ARIEL: a semantic front-end to relational DBMSs
Robert M. MacGregor · Very Large Data Bases · 1985
This paper introduces the query language ARIEL, a language which retains the formal precision of relational languages such as SQL and QUEL, while exploiting the greater expressiveness of a semantic data model. ARIEL has been implemented as a front-end query language to several relational database systems, including to a front-end distributed DBMS being developed at SDC. The most noteworthy elements of ARIEL are (1) a flexible syntax for expressing subqueries, (2) a convenient way to express outer-joins within a non-procedural framework (without the use of null values), (3) a comprehensive set of rules for defining the semantics of reference chains, (4)a light-weight view mechanism, and (5) a clean semantics for expressing aggregate functions, especially in combination with the group by operator.