Incidence matrix vs Adjacent Matrix

[John Creighto]

What is the difference between an http://en.wikipedia.org/wiki/Incidence_matrix" . They sound the same to me but this paper says they are different:
http://eprints.pascal-network.org/archive/00005332/01/barber_Newton.pdf

edit: My guess is that adjacent matrices refer to non directed graphs so the matrix will be symmetric while an incidence matrix also incidence directed graphs so need not be symmetric.

 

[John Creighto]

The deffinition at mathworld clarified it for me:

The incidence matrix of a graph gives the (0,1)-matrix which has a row for each vertex and column for each edge, and (v,e)=1 iff vertex v is incident upon edge e (Skiena 1990, p. 135). However, some authors define the incidence matrix to be the transpose of this, with a column for each vertex and a row for each edge. The physicist Kirchhoff (1847) was the first to define the incidence matrix.​

http://mathworld.wolfram.com/IncidenceMatrix.html