API version: dev

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# Grammar

Cypher Path Subset is defined as its own [ANTLR](https://www.antlr.org/) parser grammar, derived from Neo4j's Cypher
25 grammar. The railroad diagram below is generated directly from that grammar and shows every rule the parser
accepts.

\[Cypher Path Subset ANTLR railroad diagram]

[Open in new tab](/antlr/cypher-path-subset.html)

## How it differs from Cypher 25

Cypher Path Subset keeps only what is needed to describe a path pattern and return it - most of Cypher 25's surface
area is removed:

- **No write access**: `CREATE`, `INSERT`, `DELETE`, `SET`, `REMOVE` and `MERGE` are all gone - a query can only read.
- **No function calls or existence checks**: `functionInvocation`, `existsExpression` and `countExpression` are not
  part of the grammar, which rules out arbitrary computation and nested sub-queries inside the query itself.
- **No procedures or sub-queries**: `CALL` (both standalone and as a subquery), `LOAD CSV`, `FOREACH` and `USE` are
  removed.
- **A single, non-chainable pipeline**: a query is exactly one optional `UNWIND` followed by one `MATCH` followed by
  one `RETURN` - there's no `WITH` clause to chain multiple stages, and no `UNION` to combine queries.
- **A fixed, minimal `RETURN`**: `returnItem` only allows a bare variable, not arbitrary expressions or `AS` aliases -
  the query can only return the variable `paths` (see [step reference](/reference/search/cypher-path-subset.md)).

`ORDER BY`, `SKIP` and `LIMIT` on the result, as well as `WHERE` filters on patterns, are still fully supported -
see the [Cypher path query examples](/reference/search/cypher-path-subset.md#examples) for both in use.

## See also

- [Cypher 25 railroad diagram](/antlr/cypher-25.html) - the full grammar Cypher Path Subset is derived from.
- [openCypher 9 railroad diagram](/antlr/open-cypher-9.html) - the standardized core Cypher 25 itself extends.

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