A Port Graph Rewriting Approach to Relational Database Modelling

Abstract

We present new algorithms to compute the Syntactic Closure and the Minimal Cover of a set of functional dependencies, using strategic port graph rewriting. We specify a Visual Domain Specific Language to model relational database schemata as port graphs, and provide an extension to port graph rewriting rules. Using these rules we implement strategies to compute a syntactic closure, analyse it and find minimal covers, essential for schema normalisation. The graph program provides a visual description of the computation steps coupled with analysis features not available in other approaches. We prove soundness and completeness of the computed closure. This methodology is implemented in PORGY.

A Strategic Graph Rewriting Model of Rational Negligence in Financial Markets

“…A variety of GTS tools are available: among others we can cite GROOVE [19], a graph-based model checker for object oriented systems; AGG (the Attributed Graph Grammar System) [31], a graph-based language for the transformation of attributed graphs that comes with a visual programming environment; PROGRES (Programmed Graph Rewriting Systems) [29] that offers backtracking and nondeterministic constructs; GrGen (Graph Rewrite Generator) [18] that uses attributed typed multigraphs and includes features such as Java/C code generation, and GP [28], a graph programming language, where users can define rules and strategy expressions, with support for conditional rewriting. PORGY [14] has been used to model social networks [15] and database design [34,16], as well as biochemical processes [2], where non-determinism, backtracking, positioning constructs, and probabilistic rule application are key features. A distinctive feature of PORGY is that rewriting derivations are directly available to users via the so-called derivation tree, which provides a visual representation of the dynamics of the system modelled and can be used to plot parameters and generate charts as illustrated in Section 4.…”