Object Modelling

Most people find diagrams easier to work with than blocks of formatted text, or hierarchical lists, when trying to grasp the high-level organisation of objects and the relationships between them. Below are three different ways of showing information about three types (classes) of object and how they are related.  For most people, the spatial nature of the UML model  makes it the easier to see that there are 3 different things involved and two relationships between them. Those adept at reading text may find it a close call between the UML model and the source code but then we have to remember that the three snippets of source code would normally be in three different files.

public class Order {
 private List lineItems;
 private int total;
}

public class LineItem {
 private Product product;
 private int quantity;
}

public class Product {
 private int unitPrice;
}

The Unified Modeling Language(UML)  has become the de facto standard object modeling notation. Although not perfect, and some might argue far from perfect, it does mean that all mainstream object models are built using the same basic set of symbols and diagrams. UML allows extensions to be defined and one such extension is Peter Coad's definition of colour-coded class archetypes. These archetypes represent and combine together in general patterns that are found again and again in good object models. These patterns and the strategies used to combine them has become known as 'modeling in color '. Peter Coad first wrote about modeling in color in his book, Java Modeling in Color with UML .

As with all creative areas of human industry, object modeling has best practices, techniques and patterns that make building good object models easier and faster. Over the years, as they have been discovered, people like Peter Coad, Martin Fowler  and their co-authors have written about some of these in their books.

More and more model and domain-centric techniques are becoming fashionable again. Already we have a growing set of new model-centric acronyms with which to confuse people including: Model Driven Architecture (MDA), Model Driven Development (MDD), Model Driven Engineering (MDE), Agile Modeling (AM) and Domain Driven Design(DDD)

Then there is the next generation of model-centric tooling being built by the Eclipse community as part of the open-source Eclipse Modeling Project. Borland is being contributing heavily to this project and Borland Together is being increasingly built on top of the various frameworks delivered by the project.

Therefore, object modelling techniques look like they will continue to be useful for at least the next few years. 

Further Reading