CANS 2008
Semantic Web‐based Knowledge Management
in Distributed Systems
Sabin C. Buraga
“A. I. Cuza” University of Iaşi, Romania
Faculty of Computer Science
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Outline
Goal
Semantic Web – challenges & realities
Knowledge management
Case studies
Conclusions
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Goal
Using semantic Web to model knowledge
within distributed systems
distributed file systems (Buraga, LNCS, Springer, 2002)
multi‐agent systems (Hritcu & Buraga, IEEE, 2005;
Buraga, Rusu & Cioca, CRC Press, 2008)
Web services (Buraga & Gabureanu, IEEE, 2003;
Buraga & Rusu, Elsevier, 2006; Brut & Buraga, IEEE, 2008)
Grid computing (Alboaie & Buraga, IEEE, 2003;
Brut & Buraga, IEEE, 2008)
collaborative Web applications (Dumitriu & Buraga, IEEE, 2007;
Dumitriu, Girdea & Buraga, AAAI, 2007; Luca & Buraga, ICEIS, 2008)
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Realities
Information overload
Same old keyword‐based search
Identity abuse the need for social verification
Web applications are still rigid:
each site has got its data and it is not sharing it
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Realities
computers can not understand anything
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Necessity
attaching metadata to Web resources
vocabularies describing “things”:
properties, domains, persons,…
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

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Necessity
specifying relations between resources
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Necessity
managing knowledge about things
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Necessity
The implicit knowledge must be explicitly specified
“java” ≡ language, island, or coffee?
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Necessity
The implicit knowledge must be explicitly specified
Java is a programming language
CANS is a workshop organized by the University of Tg. Mureş
Distributed systems can be complex
Statements that can be figured out by (some) people…
But the computers can understand them?
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Solution
RDF (Resource Description Framework)
attach metadata and specify relations between resources
a more flexible model than relational model of databases
important brick of the semantic Web
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
RDF
RDF model is based on triples
entity has property with value
URI/IRI URI/IRI
URI/IRI literal
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
RDF – examples
:Java rdf:type :Language
:CANS rdf:type :Workshop
:CANS :organisedBy :TgMuresUniv
:DistribSystem rdfs:subClassOf :ComplexSystem
:busaco :hasName \"Sabin Buraga\"
using (standard)
vocabularies
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Semantic mash‐ups via data repositories: Linked Open Data
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Ontologies
The need of modeling classes of resources and
complex relations/restrictions between them
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Ontologies
Knowledge about resources can be shared
within a given community of practice
structuring information conform to different points of view
AAA – Anyone can say Anything about Any topic
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Ontologies
Taxonomies
ACM, North American Industry Classification System,
Open Directory, Yahoo!
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

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Ontologies
Thesauri
AGROVOC, Center for Army Lessons Learned Thesaurus,
National Cancer Institute Thesaurus, WordNet
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Ontologies
Complex ontologies
Gene Ontology, OWL‐S: Process Ontology,
Transportation Ontology, Web Service Modeling Ontology,
Wine Ontology
IEEE Standard Upper Ontology, OpenCyC
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

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Ontologies
Financial ontology – excerpt (Amit Sheth, 2006)
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Ontologies
Ontology editing tools ontology (Buraga, Cojocaru & Nichifor, 2006)
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

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Ontologies
expressed by standardized languages
OWL (Web Ontology Language)
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Ontologies – example
Class (participant intersectionOf (student young person))
Class (participant
intersectionOf (
restriction (hasPet allValuesFrom (penguin))
restriction (hasPet someValuesFrom (animal))))
Inference
Every participant must have at least one penguin,
because her/his has a pet and all pets must be penguins
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Ontologies – example
ObjectProperty (hasPet domain (person) range (animal))
Individual (Alice type (young) type (student)
value (hasPet Tux))
Alice must be a person – owners of pets are persons –
and she is a participant
Tux must be a penguin (all pets of participants are penguins)
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Beyond ontologies
Using these statements, Web applications can reason
the need of specifying rules
if P is a participant, then P is paying attention
some participants are bright
support for
making decisions
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Semantic Web
Layers of the Semantic Web (Tim Berners‐Lee, 2006)
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

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Semantic Web vs. Distributed Systems
How semantic Web technologies could be used
to model knowledge within distributed systems?
distributed file systems
multi‐agent systems
Web/Grid services
collaborative Web applications: wikis
…
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Knowledge Management Issues
Advanced Knowledge Technologies (AKT) manifesto:
6 challenges concerning the engineering and
management of knowledge:
acquiring
modeling
reusing
retrieving
publishing
maintaining
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Knowledge Management Issues
The system should acquire knowledge, and not
formatted text – provided by the end‐users
A suitable model to store knowledge is a triple‐based one
(RDF model)
Semantic markups – embedding semantics within Web pages
microformats, RDFa etc.
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Knowledge Management Issues
Information gathering involves obtaining selected
(semi)structured data from external sources
RSS/Atom feeds, microformats, Web services,
CGI scripts, RDF stores, databases
examples: GRDDL (Gleaning Resource Descriptions
from Dialects of Languages), Triplify, Yahoo! Search Monkey
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

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Knowledge Management Issues
Knowledge modeling
although each piece of information should be semantically
modeled, this approach seems almost impossible in practice
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Knowledge Management Issues
Knowledge modeling
certain important information can be expressed by following
the object‐oriented paradigm
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Knowledge Management Issues
Knowledge modeling
classes needed to be used are identified
properties are defined
information regarding the individuals (class instances)
is filled in via collaborative mechanisms by the involved users
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Knowledge Management Issues
Knowledge modeling
information can be properly organized
for both human and computer access
information of interest can be rendered according to
the user needs and preferences
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

