Towards Software Components for Non Functional Aspects

1 Introduction Solution: The act of separating the parts of any body, or the condition of undergoing a separation of parts. — Webster’s Revised Unabridged Dictionary (1913) Separation of concerns is a key engineering principle [18] applied in analysis, design, and implementation of systems. Designers want to think about one problem at a time and separation of concerns means decomposing a system into parts, each of which deals with, and encap- sulates a particular area of interest, called a concern. Software engineers learned how decomposition of a complex sys- tem into simpler sub-systems can make the problem tractable because the complete solution can be built out of sub-solutions, found relatively independently. In fact, most analysis and design notations and pro- gramming languages provide constructs for organising descriptions as hierarchical structures aggregating simpler modular units. Moreover, the development of every non trivial system necessar- ily involves many people, and it is crucial to entrust individuals with precise responsibilities, according their skills, knowledge, and expert- ise. In fact, multiple perspectives of the system must exist to cope with different development phases, different issues, different stake-holders. These different viewpoints [20] need an explicit representation in order to make possible concurrently carrying out and integrating them in co- herent analysis, design, implementation, testing and deployment arti- facts. Thus, smart techniques for expressing separate solutions to differ- ent concerns and composing them in the final system are needed at every stage of development. In particular, programming languages need proper idioms to help implementors in applying good “divide et impera” principles to their programs. Traditional programming lan- guages have supported the partitioning of software in modular units of functionality. Such parts are then assembled to get the desired func- tionality of the whole system. The history of programming languages 1