The proposal for a public library in Volos (GR) begun with a diagrammatic analysis in order to comprehend the specific needs of a public building (the program) and to conclude to a productive tool, useful for the composition process. The logic of the analysis was based upon the segmentation of the given program (reading halls, educatoria, labs, etc) into surfaces proportionate to the square metres that the program requires. The prototype surface was defined by one stable axis, the side of 38,88m of the site (on Skenderani St). Accordingly, for each program space there was a division of the its sq m with the 38,88m of the stable side (length), giving as a result the dimension of the other side of each surface (width). The minimum dimension of the width (4,6m) derived from the smallest program requirement (150sq m). As a result, a sequence of surfaces, with a stable length and different width, were placed in a way that assimilates a diagrammatic building. For the final composition step, the surfaces discarded the program that they derived from, and as plans, empty containers were filled with the program anew, taking into consideration elements such as users' circulation, flow and pauses.