A Graphical Approach to Progress for Structured Communication in Web Services

We investigate a graphical representation of session invocation interdependency in order to prove progress for the pi-calculus with sessions under the usual session typing discipline. We show that those processes whose associated dependency graph is acyclic can be brought to reduce. We call such processes transparent processes. Additionally, we prove that for well-typed processes where services contain no free names, such acyclicity is preserved by the reduction semantics. Our results encompass programs (processes containing neither free nor restricted session channels) and higher-order sessions (delegation). Furthermore, we give examples suggesting that transparent processes constitute a large enough class of processes with progress to have applications in modern session-based programming languages for web services.Comment: In Proceedings ICE 2010, arXiv:1010.530

Safety, Liveness and Run-time Refinement for Modular Process-Aware Information Systems with Dynamic Sub Processes

We study modularity, run-time adaptation and refinement under safety and liveness constraints in event-based process models with dynamic sub-process instantiation. The study is part of a larger pro-gramme to provide semantically well-founded technologies for modelling, implementation and verification of flexible, run-time adaptable process-aware information systems, moved into practice via the Dynamic Condi-tion Response (DCR) Graphs notation co-developed with our industrial partner. Our key contributions are: (1) A formal theory of dynamic sub-process instantiation for declarative, event-based processes under safety and liveness constraints, given as the DCR * process language, equipped with a compositional operational semantics and conservatively extending the DCR Graphs notation; (2) an expressiveness analysis revealing that the DCR * process language is Turing-complete, while the fragment cor-responding to DCR Graphs (without dynamic sub-process instantiation) characterises exactly the languages that are the union of a regular and an omega-regular language; (3) a formalisation of run-time refinement and adaptation by composition for DCR * processes and a proof that such re-finement is undecidable in general; and finally (4) a decidable and practi-cally useful sub-class of run-time refinements. Our results are illustrated by a running example inspired by a recent Electronic Case Management solution based on DCR Graphs and delivered by our industrial partner. An online prototype implementation of the DCR * language (including examples from the paper) and its visualisation as DCR Graphs can be found a

Experience Report: Constraint-Based Modelling and Simulation of Railway Emergency Response Plans

AbstractWe report on experiences from a case study applying a constraint-based process-modelling and -simulation tool, dcrgraphs.net, to the modelling and rehearsal of railway emergency response plans with domain experts. The case study confirmed the approach as a viable means for domain experts to analyse and rehearse emergency response plans, through the activities of formally modelling the plan and subsequently rehearsing it by simulating that model collaboratively. In particular, the constraint-based modelling notation resulted in a flexible model giving rehearsal participants freedom to explore different ways to proceed, including ways not necessarily anticipated in the paper-based emergency response plans. The case study was undertaken as part of a short research, ProSec, project funded by the Danish Defence Agency, with the aim of applying and developing methods for collaborative mapping of emergency and security processes in the danish public transport sector and their dependency on ICT

Hybrid process technologies in the financial sector

Abstract. Danish mortgage credit institutes deal with highly variable and knowledge-intensive processes. At the same time these processes are required to be strictly conformant to current regulations and laws. In addition different divisions of the business are interested in different views on the same process: whereas the IT department implementing the processes would like a complete view that shows the underlying business rules and supports all variants, the end users are only in-terested in a local view that (1) shows only the aspects of the process that they are responsible for and (2) only shows the variants of the process that are rel-evant to them. This paper reports on a project we undertook with such a credit institute where we investigated and addressed these issues by providing a hybrid solution, allowing processes to be modelled using our constraint-based modelling tools, but also supporting flow-based views of both the entire process and specific variants