A Web Service Management System (WSMS) can be well-thought-out as a consistent and a secure way of managing the web services. Web Service has become a quintessential part of the web world, managing and sharing the resources of the business it is associated with. In this paper, we focus on the query optimization aspect of handling the "natural language" query, queried to the WSMS. The map-select-composite operations are piloted to select specific web services. The main aftermath of our research is ensued in an algorithm which uses cost-based as well as heuristic based approach for query optimization. Query plan is formed after cost-based evaluation and using Greedy algorithm. The heuristic based approach further optimizes the evaluation plan. This scheme not only guarantees an optimal solution, which has a minimum diversion from the ideal solution, but also saves time which is otherwise utilized in generating various query plans using many mathematical models and then evaluating each one.