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XPath Queries over Recipes
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 1. How many calories are in Linguine alla Pescatora?

 2. Return the titles of the recipes that have more than 500 calories.

 3. Return the recipes for which at least 4 eggs are needed.

 4. Which recipe has the highest number of calories? (Do not use the
    XQuery function max!)

 5. How many ingredients are there in Ricotta Pie?

 6. How many compound ingredients (i.e., ingredients with ingredients)
    are there in Ricotta Pie?

 7. How many elementary (= non-compound) ingredients are there in
    Ricotta Pie?  (An ingredient is elementary if it does not have
    ingredients itself.)

 8. Which recipes have an ingredient whose preparation needs more
    steps than are needed for the recipe itself (i.e., top level
    steps)?

 9. What is the average number of calories per recipe?  (Do not use
    the XQuery function avg!)  Note: Since the / operator has its own
    meaning in XPath, the division operator is infix div.

10. Return the names of the ingredients of Zuppa Inglese.

11. Return the names of those ingredients of Zuppa Inglese that occur
    also in other recipes.

12. Which recipes have an ingredient in common with Zuppa Inglese?

13. Return the ingredients of recipes other than Zuppa Inglese that
    these recipes have in common with Zuppa Inglese.

14. Return the names of all elementary ingredients that occur in at
    least two recipes.

15. Return the titles of all recipes for which some form of egg is
    needed (like egg whites or egg yolk).

16. Return the titles of the recipes that have only elementary
    ingredients.

17. Return the names of those ingredients that are mentioned in a
    preparation step of their recipe.

18. Return the names of ingredients that are not mentioned in a
    preparation step of their recipe.