add meta guide

Guide.md

@@ -0,0 +1,29 @@
+# Adding new note
+Before committing a new note make sure the following apply:
+- Note has frontmatter according to schema and content
+- Check for any notes referencing your note and add a link there
+- Add links to other relevant notes if you reference their content
+
+# Changing Schema
+If you propose a schema change you are responsible for updating notes affected by it. All notes should pass the schema validation.
+Additionally update the `Meta.md` note.
+
+# Validation
+To ensure a valid repository structure, check this list before committing.
+
+## Dead Links
+Use [foam](https://github.com/foambubble/foam) or a similiar tool to search for and fix broken inter-note links. Links pointing to nowhere will show up as `Placeholders` if you are using foam.
+
+## Update Revision
+Don't forget to update the `rev` tag when changing a note. Update this tag to the date you last modified the note.
+
+## Formatting
+Make sure notes are correctly formatted. You can use VSCode's builtin `Format Document` function for this.
+
+## Schema Validation
+Use [mdlint](https://git.hydrar.de/mdtools/mdlint) and [mdq](https://git.hydrar.de/mdtools/mdq) to validate the schema of the notes frontmatter and make sure there are no errors:
+```shell
+mdq -c file.path --noheader knowledge | while IFS= read -r md; do
+    mdlint --ignore-missing-frontmatter "knowledge/schema.json" "$md"
+done
+```

Meta.md

@@ -11,6 +11,9 @@ obj: meta
 - `wiki` - Wiki link
 - `arch-wiki` - Arch Wiki link
 - `rfc` - RFC Document link
+- `rev` - Date of last change (Revision)
+- `mime` - Associated MIME Type
+- `extension` - Associated file extensions
 - `obj` - Object Type
 
 ## Common Frontmatter Tags for Object Types
@@ -26,7 +29,7 @@ obj: meta
 # Object Types
 - `Application` - Any application
 - `OS` - Operating System
-- `Codec` - Media Codec
+- `Format` - File Format
 - `FileSystem` - File System
 - `Emulator` - Emulator System
 - `Concept` - Concept

MetaIndex.md

@@ -50,9 +50,9 @@ table android-id, flatpak-id from "/" where startswith(lower(obj), "application"
 list from "/" where startswith(lower(obj), "os")
 ```
 
-### Codecs
+### Formats
 ```dataview
-list from "/" where startswith(lower(obj), "codec")
+table mime, extension from "/" where startswith(lower(obj), "format")
 ```
 
 ### Filesystems

schema.json

@@ -7,6 +7,12 @@
         "obj"
     ],
     "properties": {
+        "rev": {
+            "title": "Revision",
+            "description": "Date of last change to note",
+            "type": "string",
+            "format": "date"
+        },
         "tags": {
             "type": "array",
             "items": {