RFC: Clarify where vs when Keyword Semantics

[KrisSimon]

Problem

Two keywords express conditions with subtle distinctions:

Keyword	Usage	Example
when	Guarded statement	<Log> ... when <exists> is true.
where	Filter clause	for each <user> in <users> where <active> is true
where	Repository predicate	<Retrieve> ... where <id> is <user-id>.

Examples

(* 'when' - guards a single statement *)
<Log> the <msg> for the <console> with "Found" when <exists> is true.
(* From: FileOperations/main.aro:17 *)

(* 'where' - filters in loop *)
for each <user> in <users> where <user: active> is true { ... }
(* From: Iteration/main.aro:29 *)

(* 'where' - queries repository *)
<Retrieve> the <user> from the <user-repository> where <id> is <user-id>.
(* From: UserService/users.aro:14 *)

Issue

1. Both keywords express "if this condition holds"
2. where isn't a preposition but breaks the preposition-centric design
3. When to use which isn't obvious to newcomers

Semantic Analysis

Keyword	Semantic	Analogy
when	Temporal/conditional	"Execute when condition is true"
where	Set filtering	SQL WHERE clause

Proposed Solution

Keep both but document clearly:

• when = Statement-level guard (single statement conditional)

  • Executes statement only when condition is true
  • Short-circuit behavior

• where = Collection/query filter

  • Filters which elements to process
  • Works on sets/collections/repositories

Questions

1. Is the semantic distinction clear enough?
2. Should where become a preposition in ARO-0001?
3. Are there edge cases where both could apply?

[KrisSimon]

It should be clear, that when is a condition for the statement, while where is a filtering option for collections.
Theoretical it should be possible to have both:

<Retrieve> the <user> from the <user-repository> where <id> is <user-id> when <age> > 21.