The n-dimensional ternary Hamming space is T n , where T = f0; 1; 2g. Three points in T n form a line if they have in common excactly n Gamma 1 components. A subset of T n is closed if, whenever it contains two points of a line, it contains also the third one. A generator is a set, whose closure is T n . In this paper, we investigate several properties of closed sets and generators. Two
... [Show full abstract] alternative proofs of our main result, stating that the minimum cardinality of a generator is 2 n , are provided. The present study was motivated by some combinatorial questions concerning origin-destination matrices in transportation systems. 1 Introduction In transportation modelling, Origin-Destination (O/D) matrices are frequently used to represent travel demand. The region at hand is subdivided into a fixed number of elementary zones which are at the same time origins and destinations of possible trips. The surveyed data are organized in an O/D matrix whose generic cell (i; j) contain...