iTasks for a change: type-safe run-time change in dynamically evolving workflows

  • Authors:

  • Rinus Plasmeijer;Peter Achten;Pieter Koopman;Bas Lijnse;Thomas van Noort;John van Groningen

  • Affiliations:

  • Radboud University Nijmegen, Nijmegen, Netherlands;Radboud University Nijmegen, Nijmegen, Netherlands;Radboud University Nijmegen, Nijmegen, Netherlands;Radboud University Nijmegen, Nijmegen, & Netherlands Defence Academy, DenHelder, The Netherlands;Radboud University Nijmegen, Nijmegen, Netherlands;Radboud University Nijmegen, Nijmegen, Netherlands

  • Venue:
  • Proceedings of the 20th ACM SIGPLAN workshop on Partial evaluation and program manipulation
  • Year:
  • 2011

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Abstract

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 self-contained 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.