Intuitively, a graph is a diagram composed of a set of points and a set of arrows, each linking two of those points. The points are called the nodes of the graph and the arrows are called the arcs of the graph.
In a more formalised way, Claude Berge defines a graph G as the datum of the (X, U) pair, where X and U respectively designate, a set of points x1, x2,..., xn called set of nodes, and a family u1, u2,..., umof elements of the Cartesian product :
X × X = (x, y) / x ∈ X, y (...)
Accueil > Motsclés > anglais > Connectivity
Connectivity
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Graph
6 October 2004, by L. C. 
Theories of spatial analysis
3 December 2004, by D. P.The general theoretical position of spatial analysis consists in proposing a partial explanation as well as prediction possibilities about the state and probable evolution of geographical objects / entities, on basis of knowledge of their situation with respect to other geographical objects.
There exists not yet any general theory of geographical space that could be a theory of concentrations, of spacing, of spatial structures and of evolution of spatial systems, relying on knowledge of (...) 
Connectivity
6 October 2004, by D. P.In theory of graphs, intensity of interlinking between nodes through edges of a network; more generally, degree of internal connection of a network. As opposed to mere proximity relations, called relations in continuity, connectivity relations are those using the support of a network to link two places that may be far apart from each other.