MOMIS Extensional Hierarchy Generation
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This module manage the extensional information about the
integrated source.
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Questo modulo gestisce le relazioni estensionali relative
alle sorgenti integrate.
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Intensional and Extensional relationship:
Intensional Relationship
They are terminological relationships expressing
inter-schema knowledge for the source schemata.
Intensional relationships are defined between
classes and attributes and are specified by considering class/attributes
names, called terms.The following relationships can be specified in ODLI3
:
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SYN (Synonim-of) Defined between two
terms ti and tj with ti not equal
to tj , that are considered synonyms in every considered source.
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BT (Broader Terms) or hypernymy, defined between
two terms ti and tj such as ti has a broader,
more general meaning that tj . BT relationship is not symmetric.
The opposite of BT is NT (Narrower Terms) or hyponymy.
An intensional relationship is only a terminological
relationship ,with no implication on the extension of the two involved
classes.
Extensional Relationship
Intensional relationship SYN, BT and NT between
two classes C1 and C2 may be strengthened by establishing that they are
also extensional relationship.The following extensional relationship
can be defined in ODLI3 :
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C1 SYNEXT C2: the
instances of C1 are the same of C2
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C1 BTEXT C2: the
instances of C1 are a superset of the instances of C2
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C1 NTEXT C2: the
instances of C1 are a subset of the instance of C2
In addiction to the intensional rules there is the
relationship "Disjointness":
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C1 DISJEXT C2: the
instances of C1 are different from the instances of C2
Moreover the extensional relationships SYN,NT,BT
have some side effects:
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An extensional relationship C1 SYNEXT C2 is equivalent to two
ISA relationship C1 ISA C2 and C2 ISA C1 plus an intensional relationship
C1 SYN C2.
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An extensional relationship C1 NTEXT C2 is equivalent to an
ISA relationship C1 ISA C2 plus an intensional relationship C1 NT C2.
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An extensional relationship C1 BTEXT C2 is equivalent to an
ISA relationship C2 ISA C1 plus an intensional relationship C1 BT C2.
The ISA relationship is expressed in ODLI3 by the following
:
extrule Rule1 forall x in C1 then x in C2
The DISJOINTNESS relationship is expressed in ODLI3 by the
following:
extrule Rule2 forall x in (C1 AND C2 ) then x in BOTTOM
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