Merge pull request OAI#1150 from krishahn/edit-3.0-format

plain language edits

Author: RobDolinMS

versions/3.0.md

@@ -96,8 +96,7 @@ The available status codes are defined by [RFC7231](http://tools.ietf.org/html/r
 
 ### Format
 
-The files describing the RESTful API in accordance with this specification are represented as JSON objects and conform to the JSON standards.
-YAML, being a superset of JSON, can be used as well to represent an OAS file. 
+An API description that conforms to the OpenAPI Specification is itself a JSON object, which may be represented either in JSON or YAML format.
 
 For example, if a field has an array value, the JSON array representation will be used:
 
@@ -106,19 +105,18 @@ For example, if a field has an array value, the JSON array representation will b
    "field": [...]
 }
 ```
-
-While the API is described using JSON, it does not impose a JSON input/output to the API itself.
-
 All field names in the specification are **case sensitive**.
 
 The schema exposes two types of fields: Fixed fields, which have a declared name, and Patterned fields, which declare a regex pattern for the field name.
 
-Patterned fields can have multiple occurrences as long as each has a unique name. 
+Patterned fields MUST have unique names within the containing object. 
 
 In order to preserve the ability to round-trip between YAML and JSON formats, YAML version [1.2](http://www.yaml.org/spec/1.2/spec.html) is RECOMMENDED along with some additional constraints:
 
-- Tags MUST be limited to those allowed by the [JSON Schema ruleset](http://www.yaml.org/spec/1.2/spec.html#id2803231)
-- Keys used in YAML maps MUST be limited to a scalar string, as defined by the [YAML Failsafe schema ruleset](http://yaml.org/spec/1.2/spec.html#id2802346)
+- Tags MUST be limited to those allowed by the [JSON Schema ruleset](http://www.yaml.org/spec/1.2/spec.html#id2803231).
+- Keys used in YAML maps MUST be limited to a scalar string, as defined by the [YAML Failsafe schema ruleset](http://yaml.org/spec/1.2/spec.html#id2802346).
+
+**Note:** While APIs are described by OpenAPI documents in YAML or JSON format, the API request and response bodies and other content are not required to be JSON or YAML.
 
 ### <a name="fileStructure"></a>File Structure