Decision support system in Requirements engineering plays an important role in software development life cycle. The relationship between functional and non-functional requirements often plays a crucial role in resolving conflicts or arriving at decisions in requirements engineering phase. Goal-Oriented Requirements Engineering (GORE) methods make a good attempt of addressing these aspects which are helpful in decision support. We propose a GORE method - Integrating goals after prioritization

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... evaluation (IGAPE). The method is semi-formal in nature thereby ensuring active stakeholder participation. In this paper we elaborate the various steps of IGAPE method. The output of IGAPE is then given as input to a decision support system which makes use of Analytic Hierarchy Process (AHP) and Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS). Integration of IGAPE with AHP and TOPSIS will clearly provide a rationale for various decisions which are arrived at during the requirements engineering phase. The method is illustrated for an e-commerce application and is validated by expert analysis approach.