Some Developments in the Use of Metadata-Driven Architectures


The examples described so far are low on the "semantically aware" scale we introduced in Chapter 3. Now let's examine metadata in the semantically aware system.

A key hurdle has to be jumped for the metadata to be treated as semantically aware: The application code can no longer refer to the semantic definition as expressed in the database schema directly; it must refer to it indirectly. I'll describe two generalized examples and then conclude the chapter with a case study of an application that illustrates the value of the metadata-driven approach, taken to the architectural level.

Generating Code from a Metadata Model

Tenfold Corporation markets a product based on its Universal Application Platform architecture.[23] This product allows developers to define an application in metadata, including much of its validation logic. The system then generates code that corresponds to the semantic rules as set up in the dictionary. As long as the code is not modified, subsequent changes to the dictionary will allow the system to generate a new set of code, complete with new semantics.

The Crucial Role of Metadata for Non–Self-Describing Content

Velocity.com[24] created health care applications based on Organic Architecture (now marketed by Instantica[25]). Organic Architecture allowed developers to define a schema, and then build the application to that schema, without writing application code. The application execution engine understood the same semantics as the design tools, which meant that the application construction process obeyed assembly rules that prohibited most of the errors that plague traditional development.

These two examples point toward a future in which applications will be fully described and implemented in metadata. Applications fully defined in metadata is quite a stretch for many developers to imagine. To get a sense of how this is possible, in the following case study I focus on a smaller example that requires virtually no new technology and handles many of the issues needed to scale this to a larger endeavor.

[23]See http://www.10fold.com/ for further information.

[24]See http://www.velocity.com/ for further information.

[25]See http://www.instancia.com/ for further information.




Semantics in Business Systems(c) The Savvy Manager's Guide
Semantics in Business Systems: The Savvy Managers Guide (The Savvy Managers Guides)
ISBN: 1558609172
EAN: 2147483647
Year: 2005
Pages: 184
Authors: Dave McComb

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