On Mon, 26 Apr 2004 08:02, Tim Churches wrote:
> Basically, apart from a remote procedure call protocol, you also need an
> interface description protocol, a web service directory/discovery
> protocol, and a web service security and authentication protocol which
> is a bit more flexible than HTTP authentication. The question is whether
> the SOAP-related answers to these (WSDL, UDDI and WS-Security), or the
> (technically better, IMHO) CORBA equivalents are so flawed that they
> should be ignored. My feeling is that they can't be ignored, even if the
> more limited aim of hxp is interoperability between only FOSS health
> projects. Thus I wonder if XML-RPC is the correct foundation for hxp.
What I personally like for it's extreme flexibility and at the same time ease
of implementation and use is XML-RPC via Jabber protocol.
Jabber can take care of authentication, security, directory, discovery,
message receipts, store-and-forward on demand etc., while XML-RPC is just
the packhorse and container for the data.
I disagree re interface description protocol - why would you need one? XML-RPC
servers can (and should) be written to spit out their interface documentation
via HTTP when queried, and that's all you need to implement clients. The
actual data types are described embedded in the actual data.
The return of the interface with a call to the server should be sufficient. However,
if every server has a different interface then one has the many body problem, in that
one has to do some kind of implementation (be it JAXB , or whatever) to be able
to use each "interface". If people agree on common "interfaces" which means both
data and operations on the data, then one can begin to get interoperability. The exact
mechanism for discovering who supports what interface is a separate and less demanding
problem. It does no good to have the "actual data types" embedded in the data (which is good
and supported by many systems), unless I know what they "mean" and what to do with them,
and how to request them. These are functions of interface standards. Jabber may be fine,
but it is yet another protocol standard. How many do I have to implement to talk to people?
Dave
Horst
