Use and Collaboration Cases (System Requirements View) - Introduction

PRIMA System

The PRIMA Facility is composed of 5 systems:

Fringe Sensor Unit A for Science beam
Fringe Sensor Unit B for Reference Beam
Star Separator
Differential Delay Lines
Metrology

These 5 systems are controlled by the PRIMA Main Control Software deployed on the PRIMA WS.

Scope

The system under study is the PRIMA Metrology System. It is considered as a System per se since it can be seen as an actor of the PRIMA Main Control Software.

Main Use Cases

This document describes all the Use Cases for the PRIMA Metrology Control Software extracted from the requirements in the following documents:

VLTI Software Requirements Specification [AD 18]
Technical Specifications for the PRIMA Metrology System [AD 19]
ICD between Electro-Mechanical Hardware and Control System of the PRIMA Metrology System [AD 20]

These requirements have been checked with the general VLT and VLTI requirements.

In this Requirements View, the system must be considered as a black box and no attention must be paid to the internal system architecture. External Actors interact with the system as a whole and interactions between system components are not important.

In the following sections, all Use Cases are listed, grouped according to their function. During design, Use Cases are assigned to software packages, but at requirement level we always consider the whole system as a black box. Nevertheless, the functional groups typically map very well with packages, since they correspond in most cases to the control of specific subsystems.

Some Collaboration Cases are listed, since they map system requirements, even though they are not directly seen by primary external Actors.

The interaction of human users with the system will take place via command interfaces and graphical user interfaces. In this document the type of user interaction is not specified, unless explicitly requested by the mapped requirements.

PRIMA Metrology System

The general functions are used to command the PRIMA Metrology System as a whole and to provide information regarding its global operational state.
They provide basically the following two services:

Switch the PRIMA Metrology among different operational states, sending the proper sequence of commands to the individual sub-systems.
Compute and update continuously the PRIMA Metrology Control System global status, depending on the status of the individual sub-systems.

The PRIMA Metrology Control System global status is based on the status of sub-systems based on current operational conditions.

Level 0 Use-Case diagram

Level 1 Use-Case diagram