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The ISO 15504 framework does not set out specific standards. Other, more specific standards, set out requirements for (say) a valid test plan. What ISO 15504 is concerned about is the capability provided by the organization's management and process definition structures.
ISO 15504 is not a methodology. Although ISO 15504 sets out a list of activities that might (and should) occur in a software project, it does not set out the order in which such activities should be carried out.
ISO 15504 is, in effect, a set of categories (pigeon holes) in which the assessors can place the evidence that they collect during their assessment, so that the assessors can give an overall determination of the organisation's capabilities for delivering software.
The actual standards document for ISO 15504 is divided into 9 parts.
Part 1 of ISO 15504 explains the concepts and gives an overview of the framework.
ISO 15504 contains a reference model. The reference model defines a process dimension and a capability dimension.
The reference model is the subject of part 2 of ISO 15504.
The process dimension defines processes divided into the categories of:
For each process, ISO 15504 defines a capability level on the following scale:
| Level | Name |
|---|---|
| 5 | Optimizing process |
| 4 | Predictable process |
| 3 | Established process |
| 2 | Managed process |
| 1 | Performed process |
| 0 | Incomplete process |
ISO 15504 provides a guide for performing an assessment.
This includes:
Performing assessments is the subject of parts 3 and 4 of ISO 15504.
The assessment model is the detailed model that is used for an actual assessment. This is an elaboration of the reference model.
Part 5 of ISO 15504 provides an assessment model, but other models could be used instead, if they meet ISO 15504's criteria.
For a successful assessment, the assessor must have a suitable level of the relevant skills.
These skills include:
The competency of assessors is the subject of part 6 of ISO 15504.
ISO 15504 can be used in two contexts:
ISO 15504 can be used to inform process improvement within a technology organization. Process improvement is always difficult, and initiatives often fail, so it is important to understand the initial baseline level, and to assess the situation after an improvenent project. ISO 15504 provides a standard for assessing the organization's capacity to deliver at each of these stages.
In particular, the reference framework of ISO 15504 provides a structure for defining objectives, which facilitates specific programmes to achieve these objectives.
Process improvement is the subject of part 7 of ISO 15504.
An organization considering outsourcing software development needs to have a good understanding of the capability of potential suppliers to deliver.
ISO 15504 can also be used to inform supplier selection decisions. The ISO 15504 framework provides a framework for assessing proposed suppliers, as assessed either by the organization itself, or by an independent assessor.
The organization can determine a target capability for suppliers, based on the organization's needs, and then assess suppliers against this profile. This is particularly important in contexts where the organization (for example, a government department) is required to accept the cheapest qualifying tender. This also enables suppliers to identify gaps between their current capability and the level required by a potential customer, and to undertake improvement to make the contract.
Supplier process capability determination is the subject of part 8 of ISO 15504.
Part 9 of ISO 15504 is a vocabulary list.