This work is aimed to analyze enterprise knowledge management system integration assumptions, problems and their solutions at different complexity and quality levels. In the beginning, brief description of application classification is provided. Assuming large number of specialized applications usage enterprise-wide, we come up with the need to integrate data, contained by those applications, as well as applications themselves. Data level, message level and process level integration principles and their application analysis is made. Enterprise application integration refers to the plans, methods, and tools aimed at modernizing, consolidating, and coordinating the computer applications in an enterprise. Portals presented as tools for federating information in different sources and providing commonly used services (search engine or directory, news, email, forums and options for customization). Portal frameworks from different vendors was observed. SOA (Service Oriented Architecture) and BPEL (Business Process Execution Language) integration capabilities were analyzed. Human Capital Resource Management information system is intended to store and process data, related to human capital across organization. Three layer logical implementation and web service interface usage makes integration possible at data, message and process levels.