Architecture for an artificial agent that reasons defeasibly

Claim 2

A computer implemented method for defeasible reasoning, comprising the steps of: (a) generating a list of conclusions by monotonic reasoning and recording said conclusions in a selected one of a simple inference-graph and an and/or inference-graph each having nodes corresponding to said conclusions; (b) computing defeat-status for said nodes of said inference-graph, using a method comprising the steps of: (i) computing a list of status-assignments; (ii) computing the defeat-status of a selected node by one of the following: (A) a method for computing the defeat-status of a selected node wherein said inference-graph is an and/or inference-graph and said node is judged undefeated only if every status-assignment assigns a nonzero defeat-status to said node; and (B) a method for computing the defeat-status of a selected node wherein said inference-graph is an and/or inference-graph and said node is judged undefeated if said inference-graph contains nodes that constitute an argument for said node and all of said nodes in said argument are assigned an undefeated defeat-status by every status-assignment.

Claim 3

The method of claim 1, in which said monotonic reasoning proceeds by a method comprising the steps of: (a) selecting a set of sequents in a list input, and a set of sequents in a list ultimate-epistemic-interests; (b) categorizing said sequents in said list input as conclusions and inserting said sequents into an ordered list inference-queue, (c) categorizing said sequents in said list ultimate-epistemic-interests as interests and inserting said interests into said list inference-queue; (d) retrieving in order said conclusions and said interests of said list inference-queue; (e) for each said conclusion retrieved, performing forwards reasoning to produce new conclusions and storing said new conclusions in a data structure inference-graph and also placing said new conclusions on said list inference-queue; (f) for each said interest retrieved performing, backwards reasoning to produce new interests and storing said new interests in a data structure interest-graph and also placing said new interests list on said list inference-queue; (g) comparing each said new conclusion with said interests recorded in said interest-graph and discharging from said inference graph each said new conclusion that is the same as an interest recorded in said interest graph; and (h) comparing each said new interest with said conclusions recorded in the inference-graph, and discharging from said interest graph each said new interest that is the same as a conclusion recorded in said inference graph.

Claim 4

A method as defined in claim 2 comprising repeating indefinitely, steps (a) through (h) whereby the reasoning never terminates.

Claim 5

A method as defined in claim 2 comprising repeating steps (a) through (h) until said inference-graph is empty.

Claim 6

The method of claim 1, wherein one node of the inference-graph defeats a second node only if the maximal-degree-of-support of the first node is at least as great as the maximal degree-of-support of the second node.

Claim 7

The method of claim 1, wherein maximal-degrees of support for members of the inference-graph are computed in accordance with the weakest-link principle.

Claim 8

The method of claim 1, as exemplified by the operation make-inference-from-link, wherein a new conclusion is drawn in accordance with an interest-link only when the maximal-degree-of-support for said new conclusion is at least as great as the degree-of-interest of the link-interest for said interest-link.

Claim 9

The method of claim 1, as exemplified by the operation discharge-interest-in, wherein interest in a conclusion is discharged only when the maximal-degree-of-support for said conclusion is at least as great as the degree-of-interest for some interest that said conclusion discharges.

Claim 10

The method of claim 1, wherein undefeated-degrees-of support and degrees-of-interest are used in prioritizing the inference-queue.

Claim 11

The method of claim 1 wherein said list of conclusions is maintained and forward reasoning makes inference only from elements of that list, whereby the method avoids duplicating reasoning in connection with inference-rules and reason schemes having multiple premises.

Claim 12

The method of claim 1, wherein: (a) conclusions and interests are stored in c-lists and i-lists; (b) for each c-list, the list of corresponding-i-lists is maintained; (c) for each i-list, the list of corresponding-c-lists is maintained; and (d) searches for appropriately related interests and inference-nodes are performed by searching the corresponding-c-lists of their i-lists and corresponding-i-lists of their c-lists, as exemplified by the operations discharge-interest-in, discharge-link, make-inference-from-link, and replicate-discharges, thereby avoiding replicating searches when matching or unifying conclusions and interests.

Claim 13

The method of claim 1, wherein interest-schemes are used to direct the portion of backward-reasoning that results from instantiating backward-reasoning by instantiating the conclusion of said reasons with an interest.

Claim 14

The method of claim 1, wherein interest-links are used to direct the portion of backward-reasoning that results from instantiating interest-schemes by instantiating the forward premises of said interest-schemes with conclusions.

Claim 15

The method of claim 1, as exemplified by the operation replicate-discharges, wherein the list of discharged-right-links for an interest is maintained, and searched when new conclusions are drawn, whereby the effect of interest-discharge is repeated when said new conclusions are drawn.

Claim 16

The method of claim 1, exemplified by the operations discharge-link and discharge-interest-in, wherein backward reasoning cancels interest in inference-nodes and interests that are no longer of use, whereby said inference-nodes and interests do not occupy the resources of the reasoning.

