In the EOSC Task Force Ensure Software Quality we in subgroup #3 have focused on organizing the existing knowledge which spreads along the vast literature available, to provide a descriptive view of the attributes and metrics related to software quality. We include specific considerations and perspectives for developers, users, and service providers. From the significant number of quality attributes, we make recommendations according to each type of research software. The landscaping section, included in the report shows the large diversity to take into account when analyzing research software, necessarily from several different points of view. It is our aim that the classification and recommendations presented here will contribute and be useful to produce better research software and benefit users, developers, and service providers.