A note on "Incomplete relational database models based on intervals"

For original paper, see A. Ola and G. Ozsoyoglu, ibid., vol. 5, no. 2, pp. 293-308 (1993). In that paper, a family of relational database models (M-1 to M-5) were proposed to represent unknown values by intervals. Relational operators were extended for evaluating queries on these models. In this paper, we stultify the theorems, claiming that query evaluation in models M-2, M-3 and M-5 is sound.