a journal of a researcher

Sunday, July 25, 2004

Use WSDL for Web Services

You do not need WSDL for web services, if you know how to invoke the services. WSDL is useful in two ways: when you want to invoke a service you do not know, you need information like the methods and the methods’ signatures; secondly, WSDL plays a role exactly like IDL to bridge the different languages, i.e. different languages maps to WSDL and use SOAP for protocol. It is yet another tempt for people to provide a uniform interface over specific languages. This time, it is over HTTP and SOAP. It is easier to code than CORBA. But the complexity of using CORBA and using WSDL are comparable.

Because AXIS uses bean serializer to implement the types in WSDL, the SOAP message uses tages for the attributes and values of the objects (cf. my post on 7/22).

People can image, with additional layers of HTTP and SOAP, the web services are slower than RPC or RMI. Here is a link provided by Michael Sintek on the performance of different SOAP implementations. Hopefully the fastest JibxSoap is just a little bit slower than RMI. Well, it is difficult to say if the slow is significent or not. But it is rather faster than other SOAP implmentations. I cite: “The performance of the JibxSoap implementation is likely due to two factors. First off, the light-weight nature of the framework and efficient internal operation adds very little per-message overhead. This per-message overhead looks to be especially high with Axis (as shown by the poor performance of all the Axis versions at very low response density, where the number of messages exchanged is considerably larger than all the other test cases combined). Secondly, the JiBX data binding basis of JibxSoap allows very fast conversion between XML and Java objects, minimizing the overhead for larger messages.” It is also interesting to know that Sun wants to use binary data encoding to replace XML, in order to improve the web service performance.

Isn’t WSDL another tempt to provide a framework over specific languages? Do we always turn in circles?


  • Yes. I think people turn in circles because these same people do not actually apply whatever they "invent". If they did, they'd learn lessons... because sometimes, the reason why something is a bad idea cannot be easily explained in a textbook format, so unless you go dirty and actually do menial labor, you'll never understand why it doesn't work.

    That's why I always want examples, that's why I always want to try things out in the real world, that's why I write so much code *before* I start writing papers.

    Going binary with XML is an absolutely terrible idea. The very reason why smart people adopted XML is that they all had to reverse engineer supposedly documented binary formats. We've learned hard lessons with binary formats over the years and learned that for most things we do, text is just fine. You can link to binaries when you absolutely need to, but when in doubt, use a text format.

    Now, those of us stuck in ivory towers or in marketing-land didn't learn these lessons. Maybe they were playing too much golf or writing too many papers, whatever the reason, they can do whatever they want, but it won't catch on because the smart people who did real work in the last 10 years have been there and have seen where the road leads... to hell...

    Going back to binary formats because it is supposedly faster is just plain stupid. Why don't they rewrite AXIS in assembler while at it?

    Maybe we should address the real reasons why things are slow in the first place and not be scared to conclude "this bit is not scalable, it has to go".

    XML and Web Services can be quite scalable... so what is the problem here? Well, maybe the layers you add on top of it, or the crappy Java frameworks have to go.

    By Blogger Daniel Lemire, at 7:46 AM  

  • Should you be interested, here is another link that describes performance studies between the older Apache SOAP, XML-RPC, and RMI.


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