DAML OIL

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• DAML OIL
• an ontology language for the Semantic Web
• Peter Aronsson (pelab)
• Cécile Åberg (iislab)

2
Outline

• Ontology Language requirements
• Ontology example
• XML/RDFS are not enough
• DAMLOIL generalities
• DAMLOIL syntax
• DAMLOIL reasoning
• DAMLOIL some discussion
• DAMLOIL summary
• OilEd demo

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Ontology language requirement

• UEP Universal expressive power
• SyI Support for Syntactic Interoperability
• easy to read the data (parsers)
• easy to get a representation usable by
  applications (query-able)
• SeI Support for Semantic Interoperability
• capable of understanding the data

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Ontology example (OIL)

• class-def animal
• plants are a class that is disjoint from animals
• class-def plant subclass-of NOT animal
• it is necessary but not sufficient for a tree to
  be a plant
• class-def tree subclass-of plant
• branches are PART OF trees
• class-def branch
• slot-constraint is-part-of has-value tree
• it is necessary and sufficient for a carnivore
  to be an animal
• class-def defined carnivore subclass-of animal
• slot-constraints eats value-type animal
• herbivores eat only plants OR part of plants
• class-def defined herbivore subclass-of animal
• slot-constraint eats value-type plant OR
• (slot-constraint is-part-of has-value plant)

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XML is not enough
ltclass-defgt ltnamegtbranchlt/namegt ltslot-constraint
gt ltnamegtis-part-oflt/namegt lthas-valuegttreelt/has
-valuegt lt/slot-constraintgt lt/class-defgt

• UEP anything can be encoded in XML
• (if a grammar can be defined for it)
• SyI exists reusable XML parsers
• SeI Do not impose a common interpretation of the
  data ? only feasible for closed collaboration

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RDF/RDFS is not enough (1/2)

• UEP Can express hierarchies of objects, i.e.
  ontologies
• SyI Exists reusable RDF/RDFS parsers
• SeI
• has a specific semantic for some terms
  (subClassOf)
• there is no semantic preserving mappings between
  all objects
• RDFS can be extended to define a more
• powerful ontology language that allows
• inference

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RDF/RDFS is not enough (2/2)
oilOR
oilclassExpression
rdfstype
rdfsClass
oilAND
rdfssubClassOf
oilhasClass
carnivore
rdfstype
rdfstype
oilAND
rdfstype
oil-subclass-of
herbivore
oilhasClass
rdfstype
oilhasClass
animal
rdfsClass
class-def defined herbibore sublclass-of
animal, NOT carnivore
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3 steps to extend RDFS
Type of expression
Encoded in
Example

• Modeling primitives of
• ontology language L.

oilsubclass-of oilnot
RDF meta ontology coded in RDFS
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class-def giraffe subclass-of animal slot-constrai
nts eats value-type leaf
RDF ontology coded in meta ontology RDFS
Express specific ontology in L.
2
Produce instances of the specific ontology
animal12 -eats leaf34
RDF metaontology RDFS ontology
3
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DAML OIL

• Syntax extension of RDFS
• constraints on properties exists, forall,
  cardinality
• boolean combination of classes and restrictions
• equivalence, disjointnes, covering
• necessary and sufficient condition
• constraints on properties
• 2 well defined semantic specification
• model theoretic description logic
• axiomatization in KIF predicate logic
• Allows for machine understanding and automated
  reasoning.

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Why automated reasoning?

• Ontology design
• check class consistency and unexpected implied
  relationships
• especially needed for large, multi-authored
  ontologies
• Ontology integration/sharing
• assert inter-ontology relationships
• reasoner computes integrated class hierarchy
• Ontology deployment
• check if facts are consistent wrt ontology
• check if individuals are instance of ontology
  classes
• The semantic web needs a logic on top
• (Henry Thompson)

