personal title Dr.

Example RDF graph describing Eric Miller (RDF Primer) – machine readable format 15 http://w3.org/2000/10/swap/pic/contact#Person http://www.w3.org/1999/02/22-rdf-syntax-ns#type http://w3.org/People/EM/contact#me http://www.w3.org/2000/10/swap/pim/contact#fullName Eric Miller http://www.w3.org/2000/10/swap/pim/contact#mailbox mailto:em@w3.org http://www.w3.org/2000/10/swap/pim/contact#personalTitle Dr.

The RDF (Graph) Data model – Identification URI’s provide strong references The URIref is a an unambiguous pointer to something of meaning Nodes (“Subjects”) connect via Links (“Predicates”) to Objects Can be Nodes or Literals (plain or typed strings) 16

SPARQL – Querying the Semantic Web SPARQL is to RDF what SQL is to Relational tables Expressive, designed with the Graph data model in mind 17 Carrie Fisher starred_in Star Wars starred_in Harrison Ford starred_in Blade Runner starred_in Darryl Hannah SELECT ?actor ?movie WHERE { ?actor starred_in ?movie }

Levels of Data abstraction 18 Direct SPARQL Access O-RDF Mapper SuRF

O-RDF Mapper, Why? Clean OO design Increased productivity model is free from persistence constraints Separation of concerns and specialization ORMs often reduce the amount of code needed to be written, making the software more robust 20% to 30% less code needs to be written Less code – less testing – less errors 19

O-RDF Mapper, How? How do we see RDF data? As a SET of triples? As a SET of resources? The resource view is more suitable for the OO model How do we define an RDF resource ? All triples <S,P,O>with same subject (ActiveRDF, SuRF) And all triples <O,P,S> (SuRF) Apply Open World principles 20

SuRF – Semantic Resource Framework Inspired by ActiveRDF Developed in DERI for ruby Expose RDF as sets of resources Semantic attributes exposed as a “virtual API”, generated through introspection. Naming convention: instance.namespace_attribute cosmin.foaf_knows Finder methods Retrieve resources by type or by attributes Session keeps track of resources, when calling session.commit() only dirty resources will be persisted 22

SuRF – Architecture – Currently supported plugins 24 Add your own plugins, extend: surf.store.plugins.RDFReader surf.store.plugins.RDFWriter Redefine the __type__ attribute This is the plugin identifier To install plugins import my_plugin

SuRF - installation Available on PyPi easy_install –U surf (to get the latest) Open-source available on Google Code, BSD licence http://code.google.com/p/surfrdf/ 25

DBpedia public SPARQL endpoint - read-only Create the store proxy from surf import* store = Store(reader='sparql-protocol',endpoint='http://dbpedia.org/sparql', default_graph='http://dbpedia.org') Create the surf session print'Create the session'session =Session(store,{}) Map a dbpedia concept to an internal class PhilCollinsAlbums=session.get_class(ns.YAGO['PhilCollinsAlbums']) SuRF – simple example 27

SuRF – simple example DBpedia public SPARQL endpoint - read-only Get all Phill Collins albums all_albums=PhilCollinsAlbums.all() Do something with the albums (display the links to their covers) print'All covers'for a inall_albums: ifa.dbpedia_name: print'Cover %s for "%s"'%(a.dbpedia_cover,a.dbpedia_name) 28

SuRF – integrate into Pylons Create a blog on top of an RDF database Replace SQLAlchemy with SuRF Download and install either AllegroGraph Free Edition (preferred) or Sesame2 http://www.franz.com/downloads/clp/ag_survey Free for up to 50.000.000 triples (records) Install pylons: easy_install pylons Install SuRF: easy_install surf Create a pylons application: paster create -t pylons MyBlog cd MyBlog 30

SuRF – Pylons Blog ~/MyBlog/development.ini: In the [app:main] section add rdf_store = localhost rdf_store_port = 6789 rdf_repository = tagbuilder rdf_catalog = repositories ~/MyBlog/myblog/config/environment.py from surf import * rdf_store = Store( reader = 'sparql-sesame2-api', writer = 'sesame2-api', server = config['rdf_store'], port = config['rdf_store_port'], catalog = config['rdf_catalog'], repository = config['rdf_repository']) rdf_session = Session(rdf_store, {}) 31

SuRF – Pylons Blog ~/MyBlog/myblog/model/__ init __.py from surf import * definit_model(session): global rdf_session rdf_session = session # register a namespace for the concepts in my blog ns.register(myblog=‘http://example.url/myblog/namespace#’) Blog = rdf_session.get_class(ns.MYBLOG[‘Blog’]) Create the blog controllerpaster controller blog ~/MyBlog/myblog/controllers/blog.py import logging frommyblog.lib.baseimport * log = logging.getLogger(__name__) classBlogController(BaseController): def index(self): c.posts = model.Blog.all(0,5) return render("/blog/index.html") 32

SuRF – Pylons Blog Create the template mkdir ~/MyBlog/myblog/templates/blog ~/MyBlog/myblog/templates/blog/index.html <%inherit file="site.html" /> <%def name="title()">MyBlog Home</%def> ${len(c.posts)} new blog posts! % for post inc.posts: ${post.myblog_title} Posted on: ${post.myblog_date} by ${post.myblog_author} ${post.myblog_content} % endfor ~/MyBlog/myblog/templates/blog/site.html Start the development built in server: paster serve --reload development.ini 33

SuRF – Tapping into the Web of Data Can tap into the web of Data SPARQL endpoints Local or remote RDF Stores Plugin framework, allows for more access protocols to be defined Code is generated dynamically (pragmatic bottom up approach): Introspection, meta-programming, exposing a virtual API (defined by the data and the schema) to the developer Can easily be integrated into popular python frameworks pylons 34

exit() cosmin.basca@deri.prg http://code.google.com/p/surfrdf/ easy_install –U surf 35

SuRf – Tapping Into The Web Of Data

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