This paper discusses the means available in linear and intuitionistic logic for exact logical representation of software features for dynamic web service composition. Besides logical means for representation of data dependencies and implicit linking of services, also usage of pre-programmed control structures, alternative outcome of services, exception handling, hierarchical data structures, usage of resources and representing changes of environment are briefly considered. The goal is to describe possibilities of choice of logical instruments to a designer of a dynamic web service composition system.

Collaborative Filtering based on similarity suffers from a variety of problems such as sparsity and scalability In this paper, we propose an ontological model of trust between users on a social network to address the limitations of similarity measure in Collaborative Filtering algorithms. For enhancing the constructed network of users based on trust, we introduce an estimate of a user's trustworthiness called T-index to identify and select neighbors in an effective manner We employ T-index to store raters of an item in a so-called TopTrustee list which provides information about users who might not be accessible within a predefined maximum path length. An empirical evaluation shows that our solution improves both prediction accuracy and coverage of recommendations collected along few edges that connect users on a social network by exploiting T-index. We also analyze effect of T-index on structure of trust network to justify the results.