+A module is an instance of a class implementing the IModule interface. A module is commonly designed to provide specific functionality that may be plugged into a PRADO application and shared by all components in the application.
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+PRADO uses configurations to specify whether to load a module, load what kind of modules, and how to initialize the loaded modules. For more details, please see the configurations. +
++There are three core modules that are loaded by default whenever an application runs. They are request module, response module, and error handler module. In addition, session module is loaded when it is used in the application. PRADO provides default implementation for all these modules. +
++Developers may replace the core modules with their own implementations via application configuration, or they may write new modules to handle other tasks. For example, a module may be developed to provide common database logic for one or several pages. +
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+ ++A service is ... TBD. +
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