
| Lead Agent         | Wing Agent   |      |       |      |       |      |      |      |
|--------------------|--------------|------|-------|------|-------|------|------|------|
| FHJ                | DHJ          | FHJ  | DHJ   |      |       |      |      |      |
| Rules              | 591          | 539  | 591   | 539  |       |      |      |      |
| Number of runs (n) | 43           | 53   | 56    | 46   |       |      |      |      |
| x¯                 | s.d.         | ¯x   | s.d.  | ¯x   | s.d.  | ¯x   | s.d. |      |
| Decisions          | 8974         | 0.0  | 8974  | 0.0  | 8958  | 0.0  | 8958 | 0.0  |
| Outputs            | 109.1        | 6.71 | 142.8 | 7.03 | 1704  | 42.7 | 869  | 12.8 |
| Rule Firings       | 2438         | 122  | 2064  | 81.1 | 16540 | 398  | 6321 | 104  |
| CPU Time (msec)    | 1683         | 301  | 1030  | 242  | 12576 | 861  | 2175 | 389  |

## 4.4.1 Improving Task Decompositions

µ**TacAir-Soar DHJ agents required extensive knowledge revision. Such revision was not** unexpected. For instance, unlike the Dynamic Blocks World, µ**TAS agents remember many**
percepts, such as the last known location of an enemy aircraft. As previously described, assertions for remembering must now be located in the root level of the hierarchy, thus requiring some knowledge revision. However, other problems were discovered. In some cases, FHJ agents took advantage **of inconsistency in asserted knowledge. In other words, the** FHJ agent not only allowed inconsistency in the assertions but actually depended on those inconsistencies to apply new knowledge. There were two major categories of this knowledge. "Within-level" consistency knowledge recognized specific **inconsistencies (e.g., retraction of**
the proposal for the subtask) as a trigger for actions such as **"clean up" of the subtask**
state. "Complex subtasks" allowed the non-interruptible execution of a complex procedure regardless of the continuing acceptability of the subtask. **In both cases, agent knowledge** was modified to remove any dependence on inconsistency. Appendix A provides further explanation of the original knowledge and subsequent changes. Section 4.4.3 summarizes the changes quantitatively.

## 4.4.2 Results

Table 2 lists average data for the FHJ and DHJ lead and wing agents for the patrol/intercept scenario after the modifications to the DHJ agent's knowledge base were completed. The results in this domain are consistent with expectations: total knowledge decreases, rule firings decrease and performance improves, substantially so for the DHJ wing agent. The following sections explore each of these results in greater **detail.**

## 4.4.3 Knowledge Differences

Table 3 quantifies the changes to the Soar production rules described above.7 **Modifications include deletions, additions and changes. A rule was considered "changed" only if**
its conditions changed slightly, but it made the same type of **computation for the same**
subtask. For example, most of the "changed" within-level consistency knowledge now refers