A measurement is the topmost object in libRASCH. Measurements consists of one or more sessions, information about the measurement object (e.g. name, forename and birthday if the measurement object is a person) and zero or more evaluations.

A Session is a recording for a specific time interval without any interruptions during this time interval. In a measurement can be more than one session, but the layout of the recording (see below) must not be changed.

A recording contains the measured data (e.g. ecg-leads V1-V6). A recording has one or more channels or two or more sub-recordings. Sub-recordings are used if more than one recording device is used. For example when one ADC-system records 3 ecg-leads and one bloodpressure channel and another system records 12 eeg-leeds, the measurement consists of one top recording with two sub-recordings. The first sub-recording contains 4 channels (3 ecg and 1 bloodpressure channel) and the second sub-recording contains 12 channels (12 eeg channels).

The results of an analysis (e.g. detection of qrs-complexes in ecg's) are stored in an evaluation. An evaluation contains zero or more discrete events (like 'occurence of a qrs-complex') and/or zero or more continous events (like 'time interval with noise').

An event describes the occurence of something in a recording (e.g. a heartbeat in an ecg). An event has one or more event-properties.

An event-property is a specific property of the event (e.g. the position of the event, the type of the event). A specific event-property is allowed only once in an evaluation, for example there can be not more than one 'qrs-position' property.

An event-set describes a group of event-properties. For example the event-set 'heartbeat' contains all properties which belongs to a heart beat (like position of qrs-complex, RR interval, type of qrs-complex, systolic bloodpressure).

libRASCH makes heavy use of plugins. Plugins are small "programs" which are loaded when libRASCH is initialized. In the plugins the real work is done, the library-code coordinates that the correct plugin is used and does some other administrative tasks. In libRASCH exits three principal types of plugins:

• signal plugins

• view plugins

• process plugins

Access plugins handle the access to measurement files. They hide the differences of the various types of formats and offer an consistent interface to the measurements[1]. Most of the times, the direct usage of access-plugins with the libRASCH-API is not needed.

Process plugins perform a specifc task on the measurement (e.g. the HRT-plugin calculates the Heart-Rate Turbulence parameters for an ecg or the detect plugin performs a simple beat detection in ecg's). The usage of these plugins

View plugins allow to display the measurements on the screen. If you develop a program using a graphical user interface (GUI) all you need to display signals is to call the apropriate plugin. At the moment the following GUI's are supported:

• Qt from Trolltech (for Linux)

• MFC from Microsoft (for Windows)