EVS-EN 9320:2015

These general guidelines cover the open system acquisition and supply processes.
There is an increasing requirement for systems designed and produced by industry, particularly in the aeronautic, space and defence fields, to be used with other systems designed, produced, acquired and operated independently.
The concept of open systems is touched upon in many systems engineering documents. This document deals specifically with this subject. To this end, through the various processes applied, it provides information to stakeholders (buyers, suppliers, designers, subcontractors, supervisors, etc.) on the best practice to be adopted.
The specific nature of openness for a system is defined by all the following properties:
-  Interchangeability,
-  Interoperability,
-  Upgradability,
-  Reusability,
-  Reversibility,
-  Flexibility,
-  Affordability.
These properties are defined in the glossary for these general guidelines.
These general guidelines are largely based on the structure and system life cycle processes described in standard ISO/IEC 15288:2008.
The characteristics of openness also relate to:
-  The products or services offered by the company (target systems resulting from use of company processes).
-  The company’s processes (project systems). Several stakeholders, with their own assignments, cultures, jobs and geographical locations, different working methods, modelling frameworks, standards, tools and aids, etc. are involved in the activities, which are sometimes multidisciplinary, of the internal and external processes of a company. These diverse elements are not necessarily all suited to working together without causing certain risks, a loss of autonomy, effectiveness and/or efficiency, etc. A company must, for example, develop its ability and capacity in terms of interoperability both internally (between the systems of which it is made) and externally (with other partners), including, by way of an example:
-  Ability of each stakeholder and each department involved to maintain efficient and trusting relationships with other stakeholders, taking into account deadline, cost and quality objectives,
-  Ability to exchange, communicate and use the necessary flows (data, information, knowledge, materials, energy) autonomously, without error and dynamically throughout the life cycle of the target system,
-  Ability to coordinate, synchronise and manage common tasks and share and use resources (human, machine or application) and services efficiently and appropriately.