Creating new Program Proofs by Combining Abductive and Deductive Reasoning

We describe recent work on the Aris system that creates and verifies new formal specifications for pre-existing source code. We describe Aris in terms of the abductive reasoning system that suggest possible specifications and then uses an existing deductive verifier to evaluate these creations. This paper focuses on the abduction system that creates new formal specifications by leveraging a small set of inspiring artefacts to augment a subset of candidate problems. This employs knowledge graphs to represent the raw data (i.e., source code), discovering latent similarities between graphs using a graph-matching process. Results are presented for the C# programming language with novel creations and its sister language called Code Contracts. We outline ampliative creativity, whereby newly created artefacts drive subsequent creative episodes beyond the initially perceived limitations. We also outline some recent work towards transferring specifications between the C# and Java programming languages

Comparing performance of graph matching algorithms on huge graphs

Graph matching algorithms are gaining more and more interest in the last years from different scientific communities; indeed, they allow comparing any kind of objects represented using their intrinsic structure, represented in terms of attributed relational graphs. The challenge is to make these algorithms able to provide solutions over huge graphs, with many thousands of nodes, and in a time that is adequate for practical applications; in this paper, we propose a comparison among the best performing algorithms available in the literature on a variety of very large graph databases used for performance assessment. The chosen datasets vary in terms of graph structure, size, density, presence of symmetric or repetitive substructures; this variability makes such datasets very challenging. The aim of this paper is to characterize the performance of the compared algorithms with respect to the typology, the size and other structural properties of the graphs; in this way, the user may consciously select the best suited algorithm for a given purpose. The results of an impressive experimentation that required 556 days of machine time are here presented and extensively discussed