Title: Uncertainty and Semantic web
1Uncertainty and Semantic web
2Agenda
- Define uncertainty
- Provide background
- Show areas of research
- Highlight various approaches
- Provide a demonstration of Pronto
3Definition - Uncertainty
- Knowledge can be inaccurate or incomplete
- Knowledge can be imprecise or fuzzy
- .leads to uncertainty
4Definition - Uncertainty
- Machine-readable information
- Applications that work with random information
(image processing, geospatial, information
retrieval, etc.) - Ontology concept definitions
- Vague concepts
- Tall, Small, Big, .
- Green, Blue, .
- Few, Many, .
- Semantic web services
- .work with uncertainty
5Background Description Logic Naming Conventions
Taken from Wikipedia 12.
6Is representing uncertainty necessary?
- Tim Berner-Lee rejection of uncertainty
- Not necessary 7
- Scalability issues 7
7Can you describe knowledge using a monotonic
bivalent language7?
8What about grey?
Uncertainty
9Is it necessary?
Taken from 5 presented at the URSW 2008.
10General Approaches to Uncertainty and Semantic
Web
- Incomplete/Distorted knowledge 1
- Possibility degrees alternatives
- Inability to define concepts precisely 1
- Degree of truth
- Conflicting alternatives 1
- Degree of probability
- According to 1, since how we solve uncertainty
problems depends upon the domain, it is hard to
define a single language extension.
11Areas of Research (based upon 2007/2008 URSW
Conference agendas)
- Extending Semantic Web to support uncertainty
- Fuzzy theory
- Probability theory
- Uncertainty and Ontologies
- Uncertainty and Web Services
12Extending the Semantic Web
- Extend Semantic Web languages to support
probabilistic, possibilistic, and fuzzy reasoning - Can be at the ontology layer or the rules layer
- Within the ontology layer proposals for
- Syntax and Semantics
- Logical Formalisms
13Fuzzy Theory
- In classical set theory, the membership of
elements in a set is assessed in binary terms
according to a bivalent condition an element
either belongs or does not belong to the set. By
contrast, fuzzy set theory permits the gradual
assessment of the membership of elements in a
set this is described with the aid of a
membership function valued in the real unit
interval 0, 110
14Fuzzy Approaches
- Extending languages such as OWL with fuzzy
extensions - Extending Description Logic with fuzzy extensions
- If a language is extended, one must provide a way
to support reasoning of the language with the
fuzzy extension
15Rules and Uncertainty
- Rules Interchange Format
- Rules Markup Language
- For representing/interchanging rules
- Attempt to provide ways to represent various
types of uncertainty 1 - Not as much recent attention as ontology layer
- fuzzy RuleML defines way to specify membership
degree 1 - Example
Taken from 1.
16Fuzzy RDF
- Extends syntax and semantics of RDF
- Triple extended to support real number on the
interval 0,1 - n s p o 13
- Interpretation
- Subject, object has degree of membership to
extension of predicate 13 - Satisfies statement if
- Membership degree of subject, object to the
extension of the predicate is gt to n 13
17Fuzzy RDF
- RDFS extended
- Class extensions are fuzzy sets of domain
elements 13 - Domains are fuzzy and their assignment to
properties can also be fuzzy 13 - Inference engines can be extended to support such
fuzziness
18Fuzzy Description Logic
- Fuzzy
- One such proposal
- Solve problem of representing and reasoning of
fuzzy concepts - With concrete domains reasoning
using concrete data types - With fuzzy version domains are fuzzy
- Modifiers are supported (very, slightly, etc.)
12
19Fuzzy Description Logic
Non-fuzzy Concrete Domain
Concrete Fuzzy Domain
Taken from 12.
20Fuzzy Description Logic
- Interpretations are fuzzy
- From satisfied/unsatisfied to a degree of truth
0,1 - Satisfiability of fuzzy axiom given fuzzy
interpretation 12 - Fuzzy axiom a logical consequence of a knowledge
base iff every model in the knowledge base
satisfies the fuzzy axiom 12 - Reasoning a problem
- Computationally no calculus exists to check for
satisfiability of a fuzzy knowledge model 12
21Fuzzy OWL
- Extension of OWL
- Example (describing the safety of a location)
- Without fuzzy, the location is either safe or not
safe - With fuzzy, the location is safe to a degree
- Classes and properties are fuzzy
- A class is considered a fuzzy set 1
- A property is a fuzzy relation over a set 1
22Fuzzy OWL
- Requires extension of to map OWL
entailment to satisfiability 4 - Reasoning changes in that when concepts are
represented as nodes in forest-like
representations, a membership degree is
associated with each node indicating it belongs
to a concept 4 - Degrees added to OWL facts
23Fuzzy OWL
Taken from 4.
