Pattern - Declarative Configurations

• Pattern - Configuration Management Database
  • Pattern - Storing configuration information in a Directory Service
    • Pattern - Storing Configuration Information in DNS
  • Pattern - The Windows Registry
• Pattern - RDF Configuration File

Features

• The configuration of a system is declared in a machine readable format.
• It is not scripted, but declared, for some runtime to interpret.
• Different tools can read/write the configuration.

Advantages

• More tool-neutral that procedural configuration scripts.
• Text files can be hand edited.
• XML formats offer editor and XSL support.
• RDF representations are the ultimate tool-neutral format for pure declarative data.

Disadvantages

• It is very hard to be fully declarative.
• There are many different declarative configuration languages.
• Hand editing can be error prone.
• Requires an interpreter/runtime to instantiate the configuration.
• It is very hard to be purely declarative. You can describe the steady state of a system, and so feed into a State-driven deployment engine -but you may need to describe procedural steps along the way.

SmartFrog support

SmartFrog is a declarative configuration language, one that can be interpreted by local and remote SmartFrog runtimes.