Users' empirical evaluation of engines

Relevance and validity of results

Interface - Simple, no clutter, error tolerant

Trust - Results are objective

Coverage of topics for poly-semic queries

Pre/Post process tools provided

• Mitigate user errors (auto spell check, syntax errors, ...)
• Explicit: Search within results, more like this, refine ...
• Anticipative: related searches

Deal with idiosyncrasies

• Web specific vocabulary
  • Impact on stemming, spell-check, etc
• Web addresses typed in the search box