Moving span operation clarification to api

Feedback states that the clarification around the meaning of the
span start and end times could be more generic. Starting a proposal
around by adding an example to the API.

specification/trace/api.md

@@ -225,7 +225,21 @@ hypothetical account information:
 | `get_account/{accountId}` | Also good (using the "HTTP route") |
 
 The `Span`'s start and end timestamps reflect the elapsed real time of the
-operation. A `Span`'s start time SHOULD be set to the current time on [span
+operation.
+
+For example, an http server span should start right when the request has begun being handled by the server, and end when the response has been completely sent.
+This would include the following, if they are present in that particular
+request-response cycle:
+
+- receiving the HTTP request
+- parsing of the HTTP request
+- parsing of the body of the HTTP request
+- any web server middleware that is applied
+- business logic
+- construction of the HTTP response
+- sending of the HTTP response
+
+A `Span`'s start time SHOULD be set to the current time on [span
 creation](#span-creation). After the `Span` is created, it SHOULD be possible to
 change the its name, set its `Attribute`s, and add `Link`s and `Event`s. These
 MUST NOT be changed after the `Span`'s end time has been set.

specification/trace/semantic_conventions/http.md

@@ -96,12 +96,6 @@ For an HTTP client span, `SpanKind` MUST be `Client`.
 If set, `http.url` must be the originally requested URL,
 before any HTTP-redirects that may happen when executing the request.
 
-The span start time SHOULD be as close as possible to the time the client began
-the request.
-
-The span end time SHOULD be as close as possible to the time the client finished
-receiving the response to the request.
-
 One of the following sets of attributes is required (in order of usual preference unless for a particular web client/framework it is known that some other set is preferable for some reason; all strings must be non-empty):
 
 * `http.url`
@@ -187,12 +181,6 @@ If the route does not include the application root, it SHOULD be prepended to th
 
 If the route cannot be determined, the `name` attribute MUST be set as defined in the general semantic conventions for HTTP.
 
-The span start time SHOULD be as close as possible to the time the server began
-handling the request.
-
-The span end time SHOULD be as close as possible to the time the server completed
-the response.
-
 | Attribute name | Notes and examples                                           | Required? |
 | :------------- | :----------------------------------------------------------- | --------- |
 | `http.server_name` | The primary server name of the matched virtual host. This should be obtained via configuration. If no such configuration can be obtained, this attribute MUST NOT be set ( `net.host.name` should be used instead). | [1] |