Resumen
This article discusses composing of crosscutting concerns using composition filters (CF). According to the author, certain design concerns, such as access control, synchronization, and object interactions cannot be expressed in object-oriented programming languages as a separate software module. These crosscutting concerns generally result in implementations scattered over multiple operations. The filters in CF model can express crosscutting concerns by modular and orthogonal enhancements to objects. Modularity means that filters have well-defined interfaces and are conceptually independent of the implementation (language) of the object. Orthogonality means that filter specifications do not refer to other filters. These two properties increase adaptability and reusability of concerns because filters can be applied to different languages and can be combined easily. In the CF model concerns are specified declaratively using a simple message manipulation language. This specification allows for various implementation strategies. Filter types encapsulate the accept and reject semantics of filters.