  In this paper we present an innovative intelligent web-based computer-aided
instruction system for foreign language learning: CSIEC (Computer Simulator in
Educational Communication). This system can not only grammatically understand
the sentences in English given from the users via Internet, but also reasonably
and individually speak with the users. At first the related works in this
research field are analyzed. Then we introduce the system goals and the system
framework, i.e., the natural language understanding mechanism (NLML, NLOMJ and
NLDB) and the communicational response (CR). Finally we give the syntactic and
semantic content of this instruction system, i.e. some important notations of
English grammar used in it and their relations with the NLOMJ.
