Degree of Difficulty (1 to 10)

1 is least difficult, meaning that a bright person could read the abstract once, glance at the sample code for the pattern and understand what is going on immediately.  It would still suit that reader to glance at the “Common Pitfalls …” section.

10 is most difficult; the average person should expect to read the pattern 3 or 4 times (from several writers’ perspectives) before they really get it.

Structural Complexity (1 to 10)

This speaks to how much bulk the pattern adds to the code in terms of the extra classes and interfaces which are added to the solution to make the pattern work properly.

At first, the reader may confuse having “lots to learn” with being “hard to understand” and so these two ratings are done separately.  For example, Abstract Factory is a very straightforward pattern and is easy to understand.  However, it has a lot of components and is very bulky.  The two aspects should not be confused.

Implementation Complexity (1 to 10)

1 means you can practically cut and paste the code and search and replace the class names in your code and it is implemented.

10 means that implementation of the pattern is highly dependent on the development of domain-specific algorithms in order to flesh out the pattern.  You may be able to cut and paste the code into your solution, but it will require additional extra-pattern algorithms which are domain specific.

Implementation Specificity (1 to 10)

1 means that the inner-workings of the pattern are the same all the time.  You can cut and paste generic pattern code (or use code snippets in the case of VS2005), replace the generic class names with the implementation-specific names and you are practically done.

10 means that the actual inner-workings of the pattern change dramatically depending on the implementation.  You will usually develop the pattern code from scratch.