24Probability Theory
- ..the central objects of probability theory are
random variables, stochastic processes, and
events mathematical abstractions of
non-deterministic events or measured quantities
that may either be single occurrences or evolve
over time in an apparently random fashion 11
25PR-OWL
- Developed as an extension to OWL (basically an
upper ontology) - Represents complex Bayesian models 21
- Uses MEBN logic rather than extending OWL
- A first order Bayesian logic 21
- Consists of entities and attributes
- Attributes about entities and relationships to
each other MEBN fragments (MFrag) 21 - Represent conditional probability distribution
21 - MFrags organized into MEBN Theories (MTheories)
21 - Collectively satisfy consistency constraints 21
- Goal
- Provide a way to support Bayesian models
26PR-OWL
Taken from 21.
27BayesOWL
- Express OWL ontologies as Bayesian networks by
means of rules - For each node, a conditional probability table
(CPT) is constructed 15 - All subject and object classes translated into
concept nodes 15 - Arc drawn between 2 concept nodes if the 2
classes are related by predicate 15 - Direction based on class hierarchy
- L-Nodes generated during translation to represent
OWL logical operators - True/false value for each node indicates whether
the instance belongs to the concept - CPTs are approximated using the iterative
proportional fitting procedure (IPFP) 15 - Restricted currently to OWL-DL taxonomies 15
- Goals
- Support ontology reasoning using probabilistic
approach - Support ontology mapping
28BayesOWL
rdfssubClassOf
owlintersectionOf
owlunionOf
owlcomplementOf owlequivalentClass
owldisjointWith
Taken from 15.
29BayesOWL
- DAG constructed
- CPTs for L-Nodes specified
- Concept nodes approximated using D-IPFP
Taken from 15.
30BayesOWL
- Reasoning Support 15
- Concept satisfiability
- Concept overlapping
- Concept subsumption
- Extensions to OWL to support probabilistic
representation 15 - PriorProb
- CondProb
- Concept Mapping 15
31BayesOWL
Extensions to OWL Taken from 15.
32Pronto
- Non-monotonic probabilistic DL reasoner
- Built on top of Pellet
- Uses P-SHIQ(D) formalism 8
- Expressing uncertain axioms
- Syntax based upon Lukasiewiczs conditional
constraints 8 - Probabilistic Reasoning
- Lehmanns lexicographic entailment 8
- Represents uncertain ontological knowledge and
reasoning 8 - Capable of representing uncertainty in both ABox
and TBox axioms 8 - All inferences are done in a totally logical
way (no translation) 8 - Uses OWL 1.1 axiom annotations to associate
probability intervals with uncertain OWL axioms
8 - Doesnt scale beyond 15 generic (TBox)
conditional constraints 9
33Pronto
- Conditional constraints
- (DC)l,u
- C and D concepts in P-SHIQ(D)
- l,u closed interval within 0,1
- Supports overriding
- Can handle certain probabilistic conflicts
- Flying birds/penguin problem
- Pronto allows more specific constraints to
override more generic ones 9 - if Pronto knows that Tweety is a Penguin and
Penguin is a subclass-of Bird, it will override
the constraint (FlyingObjectBird)0.91.0 by
(FlyingObjectPenguin)0.00.05 and correctly
entail Tweety(FlyingObjectowlThing)0.00.05.
