  In this paper we present an alternative approach to formalize the theory of
logic programming. In this formalization we allow existential quantified
variables and equations in queries. In opposite to standard approaches the role
of answer will be played by existentially quantified systems of equations. This
allows us to avoid problems when we deal with substitutions. In particular, we
need no ''global'' variable separated conditions when new variables are
introduced by input clauses. Moreover, this formalization can be regarded as a
basis for the theory of concurrent logic languages, since it also includes a
wide spectrum of parallel computational methods. Moreover, the parallel
composition of answers can be defined directly -- as a consistent conjunction
of answers.