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Case Studies
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Grid Computing
Sharing, selection, and aggregation of world‐wide
distributed heterogeneous resources for solving
large‐scale problems in different areas of interest or
for proving access to massive repositories of data,
information, or knowledge
(Buyya, 2002; Abbas, 2004; Wells, 2008)
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Grid Computing
Grid resources – hardware, software, logical –
do not involve a particular central location
for their management
Simultaneous use of large number of resources
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Grid Computing
Related technologies:
peer‐to‐peer architectures
cluster computing
Internet & Web computing
cloud computing
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Grid Computing
One difficulty is a coherent management
of the Grid resources
we need to adopt a knowledge‐based methodology
very useful in the context of Semantic Web
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Semantic Grid
We propose to use this approach for modeling
the Grid services
using semantic Web‐based descriptions for Grid services,
the applications will automatically discover, invoke and
compose the desired services
inter‐operability & execution monitoring are also possible
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Semantic Grid
Example #1: attaching metadata to a Grid resource
accessed via a Web portal
XFiles (Buraga, LNCS, 2002) – a RDF/XML vocabulary
for specifying metadata regarding distributed file systems
we also adopt well‐known metadata standards:
EXIF, DCMI (Dublin Core Metadata Initiative),…
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Semantic Grid
Example #2: creating social networks of existing users
FOAF (Friend Of A Friend) vocabulary
Query via
<foaf:Person rdf:ID=\"jsbach\"> SPARQL
<foaf:name>Johann Sebastian Bach</foaf:name>
<foaf:givenname>Johann</foaf:givenname>
<foaf:family_name>Bach</foaf:family_name>
<foaf:homepage rdf:resource=\"http://www.music.org/bach\"/>
<foaf:knows rdf:resource=\"#vivaldi\" />
</foaf:Person>
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Semantic Grid Services
Grid services can be semantically enriched by
metadata and ontological descriptions
Semantic Web Services Framework (SWSF)
OWL‐S and Semantic Web Services Ontology
process ontologies for Web services
Web Service Modeling Ontology (WSMO)
Fensel et al., 2007
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Semantic Grid Services
Example #3: specifying a Grid service that offer access
to the metadata attached to a given resource
via WSMO declarations
we define basic operations regarding the resource storage,
considered as files
we can easily classify the resources by grouping them
on directories – a straightforward taxonomy
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Semantic Grid Services
Example #3: specifying a Grid service that offer access
to the metadata attached to a given resource
concepts (classes): file, owner, and directory
:File rdf:type owl:Class
:Owner rdf:type owl:Class
:Owner owl:disjointWith :File
…
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Semantic Grid Services
Example #3: specifying a Grid service that offer access
to the metadata attached to a given resource
relation: ownership
:ownership rdf:type rdf:Property
:ownership rdfs:domain :File
:ownership rdfs:range :Owner
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Semantic Grid Services
Example #3: specifying a Grid service that offer access
to the metadata attached to a given resource
axiom: restricts an owner to be effectively member
of the owner class
axiom ownershipFromOwner
definedBy ownership (?x, ?y) :−
?x [ ownerOf hasValue ?y ] memberOf owner .
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Semantic Grid Services
A possible instance could be:
instance bootstrapGlobusFile memberOf File
name hasValue ”bootstrap.jar”
hasOwner hasValue root
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Enterprise Collaborative Systems
A mechanism of knowledge management
must be provided by every collaborative Web system
a modern wiki must support user collaborative tools and
must allow attaching metadata to the concepts and relations
established between the involved concepts
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Enterprise Collaborative Systems
As a testbed, we choose XWiki
a second generation enterprise wiki
built on open technologies (Java)
architectural details in (Dumitriu, Girdea & Buraga, 2007)
www.wxiki.org
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Enterprise Collaborative Systems
The knowledge can be acquired via Web forms
the system gives the possibility to define classes, properties,
restrictions, etc. conforming to the RDF model
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Enterprise Collaborative Systems
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Enterprise Collaborative Systems
Extending XWiki to give support for microformats
(Dumitriu, Girdea & Buraga, AAAI, 2007)
generating standard microformats for each wiki document:
persons (hCard), events (hEvent),
reviews (hReview), tags (rel‐tag) etc.
defining a new microformat (hLocation) to specify
geographical locations in fuzzy terms: near, in front of,…
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Enterprise Collaborative Systems
We can model relations regarding the proximity of certain
points of interest for a given user/group
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Enterprise Collaborative Systems
A non‐intrusive microformats‐based recommender
agent (Luca & Buraga, ICEIS, 2008) is also provided
understands the behavior of a user on the Web and
filters out the irrelevant data, presenting to the user
only the information he/she is most interested in
machine learning, Java, JavaScript, native XML database
developed as a Firefox extension
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Conclusions
There are certain important challenges that concern
the engineering and management of knowledge
within complex distributed systems
One possible solution is to adopt the actual Semantic Web
technologies – metadata and ontological constructs –
for specifying the involved knowledge and processes
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Conclusions
It’s not the wires – it’s the computers
It’s not the computers – it’s the documents
It’s not the documents – it’s the things
“The last level of abstraction is the Web of real things,
built on top of the Web of documents,
which is in turn built on the network of computers.”
Tim Berners‐Lee, 2008
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Summary
Semantic Web‐based modeling of resources
– using microformats, metadata, and ontologies –
within distributed systems:
Grid applications and enterprise wikis
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco

CANS 2008
Thank you!
Questions?
Dr. Sabin‐Corneliu Buraga www.purl.org/net/busaco