9
34Uncertainty and Ontologies - Mapping
- Mapping a problem
- Existing approaches - combination of syntactic
and semantic measures 18, use machine learning,
or linguistics and natural language processing
15 - Quality varies depending upon domain 18
- Wang argues without use of a thesaurus,
inaccuracies will occur 22 - Problem
- When mapping a concept from ontology A to
ontology B there isnt always a single concept
match but rather a number of concepts that match
to some degree
35Uncertainty and Ontologies - Mapping
- A proposed truth theory solution based on the
following 18 - Dempster-Shafer, uncertain reasoning over
potential mappings - Evidence Theory
- Similarity matrix comparing all
concepts/properties - Similarity measure of a concept between O1 and O2
- DS combines evidence learned to form new belief
- Promising approach
- Multi-agent ontology mapping framework 18
- Not domain dependent
- Doesnt require large amounts of training data
36Uncertainty and Ontologies - Mapping
- A proposed solution by Wang 22
- ACAOM
- Uses WordNet to calculate similarities for node
names - Name based mapping
- Instance strategy
- More semantics more feasible to match
- Documents assigned to nodes
- Uses vector space models to rank matches
37Uncertainty and Ontologies - Mapping
- BayesOWL 15 also proposed a solution
- Argue that existing similarity approaches will
not work - If degree of similarity is not present in both
concepts being matched 15 - If concept itself is fuzzy 15
- Uses BayesOWL and belief propagation between BNs
15 - Ontologies are first translated into BNs 15
- Use probabilistic evidence reasoning to determine
match 15
38Uncertainty and Ontologies An Ontology of
Uncertainty
- Proposed by the W3C UR3W-XG group
- Provides a vocabulary for representing different
types of uncertainty - Was a good start but refinement needed 20
- Strategy to use such an ontology as a way to
drive a reasoner - Open issue coordination of reasoning of
different uncertainty models in knowledge base
19 - Uses SWRL rules to assign uncertainty to each
relation 19
39Uncertainty and Ontologies An Ontology of
Uncertainty
Taken from 20.
40Uncertainty and Web Services
- Service discovery what is best service for
request? - Matching goal to service
- Brokers used for filtering
- Semantic Web Service Framework
- Semantic Web Service Language
concepts/descriptions 17 - Semantic Web Service Ontology conceptual model
17 - It is argued that current frameworks use first
order and description logics and goal
capabilities are based on subsumption checking
or query-answering16 - Proposed approach uses Incident Calculus 16
41Demo - Pronto
- Pronto Example Breast Cancer Risk Models
- Models 2 types of risks absolute and relative
- Combining risk factors to determine likelihood of
breast cancer for a woman 8 - Distinction between known and inferred
- Pronto uses an ontology for knowledge
- Uses probabilistic statements to enable
computable inferencing 8 - The probabilistic statements complement the OWL
syntax
42Demo - Pronto
- Risk factors relevant to breast cancer are
subclasses of RiskFactor - Categories of women that have certain risk
factors are subclasses of WomanWithRiskFactors - Women with risk of developing cancer subclass
WomanUnderBRCRisk - The goal
- Compute the probability that a certain woman is
an instance of some WomanUnderBRCRisk subclass
