Updates core-principles/loose-coupling.md

Auto commit by GitBook Editor

SUMMARY.md

@@ -12,4 +12,7 @@
   * [Implementation Maturity](core-principles/implementation-maturity.md)
   * [Robustness](core-principles/robustness.md)
   * [Minimal API Surface](core-principles/minimal-api-surface.md)
+  * [Loose Coupling](core-principles/loose-coupling.md)
+  * [Versioning](core-principles/versioning.md)
+  * [Rules for Extending](core-principles/rules-for-extending.md)
 

core-principles/loose-coupling.md

@@ -0,0 +1,4 @@
+# Loose Coupling
+In addition to the [robustness principle](core-principles/robustness.md), API consumers (clients) MUST **operate independently** on API implementation's internals. Similarly the API consumers MUST NOT **assume** or **rely on** any knowledge of the API service internal implementation. 
+
+Where available, the clients SHOULD utilize **hypermedia controls as the engine of the application state**, and rely on the **protocol, message and vocabulary semantics**.

core-principles/robustness.md

@@ -2,6 +2,7 @@
 Every API implementation and API consumer MUST follow Postel's law:
 
 > "Be conservative in what you send, be liberal in what you accept."
+>
 > – [John Postel](https://en.wikipedia.org/wiki/Robustness_principle)
 
 That is, send as little as possible and be tolerant as possible while consuming another service ([tolerant reader](https://martinfowler.com/bliki/TolerantReader.html)).

core-principles/rules-for-extending.md

@@ -0,0 +1 @@
+# Rules for Extending

core-principles/versioning.md

@@ -0,0 +1 @@
+# Versioning