Simulation is aimed very often to solve problems of great complexity requiring -beyond using the advanced simulation software tools -platforms that enable the implementation of such software systems. In recent years the concept of cloud computing has emerged and is being applied more and more widely for solving such problems. This paper, beyond delineating the main trends of the development of distributed simulation over a grid, especially over the Internet through Web-based applications, highlights the concepts of service-based simulation system approach. This concept gives the possibility of implementing Web-or cloud agents and other ASP system compliant simulation services based on simulation standards. As a sample application, Fuzzy Web Service is demonstrated as a part of CASSANDRA 4.0 (Cognizant Adaptive Simulation System for Applications in Numerous Different Relevant Areas) that is developed by the McLeod Institute of Simulation Sciences Hungarian Center.