Attribute types and bracket implementations

In an object oriented system, different types of objects may have one or more attributes in common. For example different types of objects in a library system might be "loanable" or "catalogued". The first part of the paper introduces a distinction between object types and attribute types, showing that there are advantages in treating them as separate constructs of an object oriented programming language. Then generalized attribute types, (e.g. "synchronized", "journalized", "protected") are discussed. It is shown how implementations involving a technique called bracket routines can lead to clearly modeled and cleanly implemented programs. It is then shown how the bracket technique can be effectively used to introduce protection and security concepts into a system. Among the clear advantages of this technique is that it results in better reusability of code.