Kent Inge Fagerland Simonsen

Applications of Coloured Petri Nets for Functional Validation of Protocol Designs

Communication protocols constitute central building blocks in most modern IT systems as they define components, rules, and languages that make data communication possible. The development of correct protocols is a challenging engineering discipline, making modelling and validation of protocol design an important application domain for Coloured Petri Nets (CPNs). We illustrate the practical application of CPNs for protocol validation by focusing on selected aspects of four recent projects involving industrial-sized protocols. These projects demonstrate how CPNs can be used to model protocol elements and improve protocol specifications, how state space exploration can be used to verify protocol properties, and how behavioural visualisation in combination with a CPN model provides an effective way of rapidly constructing an executable prototype of a protocol design.

Generating Protocol Software from CPN Models Annotated with Pragmatics

Model-driven software engineering (MDSE) provides a foundation for automatically generating software based on models that focus on the problem domain while abstracting from the details of underlying implementation platforms. Coloured Petri Nets (CPNs) have been widely used to formally model and verify protocol software, but limited work exists on using CPN models of protocols as a basis for automated code generation. The contribution of this paper is a method for generating protocol software from a class of CPN models annotated with code generation pragmatics. Our code generation method consists of three main steps: automatically adding so-called derived pragmatics to the CPN model, computing an abstract template tree, which associates pragmatics with code templates, and applying the templates to generate code which can then be compiled. We illustrate our method using a unidirectional data framing protocol.

PetriCode: A Tool for Template-Based Code Generation from CPN Models

Code generation is an important part of model driven methodologies. In this paper, we present PetriCode, a software tool for generating protocol software from a subclass of Coloured Petri Nets (CPNs). The CPN subclass is comprised of hierarchical CPN models describing a protocol system at different levels of abstraction. The elements of the models are annotated with code generation pragmatics enabling PetriCode to use a template-based approach to generate code while keeping the models uncluttered from implementation artefacts. PetriCode is the realization of our code generation approach which has been described in previous works.

Towards a model-based development approach for wireless sensor-actuator network protocols

Model-Driven Software Engineering (MDSE) is a promising approach for the development of applications, and has been well adopted in the embedded applications domain in recent years. Wireless Sensor Actuator Networks consisting of resource constrained hardware and platform-specific operating system is one application area where the advantages of MDSE can be exploited. Code-generation is an integral part of MDSE, and using a multi-platform code generator as a part of the approach has several advantages. Due to the automated code-generation, it is possible to obtain time reduction and prevent errors induced due to manual translations. With the use of formal semantics in the modeling approach, we can further ensure the correctness of the source model by means of verification. Also, with the use of network simulators and formal modeling tools, we obtain a verified and validated model to be used as a basis for code-generation. The aim is to build protocols with shorter design to implementation time and efforts, along with higher confidence in the protocol designed.

Towards a CPN-Based Modelling Approach for Reconciling Verification and Implementation of Protocol Models

Formal modelling of protocols is often aimed at one specific purpose such as verification or automatically generating an implementation. This leads to models that are useful for one purpose, but not for others. Being able to derive models for verification and implementation from a single model is beneficial both in terms of reduced total modelling effort and confidence that the verification results are valid also for the implementation model. In this paper we introduce the concept of a descriptive specification model and an approach based on refining a descriptive model to target both verification and implementation. Our approach has been developed in the context of the Coloured Petri Nets (CPNs) modelling language. We illustrate our approach by presenting a descriptive specification model of the Websocket protocol which is currently under development by the Internet Engineering Task Force (IETF), and we show how this model can be refined to target both verification and implementation.

Implementing the WebSocket Protocol Based on Formal Modelling and Automated Code Generation

Model-based software engineering offers several attractive benefits for the implementation of protocols, including automated code generation for different platforms from design-level models. In earlier work, we have proposed a template-based approach using Coloured Petri Net formal models with pragmatic annotations for automated code generation of protocol software. The contribution of this paper is an application of the approach as implemented in the PetriCode tool to obtain protocol software implementing the IETF WebSocket protocol. This demonstrates the scalability of our approach to real protocols. Furthermore, we perform formal verification of the CPN model prior to code generation, and test the implementation for interoperability against the Autobahn WebSocket test-suite resulting in 97% and 99% success rate for the client and server implementation, respectively. The tests show that the cause of test failures were mostly due to local and trivial errors in newly written code-generation templates, and not related to the overall logical operation of the protocol as specified by the CPN model.

Pragmatics Annotated Coloured Petri Nets for Protocol Software Generation and Verification

Pragmatics Annotated Coloured Petri Nets (PA-CPNs) are a restricted class of Coloured Petri Nets (CPNs) developed to support automated generation of protocol software. The practical application of PA-CPNs and the supporting PetriCode software tool have been discussed and evaluated in earlier papers already. The contribution of this paper is to give a formal definition of PA-CPNs, motivate the definitions, and demonstrate how the structure of PA-CPNs can be exploited for more efficient verification.