16
Carlo Combi, Sara Migliorini, Barbara Oliboni, and Alberto Belussi
• A set of spatial relations. This set describes the existing relationships between
geographical objects (i.e. topological relations such as disjoint, touch, in, contains, equal, cross, and overlaps [7]).
The above-mentioned components could be only partially specified or they could
be defined at different levels of detail, making it difficult to represent the related
information within a (pre)fixed schema. A further aspect to deal with is related to the
fact that geographical information is often time varying, for example, the borders of
a town can change and their evolution must be suitably managed.
The model we propose in this chapter is named geographical multimedia temporal graphical model (GeoMTGM). A GeoMTGM graph is a directed, labeled graph
with a single root; it is based on the multimedia temporal graphical model (MTGM)
presented in [10] and allows us to represent geographical and semistructured data,
with particular attention to their temporal aspects. In particular, GeoMTGM deals
with the Valid Time (VT) (i.e. the time at which a fact is true in the considered domain) [9] of both objects and their relationships.
The GeoMTGM is a new proposal in the context of semistructured multimedia
spatiotemporal data. In Sect. 2.2, we give a brief description of the main issues related to this context.
This work is structured into three main sections. In Sect. 2.2, we present some
basic concepts that are useful for understanding the model and the rest of the work.
In Sect. 2.3, we go on with the explanation of the GeoMTGM model, in particular,
its main characteristics and structure, its formal definition, and its translation into
XML. Finally, in Sect. 2.4, we present a realized Web application based on the J2EE
[15] and the Struts [1] framework for the definition, manipulation, and translation of
GeoMTGM graphs.
2.2 Related Work
In this section we briefly recall semistructured data features, aspects of multimedia
data modeling, and some basic notions related to geographical information. Then,
we give a brief description of geography markup language (GML) [13], an XMLbased language for geographical information, and finally, introduce the data model
proposed in [14], which is, to the best of our knowledge, the unique work in the
literature addressing issues related to spatiotemporal semistructured data, proposing
an XML-based representation.
2.2.1 Semistructured Data
Semistructured data are data having some structure that may be irregular or
incomplete and does not necessarily conform to a fixed schema [3]. The structure
of semistructured data can change over time; for this reason, for this type of information, it is important to consider the temporal aspect of data.
In this context, the models proposed in the literature allow one to represent and
query changes in semistructured data. Among these, we cite here the delta object
Carlo Combi, Sara Migliorini, Barbara Oliboni, and Alberto Belussi
• A set of spatial relations. This set describes the existing relationships between
geographical objects (i.e. topological relations such as disjoint, touch, in, contains, equal, cross, and overlaps [7]).
The above-mentioned components could be only partially specified or they could
be defined at different levels of detail, making it difficult to represent the related
information within a (pre)fixed schema. A further aspect to deal with is related to the
fact that geographical information is often time varying, for example, the borders of
a town can change and their evolution must be suitably managed.
The model we propose in this chapter is named geographical multimedia temporal graphical model (GeoMTGM). A GeoMTGM graph is a directed, labeled graph
with a single root; it is based on the multimedia temporal graphical model (MTGM)
presented in [10] and allows us to represent geographical and semistructured data,
with particular attention to their temporal aspects. In particular, GeoMTGM deals
with the Valid Time (VT) (i.e. the time at which a fact is true in the considered domain) [9] of both objects and their relationships.
The GeoMTGM is a new proposal in the context of semistructured multimedia
spatiotemporal data. In Sect. 2.2, we give a brief description of the main issues related to this context.
This work is structured into three main sections. In Sect. 2.2, we present some
basic concepts that are useful for understanding the model and the rest of the work.
In Sect. 2.3, we go on with the explanation of the GeoMTGM model, in particular,
its main characteristics and structure, its formal definition, and its translation into
XML. Finally, in Sect. 2.4, we present a realized Web application based on the J2EE
[15] and the Struts [1] framework for the definition, manipulation, and translation of
GeoMTGM graphs.
2.2 Related Work
In this section we briefly recall semistructured data features, aspects of multimedia
data modeling, and some basic notions related to geographical information. Then,
we give a brief description of geography markup language (GML) [13], an XMLbased language for geographical information, and finally, introduce the data model
proposed in [14], which is, to the best of our knowledge, the unique work in the
literature addressing issues related to spatiotemporal semistructured data, proposing
an XML-based representation.
2.2.1 Semistructured Data
Semistructured data are data having some structure that may be irregular or
incomplete and does not necessarily conform to a fixed schema [3]. The structure
of semistructured data can change over time; for this reason, for this type of information, it is important to consider the temporal aspect of data.
In this context, the models proposed in the literature allow one to represent and
query changes in semistructured data. Among these, we cite here the delta object