  We are developing a rule-based implementation of a tool to analyse and
generate graphs. It is currently used in the domain of mason's marks. For
thousands of years, stonemasons have been inscribing these symbolic signs on
dressed stone. Geometrically, mason's marks are line drawings. They consist of
a pattern of straight lines, sometimes circles and arcs. We represent mason's
marks by connected planar graphs. Our prototype tool for analysis and
generation of graphs is written in the rule-based declarative language
Constraint Handling Rules. It features - a vertex-centric logical graph
representation as constraints, - derivation of properties and statistics from
graphs, - recognition of (sub)graphs and patterns in a graph, - automatic
generation of graphs from given constrained subgraphs, - drawing graphs by
visualization using svg graphics. In particular, we started to use the tool to
classify and to invent mason's marks. In principe, our tool can be applied to
any problem domain that admits a modeling as graphs.
