Fernando Orejas

We introduce a logic-based incremental approach to graph repair, generating a sound and complete (upon termination) overview of least-changing graph repairs from which a user may select a graph repair based on non-formalized further requirements. This incremental approach features delta preservation as it allows to restrict the generation of graph repairs to delta-preserving graph repairs, which do not revert the additions and deletions of the most recent consistency-violating graph update. We specify consistency of graphs using the logic of nested graph conditions, which is equivalent to first-order logic on graphs. Technically, the incremental approach encodes if and how the graph under repair satisfies a graph condition using the novel data structure of satisfaction trees, which are adapted incrementally according to the graph updates applied. In addition to the incremental approach, we also present two state-based graph repair algorithms, which restore consistency of a graph independent of the most recent graph update and which generate additional graph repairs using a global perspective on the graph under repair. We evaluate the developed algorithms using our prototypical implementation in the tool AutoGraph and illustrate our incremental approach using a case study from the graph database domain.

Attributed graph grammars can specify the transformation of complex data and object structures within a natural rule-based model of concurrency. This is crucial to their use in modelling interfaces of services and components as well as the evolution of complex systems and networks. However, the established concurrent semantics of graph grammars by unfolding does not cover attributed grammars. We develop a theory of unfolding for attributed graph grammars where attribution is represented symbolically, via logical constraints. We establish a functorial representation (a coreflection) of unfolding which guarantees it to be correct, complete and fully As a case study and running example we demonstrate the use of visual contracts to specify an escrow smart contract.

In this paper we first present three sorts of constraints (positive, negative and conditional ones) to specify that certain patterns must be satisfied in a XML document. These constraints are built on boolean XPath patterns. We define a specification as a set of clauses whose literals are constraints.Then, to reason about these specifications, we study some sound rules which permit to infer, subsume or simplify clauses. The main goal is to design a refutation procedure (based on these rules) to test if a given specification is satisfiable or not. We have formally proven the soundness of our procedure and we study the completeness and termination of the proposed method.