The success or otherwise of Software Engineering (SE) activities depends on the interactions among software engineers. Consequently, effective interactions depend largely on personality traits, which is a consistent and long-lasting tendency in behaviour. In psychology, five major trait factors (The Big Five Factors) have been generally used to assess personality of people. But, these might not be adequate in SE because of the required technical and cognitive skills. In this work, we first present Cognitive Ability as an additional factor that must be measured in order to adequately assess personality in SE. A research survey was conducted in order to capture personality requirements in SE. Based on the result of the survey conducted, we develop a model for assessing personality traits in SE. We then design an assessment technique that is based on responses to some well-structured and deductive on-line questions. The implementation of the model using Visual Basic resulted in a much-needed tool that can guide intending software engineers in choosing area of specialization in SE based on their personality traits.