Service Orchestration with Priority Constraints

Abstract

Business process management is an operational management approach that focuses on improving business processes. Business processes, i.e., collections of important activities in an organization, are represented in the form of a workflow, an orchestrated and repeatable pattern of activities amenable to automated analysis and control. Priority is an important concept in modeling workflows. We need priority to model cancelable and compensable tasks within transactional business processes. We use the Reo coordination language to model and formally analyze workflows. In this paper, we propose a constraint-based approach to formalize priority in Reo. We introduce special channels to propagate and block priority flows, define their semantics as constraints, and model priority propagation as a constraint satisfaction problem.

Compositional workflow modeling with priority constraints

“…In the case of non-synchronous channels (e.g., FIFO, AsyncDrain) and priority blocking channels (i.e., BlockSourceSync, BlockSinkSync), their ends can only have ac- quired priority. We augment the constraint-based framework for Reo [24] to capture priority and the priority propagation mechanism.…”

“…In the rest of this paper, we omit data constraints when defining behavior of Reo elements. Data constraints are irrelevant for priority flow and were thoroughly covered in [24].…”

“…In our previous work [24], we described the behavioral constraints that each Reo primitive imposes on a network as a CSP. We now extend these constraints with priority capturing variables.…”

“…In [24], we proposed to model the semantics of Reo as a Constraint Satisfaction Problem (CSP). We defined data flow in a Reo network in the form of mathematical expressions on data observed at various nodes or ports.…”

“…In this paper, we develop a theoretical foundation for priority flow modeling in Reo where the behavioral semantics of Reo circuits extended with priority-aware modeling primitives is expressed in terms of CSP. The paper revises and extends our initial ideas about applying Reo with priority flow control channels to model service orchestrations [27]. In this revision, we refine definitions, dedicate more space for case study analysis, and supplement the theory with an open-source implementation of a tool to generate CSP solutions for a given Reo circuit with priority flow.…”