A formalism to describe design patterns based on role concepts

Abstract

Design patterns are typically defined imprecisely using natural language descriptions with graphical annotations. It is also common to describe patterns using a concrete design example with implementation details. Several approaches have been proposed to describe design patterns abstractly based on role concepts. However, the notion of role differs in each approach. The behavioral aspects of patterns are not addressed in the role-based approaches. This paper presents a rigorous approach to describe design patterns based on role concepts. Adopting metamodeling and formalism, our work defines an innovative framework where generic pattern concepts based on roles are precisely defined as a formal role metamodel using Object-Z. Individual patterns are specified using these generic role concepts in terms of pattern role models. Temporal behaviors of patterns are also specified using Object-Z and integrated in the pattern role models. Patterns described this way are abstract, separating pattern realization information from the pattern description. They are also precise providing a rigorous foundation for reasoning about pattern properties. This paper also formalizes the properties that must be captured in a class model when a design pattern is deployed. These properties are defined generically in terms of role bindings from a pattern role model to a class model. They provide a precise basis for checking the validity of pattern utilisation in designs. Our work is supported by tools. We have developed an initial role metamodel using an existing modeling framework, Eclipse Modeling Framework (EMF) and have transformed the metamodel to Object-Z using model transformation techniques. Complex constraints are added to the transformed Object-Z model. More importantly, we implement the role metamodel. Using this implementation, pattern authors can develop an initial pattern role model in the same modeling framework and convert the initial model to Object-Z using our transformation rules. The transformed Object-Z model is then enhanced with behavioral features of the pattern. This tool support significantly improves the practicability of applying formalism to design patterns.

Towards a formal model of patterns and pattern languages

“…Most of the existing researches are limited to single patterns [13][14][15][16] and combination of patterns [17][18][19][20] . Note that among other purposes of presenting a formalism to describe a single pattern, having a unified visual approach will be helpful to improve pattern authors' and pattern users' perception [14,19,20,32] .…”

“…Therefore, to facilitate the process of developing supporting tools on verifying the applied patterns and PLs in practice, we need to formalize the underlying concepts [3,6] . Although the literature of the last two decades of software patterns, beginning from the publishing of the seminal Gang-of-Four (GoF) design patterns book [1] , illustrates several researches which have been concentrated on formalizing single patterns [3,[13][14][15][16] , a few of the current researches consider the patterns' inter-relationships and patterns' compositions [17][18][19][20] as well. Thus, we examine the main researches [5,6,21] which provide a solid foundation to our ongoing research regarding formalizing patterns and PLs.…”

A language-independent and formal approach to pattern-based modelling with support for composition and analysis

“…Such independence is achieved in [22] by using Object-Z, but no composition or conflict analysis techniques are given. Constraints on the use of patterns are exploited in [32] to maintain the consistency of a pattern-based software framework through the use of high-level transformations specific to each pattern.…”

Lessons Learned from Building a Graph Transformation System

“…This approach treats domain patterns as templates, where the parameters are roles, and a tool generates models from this language. Compared to our approach, the paper [22] proposes a formal way to specify the pattern embedding for the static aspect. The behavioral formalization is closely coupled with design patterns defined in UML.…”