Evangelos Zirintsis

Process support for evolving active architectures

Long-lived, architecture-based software systems are increasingly important. Effective process support for these systems depends upon recognising their compositional nature and the active role of their architecture in guiding evolutionary development. Current process approaches have difficulty with run-time architecture changes that are not known a priori, and dealing with extant data during system evolution. This paper describes an approach that deals with these issues. It is based on a process-aware architecture description language (ADL), with explicit compose and decompose constructs, and with a hyper-code representation for dealing with extant data and code. An example is given to illustrate the ease-of-use benefits of this approach.

Hyper-Code Revisited: Unifying Program Source, Executable, and Data

The technique of hyper-programming allows program representations held in a persistent store to contain embedded links to persistent code and data. In 1994, Connor et al proposed extending this to hyper-code, in which program source, executable code and data are all represented to the user in exactly the same form. Here we explore the concept of hyper-code in greater detail and present a set of abstract language-independent operations on which various concrete systems can be based. These operations (explode, implode, evaluate, root and edit) are provided by a single user interface tool that subsumes the functions of both an object browser and a program editor. We then describe a particular implementation using PJama (persistent Java) and examine the impact of several language features on the resulting system.

Reflection and Reification in Process System Evolution: Experience and Opportunity

Process systems aim to support many people involved in many processes over a long period of time. They provide facilities for storing and manipulating processes in both the representation and enactment domains. This paper argues that process systems should support ongoing transformations between these domains, at any level of granularity. The notion of creating an enactment model instance from a representation is merely one special case transformation. The case for thinking in terms of model instances is weak, especially when process evolution is considered. This argument is supported by our experience of the ProcessWeb process system facilities for developing and evolving process models. We introduce the idea of hyper-code, which supports very general transformations between representation and enactment domains, to offer the prospect of further improvements in this area.

Current Directions in Hyper-Programming

The traditional representation of a program is as a linear sequence of text. At some stage in the execution sequence the source text is checked for type correctness and its translated form is linked to values in the environment. When this is performed early in the execution process, confidence in the correctness of the program is raised. During program execution, tools such as debuggers are used to inspect the running state of programs. Relating this state to the linear text is often problematical. We have developed a technique, hyperprogramming, that allows the representations of source programs to include direct links (hyper-links) to values, including code, that already exist in the environment. Hyperprogramming achieves our two objectives of being able to link earlier than before, at program composition time, and to represent sharing and thus closure and through this the run-time state of a program. This paper reviews our work on hyper-programming and proposes some current research areas.