Graphical query specification with participation constraints

A graphical calculus-based query language is defined for a new semantic data model. The semantic data model supports participation constraints on relationship sets, and the query language takes advantage of these participation constraints to provide a new way to pose queries. In particular, it is shown how participation constraints lead to an elegant formulation of universal-quantification queries. Participation constraints also lead to an elegant formulation of queries that require counting. Examples are provided of several queries that are either difficult or impossible to pose in standard query languages, but are straightforward in the proposed calculus-based query language