  This paper focuses on defining a measure, appropriate for obtaining optimally
sparse solutions to underdetermined systems of linear equations.* The general
idea is the extension of metrics in n-dimensional spaces via the Cartesian
product of metric spaces. *The following work done, was within the completion
of my master thesis titled "Algorithms for the computation of sparse solutions
of undefined systems of equations" at the department of Mathematics, University
of Athens which was assigned to me in association with the department of
Informatics and Telecommunications, National and Kapodistrian University of
Athens.
