Added semantic conventions for the "process" resource

specification/resource/semantic_conventions/README.md

@@ -8,6 +8,7 @@ This document defines standard attributes for resources. These attributes are ty
 - [Compute Unit](#compute-unit)
   * [Container](#container)
   * [Function as a Service](#function-as-a-service)
+  * [Process](#process)
 - [Deployment Service](#deployment-service)
   * [Kubernetes](#kubernetes)
 - [Compute Instance](#compute-instance)
@@ -19,7 +20,7 @@ This document defines standard attributes for resources. These attributes are ty
 
 ## TODOs
 
-* Add more compute units: Process, AppEngine unit, etc.
+* Add more compute units: AppEngine unit, etc.
 * Add Device (mobile) and Web Browser.
 * Decide if lower case strings only.
 * Consider to add optional/required for each attribute and combination of attributes
@@ -113,6 +114,23 @@ Note: The resource attribute `faas.instance` differs from the span attribute `fa
 [ARN]:https://docs.aws.amazon.com/general/latest/gr/aws-arns-and-namespaces.html
 [FunctionDirectory]: https://github.com/Azure/azure-functions-host/wiki/Retrieving-information-about-the-currently-running-function
 
+### Process
+
+**type:** `process`
+
+**Description:** An operating system process.
+
+| Attribute  | Description  | Example  | Required |
+|---|---|---|--|
+| process.pid | Process identifier (PID). | `1234` | Yes |
+| process.executable_name | The name of the process executable. On Unix based systems, can be set to the `Name` in `proc/[pid]/status`. On Windows, can be set to the base name of `GetProcessImageFileNameW`. | `otelcol` | See below |
+| process.executable_path | The full path to the process executable. On Unix based systems, can be set to the target of `proc/[pid]/exe`. On Windows, can be set to the result of `GetProcessImageFileNameW`. | `cmd/otelcol` | See below |
+| process.command | The command used to launch the process (i.e. the command name). On Unix based systems, can be set to the zeroth string in `proc/[pid]/cmdline`. On Windows, can be set to the first parameter extracted from `GetCommandLineW`. | `cmd/otelcol` | See below |
+| process.commandline | The full command used to launch the process. This can be a nil- or space-delimited string. On Unix based systems, can be set to the full `proc/[pid]/cmdline` string. On Windows, can be set to the result of `GetCommandLineW`. | `cmd/otecol --config=config.yaml` | See below |
+| process.owner | The username of the user that owns the process. | `root` | No |
+
+At least one of `process.executable_name`, `process.executable_path`, `process.command`, or `process.commandline` is required.
+
 ## Deployment Service
 
 Attributes defining a deployment service (e.g. Kubernetes).