feat(guidelines): avoid digits in camelCase

api-guidelines/global/json/naming-conventions/rules/should-use-camel-case-for-property-names.md

@@ -4,15 +4,16 @@ id: R004010
 
 # SHOULD use camelCase for property names
 
-Property names of JSON objects should be formatted in camelCase.
+Property names of JSON objects should be formatted in camelCase, and digits should be avoided.
 
 DO
 
 ````json
 {
     "name": "John",
     "jobDescription": "product manager",
-    "vacationDays": 37
+    "vacationDays": 37,
+    "entryDate": "2023-01-15"
 }
 ````
 
@@ -22,6 +23,7 @@ DON'T
 {
     "NAME": "John",
     "job-description": "product manager",
-    "vacationdays": 37
+    "vacationdays": 37,
+    "1stDay": "2023-01-15"
 }
 ````

api-guidelines/rest/resources/naming-conventions/rules/must-use-camelcase-for-query-parameters.md

@@ -4,12 +4,12 @@ id: R000022
 
 # MUST use camelCase for query parameters
 
-Use CamelCase to delimit combined words in query parameters.
+Query parameters should be formatted in camelCase, and digits should be avoided.
 
 DO
 
-`productId`, `articleNumber`, `loginId`, `lId` etc.
+`productId`, `articleNumber`, `loginId`, `lId`, `entryDate` etc.
 
 DON'T
 
-`product_id`, `Articlenumber`, `login-id`, `LID`
+`product_id`, `Articlenumber`, `login-id`, `LID`, `1stDay`

decisions/0003-should-avoid-digits-in-camel-case.md

@@ -0,0 +1,68 @@
+# [0003] Avoid digits in camel case
+
+- Status: `accepted`
+- Decided by: <[email protected]>, <[email protected]>, <[email protected]>, API Community, AsyncAPI Community
+- Date: 2025-08-26
+
+## Context
+
+Several rules in the OTTO API guidelines refer to using camel case for naming properties, parameters, and other identifiers in APIs.
+The guidelines do not explicitly address the use of digits in camel case names, but our linter does not allow digits in camel case names.
+
+## Options
+
+### Option 1
+
+Allow digits in camel case names, e.g. `item1`, `top100LoveSongs`, as there is no explicit rule against it.
+
+Example:
+
+```yaml
+top100LoveSongs:
+  type: array
+  items:
+    type: string
+    description: The title of a love song.
+  example:
+    - "A Wonderful Song"
+    - "Another Awesome Love Song"
+    - ...
+```
+
+### Option 2
+
+Do not allow digits in camel case names.
+
+Example:
+
+```yaml
+popularLoveSongs:
+  type: array
+  description: Contains the 100 most popular love songs.
+  items:
+    type: string
+    description: The title of a love song.
+  minItems: 100
+  maxItems: 100
+  example:
+    - "A Wonderful Song"
+    - "Another Awesome Love Song"
+    - ...
+```
+
+## Decision
+
+Option 2 is chosen, as there is no known use case for digits in camel case names, and the OpenAPI specification provides features to describe ranges and array length if needed.
+The linter rule is already in place and has been used in several APIs without issues.
+This decision ensures more consistent naming conventions across all APIs and avoids potential compiling issues, if property names are starting with a digit, like in Java.
+
+## Consequences
+
+Existing guidelines referencing camel case names need to be updated to explicitly state that digits should be avoided.
+
+[rule-R000022]: ../api-guidelines/rest/resources/naming-conventions/rules/must-use-camelcase-for-query-parameters.md
+[rule-R004010]: ../api-guidelines/global/json/naming-conventions/rules/should-use-camel-case-for-property-names.md
+
+
+
+