Claim 17

The method of claim 1, wherein the list of status assignments is computed by compute-assignments.

Claim 18

The method of claim 1, as exemplified by the operation compute-assignment-tree, wherein the list of status-assignments is computed by building the assignment-tree and taking said list of status-assignments to be the list of tree-assignments for all subtrees of said assignment-tree.

Claim 19

The method of claim 1, as exemplified by the operation update-assignment-tree, wherein the list of status-assignments is updated by recomputing only those parts of the assignment-tree containing inference/defeat-descendants of newly added support-links.

Claim 20

A computer-implemented method of directing plan adoption, comprising the use of defeasible reasons governing terms comprising suitable-goals, adoptable plans, and disjunctively-adoptable-plans, wherein said terms can be taken as place-holders irrespective of whether said terms are contentful expressions.

Claim 21

A computer-implemented method of directing plan adoption, comprising the use of defeasible reasons governing terms comprising suitable-goals, adoptable plans, and disjunctively-adoptable-plans, wherein said terms can be taken as place-holders irrespective of whether said terms are contentful expressions.

Claim 22

A computer-implemented method of directing plan-execution, comprising the use of defeasible reasoning relating terms comprising adoptable-plans, disjunctively-adoptable-plans, and executable-operations, where said terms can be taken as place-holders in the reasoning irrespective of whether said terms are contentful expressions.

Claim 23

A computer-implemented method of directing plan-execution, comprising the use of defeasible reasoning relating terms comprising adoptable-plans, disjunctively-adoptable-plans, and executable-operations, where said terms can be taken as place-holders in the reasoning irrespective of whether said terms are contentful expressions.

Claim 24

A computer implemented method for defeasible reasoning, comprising the steps of: (a) generating a list of conclusions by monotonic reasoning and recording said conclusions in a selected one of a simple inference-graph and an and/or inference graph each having nodes corresponding to said conclusions: (b) computing defeat-statuses for said nodes of said inference-graph, using a method comprising the steps of: (i) computing a list of status-assignments; (ii) computing the defeat-status of a selected node by employing a method selected from the group consisting of: (A) a method for computing the defeat-status of a selected node wherein said inference-graph is an and/or inference-graph and said node is judged undefeated only if every status-assignment assigns a nonzero defeat status to said node; and (B) a method for computing the defeat-status of a selected node wherein said inference-graph is an and/or inference-graph and said node is judged undefeated if said inference-graph contains nodes that constitute an argument for said node and all of said nodes in said argument are assigned an undefeated defeat-status by every status-assignment; (c) through the use of monotonic reasoning, selecting a set of sequents in a list input, and a set of sequents in a list ultimate-epistemic-interests; (d) categorizing said sequents in said list input as conclusions and inserting sequents into an ordered list inference-queue; (e) categorizing said sequents in said list ultimate-epistemic-interests as interests and inserting said interests into said list inference-queue; (f) retrieving in order said conclusions and said interests of said list inference-queue; (g) for each said conclusion retrieved, performing forward reasoning to produce new conclusions and storing said new conclusions in a data structure inference-graph and also placing said new conclusions on said list inference-queue; (h) for each said interest retrieved performing, backward reasoning to produce new interests and storing said new interests in a data structure interest-graph and also placing said new interests list on said list inference-queue; (i) comparing each said new conclusion with said interests recorded in said interest-graph and discharging from said inference graph each said new conclusion that is the same as an interest recorded in said interest graph; and (j) comparing each said new interest with said conclusions recorded in the inference-graph, and discharging from said interest graph each said new interest that is the same as a conclusion recorded in said inference graph.

Claim 25

A computer implemented method for defeasible reasoning, comprising the steps of: (a) generating a list of conclusions by monotonic reasoning and recording said conclusions in a selected one of a simple inference-graph and an and/or inference graph each having nodes corresponding to said conclusions: (b) computing defeat-statuses for said nodes of said inference-graph, using a method comprising the steps of: (i) computing a list of status-assignments; (ii) computing the defeat-status of a selected node by employing a method selected from the group consisting of: (A) a method for computing the defeat-status of a selected node wherein said inference-graph is an and/or inference-graph and said node is judged undefeated only if every status-assignment assigns a nonzero defeat status to said node; and (B) a method for computing the defeat-status of a selected node wherein said inference-graph is an and/or inference-graph and said node is judged undefeated if said inference-graph contains nodes that constitute an argument for said node and all of said nodes in said argument are assigned an undefeated defeat-status by every status-assignment; (c) through the use of monotonic reasoning, selecting a set of sequents in a list input, and a set of sequents in a list ultimate-epistemic-interests; (d) categorizing said sequents in said list input as conclusions and inserting sequents into an ordered list inference-queue; (e) categorizing said sequents in said list ultimate-epistemic-interests as interests and inserting said interests into said list inference-queue; (f) retrieving in order said conclusions and said interests of said list inference-queue; (g) for each said conclusion retrieved, performing forward reasoning to produce new conclusions and storing said new conclusions in a data structure inference-graph and also placing said new conclusions on said list inference-queue; (h) for each said interest retrieved performing, backward reasoning to produce new interests and storing said new interests in a data structure interest-graph and also placing said new interests list on said list inference-queue; (i) comparing each said new conclusion with said interests recorded in said interest-graph and discharging from said inference graph each said new conclusion that is the same as an interest recorded in said interest graph; and (j) comparing each said new interest with said conclusions recorded in the inference-graph, and discharging from said interest graph each said new interest that is the same as a conclusion recorded in said inference graph.

