MULTIMEDIA DATABASES
Images, sounds and movies can
be stored, retrieved and played by many databases. In future, multimedia
databases will bcome a main source of interaction between users and multimedia
elements. Multimedia storage and retrieval Multimedia storage is
characterized by a number of considerations. They are:
(i) massive storage volumes
(ii) large object sizes
(iii) multiple related objects
(iv) temporal requirements for
retrieval
Massive Data Volumes
A single multimedia document
may be a combination of different media Hence indexing of documents, fi lms and
tapes is more complex. Locating massive data volumes requires searching through
massive storage files.
Locating and indexing systems
can be understood only by a few key staff personnel. Hence it requires a major
organizational eff0l1 to ensure that they are returned in proper sequence to
their original storage location.
storage technologies
There are two major mass
storage technologies used currently for storage of multimedia documents.
(i) Optical disk storage systems.
(ii) High-speed magnetic storage.
Advantages of Optical disk storage systems:
(i) Managing a few optical
disk platters in a juke box is much simpler than man;lging a large magnetic
disk farm. (ii) Optical disk storage is excellent storage system for off line
archival of old and infrequently referenced documents for significant periods
of time
Multimedia object storage
Multimedia object storage in
an optical medium serves its original purpose, only if it can be located fast
and automatically. A key issue here is random keyed Access t6 various
components of hypermedia database record. Optical media providcs very dense storage.
Speed of retrieval is another consideration.
Retrieval speed is a direct
result of the storage latency, size of the data relative to display resolution,
transmission media and speed, and decompression efficiency. Indexing is
important for fast retrieval of information. Indexing can be at multiple
levels.
Multimedia document retrieval
The simplest form of
identifying a multimedia document is by storage platter identification and its
relative position on the platter (file number). These objects can then be
grouped using a database in folders (replicating the concept of paper storage
in file folders) or within complex objects representing hypermedia documents.
The capability to access
objects using identifiers stored in a database requires capability in the
database to perform the required multimedia object directory functions. Another
important application for sound and full motion video is the ability to clip
parts of it and combine them with another set.
Indexing of sound and
full-motion video is the subject of intense debate and a number of approaches
have been used.
Database Management Systems
for Multimedia Systems
Since most multimedia
applications are based primarily on communications technologies, such as
electronic mail, the database system must be fully distributed. A number of
database storge choices are available.
The choices available are:
*
Extending the existing relational database management systems,
(RDBMSs) to support the various objects for multimedia as binary objects.
*
Extending RDBMSs beyond basis binary objects to the concepts of
inheritance and classes. RDBMSs supporting these . features provide extensions
for object-programming front ends and/or C++ support.
*
Converting to a full fledged object oriented database that supports
the standard SQL language.
*
Converting the database and the application to an objectoriented
database and using an object-oriented language, or an object-enabled SQL for
development.
Multimedia applications
combine numerical and textual data, graphics from GUI front-ends, CAD/CAM
systems and GIS applications, still video, audio and full-motion video with
recorded audio and annotated voice components. Relational databases, the
dominent database paradigm, have lacked the ability to support multimedia
databases. Key limitations of relational database systems for implementing
multimedia applications stem from two areas: the relational data model and the
relatIonal computational model.
RDBMSs have been designed to
manage only tabular alphanumeric forms of data (along with some additional data
types stored in binary form such as dates).
RDBMS EXTENSIONS FOR MULTIMEDIA
Binary Large Object (BLOB) is
a data type which has been adapted by most of the leading relational databases.
BLOBs are used for objects such as images or other binary data types.
The relational database is
extended to access these BLOBs to present the user 'with a complete' data set.
Extended relational databases provide a gradual migration path to a more
object-oriented environment. Relational database tables include location
information for the BLOBs which may be stored outside the database on separate
image or video servers. Relational databases have the strength of rigorous set
management for maintaining the integrity of the database
Object-Oriented Databases for
Multimedia
.In object databases, data remains in RMS or flat files. Object
databases can provide the fastest route to multimedia support. Object
programming embodies the principles of reusable code and modularity. This will
ease future maintenance of these databases.
Object database capabilities
such as message passing, extensibility, and the support of hierarchical
structures, are important for multimedia systems.
We can develop the
application fastest class definitions. ODBMSs are extensible. They allow
incremental changes to the database applications.
Extensibility: Extensibility .means that the set of operations, structures and
constraints that are available to
operations are not fixed, and developers can define new operations, which can
then be added as needed to their application.
Object-oriented software
technology has three important concepts. They are:
Encapsulation: It is the ability to deal with software entities
as units that interact in pre-defined and
controllable manner, and where the control routines are integral with
entity.
Association: It is the ability to define a software entity in terms of its di
fferences from another entity.
Classification: It is the ability to represent with a single software
entity a number of data items that all have
the same behavior and the same state attributes.
Object orientation helps to
organize the software in a more, modular and re-usable manner. Encapsulation allows for the
development of open systems where one part of the application does not need to know the functioning of other
part. It also provides autonomy; Autonomy
means we can interface to a variety of external programs can be built in one
class of objects and the storage of the data in another class of objects.
Database Organization for
Multimedia Applications
Data organization for
multimedia systems has some key issues. They are:
(l) Data independence (2) Common
distributed database architecture
(3)Distributed database servers· (4) Multimedia
object management.
Data Independence
Flexible access by a number
of databases requires that the data be independent from the application so that
future applications can access the data without constraints related to a
previous application.
Key features of data
independent designs are:
1.Storage design in
independent of specific applications.
2.Explicit data
definitions are independent of application program.
3.Users need not
know data formats or physical storage structures.
4.Integrity
assurance in independent of application programs.
5.Recovery in
independent of application programs.
Distributed Data servers
Distributed database servers
are a dedicated resource on a network accessible to a number of applications.
The database server is built for growth and enhancement, and the network provides
the opportunity for the growth of applications and distributed access to the
data.
Multimedia Object Management
The object management system
must be capable of indexing, grouping and storing multimedia objects in
distributed hierarchical optional storage systems, and accessing these objects
on or keyed basis.
The design of the object
management system should be capable indexing objects in such a manner that
there is no need to maintain multiple storage copies.
Multimedia transactions are
very complex transactions. We define a multimedia transaction as the sequence
of events that starts when a user makes a request to display, edit, or print a
hyper media document. The transaction is complete when the user releases the
hypermedia document and stores back the edited versions or discards the copy in
memory (including virtual memory) or local storage ..
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