Task-based entailment constraints for basic workflow patterns

ABSTRACT

Access Control decisions are based on the authorisation policies defined for a system as well as observed context and behaviour when evaluating these constraints at runtime. Workflow management systems have been recognised as a primary source for defining authorisation policies at workflow designtime, as well as generating context at runtime.

This paper analyses recent work in the workflow community regarding established control-flow patterns. We claim that there is an intrinsic relationship between these patterns and a set of task-based entailment constraints - such as Separation of Duty - that have been recently identified by the access control community. These constraints are based on a pre-determined partial order on sequence and parallel execution patterns. When, however, such an order does not exist, because of more complex control-flow patterns, ambiguous constraint evaluation situations will arise at workflow runtime.

Accordingly, this paper reviews basic workflow patterns and identifies relationships between these and task-based entailment constraints. In addition, an analysis of possible runtime ambiguities that may arise from these relationships is presented. Our approach is based on recently developed techniques for visual constraint representation at a workflow design-time.

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INDEX TERMS

Primary Classification:
  D. Software
  D.4 OPERATING SYSTEMS
      D.4.6 Security and Protection
          Subjects: Access controls

General Terms:
Security

Keywords:
access control, separation of duty, task-based entailment constraints, workflow management, workflow modelling