From the beginning, human being is interesting in knowledge. A lot of questions are discussed: what is knowledge? How knowledge is built? How is it represented in mind? How can it be kept? How can it be learned? … The notion of Knowledge is defined from the antiquity. Platon, for instance, define the thought as the intellectual model of objects. Heraclite went towards the definition of the logos as a triangle in which thought is distinguished from expression and from reality. Saussure defined the basic principle of the semiotic as: a representation of knowledge embedded in an activity and related to a specific symbol. Currently these representations are more and more used to enhance learning from expertise and past experience. So, human does making sense by recognizing concepts from his references (memory). Based on this theory, knowledge engineering approaches provide techniques that help to represent expertise as references and enhance learning from these references. We study how to capture and represent knowledge produced in daily work. This type of knowledge belongs to episodic memory. Experiences must be repeated in order to represent epistemic and semantic knowledge (references) that can be applied to face new problems. We develop techniques to capture daily knowledge in order to develop semantic classifications and enhance learning in an organization.