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

Outline
About DERI
Why Semantic Web?
SPARQL
How?
Architecture
Installation
Examples
4

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

Linked Open Data - Growth
8

9

10

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

Outline
About DERI
Why Semantic Web?
SPARQL
How?
Architecture
Installation
Examples
21

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
23

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

Outline
About DERI
Why Semantic Web?
SPARQL
How?
Architecture
Installation
Examples
26

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

Outline
About DERI
Why Semantic Web?
SPARQL
How?
Architecture
Installation
Examples
29

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
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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, {})
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~/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")
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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
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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

by cosbas on Jul 04, 2009

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