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In-Depth Information
Fig. 2.
SOAP with Attachments (SwA) - relative runtime improvement using Flex-
SwA aspects
the more complex reference component for data transfer can be introduced using
the proposed aspect framework. While the measurements only show the benefits
for synthetical echo services, applying it to the concrete multimedia workflow
also leads to a significant speedup. The plain workflow execution times without
aspects are about 4422 seconds (where the SOAP communication requires 94% of
the execution time). After weaving aspects into the services, the overall runtime
only takes about 245 seconds (where now only 8% of this execution time is
needed for communication). The overhead for the aspect handling (i.e., the time
needed for executing the AspectProvider) is about 11 seconds.
5.2 Use Case 2: Data Compression
Text detection in videos is another workflow of our motivating multimedia anal-
ysis scenario: here, large text documents might be generated, depending on a
given input video. These documents can be transported by Flex-SwA again, but
it is also desirable to compress the text data. We implemented an advice to com-
press data and encode it afterwards with BASE64 in order to embed it again
in an XML document. This aspect can reduce the message size to 60% of the
original size. Another possibility would be to use the message-based compression
offered by the web service container. Aspect-based compression allows us to use
field-specific compression algorithms for different parts of the message, which is
possible by the field operator of the pointcut description. This is reasonable since
different types of data (text, images, videos etc.) may require different compres-
sion techniques. If a better compression algorithm becomes available, it is much
easier to replace the applied compression using the proposed aspect-oriented so-
lution. Otherwise, a new compression approach would have to be realized in all
related web services' implementations.
This example indicates that the incorporation of new non-functional require-
ments via an advice is straightforward, since it effectively represents a filter