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DAMLOIL short history

• Before Ontologies, ML for Web, DL, Frame Lang.,
  etc.
• In 00 first OIL related publications (EU
  researchers)
• Aug00 kickoff meeting for DAML US project
• Oct00 DAML-ONT no inference rules
• ? DAML team looks for inference mechanisms
• ? Experiments with predicate logic
• ? OIL, EU project based on DL
• Dec00 DAML OIL 2 semantics.
• ? Most of OIL is kept except its RDF syntax.
• Nov 01 WebOnt (W3C) working group kick off
• Feb 28 WebOnt publishes OWL requirements

WebOnt WG - language features (OWL req.) -
testing/implement. - semantics - guidelines
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DAMLOIL participants
Semantic Web Resources EU
OntoWeb OIL E-business emphasis
DAML OIL
EU W3C
DAML OIL for WebOnt
Semantic Web Activity
DAML
RDF-S RDF WebOnt WG
Military emphasis
DAML
W3C
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Comparing OIL and DAML-ONT (1/2)
OIL-Standard DAML-ONT Semantics denotational
English complete, unambiguous partial,
ambiguous Meaning of a collection always
conjunctive usually conjuctive of
statements sometimes disjunctive

(domain from RDF) Capabilities Built in
Classes thing, nothing thing, nothing
Primitive Classes yes yes Defined
Classes yes maybe, ugly Class
Hierarchy yes yes, from RDF Property
Hierarchy yes yes Equivalence yes (defined
classes) maybe Disjoint, Disjoint
Cover yes yes Inverse/Transitive
Prop yes yes Union/Intersection yes,
class constructor yes, class definition
Complement yes, class constructor yes, class
definition Domain Restriction yes,
conjunctive yes, disjunctive (from RDF)
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Comparing OIL and DAML-ONT (2/2)

• OIL-Standard DAML-ONT
• Range Restrictions global and local global
  (from RDF)
• and local
• Filler Restrictions local (and global) local
  (and global)
• Cardinality Restrictions local (and global)
  global only
• Sets yes yes
• Lists no yes
• Defaults no yes
• Individuals yes yes
• Concrete Types (int, ...) yes yes
• Reasoning
• Specification complete incomplete
• Completion Possible no no
• Least Partial Model no no
• Difficulty EXPtime complete (?) unknown, at
  least NP hard

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DAMLOIL unusual DL features

• non frame syntax
• ? must use a specific editor
• organizational information lost (see e.g.
  later)
• list of axioms
• no sense of a main definition of a class or
  individual
• large collection of primitive types (int)
• allows individual to occurs in concept
  definition
• ? reasoners are difficult to construct

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DAMLOIL syntax
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DAMLOIL DL expressivity

• Basic DL ALC and, or, not
• Other DL ALC set of roles
• OIL SHIQ
• very expressive
• ALC transitive roles cardinality
  restriction max1 on roles is-a on roles
  inverse roles cardinality restriction (e.g.
  2lt)
• note no reasoning on individuals.
• DAMLOIL DL name not specified in lit.
• SHIQ some cf. list of axioms and operators
• OilEd FaCT classifier (SHIQ)
• DL classifier modal logic satisfiability tester

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DAMLOIL what you can reason about
(DAMLOIL medical terminology ontology)

• transitive roles capture patronomy, causality,
  etc.

R(a,b) and R(b,c) ? R(a, c) Cause(smoking,
cancer) and Cause(cancer, death) ? Cause(smoking,
death)
Smoking ? ?causes.Cancer plus Cancer ?
?causes.Death ? Smoking ? ?causes.Death

• multiple equality/inclusion axioms generate new
  axioms

StomachUlcer Ulcer ? ?hasLocation.Stomach plus
StomachUlcer ? ?hasLocation.LiningOfStomach ?
Ulcer ? ?hasLocation.Stomach ? OrganLiningLesion
Axiom1) stomach ulcer is an ulcer and is an
object located in the stomach Axiom2) stomach
ulcer is-an object that is located in the lining
of stomach inference) an object that is an ulcer
and is an object located in the stomach is-an
object that is located in the lining of stomach
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DAMLOIL what you can reason about

• inverse roles capture, e.g., causes/causedBy
  relationship.

if (A linked to B by R) is-a C then (B is linked
to C by the inverse of R)
E.g. causes is inverse of causedBy if death
caused by smoking is a premature death then
smoking causes premature death
Death and ?causedBy.Smoking ? prematureDeath ?
Smoking ? ?causes.PrematureDeath

• cardinality restrictions add consistency
  constraints

E.g. If blood pressure can have a value that can
be either high or low and can have only one
value, then a blood pressure can not be high and
low at the same time.

