Mitigating the obsolescence of specification models of service-based systems

Service-based systems (SBS) must be able to adapt their architectural configurations during runtime in order to keep satisfied their specification models. These models are the result of design time derivation of requirements into precise and verifiable specifications by using the knowledge about the current service offerings. Unfortunately, the design time knowledge may be no longer valid during runtime. Then, nonfunctional constraints may have different numerical meanings at different time even for the same observers. Thus, specification models become obsolete affecting the SBS' capability of detecting requirement violations during runtime and therefore they trigger reconfigurations when appropriated. In order to mitigate the obsolescence of specification models, we propose to specify and verify them using the computing with words (CWW) methodology. First, non-functional properties (NFPs) of functionally-equivalent services are modeled as linguistic variables, whose domains are concepts or linguistic values instead of precise numbers. Second, architects specify at design time their requirements as linguistic decision models (LDMs) using these concepts. Third, during runtime, the CWW engine monitors the requirements satisfaction by the current chosen architectural configuration. And fourth, each time a global concept drift is detected in the NFPs of the services market, the numerical meanings are updated. Our initial results are encouraging, where our approach mitigates effectively and efficiently the obsolescence of the specification models used by SBS to drive their reconfigurations.