OnTrack is a tool that supports workflows for railway verification that has been implemented using model driven engineering frameworks. Starting with graphical scheme plans and finishing with automatically generated formal models set-up for verification, OnTrack allows railway engineers to interact with verification procedures through encapsulating formal methods. OnTrack is grounded on a domain specification language (DSL) capturing scheme plans and supports generation of various formal models using model transformations. In this paper, we detail the role model driven engineering takes within OnTrack and reflect on the use of model driven engineering concepts for developing domain specific formal methods toolsets.

Throughout the COVID-19 pandemic, visualizations became commonplace in public communications to help people make sense of the world and the reasons behind government-imposed restrictions. Though the adult population were the main target of these messages, children were affected by restrictions through not being able to see friends and virtual schooling. However, through these daily models and visualizations, the pandemic response provided a way for children to understand what data scientists really do and provided new routes for engagement with STEM subjects. In this paper, we describe the development of an interactive and accessible visualization tool to be used in workshops for children to explain computational modeling of diseases, in particular COVID-19. We detail our design decisions based on approaches evidenced to be effective and engaging such as unplugged activities and interactivity. We share reflections and learnings from delivering these workshops to 140 children and assess their effectiveness.

Computer science (CS) curriculum reform across the UK has been subject to substantial scrutiny, as it has in many other countries around the world. However, in Wales -- one of the four nations in the UK -- various political, geographical and socio-cultural issues have historically hindered major educational policy interventions or reforms for CS. In this poster, we highlight the activities and impact of Technocamps, a pan-Wales university-based schools outreach programme founded in 2003. We showcase its wider impact on CS education, practitioners, schools, and learners in Wales over the past 20 years; especially with the start of the new bilingual Curriculum for Wales (Cwricwlwm i Gymru) from September 2022, which includes major reform of CS alongside digital competence as a statutory cross-curricular skill for all learners aged 3-16.

In this paper, we present a novel approach to providing students with hands-on learning experiences for security testing. Specifically, we give details of a Raspberry Pi-based lab architecture which we developed as part of a security course, and provide example lab tasks that such an architecture affords. We provide evidence that introducing such hands-on labs within the security course directly improved student performance. Finally, we compare our approach to other existing approaches of which we are aware that are based on virtual machines and networks.

This issue contains five papers on algebraic and logical methods for data and modelling which were solicited for The Computer Journal in honour of the 60th birthday of John V Tucker. The topic reflects the focus of Tucker’s scientific career, and the computer journal—being the flagship journal of the BCS—represents a most appropriate forum to recognize this milestone. Tucker has throughout his life been committed to progressing British computing (science, technology, history and education as well as the BCS.

1 Department of Computer Science, University of Wales Swansea, Singleton Park, Sketty, Swansea SA2 8PP, UK Email: [email protected]

We show that the expressive power of the branching time logic CTL coincides with that of the class of bisimulation invariant properties expressible in so-called monadic path logic: monadic second order logic in which set quantification is restricted to paths. In order to prove this result, we first prove a new composition theorem for trees. This approach is adapted from the approach of Hafer and Thomas in their proof that CTL coincides with the whole of monadic path logic over the class of full binary trees.

A polynomial-time algorithm is presented for deciding bisimulation equivalence of so-called Basic Parallel Processes: multisets of elementary processes combined by a commutative parallel-composition operator.

A polynomial-time procedure is presented for deciding bisimilarity of normed context-free processes. It follows as a corollary that language equivalence of simple context-free grammars is decidable in polynomial time.>

CCS is a universal formalism: any computable function is computed by some CCS agent. Moreover, one can reduce the halting problem for Turing machines to the problem of deciding bisimilarity of two CCS agents, thus demonstrating the undecidability of the equivalence checking problem. In this paper, we demonstrate the limits of decidability of CCS. In particular, we show that by simply disallowing either of communication or both restriction and relabelling, we arrive at a sublanguage which still describes a rich class of infinite state systems but for which bisimulation is decidable. We also demonstrate complete axiomatisations for these sublanguages. We compare these results with the undecidability of all other common equivalences.

The authors prove the decidability of two subclasses of recursive processes involving a parallel composition operator with respect to bisimulation equivalence, namely, the so-called normed and live processes. To accomplish this, the authors first prove a unique decomposition result for (a generalization of) normed processes, in order to deduce a necessary cancellation law. The decidability proof leads to a complete axiomatization for these process classes.>

Equatorial axiomatizations for congruences over a simple sublanguage of R. Milner's (1980) process algebra CCS (calculus of communicating systems) are examined. It is shown that no finite set of equational axioms can completely characterize any reasonably defined congruence which is at least as strong as Milner's strong congruence. In the case of strong congruence, this means that the expansion theorem of CCS cannot be replaced by any finite collection of equational axioms. Moreover, the author isolates a source of difficulty in axiomatizing any reasonable noninterleaving semantic congruence, where the expansion theorem fails to hold.>