Preparing the System Specification

The first step in the preparation of a system specification is to define the outline for listing the requirements. You can develop this outline by your own or use an existing Data Item Description (DID). In this example we will use the DID System Subsystem Specification (SSS) from MIL-STD 498 series. This DID was developed by the US Department of Defense and is used to specify the requirements of a System or Subsystem. The outline of chapter 3 provides a good overview of requirement categories you should think of while specifying your system.

The fowlling table shows slightly modified version of the outline compared to the original version in the DID.

Chapter	Title	Report(nbsp)Script	Remarks
1	Scope	Default	Heading
1.1	Identification	Default	Identifies the system to which this document applies. Example: This document establishes the systems specification for the RePoSyD Core Module (@RePoSyD/core) and is part of RePoSyD's specification tree.
1.2	System Overview	Default	Contains a brief (high level) description of the sytems to which this system specification applies.
1.3	Document Overview	Default	Contains a brief description of the outline and contents.
2	Referenced Documents	Default	Contains a list of rules and regulations or other documents referenced in this specification.
3	Requirements	Default
3.1	Operating States and Modes	Requirements	Defines the required operating modes and operating states such as operation, maintenance,emergency operation.
3.2	Capabilities and Functions	Requirements	Defines the required functions with the corresponding performance values for e.g. timing or transfer rates.
3.3	Interfaces	Requirements	Defines the interfaces to be provided by the system Interfaces and their requirements. For complex interfaces, reference can be made here to an interface specification can be referred to here.
3.4	Safety	Requirements	Defines the requirements related to safety to minimize the hazards to people and the environment
3.5	Security	Requirements	Defines the requirements for security, such as preventing direct access by unauthorized persons. Direct access by unauthorized persons or indirectly via interfaces to external external systems, e.g. via the Internet.
3.6	Environmental Conditions	Requirements	Defines the requirements regarding the environmental conditions under which the system is to be operated, such as ambient temperature, humidity and salinity of the ambient air or the altitude above sea level.
3.7	RAM	Requirements	Defines the requirements regarding reliability (R), availability (A), maintainability (M) of the system, such as the inherent and operational availability to be achieved, the maximum and operational availability, the maximum probability of failure of the system.
3.8	Design and Construction	Requirements	Defines restrictions for e.g. materials that are not to be used, restrictions to size and weight of the overall system or components.
3.9	Personel related Requirments	Requirements	Defines requirements for the operating and maintenance personnel with regard to their qualification and training. For example, the replacement of electrical components by qualified personnel.
3.10	Traning related Requirements	Requirements	Defines requirements for necessary training training material and training equipment for the operation and maintenance of the system.
3.11	Packing, Handling, Transport	Requirements	Defines the requirements regarding the packaging, handling and transport of the transport of the system, such as the provision of transport of transport lugs, the possibility of air transport.
3.12	Marking	Requirements	Defines the requirements for the of the system with, for example, operating and warning warnings, nameplates including the materials to be the materials to be used.