Preconditions:

• User has access to ingredients consisting of:
  • 9″ pie shell/crust (trader joe’s makes a good one)
  • about a dozen apples (you can use Granny Smith if you can’t get Gravenstein, but then you need more sugar)
  • sugar
  • cinnamon
  • nutmeg
  • vanilla
  • salt
  • 1 large lemon
  • 1 stick of butter
  • flour
• User has access to typically equipped United States kitchen including oven, cookie sheet, spatula, aluminum foil, pastry cutter and medium mixing bowl
• Oven is preheated to 400°

Success Case: Pie.

1. User sets the frozen pie shell out to defrost.
2. User peels the apples and slices them up thinly into bowl.
3. User drizzles a small amount of lemon juice as each apple is sliced into bowl.
   1. Acid in lemon juice destroys enzymes preventing phenols and enzymes in apples from reacting – apples brown more slowly
4. User repeats steps 2-3 until bowl is approximately 2/3 full or contents will overfill pie shell.
5. User sprinkles cinnamon and nutmeg on to apples in bowl.
6. User adds up to 1 teaspoon of vanilla
7. User adds up to 1 cup of sugar
8. User stirs contents of bowl with spatula
   1. Apples are coated with sugar/spice mixture and a syrup develops in bottom of bowl.
   2. An odor of cinnamon and vanilla permeates the area immediately surrounding the bowl.
9. User dumps contents of bowl into defrosted pie shell, mounding in middle.
10. User washes and dries bowl.
11. User adds 1 stick butter 2/3 cup flour, 2/3 cup sugar and 1/2 tsp of baking soda to bowl.
12. User repeatedly mashes butter into dry ingredients with pastry cutter
    1. Mixture takes on appearance of coarse crumbs
13. User pats handful of crumble topping onto apple mixture in pie shell. (repeat until bowl is empty)
14. User places pie shell on cookie sheet.
15. User places cookie sheet (with pie shell containing apple mixture covered in crumble topping) in oven and sets timer for 15 minutes
    1. Pie cooks, high temperature browns bottom crust
    2. Timer sounds
16. User protects edge of crust with strips of aluminum foil
17. User reduces oven temperature to  350º
    1. Filling cooks  slowly, bubbling up through crumble topping onto cookie sheet.
    2. Fructose and Sucrose oxidize resulting in caramelization
    3. Kitchen smells really good
    4. Timer sounds
18. User removes cookie sheet with pie from oven.
19. User turns off oven.
20. User sets timer for 1 hour.
    1. Pie cools.
    2. Pectin from apples gels.

OUTCOME: Delicious apple pie!

Variations

Error Case a: Pie shell not defrosted

Proceeds as in success case with the following variations:

10_a. User curses under breath, then washes and dries bowl.

Steps 11-14  unchanged.

15_a. User goes and finds something else to do for an hour, then places cookie sheet in oven.

Steps 16-20  unchanged.

Error Case b: Bowl not sufficiently dry.

Unrecoverable error. If user does not dry bowl, crumble topping will be tough and chewy, consider adding bowl dryness detection requirement.

Error Case c: Overworked Crumble-topping

Unrecoverable error. If step 12 is repeated too frequently, crumble topping will be tough and chewy, add visual inspection of consistency after each repetition?

Error Case d: Cookie sheet omitted

Proceeds as in success case with the following variations:

Step 14 omitted

15_d. User places pie shell containing apple mixture covered in crumble topping in oven and sets timer for 15 minutes

Pie cooks, high temperature browns bottom crust Timer sounds

17_d. User reduces oven temperature to  350º

1. Filling cooks  slowly, bubbling up through crumble topping onto oven heating element
2. Kitchen fills with smoke
3. Timer sounds

Proceed as in success case steps 18-20, only with more cursing.

Deferred Use Case: Eat Pie.