Web service composition needs to increase the dynamic feature of     adapt  ing   complex and unstable business environment. Thus the service selection and evaluation are very important for service composition. Although previous studies have   stated   some approaches to support dynamic composition, they are unable to balance the flexibility and verification very well in dynamic environment. Moreover,   most   service selection methods only depend on the similarity of a   pair   of single services.   These   methods are useful and concise to find substitutes for unavailable services,   but sometimes they   might be too strict to find a solution. To overcome these problems, we propose a novel approach named SPACE architecture with six basic structures, and define the service composition based on situation calculus language. SPACE estimates the similarity by the basic structures and constraints rather than the features of single service. It can help us to find non-optimal but acceptable substitutes and guarantee the verifications of composition. Finally, as a case study we consider a health care scenario to demonstrate     our approach   .
['Canghong Jin', 'Minghui Wu', 'Jing Ying']
A Structure-based Approach for Dynamic Services Composition