EXCALIBUR Adaptive Constraint-Based Agents in Artificial Environments |
[GENERATION] | [Variables] [Nonextensible Constraints] [Extensible Constraints] [Constraint Extensions] |
[ Please note: The project has been discontinued as of May 31, 2005 and is superseded by the projects of the ii Labs. There won't be further updates to these pages. ] |
(Related publication: [PUBLink])
Extensible constraints cannot be added in one step like the nonextensible constraints. Only the extensible constraint's p_{base} 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 P_{extensiblea}: The right-hand side of the addition production is equal to the constraint's embedding graph p_{base}. 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 p_{max} such that the constraint is unified with the constraint of the left-hand side (NAC without the constraint itself).
Production P_{Suma} 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 p_{base} are already existent. To prevent from deadlocks, it must be possible to create the other vertices of p_{base} independently of the extensible constraint. This is enforced by
Requirement req_{e}: 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 P_{extensiblea} 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 req_{d}):
Construction P_{extensibled}: The left-hand side of the deletion production is equal to the embedding graph p_{base}. 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 P_{Sumd} in the figure above shows an example for the Sum constraint.
req_{p} is satisfied, as P_{extensibled} is the reversal of P_{extensiblea} and the NAC cannot endanger the applicability as it is not possible that there are edges to the constraint directly after the application of P_{extensiblea}. P_{extensibled} cannot endanger the req_{min} requirement for the other constraints of p_{base} because of req_{e}.
[GENERATION] | [Variables] [Nonextensible Constraints] [Extensible Constraints] [Constraint Extensions] |
For questions, comments or suggestions, please contact us.
Last update:
May 20, 2001 by Alexander Nareyek