given that she is an instance of some
WomanWithRiskFactors subclass 8 - Infer generic probabilistic subsumption between
classes under WomanUnderBRCRisk and under
WomanWithRiskFactors 8 - Conditional constraints are used to represent
uncertain background knowledge using the OWL
1.1 axiom annotations 8 - The demo defines constraints to express how risk
factors influence the risk of developing cancer
8 - Pronto combines the factors and computes the
probability that a woman is an instance of a
subclass of WomanUnderBRCRisk
43Demo - Pronto
- ltowlObjectProperty rdfabout"hasRiskFactor"gt
- ltrdfsdomain rdfresource"Person"/gt
- ltrdfsrange rdfresource"RiskFactor"/gt
- lt/owlObjectPropertygt
- ltowlClass rdfabout"WomanTakingEstrogen"gt
- ltowlequivalentClassgt
- ltowlRestrictiongt
- ltowlonProperty
rdfresource"hasRiskFactor"/gt - ltowlsomeValuesFrom
rdfresource"Estrogen"/gt - lt/owlRestrictiongt
- lt/owlequivalentClassgt
- ltrdfssubClassOf rdfresource"Woman"/gt
- lt/owlClassgt
- Taken from http//clarkparsia.com/pronto/cancer_ra
.owl
44Demo - Pronto
- ltowlClass rdfabout"WomanWithRiskFactors"gt
- ltowlequivalentClassgt
- ltowlClassgt
- ltowlintersectionOf
rdfparseType"Collection"gt - ltrdfDescription
rdfabout"Woman"/gt - ltowlRestrictiongt
- ltowlonProperty
rdfresource"hasRiskFactor"/gt - ltowlsomeValuesFrom
rdfresource"RiskFactor"/gt - lt/owlRestrictiongt
- lt/owlintersectionOfgt
- lt/owlClassgt
- lt/owlequivalentClassgt
- ltrdfssubClassOf rdfresource"Woman"/gt
- lt/owlClassgt
- Taken from http//clarkparsia.com/pronto/cancer_ra
.owl
45Demo - Pronto
- ltowlClass rdfabout"WomanAgedUnder50"gt
- ltowlequivalentClassgt
- ltowlClassgt
- ltowlintersectionOf
rdfparseType"Collection"gt - ltrdfDescription
rdfabout"Woman"/gt - ltowlRestrictiongt
- ltowlonProperty
rdfresource"hasAge"/gt - ltowlsomeValuesFrom
rdfresource"AgeUnder50"/gt - lt/owlRestrictiongt
- lt/owlintersectionOfgt
- lt/owlClassgt
- lt/owlequivalentClassgt
- ltrdfssubClassOf rdfresource"WomanWithR
iskFactors"/gt - lt/owlClassgt
- Taken from http//clarkparsia.com/pronto/cancer_ra
.owl
46Demo - Pronto
- ltowlClass rdfabout"WomanUnderAbsoluteBRCRisk"
gt - ltowlequivalentClassgt
- ltowlClassgt
- ltowlintersectionOf
rdfparseType"Collection"gt - ltrdfDescription
rdfabout"Woman"/gt - ltowlRestrictiongt
- ltowlonProperty
rdfresource"hasRisk"/gt - ltowlsomeValuesFrom
rdfresource"AbsoluteBRCRisk"/gt - lt/owlRestrictiongt
- lt/owlintersectionOfgt
- lt/owlClassgt
- lt/owlequivalentClassgt
- lt/owlClassgt
- Taken from http//clarkparsia.com/pronto/cancer_ra
.owl
47Demo - Pronto
- ltowlClass rdfabout"WomanUnderBRCRisk"gt
- ltowlequivalentClassgt
- ltowlClassgt
- ltowlintersectionOf
rdfparseType"Collection"gt - ltrdfDescription
rdfabout"Woman"/gt - ltowlRestrictiongt
- ltowlonProperty
rdfresource"hasRisk"/gt - ltowlsomeValuesFrom
rdfresource"BRCRisk"/gt - lt/owlRestrictiongt
- lt/owlintersectionOfgt
- lt/owlClassgt
- lt/owlequivalentClassgt
- lt/owlClassgt
- Taken from http//clarkparsia.com/pronto/cancer_ra
.owl -
48Demo - Pronto
- ltowlClass rdfabout"WomanUnderIncreasedBRCRisk"
gt - ltowlequivalentClassgt
- ltowlClassgt
- ltowlintersectionOf
rdfparseType"Collection"gt - ltowlRestrictiongt
- ltowlonProperty
rdfresource"hasRisk"/gt - ltowlsomeValuesFrom
rdfresource"IncreasedBRCRisk"/gt - lt/owlRestrictiongt
- ltrdfDescription
