The work explore the opportunity to define a real property asset through rough set analysis proposed by Pawlak (Pawlak,1982). The methodology has been applied to property appraisal (díAmato,2000) obtaining interesting results , especially in mass appraisal. The procedure seems to be interesting in those markets where information is not easy to find because of ìallows the data to speak for themselvesî. The work is organized as follow, after a brief introduction, the first paragraph will offer a literature review concerning ìwithin real estateî diversification technique. In the second paragraph there will be a brief introduction to rough set analysis and an application. Final remarks will conclude the work.