Merge pull request #57 from DINA-Web/cgendreau-api-isolation

Added API Isolation section

DINA-Web-API-Guidelines.md

@@ -78,6 +78,10 @@ However, it some circumstances web api wrappers may be used where appropriate.
 
 DINA REST API standard - Specification
 ======================================
+
+API Isolation
+-----
+An API **SHOULD** only serve what its responsible for and avoid calling another API to supplement data. The caller of the API is responsible for aggregating the data from different API responses. The goal is to keep the system simple and flexible by avoiding a cascade of calls from a single API call by the client. This is also valid for data mutations since distributed transaction are not supported.
 
 Adheres to the JSON API -specification
 ------