Add semantic convention for source code attributes (#901)

CHANGELOG.md

@@ -13,6 +13,8 @@ New:
   ([#891](https://github.com/open-telemetry/opentelemetry-specification/pull/891))
 - Add resource semantic conventions for operating systems
   ([#693](https://github.com/open-telemetry/opentelemetry-specification/pull/693))
+- Add semantic convention for source code attributes
+  ([#901](https://github.com/open-telemetry/opentelemetry-specification/pull/901))
 - Add semantic conventions for outgoing Function as a Service (FaaS) invocations
   ([#862](https://github.com/open-telemetry/opentelemetry-specification/pull/862))
 - Add resource semantic convention for deployment environment

specification/trace/semantic_conventions/span-general.md

@@ -14,6 +14,7 @@ Particular operations may refer to or require some of these attributes.
 - [General remote service attributes](#general-remote-service-attributes)
 - [General identity attributes](#general-identity-attributes)
 - [General thread attributes](#general-thread-attributes)
+- [Source Code Attributes](#source-code-attributes)
 
 <!-- tocstop -->
 
@@ -158,3 +159,18 @@ Examples of where `thread.id` and `thread.name` can be extracted from:
 | Ruby                  |                                        | `Thread.current.name`              |
 | C++                   | `std::this_thread::get_id()`             |                                    |
 | Erlang               | `erlang:system_info(scheduler_id)` |                                  |
+
+## Source Code Attributes
+
+Often a span is closely tied to a certain unit of code that is logically responsible for handling
+the operation that the span describes (usually the method that starts the span).
+For an HTTP server span, this would be the function that handles the incoming request, for example.
+The attributes listed below allow to report this unit of code and therefore to provide more context
+about the span.
+
+| Attribute  | Type | Description  | Example  | Required |
+|---|---|---|---|---|
+| `code.function` | string | The method or function name, or equivalent (usually rightmost part of the code unit's name). | `serveRequest` | No |
+| `code.namespace` | string | The "namespace" within which `code.function` is defined. Usually the qualified class or module name, such that `code.namespace` + some separator + `code.function` form a unique identifier for the code unit. | `com.example.MyHttpService` | No |
+| `code.filepath` | string | The source code file name that identifies the code unit as uniquely as possible (preferably an absolute file path). | `/usr/local/MyApplication/src/main/java/com/example/MyHttpService.java` | No |
+| `code.lineno` | number | The line number in `code.filepath` best representing the operation. It SHOULD point within the code unit named in `code.function`. | `42` | No |