Oracle8i Application Developer's Guide - XML Release 3 (8.1.7) Part Number A86030-01 |
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Building n-Tier Architectures for Media-Rich Management using XML: ArtesiaTech, 4 of 13

## Function Shipping: Separating Logical and Physical Tiers

The ability to separate the logical and physical tiers is a crucial factor to the long-term viability of a system.

In a well designed, flexible system architecture, the logical separation of the three tiers does not impose constraints on the underlying hardware. Computational logic should be able to easily be shifted onto a client machine as the necessity demands, whether it be a run-time based function for load balancing or a natural part of the system evolution wherein functional areas are realigned to minimize the communication traffic generated across subsystems. This is known as function shipping.

Function shipping is the process of moving logical services to the physical areas of a system where they can be optimally run. When communication traffic between services is congested, it is often beneficial for services to reside on the same machine, although an ideal configuration is generally specific to the actual system deployment and utilization.

An essential component of function shipping is the ability to rapidly re-deploy the control logic of specific services across a myriad of disparate and frequently proprietary, operating platforms. For some, Java holds the promise to make this a reality, but ultimately, this avenue again locks the implementers into a programming language specific paradigm.

Object-oriented system behavior is ultimately governed by the messages that are passed between objects. With the goal of function shipping in mind, the method by which objects are implemented is considerably less important than how a message is serialized to be rendered cross-platform compatible and the means by which a message will ultimately be processed. XML and its derivative standards offer a suitable framework in which both of these can be effectively addressed.

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