This paper presents the Diamond Tool for knowledge management. The main objective of its specification and implementation was to create a universal and easily extendable tool for efficient work with knowledge. One of its extensions is the eTrium technology. The principal idea behind this technology is to represent explicitly the knowledge used by the information system by means of a knowledge agent built on the Diamond Tool - in contrary to current approaches, where knowledge is present implicitly (in a disintegrated form) in the program code, the database structure and internal regulations of the firm. Explicit representation of knowledge and the method of work with knowledge that is suggested in this article, allows to build information systems of much higher quality in lesser time. Equally important is also the possibility of automatic or semi-automatic verification of knowledge managed by the knowledge agent. The paper shows how this can change the way applications are created and what it can be used for. Several commercial projects has already been implemented in the Diamond Tool - by means of the eTrium technology.