This is implemented as directories. A browser is provided to navigate through this tree and manipulate the objects found there. These are either predicate definitions or subdirectories. The direct manipulation paradigm is used. This means that the objects can be moved, opened etc with the mouse.
Several browsers can coexist at the same time.
The basic functionality of GLUE is the definition of a new predicate. This predicate is charcterized by its name and arity. The arguments have types. Currently the types are only used at some places like the interaction with the user. Here only proper inputs are accepted.