Modelling and Analysis of Quantitative Quality Requirements

需求工程关注涉众对未来软件的需求的识别，满足这些需求的服务和约束的规范，以及将结果需求分配给代理（如人、硬件设备和软件组件）。功能需求描述了必须提供哪些功能来满足涉众的需求，质量需求描述了必须如何很好地提供功能来满足这些需求。质量需求的例子包括安全性、性能、可靠性、可用性、可维护性和可伸缩性等问题。虽然有许多以精确的方式引出、建模和推理功能需求的技术，但是到目前为止，在系统开发的早期阶段对质量需求的处理在很大程度上仍然是非正式的。这种情况是非常不可取的，因为质量需求对项目的成功至关重要，并且需要在开发的早期阶段就设计到系统中。质量需求的模糊陈述不能提供足够的信息来做出关键的设计决策，特别是当需要在相互竞争的质量之间做出困难的权衡时。在验证和确认过程中，模糊的质量要求陈述也是有问题的，因为它们为充分的分析和测试提供了不足的信息。因此，对于以定量的、可测试的方式表达的质量需求的启发、精确规范和分析的系统技术有强烈的需求。该项目的目的是提供一种完善的工程方法来阐述和分析质量要求。我们的方法依赖于定量目标模型的使用。这些模型帮助需求工程师以精确的、可测量的方式定义涉众的目标，并将它们与软件质量需求的精确的、可测试的规范联系起来。该模型可用于评估备选系统设计的相对价值，并指导优选设计的选择。在这个项目中，我们将开发软件工具来自动化这些模型的计算；并且我们将定义系统的技术来帮助需求工程师在保持数学形式（包括概率方程和时间逻辑）对他们隐藏的情况下详细阐述这样的模型。

Requirements engineering is concerned with the identification of stakeholders' needs concerning the future software, the specification of services and constraints that satisfy these needs, and the assignment of the resulting requirements to agents such as humans, hardware devices, and software components. Functional requirements describe what functions must be provided to satisfy the stakeholders' needs, quality requirements describe how well the functions must be provided to satisfy these needs. Examples of quality requirements include concerns such as security, performance, reliability, availability, maintainability, and scalability. While there are many techniques for eliciting, modelling, and reasoning about functional requirements in a precise way, the treatment of quality requirements during the early stages of system development has so far remained largely informal. This situation is extremely undesirable as quality requirements are critical to a project's success and need to be designed into the system since the very early stages of its development. Vague statements of quality requirements provide insufficient information to make key design decisions, particularly when difficult tradeoffs need to be made among competing qualities. Vague statements of quality requirements are also problematic during verification and validation as they provide insufficient information for adequate analysis and testing. There is therefore a strong need for systematic techniques for the elicitation, precise specification, and analysis of quality requirements expressed in a quantitative, testable way. The project aim is to provide a sound engineering approach to the elaboration and analysis of quality requirements. Our approach relies on the use of quantitative goal models. These models help requirements engineers to define stakeholder's goals in a precise, measurable way, and relate them to precise, testable specifications of software quality requirements. The models can be used to assess the relative values of alternative system designs and guide the selection of a preferred design. During this project, we will develop software tools for automating the computations of such models; and we will define systematic techniques to help requirements engineers elaborating such models while keeping the mathematical formalisms (involving probabilistic equations and temporal logic) hidden from them.