This chapter reviews briefly the semantic integration issues in multidatabase development and provides a standardized representation for classifying semantic conflicts. We begin by summarizing the methods and issues in multidatabase design. From the perspective of database integration, we identify that semantic conflict is the main issue. We explore the idea further by examining semantic conflicts and propose taxonomy to classify semantic conflicts in different groups. This taxonomy is then evaluated by two different methods. Finally, we conclude by discussing the limits of database integration and how this challenge may be addressed.