== The READER Interface ==
The [wiki:adeiClassREADER READER] class provides an abstract interface to the historical and control data of the data source. The minimal READER should provide 3 methods
 * ''!GetGroupInfo'' - returns annotated list of all logging groups.
 * ''!GetItemList'' - returns list of all channels in the specified logging group.
 * ''!GetRawData'' - returns Iterator object with requested data.

== Providing additional data using ADEI Web Interface ==

Examples of additional data are:
 * The alarms registered during the data collection by control systems
 * The system operator messages
 * The information about events registered by DAQ subsystem
 * Anything else...

This section describes how the additional data could be provided using ADEI Web Interface. The simplest approach is to provide a service generating an XML data, and XSLT stylesheet which would convert it to HTML. Of course it is possible to generate directly XHTML, but with XML+XSLT approach it is easier to alter presentation form and establish some automation (the XML service could be used by 3rd party client applications). After the service is ready, the new ADEI module (an extra page in the upper menu) should be created and registered in configuration.

So, the following steps should be taken to setup extra ADEI page:
 * Create a service and put it in the ''services/'' subdirectory (see description [wiki:adeiNewService here])
 * Create a module and put it in the ''modules/'' directory (see description [wiki:adeiNewModule here])
 * Create a XSLT stylesheet which accepts produced XML and generates HTML to be displayed and put it in the ''xslt/'' folder.
 * Optionally, if additional parameters, like ''target'' for multi-task services, should be passed to the service, special update service should be created in ''services/update/'' directory ([wiki:adeiNewModule see details])
 * The module should be registered in ''$MODULES'' variable in the configuration file ''config.php''. Be careful, some of the global configuration options specified in the config.php located in the root folder of ADEI installation may be overriden in setups by setup-specific configuration file.