rdfabout"WomanUnderBRCRisk"/gt - lt/owlintersectionOfgt
- lt/owlClassgt
- lt/owlequivalentClassgt
- lt/owlClassgt
- Taken from http//clarkparsia.com/pronto/cancer_ra
.owl
49Demo - Pronto
- ltowlClass rdfabout"WomanUnderLifetimeBRCRisk"gt
- ltowlequivalentClassgt
- ltowlClassgt
- ltowlintersectionOf
rdfparseType"Collection"gt - ltrdfDescription
rdfabout"Woman"/gt - ltowlRestrictiongt
- ltowlonProperty
rdfresource"hasRisk"/gt - ltowlsomeValuesFrom
rdfresource"LifetimeBRCRisk"/gt - lt/owlRestrictiongt
- lt/owlintersectionOfgt
- lt/owlClassgt
- lt/owlequivalentClassgt
- ltrdfssubClassOf rdfresource"WomanUnder
AbsoluteBRCRisk"/gt - lt/owlClassgt
- Taken from http//clarkparsia.com/pronto/cancer_ra
.owl
50Demo - Pronto
- ltowlClass rdfabout"WomanUnderModeratelyIncrea
sedBRCRisk"gt - ltowlequivalentClassgt
- ltowlClassgt
- ltowlintersectionOf
rdfparseType"Collection"gt - ltrdfDescription
rdfabout"WomanUnderIncreasedBRCRisk"/gt - ltowlRestrictiongt
- ltowlonProperty
rdfresource"hasRisk"/gt - ltowlsomeValuesFrom
rdfresource"ModeratelyIncreasedBRCRisk"/gt - lt/owlRestrictiongt
- lt/owlintersectionOfgt
- lt/owlClassgt
- lt/owlequivalentClassgt
- ltrdfssubClassOf rdfresource"WomanUnder
IncreasedBRCRisk"/gt - ltowldisjointWith rdfresource"WomanUnde
rStronglyIncreasedBRCRisk"/gt - lt/owlClassgt
- Taken from http//clarkparsia.com/pronto/cancer_ra
.owl
51Demo - Pronto
- ltowlClass rdfabout"WomanUnderModeratelyReduce
dBRCRisk"gt - ltowlequivalentClassgt
- ltowlRestrictiongt
- ltowlonProperty
rdfresource"hasRisk"/gt - ltowlsomeValuesFrom
rdfresource"ModeratelyReducedBRCRisk"/gt - lt/owlRestrictiongt
- lt/owlequivalentClassgt
- ltrdfssubClassOf rdfresource"WomanUnder
ReducedBRCRisk"/gt - ltowldisjointWith rdfresource"WomanUnde
rStronglyReducedBRCRisk"/gt - ltowldisjointWith rdfresource"WomanUnde
rWeakelyReducedBRCRisk"/gt - lt/owlClassgt
- Taken from http//clarkparsia.com/pronto/cancer_ra
.owl
52Demo - Pronto
- lt!--Lifetime absolute risk--gt
- lt!-- Any woman has a 12.3 risk of lifetime
breast cancer --gt - ltowl11Axiomgt
- ltrdfsubject rdfresource"Woman"/gt
- ltrdfpredicate rdfresource"rdfssubClas
sOf"/gt - ltrdfobject rdfresource"WomanUnderLifet
imeBRCRisk"/gt - ltprontocertaintygt00.123lt/prontocertaint
ygt - lt/owl11Axiomgt
- lt!-- If a woman has BRCA mutation, then the
risk is beteen 30 and 85 --gt - ltowl11Axiomgt
- ltrdfsubject rdfresource"WomanWithBRCAM
utation"/gt - ltrdfpredicate rdfresource"rdfssubClas
sOf"/gt - ltrdfobject rdfresource"WomanUnderLifet
imeBRCRisk"/gt - ltprontocertaintygt0.30.85lt/prontocertain
tygt - lt/owl11Axiomgt
- lt!-- If it's BRCA1 mutation, then the
lifetime risk is between 60 and 80 --gt
53Demo - Pronto
- lt!-- Age-related risk--gt
- ltowl11Axiomgt
- ltrdfsubject rdfresource"WomanAgedUnder
20"/gt - ltrdfpredicate rdfresource"rdfssubClas
sOf"/gt - ltrdfobject rdfresource"WomanUnderShort
TermBRCRisk"/gt - ltprontocertaintygt00.0005lt/prontocertain
tygt - lt/owl11Axiomgt
- ltowl11Axiomgt
- ltrdfsubject rdfresource"WomanAged2030"
/gt - ltrdfpredicate rdfresource"rdfssubClas
sOf"/gt - ltrdfobject rdfresource"WomanUnderShort
TermBRCRisk"/gt - ltprontocertaintygt00.004lt/prontocertaint
ygt - lt/owl11Axiomgt
- ltowl11Axiomgt
- ltrdfsubject rdfresource"WomanAged3040"
/gt - ltrdfpredicate rdfresource"rdfssubClas
sOf"/gt - ltrdfobject rdfresource"WomanUnderShort
TermBRCRisk"/gt
54Demo - Pronto
- ltowl11Axiomgt
