Accessing Relational Databases

By: W. Keller, J. Coldewey
Published in: PLoPD3
Pages: 313-343
Category: Database

Summary: Defines relational database access layers for database application design, either data-driven or representational.

Pattern: Relational Database Access Layer

Pages: 317-326

To access a relational database, use a layered architecture. A logical access layer provides the interface to the stable application kernel, while a physical access layer accesses the database. The latter can adapt to changing performance needs.

Category: Architectural, Database

• Use Query Broker to decouple the layers.
• This pattern is an application of Layered Architecture [Shaw95], Layered and Sectioned Architecture, and Layers
• A Hierarchy of Control Layers, Pedestal, Four-Layer Architecture, Layered Organization, Shape of Program, Three-Tier Architecture
• Crossing Chasms: A Pattern Language for Object-RDBMS Integration###Crossing Chasms describes how to extend this pattern to an object-oriented view of a relational database.

Pattern: Hierarchical View

Pages: 317-332

You're using Relational Database Access Layer. The database access layer should present an interface expressed in terms of the domain's problem space to the application kernel.

Category: Database

• Use Query Broker to decouple Hierarchical View from the underlying Physical View.

Pattern: Physical View

Pages: 332-335

You're using Relational Database Access Layer and Hierarchical View. To provide an easy-to-use interface to your physical database tables, encapsulate every table and every view with a ConcretePhysicalView class. Use these classes to encapsulate overflow tables and other database optimization techniques.

Category: Database

Pattern: Query Broker

Pages: 336-341

You're using Relational Database Access Layer, Hierarchical View, and Physical View. Use a broker to connect the hierarchical view and the physical view for reading and writing. The hierarchical view becomes the client side, and the physical view becomes the server.

Category: Database

• This pattern is an extension of Broker [Buschmann+96]
• Brown and Whitenack also describe a Broker [Brown+96a]