Architecture-driven System Reliability Analysis And Scenario Modeling Approach

With the development of Internet technologies,software systems is becoming much more complicated.However,users are expecting a better higher quality software system.Thus,how to ensure the high quality of complicated software system is a big challenge.To cope with this problem,software architecture designers need a more accurate quality attribute analysis technology which includes correctness,security,reliability.Reliabiliy is an important attribute of software,which indicates the probability of failure-free operation of a software system.Software designers have done a lot of work to improve systems' reliability,and fault tolerance is the most frequently used.Whereas most software estimating approaches fail to consider the impact of fault tolerance mechanisms(FTMs),which will lead to an inaccurate assessment and the resources-wasting.To analyze quality attributes,designers need a set of technologies to describe the system and combine with quality analytical technologies.System scenarios plays a key role in understanding the requirements and functionalities of a software system,the scenario-based analysis is widely used in various applications,especially in the design stage of software architectures.Consequently,designers need to specify sytem scenarios when designing the software architecture.However,existing modeling methods of software architecture do not consider scenario modelling.To address these drawbacks,this paper presents two techiniques which include a reliability estimation approach and a scenario modelling approach using Breeze/ADL.To incorporate the impact of FTMs in reliability prediction,we extend the stata-based architecture model with the consideration of correctness of components' I/O.The extended model illustrates the invocation among components in detail.Then,we leverage Discrete-Time Markov Chain(DTMC)to calculate the system reliability according to the extended model.Although researchers have proposed various scenario based approaches to analyze software architecture,there are still limitations in these researches,and a key limitation lies in that scenarios are typically not formally defined and thus may result in ambiguities.To reduce these ambiguities is an important work to improve the qualities of systems.In this paper,we extend an XMLbased architecture description language,called Breeze/ADL.We propose the vector clock algorithm to reduce the ambiguities in modeling scenarios.We implement our approach as a plugin of Breeze,and illustrate a running example of modeling an online shopping system in our case study.Results show that our approach is able to reduce ambiguities in the scenario of software architecture.