message: Workshop: -1 food, +2 production
diff: <iYield>1</iYield>
  </PrereqNatureYields>
  <YieldChanges>
  - <iYieldChange>0</iYieldChange>
  - <iYieldChange>1</iYieldChange>
  + <iYieldChange>-1</iYieldChange>
  + <iYieldChange>2</iYieldChange>
  </YieldChanges>
  <bActsAsCity>0</bActsAsCity>
  <bHillsMakesValid>0</bHillsMakesValid>
  <iAirBombDefense>5</iAirBombDefense>
  <iDefenseModifier>0</iDefenseModifier>
  <iHappinessPercent>0</iHappinessPercent>
  - <iHealthPercent>-100</iHealthPercent>
  + <iHealthPercent>0</iHealthPercent>
  <iPillageGold>5</iPillageGold>
  <bOutsideBorders>0</bOutsideBorders>
  <TerrainMakesValids>
  