Chronos: A Tool for Handling Temporal

wrendeceitInternet and Web Development

Oct 21, 2013 (3 years and 8 months ago)

79 views

Alexandros

Preventis
,
Polyxeni

Marki
,


Euripides G.M. Petrakis,
Sotirios

Batsakis

Dept. of Electronic and Computer Engineering

Technical University of Crete (TUC)

Chronos: A Tool for Handling Temporal

Ontologies in Protégé

1

OWL


OWL (Web Ontology Language) is a language that can be
used to describe the classes and relations between them.


more expressive than XML, RDF and RDF
-
S


allows to reason about the entities and check whether or not
all statements and definitions are mutually consistent


OWL directly supports binary relations.

2

Dynamic
Ontologies


Represent concepts that occur and evolve in time


A company will be established, hire personnel and
develop products


The relation “employs" and its inverse are ternary.


3

OWL
-
Time Ontology


OWL
-
Time is an OWL ontology of temporal concepts. It
provides a vocabulary for describing:


topological relations between temporal entities (instants,
intervals)


information about durations


It provides no means of representing information that changes
in time.

4

Temporal Representations


Models for representing temporal information:


Temporal Description Logics (TDLs)


Versioning


Reification


4D
-
Fluents (Welty 2006 & Batsakis 2011)


N
-
ary

Relations

5

N
-
ary

Example

6

Protégé


Protégé is a free, open
-
source editor platform for handling
ontologies:



enables users to build
ontologies

for the Semantic Web, in
particular in the W3C's Web Ontology Language (OWL)



Can be extended by means of a plug
-
in architecture and a Java
-
based Application Programming Interface (API) for building
knowledge
-
based tools and applications

7

Problem


The creation of a temporal ontology, or the conversion of a static
ontology to temporal can be a very complex, time
-
consuming and
error
-
prone procedure.


Involves intermediate relations and properties


The temporal properties in N
-
ary

apply on intermediate relations


The user must have very good knowledge of the underlying (N
-
ary

in our work) representation model.


There is no tool for crafting temporal concepts in
ontologies

easily
(i.e., similarly to static
ontologies
).

8

Chronos


We present
Chronos
, a Plug
-
In for the Protégé editor
(version 4.1,supporting OWL 2.0) that:


handles temporal
ontologies

similarly to static ones


supports restriction checking on temporal properties, classes
and individuals


supports reasoning over temporal
ontologies

using the Pellet
reasoner

with Protégé


its interface is consistent with the layout of the default Protégé
tabs


The user need not be familiar with the N
-
ary

model

9

Modified entities


Although it is feasible to create a temporal ontology using the
standard Protégé tabs, it is difficult to define temporal
properties and restrictions.


C
hanges that are applied during the conversion of:


Object Properties


Data Properties


Individuals


Classes


10

Object Properties


The changes that will take place in order to convert an object
property to temporal are:


Property domain and range


Event class is related to the Interval with the object property
during

11

Data properties


The changes that will take place in order to convert a data
property to temporal are:


Property domain


creation of an object property (named by the data property, and
followed by “OP") which will relate the static data property's
domain to the Event class.


Event class is related to the Interval with the object property
during

12

Individuals


When a property is converted to temporal, all its instances
have to be converted as well.

13

Value constraints


owl:allValuesFrom

Company employs only Programmer In
the case where `employs' is temporal object property, the
constraint is:


Company employs only (Event and (employs only
Programmer))


owl:someValuesFrom

Company employs some Programmer
In the case where `employs' is temporal object property, the
constraint is:


Company employs some (Event and (employs some
Programmer))


14

Cardinality Constrains (1/2)


owl:maxCardinality

Company employs max 2 Employee


owl:minCardinality

Company employs min 2 Employee


owl:cardinality

Company employs exactly 2 Employee


owl:FunctionalProperty

A functional property is a property that can
have only one (unique) value y for each instance x, i.e. there cannot be
two distinct values y1 and y2 such that the pairs (x, y1) and (x, y2) are
both instances of this property.


John
worksFor

Apple


A temporal functional property can have only one value in each time
interval during which the property holds. This is implemented by adding
a SWRL rule to the ontology (Batsakis2012).


15

Cardinality Constrains(2/2)


owl:inverseFunctionalProperty

If we state that P is an
owl:InverseFunctionalProperty
, then this asserts that a value y can only
be the value of P for a single instance x, i.e. there cannot be two distinct
instances x1 and x2 such that both pairs (x1, y) and (x2, y) are instances
of P.


Apple employs John


When a temporal property is inverse
-
functional the object uniquely
determines the subject for each time instant.


If a temporal property P is transitive and (x, y, interval1) is an instance
of P and (y, z, interval2) is an instance of P, then we can infer that (x, z,
interval1

interval2) is also an instance of P. In our implementation
the transitivity between instances of a temporal property takes place
only if those instances hold for same time intervals

16

Class Conversions


Chronos

provides a convenient way to convert multiple
object and data properties to temporal. This function
converts:


the object and data properties that relate members of the
selected class


the object and data properties where this class appears as a
Domain


the restrictions where one of these object or data properties
appear in

17

User Interface

18

Conclusions


Chronos
, is a tab plug
-
in for
Protege

editor that facilitates the
creation and editing of temporal OWL 2.0 ontologies.


The temporal concepts as well as the properties that evolve over
time are represented by means of the N
-
ary

Relations model, that
is a W3C recommendation.


It applies on restrictions on temporal properties, which have
different semantic meaning than those applied on static properties.


The user does not have to be familiar with the peculiarities of the
temporal representation model, thus making the manipulation of
temporal entities as easy as if they were static.


Available at: www.intelligence.tuc.gr/prototypes

19

Thank You





Questions
?

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