Video data management (VDM) is fast becoming one of seminar topics in multimedia information systems. In VDM systems, there exists an important need for novel techniques and mechanisms which can provide an efficient retrieval facility of the voluminous data stored in the databases. While "content-based" retrieval provides a direct and an intuitive approach for video data access, it is inadequate from efficient video data management viewpoint. This is because many (semantic) features of video data cannot be extracted out from the video itself automatically; moreover, video objects may share annotations or descriptions. To address these problems, we have been developing an object-oriented video database system which can complement content based access with high level (declarative) query-based retrieval. As video objects by their nature are rich in spatial and temporal semantics, a versatile modeling mechanism is devised to support Spatio-Temporal reasoning. Associated language facilities are also being developed to accommodate a wide range of video queries and annotation activities.