RE: Visibility (was Re: Introducing the Service Oriented Architec tural style, and it's constraints and properties.

>  
>  
> -----Original Message-----
> From: Mark Baker [mailto:[email protected]] 
> Sent: Wednesday, February 19, 2003 6:26 PM
> To: dorchard@bea
> Cc: [email protected]
>

> On Wed, Feb 12, 2003 at 10:01:31PM -0800, dorchard@bea wrote:
> > The RESTful SOA has the advantage better visibility, as the 
> firewall 
> > can simply examine the generic interface to determine the 
> action being
> > performed.   Intermediaries, such as HTTP routers or 
> caches, can simply look
> > at the method.  An example is that a cache can look at the 
> GET and the 
> > identifier, and return a cached representation.  This is much more 
> > difficult if the method is in arbitrary places in the POST.  
> > Re-usability can be higher as the service may be available 
> on the Web 
> > as a URI may be transferable.
> 
> I agree with him completely.

The only part I disagree with is "much" in "much more difficult."   Sure
it's easier to write a firewall that only looks at HTTP headers and not the
SOAP content of a message, but it's do-able to build XML/SOAP-aware
firewalls, it's being done, and this is practical mainly because XML and
SOAP provide a framework that is flexible enough to be useful for most
anything but "visible" via standard XML toolkits.

Obviously this extends to routers as well; SOAP-aware routers would work
with any protocol -- FTP, SMTP, BEEP, TCP/IP, MQ -- as well as HTTP.  XML
standards (e.g. Xpath) allow routing based on message content as well as the
headers.  I think of this as a feature to be valued, e.g. in spam filters.  

So again, I agree that "visibility" is an important property, but what
powers it is *standards*, not just HTTP.