| EXCALIBUR Adaptive Constraint-Based Agents in Artificial Environments |
| [GENERATION] | [Variables] [Nonextensible Constraints] [Extensible Constraints] [Constraint Extensions] |
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Extensible constraints cannot be added in one step like the nonextensible constraints. Only the extensible constraint's pbase graph can be added at once, as this is the minimal structure. Thus, the addition production for an extensible constraint is similar to the one of nonextensible constraints, but without the NAC to avoid redundancy (for an avoidance from redundancy see Section [Avoiding Redundancy]):
Construction Pextensiblea: The right-hand side of the addition production is equal to the constraint's embedding graph pbase. The left-hand side of the production contains the vertices of the right-hand side without the constraint itself. In addition, the left-hand side includes an NAC for each included constraint. An NAC consists of a constraint's maximal embedding graph pmax such that the constraint is unified with the constraint of the left-hand side (NAC without the constraint itself).
Production PSuma in the figure below shows an example for the Sum constraint.
The left-hand side of the addition production requires that the other vertices of pbase are already existent. To prevent from deadlocks, it must be possible to create the other vertices of pbase independently of the extensible constraint. This is enforced by
Requirement reqe: Constraint-usage cycles are not allowed for the base embedding graphs of extensible constraints.
There must be one deletion production per extensible constraint. It withdraws the addition of the corresponding Pextensiblea production. The production is generated according to the one of a nonextensible constraint, but must contain an NAC to forbid edges to further vertices (to satisfy reqd):
Construction Pextensibled: The left-hand side of the deletion production is equal to the embedding graph pbase. The right-hand side of the production contains the vertices of the left-hand side without the constraint itself. The left-hand side contains an NAC that has a general vertex with a general edge to the constraint.
Production PSumd in the figure above shows an example for the Sum constraint.
reqp is satisfied, as Pextensibled is the reversal of Pextensiblea and the NAC cannot endanger the applicability as it is not possible that there are edges to the constraint directly after the application of Pextensiblea. Pextensibled cannot endanger the reqmin requirement for the other constraints of pbase because of reqe.
| [GENERATION] | [Variables] [Nonextensible Constraints] [Extensible Constraints] [Constraint Extensions] |
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Last update:
May 20, 2001 by Alexander Nareyek