This book is the result of three years of research by the author to build an intelligent system to provide semantic support for Persian Learners of English. To do so, computational description of Persian Morphology and Syntax has been included. The system constructs semantic representations of the content of both the original English sentences as well as students' translations as input text. It then compares the discourse states that result from the source text and the target text and reports on a range of mismatches. It is shown that by adding a CALL component to the language teaching system, it is possible to analyze original English sentences and the students' translations and compare their semantic content using logical forms to provide diagnostic information about lexical and semantic errors made by students.