# LDC-E1309 — Fiction over an empirical relation

## What it means

A fiction deems something true by admission — but an empirical relation
is established by case facts, never by admission. A fiction whose head
reads an empirical predicate deems the observed, and the compiler warns
at the fiction so the mismatch can be moved to where facts live.

The repair is to deem what admission can establish: point the head at
an institutional predicate, or carry the observation as a case fact.
Facts stay observed; admissions stay deemed.

## Example

```law
language "law.core" version "0.2";
package demo.diagnostics version "0.1.0";
namespace "urn:law:demo:diagnostics";

entity Tenant;
relation ready(t: Tenant) kind institutional;
relation seen(t: Tenant) kind empirical;
fiction F1 defeasible {
    for t: Tenant;
    when ready(t);
    deem seen(t);
}
```

## Fix

```law
language "law.core" version "0.2";
package demo.diagnostics version "0.1.0";
namespace "urn:law:demo:diagnostics";

entity Tenant;
relation ready(t: Tenant) kind institutional;
relation noted(t: Tenant) kind institutional;
fiction F1 defeasible {
    for t: Tenant;
    when ready(t);
    deem noted(t);
}
```

## Engine message

The engine reports this in its own wording:

```text
example.law:8:9: warning LDC-E1309: fiction "F1": head over an `empirical` relation "seen" (§147) — the observed is established by a case fact, not by admission
```

## Related

- [Facts and evidence](/constructs/facts-and-evidence/) — observations and the facts that carry them.