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The vector of weights of an interpolatory quadrature rule with $n$preassigned nodes is shown to be the least-squares solution $\omega$ of anoverdetermined linear system here called {\em the fundamental system} of therule. It is established the relation between $\omega$ and the minimax solution$\stackrel{\ast}{z}$ of the fundamental system, and shown the constancy of the$\infty$-norms of the respective residual vectors which are equal to the {\emprincipal moment} of the rule. Associated to $\omega$ and $\stackrel{\ast}{z}$we define several parameters, such as the angle of a rule, in order to assessthe main properties of a rule or to compare distinct rules. These parametersare tested for some Newton-Cotes, Fej\'er, Clenshaw-Curtis and Gauss-Legendrerules.

Quadrature as a least-squares and minimax problem