Rigidity is the property that makes interface changes difficult for clients to absorb. APIs are especially rigid because software depends on exact names and request shapes: renaming a field can immediately break previously written code. By contrast, human-facing interfaces such as GUIs usually tolerate changes that are inconvenient or unattractive without becoming unusable. section 2.2
Renaming an API field
If an API changes a field name, existing client code continues requesting the old name, which no longer exists on the server. The result is a client failure rather than a merely inconvenient interface change. section 2.2
Table 2.2 Difficulty of changing various interfaces (view table figure)
Compare how audience and interface flexibility affect change difficulty, from a private monitoring console to a public API. section 2.2
