The main objective of this deliverable is to make a synthesis of existing approaches to specify non-functional properties. The term non-functional requirement has been in use for more than 20 years, there is still no consensus in the requirements and software engineering community what non-functional requirements are and how we should elicit, document, and validate them. On the other hand, there is a unanimous consensus that non-functional requirements and properties are important and can be critical for the success of a project.