Plans Vs Recipes

Biologists make the point that our genes are more like a recipe than a plan. The distinction is that one is more easily reversed than the other. A building plan can be drawn for an existing building. But, it's hard to make a cake recipe from a cake.

Is a pattern language more like a recipe than a plan? Perhaps that is why patterns pass easily from father to son through the shared act of building while it took ChristopherAlexander and colleagues ten years to construct his pattern language by examining buildings.

And yet when a cake is made from a recipe there are chemical transformations that take place, rendering the initial ingredients not readily identifiable. With a building the pieces are not changed, making reversal possible to extract the plan. When the solution to a problem is applied from a pattern language, is it reversable? Alexander was able to construct his pattern language by examining buildings. He says "But of course, the fact that these rules are simple does not mean that they are easy to observe, or easy to invent." (TimelessWayOfBuilding, p. 222) When we apply a pattern to a computer system context, will it always be reversible?