Page Definition Query improvement
Page Definition Queries are very useful, however they have the potential to be much more so. Rather than only being able to turn features on/off based on them having a field which matches (or doesn't) the page name, the ability to use SQL queries (mush like regular definition queries) would enable much greater scope for filtering features.
An example might be a a state-wide feature class containing many classes of road from major highway to dirt track. Depending on the scale of each data driven page, the level of road class dsplayed may need to be changed (i.e. only showing major highways at small scales when lower classes cause cluttering, and showing minor roads/tracks at large scales).
To facilitate this, the Index Layer would be populated with fields corresponding to layers which are to have Page Definitions applied. These fields would contain the values to be matched in the definition, in the above example the values would be road classes. The Page Definition could then contain an SQL query where the field in the road dataset containing Road Class is selected, a boolean operator is selected and the corresponding field in the Index Layer is is selected.
The below example selects the major roads (Classes 1 & 2) for display on the State-wide page.