lint.

Signed-off-by: Scott Nichols <nicholss@google.com>

extensions/dataref.md

@@ -0,0 +1,73 @@
+# Dataref (Claim Check Pattern)
+
+As defined by the term [Data](../spec.md#data), CloudEvents MAY include
+domain-specific information about the occurrence. When present, this information
+will be encapsulated within the `data` attribute.
+The `dataref` attribute MAY be used to reference another location where this
+information is stored. The information, whether accessed via `data` or `dataref`
+MUST be identical.
+
+Both the `data` and `dataref` attribute MAY exist at the same time. A middleware
+MAY drop the `data` attribute when the `dataref` attribute exists, it MAY add
+the `dataref` attribute and drop the `data` attribute, or it MAY add the `data`
+attribute by using the `dataref` attribute.
+
+## Attributes
+
+### dataref
+* Type: `URI-reference`
+* Description: A reference to a location where the event payload is stored. The
+  location MAY not be accessible without further information (e.g. a pre-shared
+  secret).
+
+  Known as the "Claim Check Pattern", this attribute MAY be used for a variety
+  of purposes, including:
+
+  * If the [Data](../spec.md#data) is too large to be included in the message,
+    the `data` attribute is not present, and the consumer can retrieve it using
+    this attribute.
+  * If the consumer wants to verify that the [Data](../spec.md#data) has not
+    been tampered with, it can retrieve it from a trusted source using this
+    attribute.
+  * If the [Data](../spec.md#data) MUST only be viewed by trusted consumers
+    (e.g.  personally identifiable information), only a trusted consumer can
+    retrieve it using this attribute and a pre-shared secret.
+
+  If this attribute is used, the information SHOULD be accessible long enough
+  for all consumers to retrieve it, but MAY not be stored for an extended period
+  of time.
+
+* Constraints:
+  * OPTIONAL
+
+# Examples
+
+The following example shows a CloudEvent in which the event producer has included
+both `data` and `dataref` (serialized as JSON):
+
+``` JSON
+{
+    "specversion" : "0.2",
+    "type" : "com.github.pull.create",
+    "source" : "https://github.com/cloudevents/spec/pull/123",
+    "id" : "A234-1234-1234",
+    "datacontenttype" : "text/xml",
+    "data" : "<much wow=\"xml\"/>",
+    "dataref" : "https://github.com/cloudevents/spec/pull/123/events/A234-1234-1234.xml"
+}
+```
+
+The following example shows a CloudEvent in which a middleware has replaced the
+`data` with a `dataref` (serialized as JSON):
+
+``` JSON
+{
+    "specversion" : "0.2",
+    "type" : "com.github.pull.create",
+    "source" : "https://github.com/cloudevents/spec/pull/123",
+    "id" : "A234-1234-1234",
+    "datacontenttype" : "text/xml",
+    "dataref" : "https://tenant123.middleware.com/events/data/A234-1234-1234.xml"
+}
+```
+

json-format.md

@@ -109,7 +109,7 @@ The following table shows exemplary mappings:
 | CloudEvents     | Type          | Exemplary JSON Value            |
 | --------------- | ------------- | ------------------------------- |
 | type            | String        | "com.example.someevent"         |
-| specversion     | String        | "0.3-wip"                           |
+| specversion     | String        | "0.3-wip"                       |
 | source          | URI-reference | "/mycontext"                    |
 | id              | String        | "1234-1234-1234"                |
 | time            | Timestamp     | "2018-04-05T17:31:00Z"          |

spec.md

@@ -1,5 +1,7 @@
 # CloudEvents - Version 0.3-wip
 
+=======
+
 ## Abstract
 
 CloudEvents is a vendor-neutral specification for defining the format of event
@@ -196,11 +198,41 @@ within the same JSON object.
 - Constraints:
   - REQUIRED
 - Examples
-  - https://github.com/cloudevents/spec/pull/123
-  - /cloudevents/spec/pull/123
-  - urn:event:from:myapi/resourse/123
+  - https://github.com/cloudevents/spec/pull
+  - /cloudevents/spec/pull
+  - urn:event:from:myapi/resource
   - mailto:cncf-wg-serverless@lists.cncf.io
 
+### subject
+
+- Type: `String`
+- Description: This describes the subject of the event in the context of the
+  event producer (identified by `source`). In publish-subscribe scenarios, a
+  subscriber will typically subscribe to events emitted by a `source`, but the
+  `source` identifier alone might not be sufficient as a qualifier for any
+  specific event if the `source` context has internal sub-structure.
+
+  Identifying the subject of the event in context metadata (opposed to only in
+  the `data` payload) is particularly helpful in generic subscription filtering
+  scenarios where middleware is unable to interpret the `data` content. In the
+  above example, the subscriber might only be interested in blobs with names
+  ending with '.jpg' or '.jpeg' and the `subject` attribute allows for
+  constructing a simple and efficient string-suffix filter for that subset of
+  events.
+
+- Constraints:
+  - OPTIONAL
+  - If present, MUST be a non-empty string
+- Example:
+  - A subscriber might register interest for when new blobs are created inside a
+    blob-storage container. In this case, the event `source` identifies the
+    subscription scope (storage container), the `type` identifies the "blob
+    created" event, and the `id` uniquely identifies the event instance to
+    distinguish separate occurrences of a same-named blob having been created;
+    the name of the newly created blob is carried in `subject`:
+    - `source`: https://example.com/storage/tenant/container
+    - `subject`: mynewfile.jpg
+
 ### id
 
 - Type: `String`
@@ -373,7 +405,8 @@ The following example shows a CloudEvent serialized as JSON:
 {
     "specversion" : "0.3-wip",
     "type" : "com.github.pull.create",
-    "source" : "https://github.com/cloudevents/spec/pull/123",
+    "source" : "https://github.com/cloudevents/spec/pull",
+    "subject" : "123",
     "id" : "A234-1234-1234",
     "time" : "2018-04-05T17:31:00Z",
     "comexampleextension1" : "value",