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 Analog/Digital converter-system records 3 ECG leads and one bloodpressure channel and another system records 12 EEG leads, 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. positions of heart beats in an ECG) are stored in an evaluation. An evaluation contains zero or more discrete events (e.g. 'occurence of a heart beat') and/or zero or more continous events (e.g. 'recording period with noise'). In measurements handled by libRASCH, more than one evaluation can be available.

When an evaluation is added to the measurement by the original recording system (e.g. the evaluation performed by commercial long-term ECG systems), then this evaluation is called the original evaluation.

If only one evaluation is available, it is no problem to choose an evaluation when the user wants to process the evaluation. When more than one evaluation is stored in a measurement, one of these evaluations has to be the default evaluation, which is used when no specific evaluation is selected. In most cases the last added evaluation is set to the default evaluation.

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 (e.g. position of the heart beat, the RR interval, the type of the heart beat, systolic blood pressure).

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 "only" coordinates that the correct plugin is used and does some other administrative tasks. In libRASCH three principal types of plugins exist:

• access 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].

Process plugins perform a specifc task on the measurement (e.g. the HRV-plugin calculates the Heart-Rate Variability parameters for an ECG or the detect plugin performs a simple beat detection in ECG's).

View plugins allow to display the measurements on the screen. At the moment the following GUI's are supported:

• Qt from Trolltech (for Linux)

• MFC from Microsoft (for Windows)