The Old Joel on Software Forum: Part 4 (of 5) - Real experience XML/HTTP .vs. WSDL/SOAP

Real experience XML/HTTP .vs. WSDL/SOAP

Hi all,

We have a great debate in our company between exposing business service as XML document over HTTP .vs. as service defined in WSDL and using the SOAP protocol (with literal or encoded payload).

For the time being, the usage is purely internal, but in the future, such service will be likely enhanced to support external partners.

As anyone any feedback on problem/limitation thru experience on any of these 2 approach ?

BobC
Wednesday, February 4, 2004

Performance wise they are both the same. SOAP/HTTP is the same 'protocol'. The parsing involved is the same.
But WSDL and SOAP means you are more standardized for external use.

Tal Rotbart
Wednesday, February 4, 2004

That's indeed what is put forward by the people in favor of WSDL/SOAP : standard and so better support by tools vendor.

However, the other camp emphasizes that interop between SOAP stacks still varies and so the simple solution (XML+HTTP) is good enough and more mature so far.

BobC
Wednesday, February 4, 2004

Are these external partners well defined yet? Do they have a preferance? Can you force them to use one versus the other?

m
Wednesday, February 4, 2004

Yes, in the previous system we want to replace, there was a single point of access using XML/HTTP used by another internal app. However, it is very likely that we will have to change the semantic of this access point (the system is being redesign) and new services will be added.

Global orientation of the IT system architecture is SOA. The question is how fast we are restructuring and if we should use WSDL/SOAP now or wait a little longer (using XML/HTTP for the time being).

Opening the new services to external partner is still just a "vision" thing, not a requirement yet.

BobC
Wednesday, February 4, 2004

We ran into an interesting scenario yesterday:

We are currently moving from HTTP XML to WSDL SOAP with a Java middle tier.

In our VB6 app we were expecting a DOM object returned but apparently the java guys decided to return a DOMSelection (result of an XPAth I assume) object which was screwing us up.

That made me start thinking: Should there be a standard that any XML returned from a web service should be a full DOM Object? (like RSS) Or should it be OK to return partial XML like this DOMSelection object scenario?

Any ideas?

GenX'er
Wednesday, February 4, 2004

SOAP doesn't have to go over HTTP. That's just the most common usage of it : a simple RPC call over HTTP with all kinds of extra stuff for features people don't use.

Sounds like the real argument here is between a REST style interface and an RPC style interface. The answer probably depends on your application and its users.

SOAP is certainly the current standard for passing XML over an RPC style interface. I think all the strange bits like XML document vs fragment, etc are probably defined.

This might be a good place to start:

http://www.intertwingly.net/stories/2002/07/20/restSoap.html

mb
Wednesday, February 4, 2004

I've found RPC over SOAP pretty easy. If
you want to just send XML messages and use
attachments it's not as easy.

son of parnas
Wednesday, February 4, 2004