1.-Introduction
The ISO 21500:2012 Standard considers that the project management processes may be viewed from the two different perspectives, i.e.:
  • as ‘Process Groups’ (for the management of the project), respectively
  • as ‘Subject Groups’ (for collecting the processes by subject).
There are not defined areas of knowledge or ‘Knowledge Areas’, as in the PMI PMBOK® 5-th Edition, 2013, although the ‘Subject Groups’ perspective resembles to the ‘Knowledge Areas’ of PMI PMBOK®.

2.-The ISO 21500 Standard’s Quality Subject Group of Processes
The Standard deals with the project management quality area through the perspective of the ‘Quality Subject Group’. 
This subject group collects three processes (not activities) by the quality subject, required to plan and establish quality assurance and quality control.

These processes action through three of the five defined Process Groups, respectively:
  1. Plan Quality, in the Planning Process Group,
  2. Perform Quality Assurance, in the Implementing Process Group,
  3. Perform Quality Control, in the Controlling process Group.
The three mentioned Quality Subject Group processes are detailed in subchapters 4.3.32-4.3.34 of the Standard, and explained in their turn with specific component activities recommended to be performed.

According to the ISO 21500 Standard, the three mentioned processes have the following purposes [I cite]:
"The purpose of Plan quality is to determine the quality requirements and standards that will be applicable to the project, the deliverables of the project and how the requirements and standards will be met based on the project objectives. 

The purpose of Perform quality assurance is to review the deliverables and the project. It includes all processes, tools, procedures, techniques and resources necessary to meet quality requirements.  

The purpose of Perform quality control is to determine whether the established project objectives, quality requirements and standards are being met and to identify causes of, and ways to eliminate, unsatisfactory performance”.

3.-The Plan Quality Process and the Quality Plan 
The most important project management deliverable product of these processes is the ‘Quality Plan’ resulting in the output of the ‘Plan Quality’ process. As primary inputs, this process needs: Project Plans, Quality Requirements, Quality Policy, and Approved Changes.

The ISO 21500 standard avoids to use the syntagm ‘Quality Management’, except one place remained in subchapter 4.3.3-page 15 where the Quality Plan, as a subsidiary plan of the ‘Project Management Plan’, is mentioned as ‘Quality Management Plan’ never presented elsewhere in the standard.

According to the figure 6 of the standard, with duplex links between Controlling, Planning and Implementing Process Groups and the single directed link from Planning to Implementing Process Groups, the ‘Quality Plan’ remains the common input deliverable product for ‘Perform Quality Assurance’ and respectively for ‘Perform Quality Control’ processes.

4.-Performing Organization Quality Policy
As mentioned by the Standard, the ‘Quality Plan’ must refer to or include the performing organization’s Quality Policy as established and approved by the senior management.

The acceptance of developed quality standards and of the performance requirements for product quality remains in the responsibility of the respective performing organization, as both processes of development and acceptance may fall outside the project boundaries.

As the Quality Policy is established by organization senior management and not by the project manager, the project manager just should use it as a primary input for the ‘Plan Quality’ process (Standard's Table 32, page 27). It should be noted that the syntagm ‘Quality Policy’ is mentioned only twice in the subchapter related to ‘Plan Quality’ process.

5.-Perform Quality Assurance Process
The term ‘audit’ is mentioned inside the ISO 21500 Standard only twice, in the subchapter related to the ‘Perform Quality Assurance’ process.

In this way, a Quality Assurance audit may be performed outside the project boundaries by other entities from the performing organization, even by project clients/customers, as the Quality Assurance allows compliance to the established organizational performance requirements and standards.

The audit is considered by the ISO 21500 Standard to “determine the performance of the whole quality process, quality control and the need for recommended action or change requests”.

6.-Perform Quality Control Process
The ‘Perform Quality Control’ process should continuously be applied during the project life cycle (actually, along the whole product life cycle which is longer than the project life cycle).

Similarly to the ‘Perform Quality Assurance’ process, the ‘Perform Quality Control’ process may be performed outside the project boundaries by other entities from the performing organization even by project clients/customers.

While change requests are project management deliverable products resulting in the output of both the ‘Perform Quality Assurance’ and ‘Perform Quality Control’ processes, the latter gives four additional deliverable products, i.e.: Quality control measurements, Verified deliverables, Inspection reports, and Corrective actions.

They help to remove the root causes of the poor process performance, low product quality aspects and related non-conforming performance to be eliminated through appropriate corrective actions and/or change requests implementation. No audit is proposed by the Standard for this process.

7.-Recommendations
Generally speaking an organizational Quality Policy is expressed through the framework of the organization’s Quality Management System-QMS. 

The performing organization’s QMS is preferred to be certified and compliant to the ISO 9001:2008  Standard. Thus, the Shewhart-Deming PDCA cycle and its iterative management method are taken into account in the respective organization quality environment.

The ISO 21500 Standard guidelines and recommendations become easier to be implemented in the respective QMS Operational Procedures for project management at organizational level. Usually the PMOs from project-oriented organizations are performing this task with greater rate of success.

The ISO 21500 Standard is non-prescriptive. An advanced sensible analysis and great care should be taken when considering similarities with ISO 9001:2008 Standard’s quality statements for embedded  implementation. 

Also, consider all Standard process connections when mapping the ISO 21500 Quality Subject Group processes to the Shewhart-Deming PDCA cycle for product quality continuous improvement along project and product life cycles.