Co-occurrence agreement probability

Co-occurrence agreement probability is defined as:

$P(agreement)=\sum _{(i,j)}D(i,j)\delta _{R}(i,j)\oplus \delta _{H}(i,j)$

where $D(i,j)$ is a probability distribution over the distances between words in a document; the $\delta$ functions are 1 if the two words fall in the same segment and 0 otherwise; and $\oplus$ function indicates agreement between the operands.