metadata or not

The question whether web services require metadata is certainly an
interesting one and goes way back. You can look at an email posted to the
SOAP mailing list in December '99, where Don Box divided "SOAP use cases"
into 3 categories:

1.) type-unaware
2.) statically/strongly typed
3.) dynamically typed

I still think Don's basic categorization is valid. A service of one kind
(say, strongly typed) is not a priori better than a service of another type
(type-unaware); the two services simply have different
characteristics/applications.

For example, if a web service returns a set of rows and a client just wants
to display them in a table, the client may not need to know anything about
the service's metadata; browsers manage this sort of interaction all the
time. On the other hand, if the web service is going to update a bank
account, then, maybe both the client and the service better know in advance
the type and location of the <amount> element.

F

[1] http://discuss.develop.com/archives/wa.exe?A2=ind0001&L=SOAP&D=0&P=5555

> -----Original Message-----
> From: xml-dist-app-request@w3.org [mailto:xml-dist-app-request@w3.org]On
> Behalf Of christopher ferris
> Sent: Tuesday, April 03, 2001 3:58 PM
> To: Andrew Layman
> Cc: xml-dist-app@w3.org
> Subject: Re: Announce: A brief history of SOAP
>
>
> I totally concur with Andrew on this. Personally, I would
> prefer a standardized representation as it would enable
> a better class of tools.
>
> Cheers,
>
> Chris
> Andrew Layman wrote:
> >
> > If I send you a message such as
> >
> >         <Translate>
> >                 <gamma>123.45</gamma>
> >                 <epsilon>.67</epsilon>
> >                 <pi>3.14159</pi>
> >         </Translate>
> >
> > then you presumably either have somehow got some idea what this message
> > means and what its structure is etc., or you don't and cannot process it
> > (except as generic XML).  However you got the knowledge, that was the
> > metadata.
> >
> > In the case of the messages sent to the "SOAP Validator" at UserLand's
> > site, the documentation describing the messages is the metadata.
> >
> > I don't think you can do much without some metadata.  The only issue is
> > the form that the metadata takes, largely whether it is in a standard
> > form or not.
> >
> > -----Original Message-----
> > From: Dave Winer [mailto:dave@userland.com]
> > Sent: Tuesday, April 03, 2001 3:31 PM
> > To: xml-dist-app@w3.org
> > Subject: Re: Announce: A brief history of SOAP
> >
> > Andrew I don't know enough about the kinds of environments you use, but
> > I'm
> > with Fredrik on this. We do just fine without any meta data. No
> > "requires"
> > here. Dave
> >
> > ----- Original Message -----
> > From: "Andrew Layman" <andrewl@microsoft.com>
> > To: <xml-dist-app@w3.org>
> > Sent: Tuesday, April 03, 2001 12:07 PM
> > Subject: RE: Announce: A brief history of SOAP
> >
> > > I think that the point is that any exchange of messages via SOAP (or
> > > otherwise) requires that the parties have mutual access to some sort
> > of
> > > metadata describing the types of the data being exchanged.  WSDL
> > > provides such metadata in an implementation-neutral way that supports
> > > and leverages the W3C specifications such as Schema.
> > >
> > > -----Original Message-----
> > > From: Fredrik Lundh [mailto:fredrik@pythonware.com]
> > > Sent: Saturday, March 31, 2001 2:35 AM
> > > To: Box, Don
> > > Cc: xml-dist-app@w3.org
> > > Subject: Re: Announce: A brief history of SOAP
> > >
> > >
> > > > You can read it at http://www.develop.com/dbox/postsoap.html
> > >
> > >     "Does SOAP/XML Messaging make sense without something like
> > >     WSDL? No way"
> > >
> > > huh?  I've got lots of users for my python soap implementation,
> > > and now you're saying that what they do doesn't make sense?
> > >
> > > what have we missed?
> > >
> > > Cheers /F
> > >

Received on Tuesday, 3 April 2001 20:29:05 UTC