That is completely inadequate. I had read it several times before posting my message. If I did not understand it, few people will. Class hierarchies are abstract. People do not learn how to use an abstraction by reading the abstraction. They learn abstractions by learning examples. Your documentation needs to be more concrete. It should be based on using a wiki, not on looking at the Smalltalk code. Once people know what SmallWiki does then you can give them class diagrams and they will make sense. "Structure" is a wretched name. It is too vague. Section 3.2 is too abstract. It says little that I couldn't get by reading the code. The result is that the section makes sense only AFTER someone has figured out SmallWiki. A structure "represents the model of a single page". But there is a Page class, as well. This is confusing. I think that what is important about Structure is that it has a URL. Though actions also have URLs. If a structure is a model, what are its observers? The storage manager is one. Anything else? -Ralph