Claim 26

The method of claim 21, wherein one node of the inference-graph defeats a second node only if the maximal-degree-of-support of the first node is at least as great as the maximal degree-of-support of the second node.

Claim 27

The method of claim 22, wherein maximal-degrees of support for members of the inference-graph are computed in accordance with the weakest-link principle.

Claim 28

The method of claim 23, as exemplified by the operation make-inference-from-link, wherein a new conclusion is drawn in accordance with an interest-link only when the maximal-degree-of-support for said new conclusion is at least as great as the degree-of-interest of the link-interest for said interest-link.

Claim 29

The method of claim 24, as exemplified by the operation discharge-interest-in, wherein interest in a conclusion is discharged only when the maximal-degree-of-support for said conclusion is at least as great as the degree-of-interest for some interest that said conclusion discharges.

Claim 30

The method of claim 25, wherein interest-links are used to direct the portion of backward-reasoning that results from instantiating interest-schemes by instantiating the forwards premises of said interest-schemes with conclusions.

Claim 31

A computer-implemented method of directing plan adoption and plan-execution comprising the steps of: (a) directing plan adoption using defeasible reasons governing terms comprising suitable-goals, adoptable plans, and disjunctively-adoptable-plans, wherein said terms can be taken as place-holders irrespective of whether said terms are contentful expressions; and (b) directing plan-execution using defeasible reasons relating adoptable-plans, disjunctively-adoptable-plans, and executable-operations, where said terms can be taken as place-holders in the reasoning irrespective of whether said terms are contentful expressions.

Claim 32

A computer-implemented method of directing plan adoption and plan-execution comprising the steps of: (a) directing plan adoption using defeasible reasons governing terms comprising suitable-goals, adoptable plans, and disjunctively-adoptable-plans, wherein said terms can be taken as place-holders irrespective of whether said terms are contentful expressions; and (b) directing plan-execution using defeasible reasons relating adoptable-plans, disjunctively-adoptable-plans, and executable-operations, where said terms can be taken as place-holders in the reasoning irrespective of whether said terms are contentful expressions.

Claim 33

A computer implemented method for reasoning, comprising the steps of: (a) using forward-inference rules EI and UI and backward-logical reasons EG and UG to skolemize interest-formulas and conclusion formulas; (b) using unification to compute common instances of forwards-reasons and the node-formulas in inference-nodes, and using unification to compute conclusions to be inferred from said inference-nodes in accordance with said forwards-reasons; (c) when a supposition is generated by an interest, the interest-variables of the interest are made the node-variables of the inference-node recording the supposition; and (d) discharging interests by unifying the node-formula of an inference-node and the interest-formula of an interest to produce a unifier, applying said unifier to their suppositions, and then unifying the resulting node-supposition into the resulting interest-supposition.

Claim 34

A computer implemented method for reasoning, comprising the steps of: (a) using forward-inference rules EI and UI and backward-logical reasons EG and UG to skolemize interest-formulas and conclusion formulas; (b) using unification to compute common instances of forwards-reasons and the node-formulas in inference-nodes, and using unification to compute conclusions to be inferred from said inference-nodes in accordance with said forwards-reasons; (c) when a supposition is generated by an interest, the interest-variables of the interest are made the node-variables of the inference-node recording the supposition; and (d) discharging interests by unifying the node-formula of an inference-node and the interest-formula of an interest to produce a unifier, applying said unifier to their suppositions, and then unifying the resulting node-supposition into the resulting interest-supposition.

Claim 35

A computer implemented method for reasoning, comprising the steps of: (a) using procedure adopt-reductio-interest to create reductio-interests having schematic supposition; and (b) using procedures discharge reductios and discharge-retrospective-reductios to discharge reductio-interests having schematic suppositions.

Claim 36

A computer implemented method for reasoning, comprising the steps of: (a) using procedure adopt-reductio-interest to create reductio-interests having schematic supposition; and (b) using procedures discharge reductios and discharge-retrospective-reductios to discharge reductio-interests having schematic suppositions.