TaggingRules provides a way of storing additional information with a selection, for example, to be used by other programs in processing a notebook. It can be set to a list of one or more strings.
With the default setting TaggingRules->None, no additional information is associated with the selection.
Typically, structured metadata is broken up into pieces that can be identified using selector names in the form "selector"->data. The selector can then be individually queried using CurrentValue.
Another typical method for storing highly structured data is to use subselectors inside of selectors. For example, . The subselectors can then be queried using CurrentValue. Subselectors can have their own subselectors, to an arbitrary depth.
TaggingRules can be set at the cell, notebook, and global level.