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The number of web services capable of processing multimedia data is growing. Typically, a multimedia web service realizes only a specific algorithmic processing step, such as video decoding. Thus, it is desirable to compose several web services hosted on different sites into a new value-added workflow. However, the transfer of large amounts of multimedia data within workflows based on SOAP as the prevalent communication paradigm between web services induces redundant data transfers. In previous work, we have presented a reference technique called Flex-SwA that solves this problem. However, its usage is accompanied by additional software development efforts that have to be repeated when a new service or client is implemented. In this paper, we present an aspect-oriented programming approach that significantly reduces these software development efforts. The solution allows developers to easily extend existing multimedia web services with the capability of efficient data transmission without modifying the implementations of the original services, while at the same time the advantages of SOAP web services are still maintained. Experimental results for a distributed video analysis workflow demonstrate the feasibility of the presented approach. |
