“…languages that extend SQL as the common standard for querying relational databases or follow an SQL-like approach, like WebSSQL [34] or SQL/MM [25], 2. languages that build or extend query languages for object oriented databases like MOQL [21] or POQL MM [16], 3. languages that are focusing an XML metadata structure, like MMDOC-QL [22] or XQuery [5] (which is not explicitly build for Multimedia), 4. visual query languages, like MQuery [11] (that focus on visual timeline retrieval) or VisualMOQL [26], 5. approaches that allow query-by-example, like [17] or WS-QBE [28], and 6. languages that try to build a meta-language, which are metadata agnostic and thus can be shared/distributed over several storage backends, like MPQF [12].…”