Big Picture General Question about XML SOAP and WSDL Web Services

[jm]

I understand how an XML formatted SOAP message is used to request
items from a web service and how the XML formatted SOAP response is
used. I am still missing the big picture, however.

When is this used?

For example, let's say that I have three systems.

An Oracle system, SQL Server 2000 system and a DB2 legacy system.

Why would web services be better than simply using an scripting page
over HTTP to bring back the data? So, I could use ASP.NET to hit all
three databases and and bring them back on a single page, seamless to
the end user. For that matter, an individual page could be used for
each system (if the data were unrelated for example).

What am I missing here? How would Web Services help me? I know it
would; I just can't picture it.

Thanks for your help.

 

[Andy Dingley]

Why would web services be better than simply using an scripting page
over HTTP to bring back the data?

A "scripting page over HTTP"_is_ a web service

As to why it's better than a SOAP web service, then that depends on
robustness and maintainability.

One in-house SOAP service is no better than an in-house web service
built from wet string and Perl. A family of such services, or a
service that connects to an external source, soon becomes
unmaintainable if it's not built to a single industry-wide standard.
You need a stable standard to code against, not an ad hoc one that
varies for every service and is not guaranteed to be stable in the
future.

There's also WSDL (which is particularly visible with .NET). By
formalising the deescription of a service, your client-building tools
can be automated. You could do this with an ad hoc service too, except
that no-one does (too much trouble for a one-off) and you certainly
won't see 3rd party support for it from an independent tools vendor.

So, I could use ASP.NET to hit all three databases and and bring them back on a single page,

This is aggregation, rather than web services. You could use three
random number generators and feed them onto one page. The "advantages
of web services", whatever they might be, are to do with the cost of
implementing each back-end link, not the benefits of combining the
three onto one presentation page.

 

[Christopher Browne]

I understand how an XML formatted SOAP message is used to request
items from a web service and how the XML formatted SOAP response is
used. I am still missing the big picture, however.

When is this used?

For example, let's say that I have three systems.

An Oracle system, SQL Server 2000 system and a DB2 legacy system.

Why would web services be better than simply using an scripting page
over HTTP to bring back the data? So, I could use ASP.NET to hit all
three databases and and bring them back on a single page, seamless to
the end user. For that matter, an individual page could be used for
each system (if the data were unrelated for example).

What am I missing here? How would Web Services help me? I know it
would; I just can't picture it.

Web Services is NOT about "web pages;" it is much more analagous to a
(dumbed-down) version of CORBA.

If you have interfaces to Oracle/SQL Server/DB/2 that you're happy
with, then SOAP may not provide anything of value to you. It's sure
to be less efficient than the "native" DB interfaces.

Web Services would be valuable if you wanted to be able to publish a
single seemingly-seamless API for _other_ people to use to access the
data. If that "unification" isn't so valuable that you can live with
the loss of efficiency involved in a heavyweight protocol like SOAP,
then it may not really be a help to you.

 

[jm]

Web Services is NOT about "web pages;" it is much more analagous to a
(dumbed-down) version of CORBA.

If you have interfaces to Oracle/SQL Server/DB/2 that you're happy
with, then SOAP may not provide anything of value to you. It's sure
to be less efficient than the "native" DB interfaces.

Web Services would be valuable if you wanted to be able to publish a
single seemingly-seamless API for _other_ people to use to access the
data. If that "unification" isn't so valuable that you can live with
the loss of efficiency involved in a heavyweight protocol like SOAP,
then it may not really be a help to you.

Are web services using XML and SOAP a passing thing or is there
something else I should be looking to. I spoke to some Java guys who
didn't like it, but I think they just may not have like Microsoft (who
has an interest in SOAP?).

Thanks for comments.

 

[GIMME]

WebServices are here to stay. Peruse around here ...

http://dev2dev.bea.com/technologies/webservices/articles.jsp