  Developing Question Answering systems has been one of the important research
issues because it requires insights from a variety of
disciplines,including,Artificial Intelligence,Information Retrieval,
Information Extraction,Natural Language Processing, and Psychology.In this
paper we realize a formal model for a lightweight semantic based open domain
yes/no Arabic question answering system based on paragraph retrieval with
variable length. We propose a constrained semantic representation. Using an
explicit unification framework based on semantic similarities and query
expansion synonyms and antonyms.This frequently improves the precision of the
system. Employing the passage retrieval system achieves a better precision by
retrieving more paragraphs that contain relevant answers to the question; It
significantly reduces the amount of text to be processed by the system.

Computation and Language;Information Retrieval