xml-dev - Re: Storing Lots of Fiddly Bits (was Re: What is XML for?)

[uche.ogbuji@fourthought.com]

> > > > I don't think it makes sense to build a business-object model
> > on top of DOM,
> >
> 
> and then:
> 
> > I have often ended up using DOM because I'm
> > working in a
> > distributed environment, using CORBA, and it makes it very easy
> > and natural to
> > just call DOM interfaces across the ORB

I hope you're not pointing out the above as a contradiction.  If so, context 
should have made it clear that when I do use DOM, it is never as a basis of 
the core business-object model, but as a UI or serialization interface.

> 	I too work in a distributed environment, until the last year in DCOM but
> increasingly using HTTP.
> 
> 	In the multi-tier model, the client communicates with the middleware or
> business-object tier using an RPC or distributed object protocol. For the
> sake of discussion, lets assume that the DCOM wire protocol and CORBA IIOP
> have roughly similar functionality as object RPC protocols.
> 
> 	Good practices in such systems dictate that round-trips between the client
> and business object layers be minimized (in fact round trips between tiers
> in general should be minimized except that when objects exist in the same
> process, or memory space, an object call as efficient as other in-process
> calls. (e.g. in C++ this is a vtable call, the difference in Java is the
> difference between a normal Java method invocation and an RMI invocation).
> 
> 	Failure to mininize round trips is often the single biggest performance
> drain on such systems otherwise well designed. This is a tenet of
> distributed object systems design.
> 
> 	While I have advocated judicious application of the DOM interfaces in
> object systems, the DOM is best not employed as a business object itself
> (i.e. the client ought not communicate directly with a distributed DOM), for
> reasons outlined by Paul Prescod, as well as the fact that this use of the
> DOM will *maximize* client-server roundtrips. For example a when a NodeList
> is returned from a distributed DOM call, the client obtains a *proxy* to the
> NodeList, and iteration through this proxy results in a server roundtrip for
> each call.

I am aware of DO network latency issues, but for the scale in which I have 
worked, a few basic optimizations minimize the ORB requests.

And your post does make me mind the fact that I should be careful when 
discussing such matters here.  Paul has spoken of needing to manage terabytes 
of data for his clients, and I don't know what size/structure DBs you usually 
work with, but I do not have experience deploying solutions invloving more 
than 20GB or so of data.  It is possible that what to me is a minor and 
unnoticeable dilation would scale to unusability in a large-enterprise 
application.

-- 
Uche Ogbuji
FourThought LLC, IT Consultants
uche.ogbuji@fourthought.com	(970)481-0805
Software engineering, project management, Intranets and Extranets
http://FourThought.com		http://OpenTechnology.org



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