An Executable and Testable Semantics for iTasks

Proceedings of the 20th ACM SIGPLAN Workshop on Partial Evaluation and Program Manipulation

Koopman

et al. 2011

Workflow management systems (WFMS) are software systems that coordinate the tasks human workers and computers have to perform to achieve a certain goal based on a given workflow description. Due to changing circumstances, it happens often that some tasks in a running workflow need to be performed differently than originally planned and specified. Most commercial WFMSs cannot deal with the required run-time changes properly. These changes have to be specified at the level of the underlying Petri-Net based semantics. Moreover, the implicit external state has to be adapted to the new task as well. Such low-level updates can easily lead to wrong behaviour and other errors. This problem is known as the dynamic change bug. In the iTask WFMS, workflows are specified using a radically different approach: workflows are constructed in a compositional style, using pure functions and combinators as selfcontained building blocks. This paper introduces a change concept for the iTask system where self-contained tasks can be replaced by other self-contained tasks, thereby preventing dynamic change bugs. The static and dynamic typing system furthermore guarantees that these tasks have compatible types.

Section: The Itask Core Reference Implementationmentioning

confidence: 99%

iTasks for a change

Proceedings of the 20th ACM SIGPLAN Workshop on Partial Evaluation and Program Manipulation

Koopman

et al. 2011

“…To overcome these problems we develop a high level operational semantics for iTasks in this paper. The semantics in this paper is an extended version of our earlier work published in [9]. This semantics is used to explain the behavior of the iTask system, and to reason about the desired behavior of the system.…”

Section: A Semantics For Itasksmentioning

confidence: 99%

An Effective Methodology for Defining Consistent Semantics of Complex Systems

Koopman

Central European Functional Programming School

2010

This paper has two contributions. First, it gives a semantics for the iTask workflow management system. Second, it describes an effective methodology to construct such a semantics.Semantics is a formal description of the meaning of language constructs. Just like any other formal description there are umpteen ways of introducing flaws in such a description. Even trained people are not very effective in spotting issues in formal text. In this paper we show that it is very well possible to describe semantics of programming languages using a modern functional programming as carrier of the specification. This enables automatic sanity checks by the language compiler, simulation of the described semantics to validate the specification, and automatic testing of properties of the semantics.We illustrate this technique with the well-known example of simple imperative language as well as the iTask workflow management system. In our experience this methodology works very well. The combination of sanity checks, simulation and automatic testing of properties really helped to construct a trustworthy semantics for the iTask system.

“…-Tasks can become web applications including GUI elements like buttons, dialogues, windows and menus [15]. -The semantics of iTask combinators has been formally described [11,17].…”

Section: Introductionmentioning

confidence: 99%

Defining Multi-user Web Applications with iTasks

Central European Functional Programming School

Lijnse

et al. 2012

Self Cite

In these lecture notes we explain how multi-user web applications can be developed in a programming style that favors tasks as main building block for the construction of such systems. A task is work that has to be performed by human-beings and computers working together on the internet. This concept has been implemented in the iTask framework as a monadic combinator library that is embedded in the pure and lazy functional programming language Clean. These lecture notes consist of many examples and exercises, and also discusses the foundation of both the iTask system and task-oriented programming.