ControlSystemsDesign Part: FS
Slovak University of TechnologyFaculty of Material Science and Technology in Trnava
2007
Functional Specification Purpose General guidelines
Ambiguity, duplication and contradiction has to be avoided
All limitation should be explicitly defined
Consistent and intuitive naming has to be used
Each function and facility has to be testable
Each specification should be traceable (traceability matrix)
Functional Specification
Introduction
Author of the document, his authority and for what purpose the document has been produced
The contractual.status of the document
Relationship to other documents
Functional Specification Overview
Key objectives and benefits
Reference to relevant standards and regulations
High level description
The main interfaces from the system to other systems or the environment
Functional Specification
Overview - continued
Assumptions: it defines any design or implementation assumptions or limitations as use of standard packages, program libraries, operating systems, hardware...
Non-conformance with User Requirements Specification; any divergence between the Functional Specification and the User Requirements Specification has to be noted.
Functional Specification Functions
The objective of the function or facility, and the details of its use, including interface with other parts of the system. Critical calculation and algorithms has to highlighted.
Performance, response and accuracy
Safety and security: action in case of HW/SW failures, I/O variables checking, redundancy, access restrictions, self diagnostic, data recovery, time-outs...
Functions which are configurable and any limits within which the configuration can take place
Traceability to specified requirements in User Requirements Specification
Functional Specification Functions - continued
Functions which are configurable and any limits within which the configuration can take place
Traceability to specified requirements in User Requirements Specification
Functional Specification Data
Data definition in a hierarchical manner with complex objects being built up from simpler objects. Critical parameters has to be highlighted.
Data access (which subsystems need read or write, access to each data item, access method, speed and update time, read/write interlocks)
Data capacity, retention time, and details about data archiving
Data integrity and security
Functional Specification Interfaces
Interface with users is defined by terms as operator, administrator, system manager. Topics to consider include facilities available, types of peripherals, general format of displays and reports, error handling and reporting
Interface with other systems; nature of the interaction, and the methods and rules governing the interaction
Functional Specification Interfaces - topics
Data transmitted and received
Data type, format, ranges, and meaning of values
Timing
Rate of data transfer
Communications protocol – initiation and order of execution
Any data haring, creation, duplication, storage, or destruction
Functional Specification Interfaces - topics continued
Mechanism for invocation and interruption
Communication through parameters, common data areas, or messages
Direct access to internal data
Error handling, recovery, and reporting
Security
Functional Specification Non-functional Attributes
Availability – reliability, redundancy, error checking, stand-by operation
Maintainability – expansion and enhancement possibilities, spare capacity, likely changes in environment, lifetime.
Functional Specification
Glossary Section
This Section contains definitions or explanations of any terms that may be unfamiliar to the readership of the document
