1. An apparatus for constructing and executing a fusion search for searching a multimedia database, said apparatus comprising: a graphical user interface for forming a plurality of searches that produce intermediate search results, wherein a user builds a fusion search constructed as a text string interactively by sequentially choosing among descriptors and data sources and by selecting from various combining and score aggregation functions to fuse results of each individual search technique, and wherein each of the plurality of searches utilizes a different search technique, and wherein said search techniques consist of: content-based retrieval which allows searching and matching based on perceptual similarity of multimedia content, wherein a user provides at least one example of multimedia content and result similarity is based on distance in feature space; and model-based retrieval which allows searching based on automatically extracted concept labels produced by statistical models, wherein a user provides desired label text and matches are ranked using D=1−C, with distance D derived from a confidence score C associated with each automatically assigned label; an arrangement for a graphical user interface interactively integrating the plurality of searches to selectively direct each search to multiple individual search tools and provide desired matches from multiple disparate data sources based on the search technique and content type; an input interface for permitting the selection of at least one fusion method to be used in combining a plurality of results of said searches the intermediate search results; an arrangement for combining the intermediate search results of said searches interactively based on the intermediate search results of the searches until a final results list is achieved; an arrangement for returning the plurality of results intermediate search results to a user; and an arrangement for returning a fused result the final results list to a user; wherein the plurality of intermediate search results of said searches include multimedia; and wherein the apparatus is configured to execute a cascade of sequential operations, the cascade of sequential operations comprising conducting the plurality of searches that produce the intermediate search results, normalizing the intermediate search results, fusing the intermediate search results to produce fused results, and using the fused results as input for further normalization and fusion with subsequent intermediate results of a subsequent search until the final results list is achieved.