Blockchain technology enables the execution of collaborative business processes involving mutually untrusted parties. Existing tools allow such processes to be modeled using high-level notations and compiled into smart contracts that can be deployed on blockchain platforms. However, these tools do not provide mechanisms to cope with the flexibility requirements inherent to open and dynamic collaboration environments. In particular, existing tools adopt a static role binding approach wherein roles are bound to actors upfront when a process instance is created. Also, these tools do not allow participants to collectively make choices regarding alternative sub-processes or branches in the process model, at runtime. This paper presents a model for dynamic binding of actors to roles in collaborative processes and an associated binding policy specification language. The proposed language is endowed with a Petri net semantics, thus enabling policy consistency verification. Furthermore, the paper introduces a model for consensus-based control-flow flexibility, wherein participants in a process can collectively agree on how to steer the business process within the boundaries defined by control-flow agreement policies. The paper also outlines an approach to compile policy specifications into smart contracts for enforcement. An experimental evaluation shows that the cost of policy enforcement increases linearly with the number of roles, control-flow elements, and policy constraints.

区块链技术可以执行涉及相互不信任方的协作业务流程。现有工具允许使用高级符号对此类流程进行建模，并编译为可部署在区块链平台上的智能合约。但是，这些工具没有提供机制来应对开放和动态协作环境固有的灵活性要求。特别地，现有工具采用静态角色绑定方法，其中在创建流程实例时将角色预先绑定到参与者。而且，这些工具不允许参与者在运行时集体选择关于流程模型中替代子流程或分支的选择。本文提出了一个模型，用于将参与者动态绑定到协作过程中的角色，以及一种相关的绑定策略规范语言。所提议的语言具有Petri网络语义，因此可以进行策略一致性验证。此外，本文介绍了基于共识的控制流灵活性的模型，其中流程的参与者可以集体商定如何在控制流协议策略定义的边界内引导业务流程。本文还概述了一种将策略规范编译为智能合约以执行的方法。实验评估表明，策略执行的成本随角色，控制流元素和策略约束的数量线性增加。从而启用策略一致性验证。此外，本文介绍了基于共识的控制流灵活性的模型，其中流程的参与者可以集体商定如何在控制流协议策略定义的边界内引导业务流程。本文还概述了一种将策略规范编译为智能合约以执行的方法。实验评估表明，策略执行的成本随角色，控制流元素和策略约束的数量线性增加。从而启用策略一致性验证。此外，本文介绍了基于共识的控制流灵活性的模型，其中流程的参与者可以集体商定如何在控制流协议策略定义的边界内引导业务流程。本文还概述了一种将策略规范编译为智能合约以执行的方法。实验评估表明，策略执行的成本随角色，控制流元素和策略约束的数量线性增加。本文还概述了一种将策略规范编译为智能合约以执行的方法。实验评估表明，策略执行的成本随角色，控制流元素和策略约束的数量线性增加。本文还概述了一种将策略规范编译为智能合约以执行的方法。实验评估表明，策略执行的成本随角色，控制流元素和策略约束的数量线性增加。