From DASCo to MOOSCo: MOO with Separation of Concerns

Separation of concerns is considered a key technique in software engineering [5]. This technique consists of treating separately different aspects of program construction in order to control complexity, in accordance with a divide and conquer approach. For instance, the separation between a program’s functional and non-functional concerns allows the construction of an initial version supporting only its functionality in terms of expected input and output, and its later enrichment to support other aspects, such as performance, reliability and computational constraints. Problems handled by functional and non-functional concerns are specified, respectively, by a program’s functional and non-functional requirements. The construction of concurrent and distributed programs is especially complex due mainly to the inherent nondeterminism of their execution, which makes it difficult to repeat test scenarios and to the diverse existing technological supports. It should be noted that the execution order of two concurrent activities is influenced by external programming conditions, such as processor load and interruptions. Moreover, different technology introduces slights differences which bias the application design and its further evolution in term of technology infrastructure replacement. DASCo (Development of Distributed Applications with Separation of Concerns [1]) is an approach defined for constructing concurrent and distributed programs which separately handles, during the development process, functional and non-functional concerns. The approach defines solutions for each non-functional concern related to concurrency and distribution, such as object synchronization or configuration, and integrates those solutions as well as their composition in an incremental development process of concurrent and distributed programs. In addition, the approach allows the most appropriate solution for each concern to be customized by the programmer to take into account the specific needs of the program being built. Furthermore, predefined customizations are offered for each concern. The programmer is able use them without needing to be aware of the underlying complexity associated with both the problem the concern deals with and the construction of the solution. Concern solutions are based on micro-architectures of cooperating objects which may be applied and customized in various programs. MOOs (Multi-user Object-Oriented environments) are object-oriented environments where multiple users synchronously and asynchronously interact in the context of virtual worlds. MOO applications are a particular case of concurrent and distributed programs where each user realizes that other users may be in a remote site and that information is shared. This paper describes how we believe that DASCo approach can be applied for the design and implementation of MOOs. The rest of this paper is structured as follows. Section 2 presents DASCo features and Section 3 describes MOO technical requirements. In Section 4 its is discussed how separation of concerns can be applied in MOOs development. Section 5 presents the conclusions.