We propose a method to specify, in a modular way, complex systems formed by interacting agents. The method is based on the notion of view, that is a partial representation of the system, reflecting one of its specific aspects. By composing the different views, we get the overall system, described as a special kind of transition system. By means of a suitable logical language, we can express interesting properties of the system; model-checking techniques can then be used to assess their validity. Views can be specified using different languages or notations, provided they can be translated in so-called agent aware transition systems. The method is explained with the help of a simple, but non trivial example.