Database Reference
In-Depth Information
Figure 2. Example of a RDFS schema
(relation or attribute) is a functional proper-
ty. For example, PF(
located
) and PF(
name
)
express respectively that a cultural place is
located in one and only one address and
that a cultural place has only one name.
These constraints can be generalized to a
set {
P
1
,...,
P
n
} of relations or attributes to
state a combined constraint of functional-
ity that we will denote PF(
P
1
,...,
P
n
).
Constraints of inverse functionality of
Data Description and their Constraints
A datum has a reference, which has the form of
a URI (e.g. http://www.louvre.fr, NS-S1/paint-
ing243), and a description, which is a set of
RDF facts involving its reference. A RDF fact
can be:
•
either a class-fact
C(i)
, where
C
is a class
and
i
is a reference,
or a relation-fact
•
•
R
(
i
1
,
i
2
), where
R
is a rela-
tion and
i
1
and
i
2
are references,
or an attribute-fact
properties: PFI(
P
) is used to declare that
the property
P
(relation or attribute) is an
inverse functional property. For example,
PFI(
contains
) expresses that a painting
cannot belong to several cultural places.
These constraints can be generalized to
a set {
P
1
,...,
P
n
} of relations or attributes
to state a combined constraint of inverse
functionality that we will denote PFI(
P
1
,...,
P
n
). For example, PFI(
located
,
name
) ex-
presses that one address and one name can-
not be associated to several cultural places
(i.e. both are needed to identify a cultural
place).
•
A
(
i
,
v
), where
A
is an
attribute,
i
a reference and
v
a basic value
(e.g. integer, string, date).
The data description that we consider is com-
posed of the RDF facts coming from the data
sources enriched by applying the RDFS entail-
ment rules (Hayes, 2004). We consider that the
descriptions of data coming from different sources
conform to the same RDFS+ schema (possibly
after schema reconciliation). In order to distinguish
the data coming from different sources, we use
the source identifier as the prefix of the reference
of the data coming from that source. Example 1
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