Tool Support for Functional Graph Rewriting with Persistent Data Structures - GrapeVine

Existing graph transformation (GT) tools treat graphs as ephemeral data structures, i.e., the successful application of a GT rule to a graph G rewrites that graph to produce a modified graph G'. The original graph G is lost during that update. In contrast to ephemeral data structures, persistent data structures preserve access to all previous versions when data is modified and fully persistent data structures even allow all previous versions to be modified. In earlier work, we introduced the Graph Rewriting and Persistence Engine Grape as a tool for specifying and executing transformations on large-scale graphs and integrated it with a computational notebook platform (GrapePress). While the term "persistence" has been in the tool's acronym from the start, it was chosen to indicate that graphs were maintained in a database with transactional support. Until now, Grape (and GrapePress) treated graphs as ephemeral data structures, i.e., previous graph versions were not retained upon modification. This paper presents a major revision of the tool (called GrapeVine) to support functional graph rewriting based on a fully persistent data structure.