Let L 0 be a closed densely defined symmetric semi-bounded operator with nonzero defect indexes in a separable Hilbert space H. It determines a Green system {H, B; L 0 , Γ 1 , Γ 2 }, where B is a Hilbert space, and Γ i : H → B are the operators related through the Green formula

We deal with two dynamical systems associated with a Riemannian manifold with boundary. The first one is a system governed by the scalar wave equation, the second is governed by the Maxwell equations. Both of the systems are controlled from the boundary. The inverse problem is to recover the manifold via the relevant measurements at the boundary (inverse data). We show that the inverse data determine a C*-algebras, whose (topologized) spectra are identical to the manifold. By this, to recover the manifold is to determine a proper algebra from the inverse data, find its spectrum, and provide the spectrum with a Riemannian structure. The paper develops an algebraic version of the boundary control method, which is an approach to inverse problems based on their relations to control theory

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