Content-Based Querying

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 objects. The contents of the multimedia objects may be queried from different aspects, depending on the type of the multimedia objects. For example, subject queries apply to all multimedia types whereas spatial queries apply only to images and video, and temporal queries apply only to video. This paper proposes an object-oriented multimedia representation model and overviews content-based searching in text, image, and video database systems.