Intervals as a Model of Real Type

What are the desired properties for a model of real type? 1) It must be a field or work like it, etc. I intend to endow intervals with a weak notion of equivalence, what make it works like a field, what will enable us to use intervals an representations of real numbers. What are the desired properties that the resulting structure must satisfy. Some bibliography is welcome. My Best Regards Regivan ------------------------ Prof. Dr. Regivan H. N. Santiago Programa de Mestrado em Sistemas e Computação. Departamento de Informática e Matemática Aplicada - DIMAp Universidade Federal do Rio Grande do Norte - UFRN e-mail: regivan@dimap.ufrn.br