Collaborative systems Quality management discipline requires a set of assessment mechanisms to evaluate external quality characteristics influenced by environmental parameters and impacted by ecosystem factors. The present paper suggests a new assessment oriented model to assess and monitor quality performance. The proposed model, named RatQual, gives a hierarchical categorization for collaborative systems quality factors. RatQual is designed to quantify dependent-environment qualities by considering internal, external and in use aspects. This model is supported by a tool that automates the assessment process. This tool gives assistance in quality evolution planning and serves for periodical monitoring operations used to enhance and improve information system quality.