Recently, service oriented architecture (SOA) has been popularized with the emergence of standards like Web services. Nevertheless, the shift to this architectural paradigm could potentially involve significant risks including projects abandonments. With this in mind, the question of evaluating SOA quality arose. The appearance of methods like ATAM or SAAM propelled software architecture evaluation to a standard stage for any paradigm. However, there still are a number of concerns that have been raised with these methods; in particular their cost in terms of time and money, essentially because of the hand-operated nature of the evaluations conducted. The model proposed in this paper for evaluating SOAs takes as a starting point the McCall model; it allows the whole architecture to be decomposed in three types of quality attributes (factor, criterion and metric)