- ltrdfsubject rdfresource"WomanAged4050"
/gt - ltrdfpredicate rdfresource"rdfssubClas
sOf"/gt - ltrdfobject rdfresource"WomanUnderShort
TermBRCRisk"/gt - ltprontocertaintygt00.025lt/prontocertaint
ygt - lt/owl11Axiomgt
- ltowl11Axiomgt
- ltrdfsubject rdfresource"WomanAged5060"
/gt - ltrdfpredicate rdfresource"rdfssubClas
sOf"/gt - ltrdfobject rdfresource"WomanUnderShort
TermBRCRisk"/gt - ltprontocertaintygt00.035lt/prontocertaint
ygt - lt/owl11Axiomgt
- ltowl11Axiomgt
- ltrdfsubject rdfresource"WomanAged6070"
/gt - ltrdfpredicate rdfresource"rdfssubClas
sOf"/gt
55Demo - Pronto
- lt!--owl11Axiomgt
- ltrdfsubject rdfresource"Julie"/gt
- ltrdfpredicate rdfresource"rdftype"/gt
- ltrdfobject rdfresource"WomanAged3040"/
gt - ltprontocertaintygt11lt/prontocertaintygt
- lt/owl11Axiomgt
- ltowl11Axiomgt
- ltrdfsubject rdfresource"Mary"/gt
- ltrdfpredicate rdfresource"rdftype"/gt
- ltrdfobject rdfresource"WomanWithBRCA1M
utation"/gt - ltprontocertaintygt11lt/prontocertaintygt
- lt/owl11Axiomgt
- ltowl11Axiomgt
- ltrdfsubject rdfresource"Ann"/gt
- ltrdfpredicate rdfresource"rdftype"/gt
- ltrdfobject rdfresource"WomanWithMother
BRCAffected"/gt - ltprontocertaintygt11lt/prontocertaintygt
56Demo - Pronto
- ltowl11Axiomgt
- ltrdfsubject rdfresource"Helen"/gt
- ltrdfpredicate rdfresource"rdftype"/gt
- ltrdfobject rdfresource"PostmenopausalW
oman"/gt - ltprontocertaintygt11lt/prontocertaintygt
- lt/owl11Axiomgt
- ltowl11Axiomgt
- ltrdfsubject rdfresource"Helen"/gt
- ltrdfpredicate rdfresource"rdftype"/gt
- ltrdfobject rdfresource"WomanTakingEstr
ogen"/gt - ltprontocertaintygt11lt/prontocertaintygt
- lt/owl11Axiomgt
- ltowl11Axiomgt
- ltrdfsubject rdfresource"Helen"/gt
- ltrdfpredicate rdfresource"rdftype"/gt
57Demo - Pronto
- ltowl11Axiomgt
- ltrdfsubject rdfresource"AshkenaziJewis
hWoman"/gt - ltrdfpredicate rdfresource"rdfssubClas
sOf"/gt - ltrdfobject rdfresource"WomanWithBRCAMu
tation"/gt - ltprontocertaintygt0.0250.025lt/prontocert
aintygt - lt/owl11Axiomgt
- ltowl11Axiomgt
- ltrdfsubject rdfresource"WomanWithBRCAM
utation"/gt - ltrdfpredicate rdfresource"rdfssubClas
sOf"/gt - ltrdfobject rdfresource"WomanUnderLifet
imeBRCRisk"/gt - ltprontocertaintygt0.30.85lt/prontocertain
tygt - lt/owl11Axiomgt
58Demo - Pronto
- Running query (generic TBox conditional
constraint) (CD)l,u 9 - entail http//clarkparsia.com/pronto/cancer_ra.owl
AshkenaziJewishWoman http//clarkparsia.com/pront
o/cancer_ra.owlWomanUnderLifetimeBRCRisk
59Demo - Pronto
- Query entail
- Result 34 (WomanUnderLifetimeBRCRiskAshkenaziJe
wishWoman)0.00750.123 - Explanation
- Explaining the generic constraint 34
(WomanUnderLifetimeBRCRiskAshkenaziJewish - Woman)0.00750.123
- Lower bound is because of
- 8 (WomanWithBRCAMutationAshkenaziJewishWoman)
0.0250.025, 7 (WomanUnderLi - fetimeBRCRiskWomanWithBRCAMutation)0.30.85
- Upper bound is because of
- 10 (WomanUnderLifetimeBRCRiskWoman)0.00.123
- Result computed in 6266ms
60Want to learn more?
- Attend the 2009 URSW Conference
- http//c4i.gmu.edu/ursw/2009/
- Visit W3C Uncertainty Reasoning for the World
Wide Web Incubator Group - http//www.w3.org/2005/Incubator/urw3/
- Review presentations from last years conference
- http//c4i.gmu.edu/ursw/2008/
- Download Pronto
- http//pellet.owldl.com/pronto/
- Download FiRE
- http//www.image.ece.ntua.gr/nsimou/FiRE/
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