Peter Y. H. Wong

A Process Semantics for BPMN

Business Process Modelling Notation (BPMN), developed by the Business Process Management Initiative (BPMI), intends to bridge the gap between business process design and implementation. However, the specification of the notation does not include a formal semantics. This paper shows how a subset of the BPMN can be given a process semantics in Communicating Sequential Processes. Such a semantics allows developers to formally analyse and compare BPMN diagrams. A simple example of a business process is included to demonstrate the application of the semantics; some theoretical results about the semantics are briefly discussed.

A process-algebraic approach to workflow specification and refinement

This paper describes a process-algebraic approach to specification and refinement of workflow processes. In particular, we model both specification and implementation of workflows as CSP processes. CSPs behavioural models and their respective refinement relations not only enable us to prove correctness properties of an individual workflow process against its behavioural specification but also allows us to design and develop workflow processes compositionally. Moreover, coupled with CSP is an industrial strength automated model checker FDR, which allows behavioural properties of workflow models to be proved automatically. This paper details some CSP models of van der Aalst et al.s control flow workflow patterns, and illustrates behavioural specification and refinement of workflow systems with a business process scenario.

A Relative Timed Semantics for BPMN

We describe a relative-timed semantic model for Business Process Modelling Notation (BPMN). We define the semantics in the language of Communicating Sequential Processes (CSP). This model augments our untimed model by introducing the notion of relative time in the form of delays chosen non-deterministically from a range. We illustrate the application by an example. We also show some properties relating the timed semantics and BPMNs untimed process semantics by exploiting CSP refinement. Our timed semantics allows behavioural properties of BPMN diagrams to be mechanically verified via automatic model-checking as provided by the FDR tool.

Modeling Spatial and Temporal Variability with the HATS Abstract Behavioral Modeling Language

The Abstract Behavioral Specification (ABS) language facilitates to precisely model the behavior of highly configurable, distributed systems. Its basis is Core ABS which is a strongly typed, abstract, object-based, concurrent, fully executable modeling language. Spatial variability of ABS models is represented by feature models, delta modules containing modifications of ABS models, product line configurations linking delta modules with product features and product selections specifying actual product instances. Temporal variability is captured by dynamic delta modules that can be applied to perform runtime updates. The feasibility of ABS is demonstrated by modeling an industrial-scale web merchandising system.

Formalisations and applications of BPMN

We present two formalisations of the Business Process Modelling Notation (BPMN). In particular, we introduce a semantic model for BPMN in the process algebra CSP; we then study an augmentation of this model in which we introduce relative timing information, allowing one to specify timing constraints on concurrent activities. By exploiting CSP refinement, we are able to show some relationships between the timed and the untimed models. We then describe a novel empirical studies model, and the transformation to BPMN, allowing one to apply our formal semantics for analysing different kinds of workflows. To provide a better facility for describing behaviour specification about a BPMN diagram, we also present a pattern-based approach using which a workflow designer could specify properties which could otherwise be difficult to express. Our approach is specifically designed to allow behavioural properties of BPMN diagrams to be mechanically verified via automatic model checking as provided by the FDR tool. We use two examples to illustrate our approach.

Verifying Business Process Compatibility (Short Paper)

We describe a process-algebraic approach to verifying process interactions for business collaboration described in business process modelling notation. We first overview our process semantics for BPMN in the language of communicating sequential processes; we then use a simple example of business collaboration to demonstrate how our semantic model may be used to verify compatibility between business participants in a collaboration.

The ABS tool suite: modelling, executing and analysing distributed adaptable object-oriented systems

Modern software systems must support a high degree of variability to accommodate a wide range of requirements and operating conditions. This paper introduces the Abstract Behavioural Specification (ABS) language and tool suite, a comprehensive platform for developing and analysing highly adaptable distributed concurrent software systems. The ABS language has a hybrid functional and object- oriented core, and comes with extensions that support the development of systems that are adaptable to diversified requirements, yet capable to maintain a high level of trustworthiness. Using ABS, system variability is consistently traceable from the level of requirements engineering down to object behaviour. This facilitates temporal evolution, as changes to the required set of features of a system are automatically reflected by functional adaptation of the system’s behaviour. The analysis capabilities of ABS stretch from debugging, observing and simulating to resource analysis of ABS models and help ensure that a system will remain dependable throughout its evolutionary lifetime. We report on the experience of using the ABS language and the ABS tool suite in an industrial case study.

Formal modeling and analysis of resource management for cloud architectures: an industrial case study using Real-Time ABS

We demonstrate by a case study of an industrial distributed system how performance, resource consumption, and deployment on the cloud can be formally modeled and analyzed using the abstract behavioral specification language Real-Time ABS. These non-functional aspects of the system are integrated with an existing formal model of the functional system behavior, achieving a separation of concerns between the functional and non-functional aspects in the integrated model. The resource costs associated with execution in the system depend on the size of local data structures, which evolve over time; we derive corresponding worst-case cost estimations by static analysis techniques and integrate them into our resource-sensitive model. The model is further parameterized with respect to deployment scenarios which capture different application-level management policies for virtualized resources. The model is validated against the existing system’s performance characteristics and used to simulate, analyze, and compare deployment scenarios on the cloud.

Property specifications for workflow modelling

Previously we provided two formal behavioural semantics for the Business Process Modelling Notation (BPMN) in the process algebra CSP. By exploiting CSPs refinement orderings, developers may formally compare their BPMN models. However, BPMN is not a specification language, and it is difficult and sometimes impossible to use it to construct behavioural properties against which other BPMN models may be verified. This paper considers a pattern-based approach to expressing behavioural properties. We describe a property specification language PL for capturing a generalisation of Dwyer et al.s Property Specification Patterns, and present a translation from PL into a bounded, positive fragment of linear temporal logic, which can then be automatically translated into CSP for simple refinement checking. We present a detailed example studying the behavioural properties of an airline ticket reservation business process. Using the same example we also describe some recent results on expressing behavioural compatibility within our semantic models. These results lead to a compositional approach for ensuring deadlock freedom of interacting business processes.

Deadlock Analysis of Concurrent Objects: Theory and Practice

We present a framework for statically detecting deadlocks in a concurrent object language with asynchronous invocations and operations for getting values and releasing the control. Our approach is based on the integration of two static analysis techniques: (i) an inference algorithm to extract abstract descriptions of methods in the form of behavioral types, called contracts, and (ii) an evaluator that computes a fixpoint semantics returning a finite state model of contracts. A potential deadlock is detected when a circular dependency is found in some state of the model. We discuss the theory and the prototype implementation of our framework. Our tool is validated on an industrial case study based on the Fredhopper Access Server (FAS) developed by SDL Fredhoppper. In particular we verify one of the core concurrent components of FAS to be deadlock-free.