This document studies in some detail the recently developed concept of aspect at the architecture level. This concept introduces a novel kind of modularization and composition in software, and therefore it defines new structures which must be studied by Software Architecture, determining the architectural features of aspects. However the opposite strategy can also be considered; namely, a new conceptual model can be defined, including an architecture-level notion of aspect. This would provide a new abstraction to describe software structures, thus effectively providing an additional dimension in architecture description, and would enable the study of the specific compositional problems in this dimension. The document starts by addressing the relevance of this kind of study, and continues by discussing why the new notions are necessary. Then it continues by including a brief enumeration of the more relevant notions derived from this aspectual framework, with particular emphasis on their relationship with software components. Next the document explores the different forms in which these notions could be incorporated into the context of Software Architecture, revealing a rather extensive variety of approaches, and also the relationships and partial equivalences between them.The paper concludes by noting a number or open questions and futures areas of research within this context.