Superspace: top-space

Result type: Operator Proposal

Problem Space Overview:
Create-operator generates the symbol for a new u-constructor or s-constructor. Once the implementation has been learned in one of its subspaces, either u-construct space or s-construct space, a proposal is returned to the top-space by the return-operator operator. The proposal of a u/s-constructor operator will terminate the top-space operator no-change impasse to which this problem space responds. This is because a u/s-constructor operator is always preferred over a learn-language operator and the learn-language operator will be reconsidered when a u/s-constructor has been successfully built. Note that although the create-operator space returns a u/s-constructor proposal, the implementation of the u/s-construct operator is built as a by-product, so implementation chunks fire immediately after the proposed operator is selected in the top-space.

When comprehension is running blippably the no-change impasse that results in the use of this problem space may disappear before the u/s-constructor proposal is returned to the top-space. Under these conditions some implementation chunks may have already been built. Since they are tied to the gensym of a u/s-constructor that is never returned, however, they will never fire. It should be noted, however, that running blippably does not mean that the relevant u/s-constructor will never be built. If subprocessing in service of the learn-language has resulted in chunks in lower spaces (e.g. link chunks), a subsequent trial over the same (or similar) input may still result in a u/s-constructor proposal even when processing occurs in the blippable mode. Speedup of the overall process is possible when speedup in the lower spaces occurs through chunk firings.

The create-operator space is always the response to an operator no-change impasse from the learn-language operator, regardless of how many (could be zero or more) u/s-constructors have fired for a new word. This means that the u/s-constructors returned from this impasse may do any of the following:

The ^annotation u/s-model-success is used to flag the completion of the u/s-construction for a new word. See completion space for more details.

Problem Space Proposal:
The problem space is proposed in response to an operator no-change impasse on the learn-language operator.

Initial state:
A lean copy of the Top state which contains the A/R set, the ordering and adjacency information and other necessary information required for the eventual implementation of the u/s-constructors. However, note that ^sentence,^ordering-info and ^adjacency-info are shared. The copy effectively walls off the top state, preventing spurious changes to processing in the subgoal as a result of new words coming in.

Operators in Problem Space:

Search control:
Creation of u-constructors is preferred over s-constructors. However, if the last word on ^adjacency-info has u-model-success flag marked, the creation of u-constructors is rejected on the assumption that there is no furthur knowledge that can be applied on that particular word and that we do not need to go back and do work for previous words.
Productions for the nl9702 version can be found through the file : create-operator.load

Back to the problem-space hierarchy.

This page written by Jill Fain Lehman ( and Han Ming Ong (

updated by Julie Van Dyke (, August 1997