Multimedia Systems Institute of Crete (MUSIC)
Technical University of Crete
Chania 73100, Greece
Multimedia Database Systems (MMDS) support rich data types, such as text, images, video, and
sound. Queries in MMDSs may refer to the content of the stored multimedia objects. This is called
content-based querying. However, manual entry of content descriptions is very difficult and subjective.
A better approach is to provide automatic content-based retrieval through image, text, and sound
interpretation. To support queries by content in a MMDS, multimedia data should be analyzed so that
description of their content can be extracted and stored in the database together with the original data.
These descriptions are then used to search the MMDS and determine which multimedia objects satisfy
the query selection criteria. Because content-based queries tend to be imprecise, database search
should be approximate and multimedia objects up to a prespecified degree of similarity with the query
specification should be retrieved. This implies the definition of some distance measure between the
query and the stored multimedia objects which captures what humans perceive as similarity between the