# Using matches operator in AQL

**Category:** [AQL](https://discourse.openehr.org/c/aql/43)
**Created:** 2022-04-25 12:10 UTC
**Views:** 566
**Replies:** 1
**URL:** https://discourse.openehr.org/t/using-matches-operator-in-aql/2547

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## Post #1 by @thomas.beale

To date, the use of the [matches operator in AQL](https://specifications.openehr.org/releases/QUERY/latest/AQL.html#_matches) has been limited to:
* primitive value matching
* URI matching
* special functions like `TERMINOLOGY()`

However, we could use AQL matching in a generalised ADL mode, which pretty much replicates what GraphQL does, but better.

Here's an example that I can parse with my current EL parser. We can ignore the `val :=` at the start, it's just for testing. The `baby_weight` and `age` are assumed to be bound to archetype paths. So the part coming after `val :=` could be an AQL WHERE condition.

```
val := baby_weight ∈ {
           DV_QUANTITY ∈ {
               [units, magnitude] ∈ {
                   [{"kg"}, {|<1.2|}],
                   [{"g"}, {|<1200|}],
                   [{"lb"}, {|<2.5|}],
                   [{"oz"}, {|<40|}]
               }
           }
       }
       OR
       age ∈ {|<-P2M|}
```

There are some differences from strict ADL, mainly that node identifiers need to be optional.

See [here for the Antlr grammar for cADL matcher objects](https://github.com/wolandscat/openEHR-antlr4/blob/master/combined/src/main/antlr/Cadl2Parser.g4#L108) (allowing optional node ids).

[Here is where it connects into the EL grammar](https://github.com/wolandscat/openEHR-antlr4/blob/master/combined/src/main/antlr/ElParser.g4#L106).

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## Post #2 by @joostholslag

Cool. It makes me dream about trial inclusion and exclusion criteria expressed and published as AQL statements.

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**Canonical:** https://discourse.openehr.org/t/using-matches-operator-in-aql/2547
**Original content:** https://discourse.openehr.org/t/using-matches-operator-in-aql/2547