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# Model Navigation

In order to assist the user in creating and manipulating a complicated hierarchical model structure, there is a whole family of editor commands for examining and searching the database. In addition, on all keyboard commands, UNIX-style regular-expression pattern matching, such as ``*axle*'' or ``wheel[abcd]'', can be used. The simplest editor command (t) prints a table of contents, or directory, of the node names used in the model. If no parameters are specified, all names in the model are printed, otherwise only those specified are printed. The names of solids are printed unadorned, while the names of combination (non-terminal) nodes are printed with a slash (``/'') appended to them.

If the user is interested in obtaining detailed information about the contents of a node, the list (l) command will provide it. For combination (non-terminal) nodes, the information about all departing arcs is printed, including the names of the nodes referenced, the boolean expressions being used, and an indication of any translations and rotations being applied. For leaf nodes, the primitive solid-specific ``describe yourself'' function is invoked, which provides a formatted display of the parameters of that solid.

The tops command is used to find the names of all nodes which are not referenced by any non-terminal nodes; such nodes are either unattached leaf nodes, or tree tops. To help visualize the tree structure of the database, the tree command exists to print an approximate representation of the database subtree below the named nodes. The find command can be used to find the names of all non-terminal nodes which reference the indicated node name(s). This can be very helpful when trying to decide how to modify an existing model. A related command (paths) finds the full tree path specifications which contain a specified graph fragment, such as ``car/axle/wheel''. In addition to these commands, several more commands exist to support specialized types of searching through the model database.

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