Global Positioning System Reference
In-Depth Information
describing properties and relations between concepts such as ''fl ooding
area is next to river'' in which ''next'' is a spatial relation and ''fl ooding
area'' and ''river'' are concepts or terms. In Buccella et al. (2009), a survey
of approaches based on ontology for geographic information integration
has been given.
In the rest of this chapter, we focus on Lin, Dice, MDSM, and GSim
approaches, which are selected as representative semantic similarity
methods defi ned in the literature.
Basic Concepts
In this section, we refer to a simple object-oriented geographic data
model, which is characterized by the notion of
geographic class
informally
defi ned below (Pourabbas 2003; Formica and Pourabbas 2009; Formica et
al. 2012; Formica et al. 2013). Essentially, a
geographic class
describes a set
of geographic objects having the same set of
attributes
(or
properties
). It is
specifi ed by a
name
and a class
expression
. The class expression contains a
tuple
of typed attributes, and one or more
geometric
types from {
point, polyline,
polygon
}. Each attribute is associated with an atomic type (e.g.,
integer
,
string
,
boolean
, etc.). A set of geometric types can be associated with a geographic
class depending on the scale or because in multiple-representation database
the geometric type may change. For instance,
county
can be conceived as
a
polygon
or as a
point
. With each geometric type a set of (unary or binary)
operations involving the topological relationships among geographic objects
is associated. These relationships have been extensively discussed in the
literature (for more details see, Egenhofer and Franzosa 1991; 1995) and
their defi nition go beyond the scope of this work.
In order to formalize the defi nition of geographic class, we assume
that countable sets
N
,
A
of class names and attribute names, are given,
respectively. Let
T
and
G
be the sets of atomic and geometric types defi ned,
respectively, as follows:
T
= {
string, boolean, integer, real
}
G
=
{
point, polyline, polygon
}
Defi nition
1: A
geographic class
(
class
for short) is defi ned by a name and an
expression as follows:
n
=<
{
a
1
:
t
1
, ... ,
a
k
:
t
k
},
G >, k
≥ 1
where
n
is the
name
of the class from
N
, the
a
i
'
s
are attribute names from
A
, the
t
i
'
s
are types from
T
, and
G
¡
G
is the set of geometric types of the
class
n
.
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