ESQL: a query language for the relation model supporting image domains

It is shown that by simply extending the relational data model to support image domains, the model becomes rich enough for many advanced applications. Extensions to the relational algebra and the relational calculus are developed to exploit the semantics of image domains. The extended calculus is incorporated in the query language ESQL, which is a strict superset of the structured query language (SQL). A technique to implement ESQL using a preprocessor to SQL is shown. A noteworthy observation is that it is possible to incorporate multirelations without any modifications to the storage structures and data definition language of SQL. It is also possible to support queries of multirelations in ESQL without modifying the features of SQL in any way as far as traditional data manipulation is concerned