chore: clarify VersionOrAliasName and make clear ctf impl is optional

On-behalf-of: SAP <matthias.bruns@sap.com>
Signed-off-by: Matthias Bruns <git@matthiasbruns.com>

Author: matthiasbruns

doc/03-persistence/01-operations.md

@@ -100,9 +100,9 @@ that resolves to exactly one component version at any point in time. Alias names
 
 - **`AddComponentVersionAlias(ComponentId, VersionOrAliasName, AliasName) error`**
 
-  Attach a symbolic alias to an existing component version (or to another alias, enabling
-  alias chains). `AliasName` **MUST NOT** be a valid OCM version string. If the alias
-  already exists it is updated to point to the new target.
+  Attach a symbolic alias to an existing component version. `VersionOrAliasName` is either
+  a version or an existing alias; `AliasName` **MUST NOT** be a valid OCM version string.
+  If the alias already exists it is updated to point to the new target.
 
 - **`RemoveComponentVersionAlias(ComponentId, AliasName) error`**
 

doc/04-extensions/03-storage-backends/ctf.md

@@ -57,13 +57,14 @@ Local blobs are always stored as blobs.
 
 ## Alias Management Operations
 
-CTF archives support the optional version alias operations defined in
+CTF archives **MAY** implement the optional version alias operations defined in
 [Version Alias Operations](../../../doc/03-persistence/01-operations.md#version-alias-operations).
+The following describes how each operation maps onto the CTF artifact index.
 
 **`AddComponentVersionAlias`**
 
-The alias is recorded in `artifact-index.json` as a tag pointing to the same digest as the
-target component version. If the tag already exists it **MUST** be updated to point to the
+The alias is recorded in `artifact-index.json` as a tag pointing to the same digest as
+`VersionOrAliasName` (a version or existing alias). If the tag already exists it **MUST** be updated to point to the
 new digest. `AliasName` **MUST NOT** be a valid OCM version string.
 
 **`RemoveComponentVersionAlias`**

doc/04-extensions/03-storage-backends/oci.md

@@ -864,21 +864,16 @@ are implemented against an OCI registry.
 
 **`AddComponentVersionAlias`**
 
-Implementations **MUST** resolve `VersionOrAliasName` as an OCI tag or digest in the
-component's repository, validate that the resolved descriptor represents a valid OCM
-component version, and then push the alias as an OCI tag pointing to that descriptor
-using the [OCI Distribution Specification manifest push](https://github.com/opencontainers/distribution-spec/blob/v1.1.1/spec.md#pushing-manifests)
+Implementations **MUST** resolve `VersionOrAliasName` (a version or existing alias) as an OCI tag in the component's
+repository, validate that the resolved descriptor represents a valid OCM component version,
+and then push the alias as an OCI tag pointing to that descriptor using the
+[OCI Distribution Specification manifest push](https://github.com/opencontainers/distribution-spec/blob/v1.1.1/spec.md#pushing-manifests)
 mechanism.
 
 `AliasName` **MUST** be rejected if it is a valid OCM version string.
 
-Because `VersionOrAliasName` **MAY** itself be a non-version alias, implementations
-**MUST** accept non-semver names there and resolve them to their underlying descriptor
-before tagging. This enables alias chains: e.g., pointing `edge` to wherever `latest`
-currently resolves.
-
-After a successful push the alias tag in the registry **MUST** resolve to the descriptor
-identified by `VersionOrAliasName`. If the tag already pointed elsewhere it is overwritten.
+After a successful push the alias tag **MUST** resolve to the descriptor identified by
+`VersionOrAliasName`. If the tag already pointed elsewhere it is overwritten.
 
 **`RemoveComponentVersionAlias`**