title: Is it possible in json schema to define a constraint between two properties
body: <p>I have two fields in my schema - one is a required property called "name" and the other is optional (used to define a sorting property) called "nameSort" and I want to express </p>
  
  <p>If the "nameSort" field is defined, the "name" field should also be defined as the same value.</p>
  
  <p>Is it possible to express such an "inter-element" constraint with JSON schema? My cursory read of JSON Schema here <a href="http://json-schema.org/latest/json-schema-validation.html" rel="noreferrer">http://json-schema.org/latest/json-schema-validation.html</a> says no.</p>