EN ISO 21351:2005

Foreword
Introduction
1 Scope
2 Normative references
3 Terms, definitions and abbreviations
  3.1 Terms and definitions
  3.2 Abbreviated terms
4 Functional specification and technical specification
  purpose and description
  4.1 Functional specification purpose and description
  4.2 Technical specification purpose and description
  4.3 FS and TS content
5 Process for establishing a functional specification and
  a technical specification
  5.1 General
  5.2 Process for establishing a functional specification
  5.3 Process for establishing a technical specification
6 Technical requirements description
  6.1 General description
  6.2 Identification of attributes assigned to technical
      requirements
      6.2.1 Introduction
      6.2.2 Functional requirements description
      6.2.3 Mission requirements description
      6.2.4 Interface requirements description
      6.2.5 Environmental requirements description
      6.2.6 Physical requirements description
      6.2.7 Operational requirements description
      6.2.8 Human factor requirements description
      6.2.9 (Integrated) logistics support requirements
             description
      6.2.10 Product assurance (PA) requirements description
      6.2.11 Configuration requirements description
      6.2.12 Design requirements description
7 Requirements and recommendations for functional
  specifications and technical specifications
  7.1 Requirements and recommendations common to FS and TS
      7.1.1 General
      7.1.2 Responsibility
      7.1.3 Technical requirements organisation
      7.1.4 Unique technical reference
      7.1.5 Configuration management
      7.1.6 Format
      7.1.7 Supplementary information
      7.1.8 Restrictions
      7.1.9 Severity classification
  7.2 Requirement specific to the functional specification
8 Requirements and recommendations for characterizing the
  technical requirements
  8.1 Requirements and recommendations for the characteristics
      of a technical requirement common to FS and TS
      8.1.1 Performance
      8.1.2 Justification
      8.1.3 Configuration management and traceability
      8.1.4 Ambiguity
      8.1.5 Uniqueness
      8.1.6 Identifiability
      8.1.7 Singularity
      8.1.8 Completeness
      8.1.9 Prioritization
  8.2 Requirements and recommendations for the characteristics
      of a technical requirement in the FS
      8.2.1 Flexibility
      8.2.2 Severity
      8.2.3 Maturity
  8.3 Requirements and recommendations for the characteristics
      of a technical requirement in the TS
      8.3.1 Verification
      8.3.2 Attainability
      8.3.3 Tolerance
      8.3.4 Risk
  8.4 Requirements and recommendations for the wording
      8.4.1 General format
      8.4.2 Required verbal form
      8.4.3 Format restrictions
Bibliography
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ISO 21351:2005 provides an overview of the respective purposes and positions of functional and technical specifications, their required contents, and the process for developing these documents.ISO 21351:2005 is applicable to all types of space systems, all product elements, and projects.