OPERATOR: SNIP

Problem space: u-construct

Operator Overview:

This operator may form part of the u-constructor being constructed. It removes a link relation between an assigner, A and a receiver, R set up previously by a link operator.

Operator Proposal:

A snip operator is generally proposed when local inconsistencies in the u-model are detected. These inconsistencies occur when two mutually incompatible bits of structure exist simultaneously in the u-model. As an example, consider "the green man is old." Since green can be both an NP and a AP, when [NP man] arrives, we would get two different legitimate structures

[NP [DET the] [N' green]] and

[NP [DET the] [N' [AP green] [N' man]]]

NL-Soar perceives this phenomenon as an inconsistency because the u-model representation does not systematically support multiple interpretations. A snip operator is triggered by the presence of syntactic structure attached to competing senses of the same lexical token. The more recent structure is prefered because it is complete (in the sense that all the words are in the structure) and so in the above example, snip breaks the link between [DET the] and [NP green]. Note that snip does not actively repair the structure, it just removes a previous link relation and then NL-Soar takes over to propose other appropriate link operators.

Operator Application:

Notice that assigner A is always in the A/R set but receiver R has already been removed (that's the way the A/R set is implemented) during the link operation. So, the snip operator re-introduces receiver R into the receivers set, and effectively removes the link by changing the attribute-value pair in assigner A. It also updates ^receivers-id with the word associated with R, so that the word is available again for linking.

For example, if we had a link operator that links [DET the] to [NP green] (in this case, [NP green] is the assigner A that assigns the syntactic relation SPEC to the receiver R, [DET the]), then A would have an attribute-value pair ^SPEC R. If we now have a snip operator that snips R from A, A would now have the attribute-value pair ^SPEC *empty*.

Operator Reconsider:

Upon application.

Back to the operator hierarchy.

This page written by Han Ming Ong(hanming@cs.cmu.edu)