Re: Storing Lots of Fiddly Bits (was Re: What is XML for?)
> > > > 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@f... (970)481-0805 Software engineering, project management, Intranets and Extranets http://FourThought.com http://OpenTechnology.org xml-dev: A list for W3C XML Developers. To post, mailto:xml-dev@i... Archived as: http://www.lists.ic.ac.uk/hypermail/xml-dev/ and on CD-ROM/ISBN 981-02-3594-1 To (un)subscribe, mailto:majordomo@i... the following message; (un)subscribe xml-dev To subscribe to the digests, mailto:majordomo@i... the following message; subscribe xml-dev-digest List coordinator, Henry Rzepa (mailto:rzepa@i...)
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