SWE.1 Software Requirements Analysis#

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Characteristics of requirements are defined in standards such as ISO IEEE 29148, ISO 26262-8:2018, or the INCOSE Guide for Writing Requirements.

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Examples for defined characteristics of requirements shared by technical standards are verifiability (i.e., verification criteria being inherent in the requirements text), unambiguity/comprehensibility, freedom from design and implementation, and not contradicting any other requirement.

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In case of software-only development, the system requirements and the system architecture refer to a given operating environment. In that case, stakeholder requirements can be used as the basis for identifying the required functions and capabilities of the software.

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The hardware-software-interface (HSI) definition puts in context hardware and therefore it is an interface decision at the system design level. If such a HSI exists, then it may provide input to software requirements.

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Examples for structuring criteria can be grouping (e.g., by functionality) or expressing product variants.

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Prioritization can be done according to project or stakeholder needs via e.g., definition of release scopes. Refer to SPL.2.BP1.

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See MAN.3.BP3 for project feasibility and MAN.3.BP5 for project estimates.

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Technical feasibility can be evaluated based on e.g., platform or product line, or by prototyping.

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Redundant traceability is not intended.

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There may be non-functional system requirements that the software requirements do not trace to. Examples are process requirements or requirements related to later software product lifecycle phases such as incident handling. Such requirements are still subject to verification.

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Bidirectional traceability supports consistency, and facilitates impact analysis of change requests, and demonstration of verification coverage. Traceability alone, e.g., the existence of links, does not necessarily mean that the information is consistent with each other.

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In case of software development only, the system requirements and system architecture refer to a given operating environment. In that case, consistency and bidirectional traceability can be ensured between stakeholder requirements and software requirements.