Figure 3 is a close-up of any of these triangles. From now on we describe the term level, which is the more general. The surface of every triangle can be plain or wrinkled, depending on the existence of documents related to any the surrounding terms or not. As the arrow head is a piramid of triangular base, arrows have a triangular shadow. Corners of the container triangle stand for terms.
Every arrow stands for a document.
The fact that a document can be described by more than three terms implies that it can appear in more than one triangle, exactly in C 3,n of them. Thus any document is seen not as a whole, but projected in many triangles made of the terms that describes the document. Anyway, many times three terms are enough for describe a document at a general level, as it can be seen that the number of keywords in scientific papers is many times around three. For any tool is as important how good it is designed as how well it can be handled. Given that our map is a tool, it should be easy to handle to let the user filter, analyze and understand the body of knowledge that the map represents.