Talk:Directed graph

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I feel this page does not contain enough information about the context of its subject. It is not made clear in what scientific or mathematical fields one is likely to encounter a digraph, nor is any information presented about how they are useful. 75.162.233.85 (talk) 05:56, 15 October 2008 (UTC)

[edit] Three pieces of data?

Why is the third of these needed? Seems to me that it is superfluous; a digraph is a set of nodes, and a (multi)set of ordered pairs (arcs) node→node. I guess the nodes need to all be connected too, but that does't follow from the article, which says:

• a set V, whose elements are called vertices or nodes,
• a set A of ordered pairs of vertices, called arcs, directed edges, or arrows, and
• two maps from A to V that associate to an arc its head and its tail.

JöG (talk) 12:22, 22 November 2008 (UTC)

You are right: "two maps" is not part of the mathematical definition. Although they may appear useful in some computer representations of digraphs. Twri (talk) 00:10, 25 November 2008 (UTC)