(4) For an event expression ee1 ∨ ee2, where ee1 and ee2 are two event expressions,
Implementation Details. An event expression ee can be represented by a binary tree T where each leaf node denotes a basic event identifier and each non-leaf node denotes an operator ∧, ∨ or ∼. Figure 12.4 gives an example of a binary tree which represents the event expression (e1∧ ∼e2) ∨ (e3∧ ∼e4) ∨ (e5∧ ∼e6).
For each node