This paper presents a computational model for pattern analysis and classification using symmetry group theory. The model was designed to be part of an integrated management system for pattern design cataloguing and retrieval in the textile and tile industries. While another reference model [6], uses intensive image processing operations, our model is oriented to the use of graphic entities. The model starts by detecting the objects present in the initial digitized image. These objects are then transformed into Bezier curves and grouped to form motifs. The objects and motifs are compared and their symmetries are computed. Motif repetition in the pattern provides the fundamental parallelogram, the deflexion axes and rotation centres that allow us to classify the pattern according its plane symmetry group. This paper summarizes the results obtained from processing 22 pattern designs from Islamic mosaics in the Alcazar of Seville.