HEARSAY - 1980 - Speech Understanding

Entire system consists of a set of independent modules (knowledge sources KS's)
that contain domain-specific knowledge and a blackboard - a shared data structure to which all the KS's have access. (like demons - triggers)

Mechanisms that affect a message (speech):

psychology of the speaker
semantics
rules of discourse
syntax
lexicon (meaning of word)
prosodic system (science/art of versification)
phonemic system (distinguish utterances)
speaker's artculatory apparatus
ambient environmental noise

till Bob rings
tell Bob rings
till Bob brings
tell Bob brings

stay right there
stare at their

eg. script

C /-\ T

Interpretations: higher level interpretations incorporate lower level ones

Hypotheses on the blackboard are arranged along two diminsions:

level - (from small, low-level hyp. about individual sounds to large, high-level hyp. about the meaning of the entire sentence)

time - time periods of the utterance being analyzed

Associated with each KS is a set of triggers for activation

When a trigger fires, it creates an activation record describing (1) the KS that should be activated and (2) the specific event that fired the trigger.

The determination of which KS should be activated next is done by a special KS called the Scheduler. (like Executive in Hayes-Roth)

Main Points:

Modularity with respect to task

Communication

HEARSAY III

• domain-independent

• time dimension removed (not appropriate for all domains)

• two blackboards:
  • hypotheses about problem (units)

  • scheduling (broken down into set of independent KS about scheduling)

BB1 blackboard control architecture

Hierarchical family of tools used to modify the

global data structure called the blackboard:

Top level:

Knowledge structures for representing all actions, states, events, and facts in a system.

Wide range of problem classes, methods, and domains. This level is control of overall system.

A system may have 3 classes of know. sources.

1. domain knowledge sources

2. control knowledge sources

3. learning knowledge sources (modify KSs and facts in knowledge base)

Next level:

Knowledge structures for representing all actions, states, events, and facts involved in addressing a particular class of problems with a particular problem-solving method.

(Generic Tasks)

Lowest level:

Individual applications for particular classes of problems with particular problem-solving methods in particular subject-matter domains

(Domain knowledge)

Boeing Blackboard System

derived from BB1

In problem-solving ... use of "domain-specific problem solving strategies". not well said

significance of user-interface

note term: event-driven system