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by Meghraj Thakkar
Oracle8 is an object-relational database management system. In addition to supporting relational data, it allows you to have object types.
Oracle’s Network Computing Architecture (NCA) is a very appropriate environment for distributed computing. NCA is a three-tier approach consisting of the following components:
There are several benefits of using the NCA approach:
The Network Computing Architecture makes use of three categories of cartridges:
Client Cartridge
In a client/server model, operations on server data are typically executed on the server, but applications can be executed either on the client or the server. This results in thick clients. The client cartridges, on the other hand, are used to support thin clients. It is important to carefully define and distinguish what constitutes direct and necessary GUI support and what constitutes application functions. NCA’s CORBA/IIOP communication mechanisms are used for inter-cartridge communication.
Application Cartridge
In the NCA, the application cartridge contains all the substantial application logic. The application server provides a mechanism for enabling applications, programs, and objects to communicate with each other. The Oracle Web Application Server uses and extends the HTTP-based communication mechanism. It also supports CORBA/IIOP-based communication methods. The applications, programs, and objects should have the following features:
An application cartridge is an object that uses the services of an application server and/or other cartridges to do the following:
Tip:
Even though application cartridges are managed by the application server, they can communicate with each other without the help of the application server (through the use of Java RMI, for example). When the cartridges communicate with each other without the help of the application server, they will not be able to take advantage of features such as load balancing.
In a complete solution, the application cartridge typically makes use of another stand-alone application, such as a browser, to handle the user interface and database servers to provide data storage and transaction control functions.
Application cartridges can add to the services provided by the application server. Other application cartridges, with or without involving the application server, can use these services. For example:
It should be noted that application cartridges can be anything, but they should be managed by the application server and make use of the underlying communication-related services. Unlike database servers, which have the notion of datatypes, the application server has no notion of datatypes. Application servers do not impose any programming methodology. Application cartridges should use HTTP-based or CORBA-based methods to communicate with other cartridges and applications.
Data Cartridges
A data cartridge is a software component that consists of datatypes, methods, and interfaces for a domain. These data cartridges extend the object type support provided by Oracle8 within the framework of Oracle’s Network Computing Architecture.
Table 28.1 shows examples of some cartridges provided by Oracle8.0.4.
| Data Cartridge | Database Model | Supported Behavior |
|---|---|---|
| Time Series | Ordered List of Tuples | Rolling averages, period comparisons, calendars |
| Text | Tokenized serial byte stream | Display, compress, reformat, and index |
| Video | structured large object of serial image data | Play, compress, rewind, pause, and skip |
| Network | Object types of nodes, connections, and routes | Configuration of the network topology |
| Spatial | Geometric objects such as points, lines, polygons, and so on | Intersect, contain, and so on |
| Image | Structured large object | Crop, rotate, reformat, and so on |
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