  Spreadsheets are end-user programs and domain models that are heavily
employed in administration, financial forecasting, education, and science
because of their intuitive, flexible, and direct approach to computation. As a
result, institutions are swamped by millions of spreadsheets that are becoming
increasingly difficult to manage, access, and control.
  This note presents the XLSearch system, a novel search engine for
spreadsheets. It indexes spreadsheet formulae and efficiently answers formula
queries via unification (a complex query language that allows metavariables in
both the query as well as the index). But a web-based search engine is only one
application of the underlying technology: Spreadsheet formula export to web
standards like MathML combined with formula indexing can be used to find
similar spreadsheets or common formula errors.
