Describe the use cases for events in greater detail (#3969)

Resolves #3254 and #4045 

The PR adds clarity to the features provided by Events, as well as
guidance on when it is appropriate to use the Event API.

## Changes

* Reorganized the Data Model section for clarity
* Include MUST for the requirement that Event `Body` and `Attributes`
fields conform to a schema.
* Include use cases for when Events are appropriate.
* Include a warning that advanced logging features are not currently
accessible when using Events.

specification/logs/event-api.md

@@ -9,7 +9,8 @@
 
 <!-- toc -->
 
-- [Data model](#data-model)
+- [Event Data model](#event-data-model)
+- [Event API use cases](#event-api-use-cases)
 - [EventLoggerProvider](#eventloggerprovider)
   * [EventLoggerProvider operations](#eventloggerprovider-operations)
     + [Get an EventLogger](#get-an-eventlogger)
@@ -25,28 +26,58 @@
 
 The Event API consists of these main components:
 
-* [EventLoggerProvider](#eventloggerprovider) is the entry point of the API. It provides access to `EventLogger`s.
+* [EventLoggerProvider](#eventloggerprovider) is the entry point of the API. It
+  provides access to `EventLogger`s.
 * [EventLogger](#eventlogger) is the component responsible for emitting events.
 
-## Data model
+## Event Data model
 
 Wikipedia’s [definition of log file](https://en.wikipedia.org/wiki/Log_file):
 
 >In computing, a log file is a file that records either events that occur in an
 >operating system or other software runs.
 
 From OpenTelemetry's perspective LogRecords and Events are both represented
-using the same [data model](./data-model.md).
-
-However, OpenTelemetry does recognize a subtle semantic difference between
-LogRecords and Events: Events are LogRecords which have a `name` which uniquely
-defines a particular class or type of event. All events with the same `name`
-have `Body` that conform to the same schema, which assists in analysis in
-observability platforms. Events are described in more detail in
-the [semantic conventions](https://github.com/open-telemetry/semantic-conventions/blob/main/docs/general/events.md).
-
-Unlike the [Logs Bridge API](./bridge-api.md), application developers and
-instrumentation authors are encouraged to call this API directly.
+using the same [data model](./data-model.md). An Event is a specialized type
+of LogRecord, not a separate concept.
+
+Events are OpenTelemetry's standardized semantic formatting for LogRecords.
+Beyond the structure provided by the LogRecord data model, it is helpful for
+logs to have a common format within that structure. When OpenTelemetry
+instrumentation emits logs, those logs SHOULD be formatted as Events. All
+semantic conventions defined for logs MUST be formatted as Events.
+
+The Event format is as follows. All Events have a `name` attribute, and all
+Events with the same `name` MUST conform to the same schema for both their
+`Attributes` and their `Body`.
+
+## Event API use cases
+
+The Events API was designed to allow shared libraries to emit high quality
+logs without needing to depend on a third party logger. Unlike the
+[Logs Bridge API](./bridge-api.md), instrumentation authors and application
+developers are encouraged to call this API directly. It is appropriate to
+use the Event API when these properties fit your requirements:
+
+* Logging from a shared library that must run in many applications.
+* A semantic convention needs to be defined. We do not define semantic
+  conventions for LogRecords that are not Events.
+* Analysis by an observability platform is the intended use case. For
+  example: statistics, indexing, machine learning, session replay.
+* Normalizing logging and having a consistent schema across a large
+  application is helpful.
+
+If any of these properties fit your requirements, we recommend using the Event API.
+Events are described in more detail in the [semantic conventions](https://github.com/open-telemetry/semantic-conventions/blob/main/docs/general/events.md).
+
+Please note that the OpenTelemetry Log SDK currently lacks a number of advanced
+features present in popular logging libraries. For example: pattern logging, file
+rotation, network appenders, etc. These features cannot be used with the
+OpenTelemetry Event SDK at this time.
+
+If a logging library is capable of creating logs which correctly map
+to the Event data model, logging in this manner is also an acceptable way to
+create Events.
 
 ## EventLoggerProvider