Teleological Modeling and Reasoning for Automated Software Adaptations

The design of a long-living software artifact evolves through many versions. Changes in the design requirements from one version to the next typically are incremental and sometimes quite small (deltas). A software engineer (or a team of software engineers) formulates the requirements of a new version, adapts the design of the previous versions to meet the new requirements, implements and evaluates the modified design. Of course, the ordering of these tasks is not necessarily linear; the design requirements, for example, may evolve during the design episode, and if the proposed design fails in the evaluation task, it may need to be redesigned. Thus, adaptive design includes both proactive adaptation (adapting a design to meet new requirements) and retrospective adaptation (redesigning a proposed design). AI research on conceptual design of physical devices has revealed the central role that teleological knowledge and reasoning play in automated adaptive design [1] [2] [3] [4] [5] [6] [7] [8]: (i) a declarative teleological model of a physical device that explicitly captures the teleological relationships among the structure, behaviors and functions of its design enables localization of the modifications needed to the structure to achieve new functions, and (ii) the ontology of teleological models provides a vocabulary for classifying, representing, indexing and accessing specific design cases, generic adaptation plans, primitive design components, and abstract design patterns. In analogy to physical devices, we view software artifacts as abstract devices, i.e., as abstract teleological artifacts with structures and behaviors that result in the accomplishment of desired functions [9] [10] [11] [12] [13]. Recent AI research on self-adaptation in software agents makes a further analogy between adaptive design of physical and software devices [14] [15] [16] [17] [11] [18] [19] [20]. This leads to our research hypothesis: function and teleology are basic organizational principles of adaptive software design.