Databases Reference
In-Depth Information
The last part of the scenario handles the presentation termination,
which will occur when _ExitEvent occurs. An application timer limits
the duration of the scenario through the _AppTimer event.
That rich example generates requirements for modeling and retrieval, central
issues for an MM-DBMS capable of dealing with IMDs. As for modeling, we
have to look into the specific features of an IMD, such as interaction model-
ing and spatiotemporal composition of the media objects to adhere to the
authors specifications. Another important issue is assurance of the docu-
ment integrity in temporal and spatial terms. Then having the IMD in an
MM-DBMS, we need to retrieve and present it according to the scenario
specifications. That means internal and external interaction has to be
detected and the spatial and temporal relationships among objects rendered
in the output device.
Another important requirement is the retrieval of IMDs from the
MM-DBMS, according to several criteria, among which the spatial/temporal
ones play a significant role.
8.3
Design of an MM-DBMS for IMDs
The design requirements in the context of an MM-DBMS can be classified
into two groups: one related to the data model and the other related to
retrieval issues. In an MM-DBMS, monomedia objects (i.e., single media
objects) or IMDs are stored. The modeling requirements of the latter are
unarguably richer and certainly are a superset of monomedia objects. This
section presents the requirements for modeling IMDs as MM-DBMS
objects.
8.3.1 Modeling IMDs
In regard to the data model, we will discuss the following features, which are
specific to multimedia information: interaction, multidimensionality, space
and time dependencies, complexity, and temporal integrity. An IMD
involves a variety of individual multimedia objects presented according to a
set of specifications called the IMD scenario. The multimedia objects that
participate in the IMD are transformed, either spatially or temporally, to be
presented according to the authors requirements. Moreover, the author has
to define the spatial and temporal order of objects within the document con-
text and the relationships among them. Finally, the way that the user will
interact with the presentation session as well as the way that the application
