The Parallel Expert Parser: A Meaning-Oriented, Lexically-Guided, Parallel-Interactive Model of Natural Language Understanding

G. Adriaens


Abstract
The Parallel Expert Parser (PEP) is a natural language analysis model belonging to the interactive model paradigm that stresses the parallel interaction of relatively small distributed knowledge components to arrive at the meaning of a fragment of text. It borrows the idea of words as basic dynamic entities triggering a set of interactive processes from the Word Expert Parser (Small 1980), but tries to improve on the clarity of interactive processes and on the organization of lexically-distributed knowledge. As of now, especially the procedural aspects have received attention: instead of having wild-running uncontrollable interactions, PEP restricts the interactions to explicit communications on a structured blackboard; the communication protocols are a compromise betwenn maximum parallelism and controllability. At the same time, it is no longer just words that trigger processes; words create larger units (constituents), that are in turn interacting entities on a higher level. Lexical experts contribute their associated knowledge, create higher-level experts, and die away. The linguists define the levels to be considered, and write expert processes in a language that tries to hide the procedural aspects of the parallel-interactive model from them. Problems include the possiblity of deadlock situations when processes wait infinitely for each other, the way to efficiently pursue different alternatives (as of now, the system just uses don’t-care determinism), and testing whether the protocols allow linguists to fully express their needs. PEP has been implemented in Flat Concurrent Prolog, using the Logix programming environment. Current research is oriented more towards the problem of distributed knowledge representation. Abstractions and generalizations across lexical experts could be made using principles from object-oriented programming (introducing generic, prototypical experts; cp. Hahn 1987). Thoughts also go in the direction of an integration of the coarse-grained parallelism with knowledge representation in a fine-grained parallel (connectionist) way.
Anthology ID:
W89-0232
Volume:
Proceedings of the First International Workshop on Parsing Technologies
Month:
August
Year:
1989
Address:
Pittsburgh, Pennsylvania, USA
Venues:
IWPT | WS
SIG:
SIGPARSE
Publisher:
Carnegy Mellon University
Note:
Pages:
309–319
Language:
URL:
https://www.aclweb.org/anthology/W89-0232
DOI:
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PDF:
http://aclanthology.lst.uni-saarland.de/W89-0232.pdf