FORTRAN access to .NET web services

[Doug Tody]

Hi Martin -

On Fri, 17 Oct 2003, martin hill wrote:

> I would be interested to know how the folks on this list feel about
> creating various web services.  I get the impression that people are happy
> creating http/get-based ones (like the NVO cone search is, and the SIAP
> and SSA will be) but feel a bit more wary of document-based ones (whether
> http/get-serviced or Remote-Procedure-Call serviced) and very sceptical
> about fully RPC-ones.  Yet I am told that in fact making WSDL-described
> RPC services is as easy or easier than http/get based ones. This was by
> software engineers though; I expect to get to grips with both over the
> next few weeks, and if people are interested I will report back to this
> group (and DAL) about how easy it was/wasnot.

The initial DAL services like Cone and SIA were based on HTTP GET to
make them simpler for people to deal with who have to write the code
"from the ground up".  Sure, SOAP-based web services can be easy to deal
with if you have invested in some Web Services platform like Axis or
.NET, but not if you developing from the ground up to, e.g., interface
VO services to a legacy system written in a compiled language.  Also,
web services technology has been evolving rapidly, certainly it has over
the past year.  Support for different languages can vary greatly, there
can still be interoperability issues, and so forth.  I think it is time
now to start providing web service versions of the DAL services, but it
would have been a mistake to push this too much a year ago.

In the longer term we probably want both document and RPC-based services.
Complex data like VOTable, ADQL, etc., are always going to be best
dealt with as documents.  Asynchronous messaging will also want to be
document based.  RPC using WSDL currently looks good for most simple web
services.  In many cases it will still be possible to retain HTTP GET as
a simplest-possible form of method invocation, for cases where only a few
simple parameters need to be passed in.  If we do this right, we should
be able to use any of these protocols to invoke the same service code.
Using the document-based approach for anything complicated should make
this much easier.

	- Doug