  The paper addresses the problem of defining families of ordered sequences
$\{x_i\}_{i\in N}$ of elements of a compact subset $X$ of $R^d$ whose prefixes
$X_n=\{x_i\}_{i=1}^{n}$, for all orders $n$, have good space-filling properties
as measured by the dispersion (covering radius) criterion. Our ultimate aim is
the definition of incremental algorithms that generate sequences $X_n$ with
small optimality gap, i.e., with a small increase in the maximum distance
between points of $X$ and the elements of $X_n$ with respect to the optimal
solution $X_n^\star$. The paper is a first step in this direction, presenting
incremental design algorithms with proven optimality bound for one-parameter
families of criteria based on coverings and spacings that both converge to
dispersion for large values of their parameter. The examples presented show
that the covering-based method outperforms state-of-the-art competitors,
including coffee-house, suggesting that it inherits from its guaranteed 50\%
optimality gap.
