CDS XML Web services are easy to consume but it is very important to show users how to use a SOAP architecture in one of their programming languages. The CDS XML Web Services portal has been designed in this way and it gives a lot of useful information. For those who need a very high availability of the services, it is possible to register. Registered users are informed about technical and software maintenance which may cause short interruptions. Support is also provided through the firstname.lastname@example.org mailbox, as are the other CDS online services.
Our goal is not to publish an increasing list of XML Web Services but to take into account the user real needs. In a first step, XML Web Services like the Sesame name resolver and the UCD resolver were interesting for testing the Axis/ Tomcat server reliability and for developing the portal. In a second step other services like the VizieR Access (which may increase severely the load on our XML Web Services server) have been implemented. We are currently developing other services like coordinate transformation or unit conversion.
How-to pages (Figure 2) are available for the CDS XML Web Service. For each service, the existing methods are listed, like metaAll which gives all the meta information about VizieR catalogues, cataloguesData which gives the results of a query to VizieR, etc... These operations are detailed (input parameters and results) with examples. Examples of client source code are also given in Java or Perl. Direct access to the WSDL file, and examples of SOAP requests and answers are also provided. Note that it is not necessary to deal with the contents of a SOAP file to have client access to the CDS XML Web Services.
The availability and the reliability of our XML Web Services are major points of our activity. One solution is the creation of mirrors to minimize the access failure rate. We have also created XWSEA (XML Web Service Easy Access), a light client-side Java or C# SOAP API which provides a very easy way to use SOAP in Java standalone applications as well as in applets. This API is not restricted to CDS XML Web Services and is user friendly since it requires only very basic skills in XML Web Services technologies. XWSEA has not been created from scratch but is an overlay on kSOAP which is small, fast and free. Other works related to Web Services are ongoing at CDS and will be published on the XML Web Service portal (information, examples, help, etc. ).
CDS XML Web Services are now in a full exploitation phase and will be developed in the Virtual Observatory framework depending on the user needs. Development of additional tools and mirroring of the services are among the most important ongoing activities.
Axis - http://ws.apache.org/axis/
C# - http://msdn.microsoft.com/vcsharp/
Java - http://java.sun.com
kSOAP - http://ksoap.enhydra.org/
SOAP - http://www.w3.org/2000/xp/Group/
Tomcat - http://jakarta.apache.org/tomcat/
WSDL - http://www.w3.org/2002/ws/