Computational tools and Interoperability in Comparative ... - CBS

EMBRACE: An EU initiative for enhance interoperability
Web Services described by WSDL files where data structures are typed using the XSD
format.
4.3.1 Quasi - a light-weight SOAP server
One of the main obstacles for many SOAP servers and clients is the computational overhead
and memory consumption involved in parsing large and complex XML structures.
For the BLASTatlas service, this was a limitting factor. Trying a conventional server package
called SOAP::Lite, rendered the submit process to require more memory than what is
in a modern desktop computer while taking around 20 minutes just to prepare the message
before submit. Once submitted, the server required the same overhead to parse the incoming
XML. The XML::Compile package for Perl prooved superior as a client framework.
However, for the server side, there was a demand for speed, flexibility and custom adjustment
which led to the development of a light-wight SOAP server called ’quasi’ (’QUite
A Soap Implementaion’ or ’QUAsi Soap Implementation’). Apart from the speed it has
further advantages:
• The server can be launched both remotely and locally. The later allows quick and
easy testing of services by reading SOAP message from STDIN
• XML parsing method (e.g. XML::Simple or XML::Twig) may be chosen independently
for each operations and even postponed until after the job is placed in the
queue and the job id is returned. This is an advantage for very big messages
• Control over the code stack enable implementation of custom functionality much
faster.
4.3.2 quasi mktemp - From template to Web Service
To take the ease-of-implementation to a new step, a template creator was written which
reads from a standard CBS template an example Web Service. The user provides the
name and version of the service and the tool prepares an entire installation of the service
on the servers. The template created gives the following :
• Creates automatically WSDL and XSD files for the name and version of the service,
placed in the proper location of the file system
• Example directory with a working Perl example using the service
• Has built-in templates for both syncrhonous and asynchronous access
• Creates the proper entry in the central services database table
• When the template creator has run a web page will be available describing the
service and providing links to WSDL and XSD files as well as WSDL-embedded
documentation
When designing Web Services, it is not a trivial task to keep track of namespaces,
declerations of input/output objects, operation names etc. The feedback received so far
for this tool indicates that functioning examples clearly reduces chances for mistakes. The
manual for the software is found in appendix D.6.
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