Abstract. Refactoring is the process of improving the design of existing programs without changing their functionality. These notes cover refactoring in functional languages, using Haskell as the medium, and introducing the HaRe tool for refactoring in Haskell. 1

Program refactoring --- transforming a program to improve readability, structure, performance, abstraction, maintainability, or other characteristics --- is not applied in practice as much as might be desired. One deterrent is the cost of detecting candidates for refactoring and of choosing the appropriate refactoring transformation. This paper demonstrates the feasibility of automatically finding places in the program that are candidates for specific refactorings. The approach uses program invariants: when particular invariants hold at a program point, a specific refactoring is applicable. Since most programs lack explicit invariants, an invariant detection tool called Daikon is used to infer the required invariants. We developed an invariant pattern matcher for several common refactorings and applied it to an existing Java code base. Numerous refactorings were detected, and one of the developers of the code base assessed their efficacy.

Refactoring ---transforming code while preserving behaviour --- is currently considered a key approach for improving object-oriented software systems. Unfortunately, all of the current refactoring tools depend on language-dependent refactoring engines, which prevents a smooth integration with mainstream development environments. In this paper we investigate the similarities between refactorings for Smalltalk and Java, derive a language-independent meta-model and show that it is feasible to build a languageindependent refactoring engine on top of this meta-model. Our feasibility study is validated by means of a tool prototype which uses the same engine to refactor both Smalltalk and Java code. Using our approach we minimize the language -dependent part of refactoring tools, providing a standard way for programmers and tools to perform refactorings no matter what language they work in. 1. Introduction Refactoring is defined as "changing a system to improve its internal structure withou...

Software developers spend most of their time modifying and maintaining existing products. This is because systems, and consequently their design, are in perpetual evolution before they die. Nevertheless, dealing with this evolution is a complex task. Before evolving a system, structural modifications are often required. The goal of this kind of modification is to make certain elements more extensible, permitting the addition of new features. However, designers are seldom able to evaluate the impact, on the whole model, of a single modification. That is, they cannot precisely verify if a change modifies the behavior of the modeled system. A possible solution for this problem is to provide designers with a set of basic transformations, which can ensure behavior preservation. These

The notion of refactoring —transforming the source-code of an objectoriented program without changing its external behaviour — has increased the need for a precise definition of refactorings and their properties. This paper introduces a graph representation of those aspects of the source code that should be preserved by a refactoring, and graph rewriting rules as a formal specification for the refactoring transformations themselves. To this aim, we use type graphs, forbidden subgraphs, embedding mechansims, negative application conditions and controlled graph rewriting. We show that it is feasible to reason about the effect of refactorings on object-oriented programs independently of the programming language being used. This is crucial for the next generation of refactoring tools.

In this paper, we show how elaborate support for framework-based software evolution can be provided based on explicit documentation of the hot spots of object-oriented application frameworks. Such support includes high-level transformations that guide a developer when instantiating applications from a framework by propagating the necessary changes, as well as application upgrading facilities based on these transformations. The approach relies on active declarative documentation of the design and evolution of the framework's hot spots, by means of metapatterns and their associated transformations.

This article presents a mathematical characterization of object-oriented concepts by defining an observation-oriented semantics for a relational objectoriented language with a rich variety of features including subtypes, visibility, inheritance, type casting, dynamic binding and polymorphism. The language is expressive enough for the specification of object-oriented designs and programs. We also propose a calculus based on this model to support both structural and behavioral refinement of object-oriented designs. We take the approach of the development of the design calculus based on the standard predicate logic in Hoare and He’s Unifying Theories of Programming (UTP). We also consider object reference in terms of object identity as values and mutually dependent methods.

This dissertation proposes micro-workflow, a new workflow architecture that bridges the gap between the type of functionality provided by current workflow systems and the type of workflow functionality required in object-oriented applications. Micro-workflow provides a better solution when the focus is on customizing the workflow features and integrating with other systems. In this thesis I discuss how micro-workflow leverages object technology to provide workflow functionality. As an example, I present the design of an object-oriented framework which provides a reusable micro-workflow architecture and enables developers to customize it through framework-specific reuse techniques. I show how through composition, developers extend micro-workflow to support history, persistence, monitoring, manual intervention, worklists, and federated workflow. I evaluate this approach with three case studies that implement processes with different requirements

Separation of concerns is a basic engineering principle that is also at the core of object-oriented analysis and design methods in the context of the Unified Modeling Language (UML). The UML gives the designer a rich, but somehow disorganized, set of views on her model as well as many features, such as design pattern occurrences, stereotypes or tag values, allowing her to add nonfunctional information to a model. Aspect-oriented concepts are applied to manage the multitude of design constraints. However, it can then be an overwhelming task to reconcile the various aspects of a model into a working implementation. In this paper, we present our UMLAUT framework as a toolkit for easily building application specific "weavers" for generating detailed design models from high level, aspect oriented UML models. This is illustrated with a toy example of a distributed multimedia application with a weaving generating an implementation model. More ambitious applications are briefly outlined in the conclusion. 1.

Refactoring is an essential approach toward improving the internal structure of a software system while preserving its external behavior. Traditional refactoring techniques have focused on the implementation stage, with source code as the primary artifact of the refactoring process. However, a recent trend is to apply the concepts of refactoring to higher levels of abstraction. Consequently, model refactoring is emerging as a desirable means to improve design models using behavior-preserving transformations.