• BloodPressure ?
• hasValue.(high ? low) ? ? 1hasValue plus High ? ?
  low
• ? HighLowBloodPressure ? ?

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DAMLOIL what you can not reason about

• No property construct
• e.g. parent o brother ? uncle, ancestor
  parent
• No variable
• Ulcer ? ?haslocation.?r ? ?haslocation.(?LiningOf.
  ?x)
• Only unary and binary predicates
• can not express directly P(x, y, z)
• Language extensions are possible but have a cost
• ? tractability vs. expressivity problem

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DAMLOIL and OWL requirements (1/2)

• yes, / partial
• R1 shared (damlontology, ns, classes)
• R2 extension (damlimport)
• R3 evolution (damlversionInfo)
• R4 interoperability (rdfssubClassOf/subPropertyOf
  ,...)
• R5 inconsistency detection (DL reasoner)
• R6 scalability
• R7 ease of use ( classes, frame (DL), - RDF)

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DAMLOIL and OWL requirements (2/2)

• R10 XML syntax
• R12 ontology based search (can be done)
• R14 expressiveness (limited to the chosen DL)
• R18 explainability (inferences rules available)
• no consensus
• R8 data persistence, R9 security, R13 querying,
  R15 proof checking, R16 Trust, R17 Tagging
• other requirements (from other groups)
• R19 default info, R20 part whole info R10 XML
  syntax

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Problem Sharing (exchanging) ontologies

• Consistent interpretation
• requires syntactic and semantic understanding
• the intention of the author is clear for the
  agent using the ontology
• requires semiotic understanding
• DAMLOIL venture looses the original OIL semiotic
  support provided by frame languages
• grouping axioms specific to a class

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Class-def defined White-van-man subclass-of
Man slot-constraint drives has-values
White-van covered White-van-man by
Aggressive-driver
ltrdfsClass rdfIDWhite-van-mangt
ltrdfssubClassOfgt ltrdfsClass
rdfaboutAggressive-driver/gt
lt/rdfssubClassOfgt lt/rdfsClassgt ltrdfsClass
rdfaboutWhite-wan-mangt ltdamlsameClassAsgt
ltrdfsClassgt ltdamlintersectionOfgt
ltrdfsClass rdfaboutman/gt
ltdamlRestrictiongt ltdamlonProperty
rdfresourcedrives/gt ltdamlhasClass
rdfresourcesWhite-van/gt
lt/damlRestrictiongt lt/damlintersectionOfgt
lt/rdfsClassgtlt/...gtlt/rdfsClassgt

• Class-def
• primitive White-van-man
• equivalent
• White-van-man
• (Man and
• slot-constraint drives has-values White-van))
• covered White-van-man by Aggressive-driver

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Extending DAML OIL

• Work in progress on datatypes
• supporting some of XMLS datatypes
• making datatypes disjoint from abstract classes
  and only accessible via properties
• maintains decidability and tractability of
  language
• Further implementation in upper layers
• DAML-RULES, DAML-S
• upper layers use DAMLOIL as DAML uses RDFS

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DAMLOIL status

• annotated walkthrough
• examples
• full syntactic definition (RDFS)
• denotational and axiomatic semantic published
• 1st formal semantics for a web language
• Proposal to W3C for standardization ongoing
  (WebOnt)
• Daml ontology library 140 ontologies
• Web tools annotation, API, browser, editor,
  validator, inference engine, ontology editor,
  query, etc.

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DAMLOIL Summary

• Ontology Language for the Semantic Web
• Extends RDFS
• more expressive power
• well defined semantics
• 100 mapping in XML
• Implementable
• decidable and tractable reasoning
• cost restriction on the expressivity
• Extensible loosing some decidability and/or
  tractability
• Usage DAML library of ontologies web services

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OilEd Demo