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In this paper we investigate the problems in
the relational views updating particularly impossible cases. A review of the past works in
this field and the definition of formal view and its
advantages are presented. In this study we have devided the relational views into three principle
cathegories: views without difficulty, views with difficulty and inupdatable views. In spite of the
variety of view derivation mechanisms, we show that most of the views fall into the second and
third cathegories. The inupdatability of most views is a serious drawback in relational data model
which has not been removed.