6 Part 6: V-Modell Reference Activities

6.3 Activities

6.3.9 System Specifications

6.3.9.4 Preparing Hardware Specification

Purpose

In the specification, the requirements and interfaces for each respective hardware element (hardware unit, hardware component or hardware module) that will have to be described shall be defined and accurately described.

For the preparation of the specification (see Figure 21) - analogous to the »System Specification - interfaces and non-functional requirements for the hardware element will be defined, followed by the parallel refinement and assignment of those interfaces and requirements on the basis of the super-ordinate hardware unit or hardware component. The design decisions shall be documented in the hardware specification. If the prepared realization proves to be workable, it will be possible to proceed to the requirement tracking survey. If this is not the case, the realization will have to be revised.

Requirements usually will be described in text form. The specification of the interface may be formalized in various ways. Usually this will be done by using graphic description methods in combination with explanatory text.

6.3.9.4.1 Identifying Interfaces and Non-Functional Requirements

Assigned super-ordinate interfaces (see the interface description) and non-functional requirements will have to be identified. At the level of the »Hardware Components the assigned interfaces and non-functional requirements of the super-ordinate »Hardware Unit will be for example adopted without refinement and change as a starting point.

6.3.9.4.2 Refining Interfaces and Non-Functional Requirements

The refining of the interfaces (see the »Interface Specification) and the non-functional requirements will include the following steps:

• With the identified interfaces and non-functional requirements, solutions will have to be defined. In this process the way of looking at the higher level of the architecture will be changed from considering it a "black box" to considering it a "white box". This will mean for example naming the »Hardware Modules in the specification of a »Hardware Component.
• On the basis of the "white box", the identified super-ordinate interfaces and non-functional requirements will be refined.
• In this process also additional, previously unconsidered interfaces and »Non-Functional Requirements may be defined.

It must be possible to verify all interfaces and non-functional requirements and to assign them to the next lower hierarchy level.

6.3.9.4.3 Allocating Interfaces and Non-Functional Requirements

The refined and additionally defined interfaces and non-functional requirements shall be allocated to the hardware elements identified in the "white box". It is recommended to make this description in tabular form.

6.3.9.4.4 Preparing Requirements Trace Overview

Within the scope of the requirement tracking survey, it will be made sure that all requirements and interfaces will be refined. It shall be checked whether

• for each requirement or interface of a »Hardware Unit there will at least one representation at the level of the »Hardware Components,
• for each requirement or interface of a hardware component there will be at least one representation at the level of the »Hardware Modules,
• with a distributed assignment of a requirement or an interface (the sum of the weight requirements for hardware components is for example equal to the weight requirement defined in the associated hardware unit) this will be fulfilled to the full extent by the subordinate hardware elements.

In every hierarchical design step (e. g. from a hardware unit to hardware components) this requirement shall be tracked.