ISO/IEC 15504-2:2003 defines the requirements for performing process assessment as a basis for use in process improvement and capability determination.
Process assessment is based on a two dimensional model containing a process dimension and a capability dimension. The process dimension is provided by an external process reference model, which defines a set of processes characterized by statements of process purpose and process outcomes. The capability dimension consists of a measurement framework comprising six process capability levels and their associated process attributes.
The assessment output consists of a set of process attribute ratings for each process assessed, termed the process profile, and may also include the capability level achieved by that process.
ISO/IEC 15504-2:2003 identifies the measurement framework for process capability and the requirements for:

• performing an assessment;
• process reference models;
• process assessment models;
• verifying conformity of process assessment.

The requirements for process assessment defined in ISO/IEC 15504-2:2003 form a structure which:

• facilitates self-assessment;
• provides a basis for use in process improvement and capability determination;
• takes into account the context in which the assessed process is implemented;
• produces a process rating;
• addresses the ability of the process to achieve its purpose;
• is applicable across all application domains and sizes of organization; and
• may provide an objective benchmark between organizations.

The minimum set of requirements defined in ISO/IEC 15504-2:2003 ensures that assessment results are objective, impartial, consistent, repeatable and representative of the assessed processes. Results of conformant process assessments may be compared when the scopes of the assessments are considered to be similar; for guidance on this matter, refer to ISO/IEC 15504-4.