B.5.RC:4.2 - Recover the operations

Read the description for ways of forming, transforming or combining the objects. For each operation needed by the case, recover:

• what it takes as input;
• the conditions under which it can be used;
• what it produces.

This information can appear in a definition, diagram, earlier construction or convention used by the source. A verb such as “combine” is enough only when its operation is already recoverable. Otherwise ask which parts are combined and how.

In a mathematical account, include the formation and equality rules that the construction uses. A rule for forming an object and a claim about its properties do different work: the first supplies an object for a later operation, while the second may justify applying that operation. Both can be needed.

Use the rules of the account being recovered. For a physical assembly, a joining operation may require compatible fittings and available components. For a mathematical expression, using one value at two places depends on the rules of that expression. Recover the relevant condition where the construction actually relies on it.