Merge pull request OAI#1180 from krishahn/callback-object

Callback object

Author: Ron

versions/3.0.md

@@ -1729,16 +1729,16 @@ The key value used to identify the callback object is an expression, evaluated a
 ##### Patterned Fields
 Field Pattern | Type | Description
 ---|:---:|---
-<a name="callbackExpression"></a>{expression} | [Path Item Object](#pathItemObject) | A Path Item Object used to define a callback request and expected responses
+<a name="callbackExpression"></a>{expression} | [Path Item Object](#pathItemObject) | A Path Item Object used to define a callback request and expected responses.
 
 This object can be extended with [Specification Extensions](#specificationExtensions). 
 
 ##### Key Expression
 
-The key used to identify the [Path Item Object](#pathItemObject) is a variable expression that can be evaluated in the context of a runtime HTTP request/response to identify the URL to be used for the callback request.
-A simple example might be `$request.body#/url`.
-However, using [variable substitution](#variableSubstitution) syntax the complete HTTP message can be accessed.
-This includes accessing any part of a body that can be accessed using a JSON Pointer [RFC6901](https://tools.ietf.org/html/rfc6901).
+The key that identifies the [Path Item Object](#pathItemObject) is a variable expression that can be evaluated in the context of a runtime HTTP request/response to identify the URL for the callback request.
+A simple example is `$request.body#/url`.
+However, using [variable substitution](#variableSubstitution) syntax, the complete HTTP message can be accessed.
+This includes accessing any part of a body that a JSON Pointer [RFC6901](https://tools.ietf.org/html/rfc6901) can reference.
 
 For example, given the following HTTP request: