Verification of communication protocols in web-services

The last decade has seen a massive migration towards the service oriented paradigm that has resulted in 1) resolving the software interoperability issues, 2) increased re-usability of the code, 3) easy inter-application communications, and 4) significant cost reduction. However, individual web-services seldom meet the business requirements of an application. Usually an application life-cycle involves interacting with several web-services based on its workflow. Considering that this might require 1) sharing data with multiple services, 2) tracking the response for each service request, 3) tracking and compensating the service failures, etc., usually a domain-specific language is used for service composition. Each service has an interface to outline its functionality and they are composed based on these interfaces. Nevertheless, any error or omission in these exposed interfaces could result in a myriad of glitches in the composition and the overlying application. This is further exacerbated by dynamic service composition techniques wherein services could be added, removed or updated at runtime. Consequently service consuming applications heavily depend on the verification techniques to vouch for their reliability and usability. The scope of applications based on service composition is rapidly expanding into critical domains where the stakes are high (e.g. stock markets). Consequently their reliability cannot be solely based on testing, wherein educated guesses are involved. Model-checking is a formal method that has an unprecedented ability to endorse the correctness of a system. It involves modeling a system before verifying it for a set of properties using a model-checking tool. However it has hitherto been sparingly used because of the associated time and memory requirements. This thesis proposes novel solutions to deal with these limitations in verifying a service composition. We propose a technique for modeling a service composition prior to verifying it using a model-checking tool. Compared to existing techniques that are ad-hoc and temporary, our solution streamlines the transformation by introducing a generic framework that transforms the composition into intermediate data transfer objects (DTOs) before the actual modeling. These DTOs help in automating the transformation by allowing access to the required information programmatically. The experimental results indicate that the framework takes less than a second (on average) in transforming BPEL specifications. The solution is made more appealing by further reducing the aforementioned time and memory requirements for model-checking. The additional reduction in memory is attributed to storing the states as the difference from an adjoining state. The reduction in time is realized by exploring the modules of a hierarchical model concurrently. These techniques offer up to 95% reduction in memory requirements and 86% reduction in time requirements. Furthermore, the time reduction technique is also extended to non-hierarchical models. This involves introducing hierarchy into a flat model in linear time before applying the time reduction techniques. As compared to other techniques, our method ensures that the transformed model is equivalent to the original model

Development and evaluation of a framework for semantic validation of performance metrics for the IBM InfoSphere Optim Performance Manager

Validation is an important field in the software development process. It helps to increase the software quality but is also very expensive and time consuming. To decrease the costs approaches to automate the validation process are necessary. In this thesis a framework is developed, which does not need user interaction to validate the IBM InfoSphere Optim Performance Manager semantically. It is able to validate values of different behavioral patterns. It covers deterministic, semi-deterministic and non-deterministic behavior. The thesis describes the process of the development of the framework. It introduces available approaches and examines them with regard to the suitability for the framework. The found solution is described in theory and a prototype is implemented to apply the solution to praxis. This prototype is evaluated on the latest version of the IBM InfoSphere Optim Performance Manager

Memory efficient state-space analysis in software model-checking

Formal methods have an unprecedented ability to endorse the correctness of a system. In spite of that, it has been limited to safety-critical and mission-critical systems owing to significant time and memory costs involved. Lately, our ever increasing dependency on software in all walks of our life has necessitated using formal methods for a wider range of softwares. In this paper, we propose an algorithm to make this possible by reducing the memory requirement for model checking, a widely used formal method. A modelchecker stores all explored states in memory to ensure termination. The proposed algorithm slash memory costs by storing these states in compressed form. In compressed form, a state is stored as how different it is from its previous state. Our experiments report a memory reduction of 95% with only doubling of computation delay. Aforesaid reduction allows model checking in a machine with only a fraction of memory needed otherwise. Consequently the advantage is twofold, 1)enormous savings as only a small physical memory is required and 2)as more states can now be stored in a memory of same size, the chances of complete state-space analysis is exceedingly high