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planes outnumber or equal enemy planes. Defensive attack **is used when enemy planes**
outnumber friendly planes.

Choosing between offensive and defensive attack requires counting the current aircraft in the area. Figure 5 shows the evolution of an executing example decomposition. The agent must count relevant **enemy and friendly planes. Determining a plane's "side" and**
its relevance to the count often requires remembering and is **sufficiently complex that entailment of the count is not possible. For instance, non-combatant aircraft should not be**
counted, requiring some reasoning about the type of each aircraft. If the agent determines that enemy planes outnumber friendly ones, the agent selects defensive-attack**, leading** to further decomposition.

What happens if an enemy plane flees, thus reducing the actual **count of relevant enemy planes by one? The count maintained by the agent is now invalid. Standard TMS**
mechanisms are insufficient because the count was asserted as **an assumption. If the actual**
number of enemy and friendly planes is now equal, then the agent should switch its tactic to offensive attack. Continuing the defensive attack is not consistent with the agent's knowledge. Additionally, other "friendly" agents participating in the attack may base their behavior on the expectation that the agent is pursuing an offensive attack. Thus the agent needs to recognize the inconsistency and remove the current **count.**
Figure 6 presents a conceptual illustration of the problem. **Assumptions are represented**
as squares, entailments as circles. The horizontal line represents a hierarchical relationship between the assertions (i.e., assumptions and entailments) in the hierarchical context (above the line) and assertions in a local subtask (below the line). **The arrowed lines represent** dependence in the creation of an assertion. As in the previous examples, some reasoning in the subtask may require persistence, leading to the creation of an assumption such as assumption 1**. However, the persistent assertion may still depend on other assertions. This** work focuses on the dependent assertions in the higher level **context, such as** A, B, C, D,
and E1 **in the figure.**
Suppose the world changes so that E1 is retracted from memory and E2 **is asserted.**
Assumption 1 remains in memory. If E2 would not also lead to 1 **(e.g., it could lead to some**
new assumption 2, as shown), then 1 **is no longer justified and may not be consistent with**
the higher level context. Whether or not this potential inconsistency among the assertions leads to inconsistent behavior depends on the use of assumption 1 **in later reasoning.**