Tree Component Alternatives to the Composite Design Pattern

The Composite design pattern is commonly employed in object-oriented languages to design a system of objects that form a part-whole hierarchical structure with composite objects formed out of primitive objects. The composite hierarchy effectively forms a tree-like hierarchical grouping of objects. From a software engineering perspective, there are at least two problems with the Composite pattern. First, it does not maintain a separation of concerns between the structure of the objects in a system and the objects themselves. This limits the ability of programmers to reuse the system s structural information. Secondly, there is no mechanism for encapsulating the system as a whole. This makes it difficult to specify and reason about global system properties. To overcome these difficulties, a component which extends the traversable tree is presented. A formal specification for each tree component is presented in the Tako language a Java-like language with alias avoidance. A case study is presented that shows how the indexed tree can be used and reasoned about in an application a text-based adventure game.

Autorentext

Arun Sudhir did his Masters in Computer Science from Virginia Polytechnic Institute and State University, VA, USA and is currently with Microsoft Corporation. His interests include Design Patterns, Component-Based Software Engineering, Programming Languages and Algorithm Analysis.