Contract-based design is an emerging paradigm for correct-by-construction hierarchical systems: components are associated with assumptions and guarantees expressed as formal properties; the architecture is analyzed by verifying that each contract of composite components is correctly refined by the contracts of its subcomponents. The approach is very efficient, because the overall correctness proof is decomposed into proofs local to each component. However, the process for the contract specification and refinement is quite expensive because the requirements are formalised into formal properties, where part of the complexity is delegated to the designer, who has the burden of specifying the contracts. Typical problems include understanding which contracts are necessary, and how they can be simplified without breaking the correctness of the refinement and other refinements in case some subcontracts are shared. In this paper, we tackle these problems by proposing a technique to understand and simplify the contract refinements of a system architecture during the development process for the contract specification and refinement. The technique, called tightening, is based on parameter synthesis. The idea is to generate a set of parametric proof obligations, where each parameter evaluation corresponds to a variant of the original(s) contract refinement(s), and to search for tighter variants of the contracts that still ensure the correctness of the refinement(s). We cast this approach in the OCRA framework, where contracts are expressed with LTL formulas, and we evaluate its performance and effectiveness on a number of benchmarks.

中文翻译：

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收紧系统架构的契约细化

基于契约的设计是一种新的构造正确的分层系统范式：组件与表示为形式属性的假设和保证相关联；通过验证复合组件的每个合同是否由其子组件的合同正确细化来分析架构。该方法非常有效，因为整体正确性证明被分解为每个组件本地的证明。然而，合同规范和细化的过程是相当昂贵的，因为需求被形式化为正式的属性，其中部分复杂性委托给设计者，他有责任指定合同。典型的问题包括了解哪些合同是必要的，以及如何在不破坏细化和其他细化的正确性的情况下简化它们，以防共享一些分包合同。在本文中，我们通过提出一种在合同规范和细化的开发过程中理解和简化系统架构的合同细化的技术来解决这些问题。这种称为紧固的技术基于参数合成。这个想法是生成一组参数证明义务，其中每个参数评估对应于原始合同细化的变体，并搜索仍然确保细化正确性的更紧密的合同变体（ s)。我们在 OCRA 框架中采用这种方法，其中合同用 LTL 公式表示，