nologies used are determined by the nature of the product which the user will use). If the system includes hardware (for and the telecommunications systems are diverse: example a telephone handset), producing a computer model of the hardware may help the user to understand his own needs more 1. They can be large. Some public switching software can demand clearly. of the order of 20 million lines of code. This puts it in the class It is frequently necessary to demonstrate compliance to a set of of major computer operating systems. requirements. This is done by labelling each requirement and refer- 2. They can be real time. Much telecommunications software is encing back to the requirement during the analysis and design embedded, and required to operate under severe timing con- stages. This is called Requirements Traceability. Note that the straints. requirements generated by the use may well be ambiguous and 3. They can be flexible. Dynamic reconfigurability is a common conflicting. In situations where requirements specification docu- requirement. The ability to interwork across vendor boundaries ment is sufficiently large to hamper detection of anomalies, there is becoming SO. are software tools to allow the user to pick out key words, phrases 4. They can be distributed. Sometimes the only way to provide the and concepts and to organise the data in such a way that these required service with the required performance is to exploit the anomalies may be recognised. Hypertext technology is applicable most advanced distribution platforms. here. (Pankaj, 1990.) 5. They can involve very large volumes of data. Some of the It is very important that any requirements documents or proto- directory assistance systems call for leading edge relational types generated by the software team are validated and signed off data base technology. by the users, as they can then form the basic definition for the main 6. They demand intelligence. Knowledge based systems are ap- development. plied in alarm analysis and in configuration. 7. 