  Well-defined formal definitions for sentiment and opinion are extended to
incorporate the necessary elements to provide a formal quantitative definition
of reputation. This definition takes the form of a time-based index, in which
each element is a function of a collection of opinions mined during a given
time period. The resulting formal definition is validated against informal
notions of reputation. Practical aspects of data procurement to support such a
reputation index are discussed. The assumption that all mined opinions comprise
a complete set is questioned. A case is made that unexpressed positive
sentiment exists, and can be quantified.
