Summary Still today informal methods are the most common for informational systems design. They don‘t allows unambiguously understand formulating tasks, moreover availably specifications not always are complete. Because of this informational system does not correspond to users needs. Using informal methods specification transformation to software code isn‘t always possible. In real time informational systems problematic domain is varying in time. Thus are changing requirements for informational systems. Using informal methods, to solve this problem, usually we need to rewrite software. Using formal methods we don‘t have to rewrite software, it is enough organization business instructions specified in Z transform to software code. In this paper we present research results about Z specification method use for formal requirements specification for informational systems design. Using Z/EVES - an interactive system for composing, checking, and analyzing Z specifications, was accomplished Z specification validation, theretofore reviewing the list of available Z specification validation tools. Z specification language was compared with object-oriented language Object–Z to find out advantages and disadvantages of these two formal specification languages. Were discussed questions about Z specification transformation to Object-Z, which facilities an object-oriented specification extension to object-oriented programming languages. In this paper transformation methodology from object-Z... [to full text]