I want to appear for the SCDJWS exam. What are the pre-requisites for this? I have done SCJP 1.4 almost two years back. I have no knowledge about Web services or XML technologies. Is knowing XML necessary to understand Webservices? If that is the case I shall first go for XML certification from IBM.
The only firm prerequisite is that you must hold a valid SCJP before you can sit for this exam. (Which, as you've mentioned, you have.)
I would recommend understanding XML to a certain extent, since that is the markup language used for the messages, but it's not required to know the ins and outs as detailed as would be required for passing IBM's 142 exam.
If you have "no knowledge" of web services, then I think that rather than plowing straight into the exam, it might be a good time to get some experience with the technologies involved and get some practice and learning under your belt before you start worrying about whether or not this is the exam for you.
Theodore Jonathan Casser
SCJP/SCSNI/SCBCD/SCWCD/SCDJWS/SCMAD/SCEA/MCTS/MCPD... and so many more letters than you can shake a stick at!