1. A computer-readable medium storing a data structure configured for use in exposing commands in a software application program, the data structure comprising: a root node having a value; multiple nodes associated with the root node each of which having a value, the root node and multiple nodes being arranged to define various parent/child relationships and collectively representing an expression that defines a condition that describes one or more aspects of a user's interaction with the application program; each of the multiple nodes representing either an operation or an operand, individual multiple nodes being configured in a manner such that: a change in value generates a notification to the node's parent; and a notification of a change in value from a child node causes a re-evaluation of the node's value; the root node being configured such that a change in its value causes either the automatic display or removal of a set of context-sensitive commands that are appropriate for the user's context within the application program, wherein the user's context is determined by the user's interaction with a document provided by the application program, wherein determining a user's context includes ascertaining text portions of the document that have been selected by the user using a cursor, and wherein at least one command is selectable by the user to perform a formatting action on the selected text portions of the document; a tree formed by the root node and the multiple nodes, the tree having nodes associated with and representing either an operation or an operand, said nodes collectively describing conditions associated with a user's interaction with an application-provided document; and said nodes being configured for evaluation responsive to a user's interaction with the application-provided document such that context blocks associated with the user's context automatically appear, and, when the user's context changes, said context blocks automatically disappear, wherein said context blocks include one or more individual commands associated with the user's context, and wherein at least one command is selectable by the user to perform an action on the application-provided document, wherein at least some of said context blocks expose multiple commands for selection by the user and are modeless; wherein individual context blocks comprise a title bar area and a controls area with multiple selectable commands; and wherein the individual context blocks are configured to be displayed in a dedicated context area positioned adjacent to a context area of the application program, each of the individual context blocks including at least one command button that automatically appears or disappears as the user's changes context.
3. The one or more computer-readable media of claim 1 , wherein the nodes collectively define Boolean expressions that describe conditions associated with the user's interaction with the application-provided document.