Dear Luiz, thanks for the quick response and suggestion. I will search the published literature for discrete multicriteria decision aiding to get a better understanding of this approach, and get intouch if I will need further help thanks.

Thanks Luiz for the suggestions and I will definitely Google under those keywords, since my search for decision support tools in ERP upgrading didn't reveal much information so far. In regards to the papers I will search for them through my university journals and conferences subscriptions. It would have been nice to get access to the case studies, unfortunately I don’t read Portuguese.

Your question fits to general problem of selecting software or software tools where you have to select a relevant set of criteria and use that to solve this multicriteria problem. Hence earlier suggestions are useful. However, there is the assumption that all the conditions are objective. But there many subjective variables that need to be considered. For instance the environment where ERP is implemented may influence the factors that will influence the successful implementation of an ERP system. Hence fuzzy type of solutions may be appropriate where you may not be able to specify in certainty quantitative values. In that case, Interpretive studies may offer guidelines in selecting appropriate software. For instance a study explained why organizations in South East Asia preferred ERP systems that are not developed by big ERP vendors such as ERP and Oracle.

Thanks Francis Andoh-Baidoo. After some reading on the MCDM methodologies I am leaning towards a fuzzy type solution to cater for subjective variables. Your suggestion supports the direction of my thinking and adds to my argument on why I should opt for fuzzy type solution.