Due to the web services' heterogeneous nature, which stems from the definition of several XML-based standards to overcome platform and language dependence, web services have become an emerging and promising technology to design and build complex inter-enterprise business applications out of single web-based software components. To establish the existence of a global component market, in order to enforce extensive software reuse, service composition experienced increasing interest in doing a lot of research effort. This paper discusses the urgent need for service composition, the required technologies to perform service composition. It also presents several different composition strategies, based on some currently existing composition platforms and frameworks, re-presenting first implementations of state-of the-art technologies, and gives an outlook to essential future research work.