Fifty years of Hoare's Logic

We present a history of Hoare's logic.Comment: 79 pages. To appear in Formal Aspects of Computin

Preserving Liveness Guarantees from Synchronous Communication to Asynchronous Unstructured Low-Level Languages

In the implementation of abstract synchronous communication in asynchronous unstructured low-level languages, e.g. using shared variables, the preservation of safety and especially liveness properties is a hitherto open problem due to inherently different abstraction levels. Our approach to overcome this problem is threefold: First, we present our notion of handshake refinement with which we formally prove the correctness of the implementation relation of a handshake protocol. Second, we verify the soundness of our handshake refinement, i.e., all safety and liveness properties are preserved to the lower level. Third, we apply our handshake refinement to show the correctness of all implementations that realize the abstract synchronous communication with the handshake protocol. To this end, we employ an exemplary language with asynchronous shared variable communication. Our approach is scalable and closes the verification gap between different abstraction levels of communication

AI-based component management system for structured content creation, annotation, and publication

Nowadays, the ever changing and growing amount of information, regulations, and data requires large organizations to describe on the web increasingly complex and interdependent business processes and services, ideally creating user-profiled content that is clear and up to date. To successfully achieve this goal, as off-the-shelf solutions are missing, institutions have to embark in a digital transformation process fully endorsed by governance, led by a multidisciplinary team of experts, and strongly integrated with artificial intelligence (AI) tools. In this paper we describe how a content service platform, that integrates human processes and state-of-the-art AI services, was successfully employed in our institution (UniGe) to manage, and support a system of about 200 websites. Following a single-sourcing paradigm, its advent allowed for the decoupling of content and technology, preparing UniGe for the future needs of the semantic web

A Graph Transformation Approach for Modeling and Verification of UML 2.0 Sequence Diagrams

Unified Modeling Language (UML) 2.0 Sequence Diagrams (UML 2.0 SD) are used to describe interactions in software systems. These diagrams must be verified in the early stages of software development process to guarantee the production of a reliable system. However, UML 2.0 SD lack formal semantics as all UML specifications, which makes their verification difficult, especially if we are modeling a critical system where the automation of verification is necessary. Communicating Sequential Processes (CSP) is a formal specification language that is suited for analysis and has many automatic verification tools. Thus, UML and CSP have complementary aspects, which are modeling and analysis. Recently, a formalization of UML 2.0 SD using CSP has been proposed in the literature; however, no automation of that formalization exists. In this paper, we propose an approach on the basis of the above formalization and a visual modeling tool to model and automatically transform UML 2.0 SD to CSP ones; thus, the existing CSP model checker can verify them. This approach aims to use UML 2.0 SD for modeling and CSP and its tools for verification. This approach is based on graph transformation, which uses AToM3 tool and proposes a metamodel of UML 2.0 SD and a graph grammar to perform the mapping of the latter into CSP. Failures-Divergence Refinement (FDR) is the model checking tool used to verify the behavioral properties of the source model transformation such as deadlock, livelock and determinism. The proposed approach and tool are illustrated through a case study

A shared memory algorithm and proof for the alternative construct in CSP

technical reportCommunicating Sequential Processes (CSP) is a paradigm for communication and synchronization among distributed processes. The alternative construct is a key feature of CSP that allows nondeterministic selection of one among several possible communicants. Previous algorithms for this construct assume a message passing architecture and are not appropriate for multiprocessor systems that feature shared memory. This paper describes a distributed algorithm for the alternative construct that exploits the capabilities of a parallel computer with shared memory. The algorithm assumes a generalized version of Hoare's original alternative construct that allows output commands to be included in guards. A correctness proof of the proposed algorithm is presented to show that the algorithm conforms to some safety and liveness criteria. Extensions to allow termination of processes and to ensure fairness in guard selection are also given. Keywords: communicating sequential processes; alternative operation; shared memory multiprocessor; parallel processing