n3writer-wrapper

Helpers that improve the readability of n3.js Turtle/TriG output:

| Function | What it does | |---|---| | topoWrite(writer, quads) | Feeds quads to an N3 Writer using nested [ ] notation for blank nodes that appear as an object exactly once | | reindent(turtle, step?) | Normalises n3.Writer's mixed 4-space/2-space indentation to a uniform step (default: 2 spaces) at every nesting depth | | expandLiterals(turtle) | Converts "string\nwith\nescapes" to """stringwithnewlines""" for readability |

Install

npm install n3writer-wrapper

n3 itself is a peer dependency (optional — the structural types mean any compatible writer works):

npm install n3

Usage

import { Writer } from 'n3';
import { topoWrite, reindent, expandLiterals } from 'n3writer-wrapper';

const writer = new Writer({ format: 'Turtle', prefixes: { ex: 'http://example.org/' } });
topoWrite(writer, quads);
const turtle = await new Promise<string>((resolve, reject) =>
  writer.end((err, result) => (err ? reject(err) : resolve(result)))
);
const pretty = expandLiterals(reindent(turtle));

Sample output

Given examples/fhir-provenance.ttl — a FHIR Provenance resource co-signing a Bundle, where every blank node is single-use:

PREFIX fhir: <http://hl7.org/fhir/>
PREFIX xsd:  <http://www.w3.org/2001/XMLSchema#>

<http://something4> a fhir:Provenance ;
  fhir:id [ fhir:v "prov1" ] ;
  fhir:target [ fhir:reference [ fhir:v "Bundle/signed" ] ] ;
  fhir:recorded [ fhir:v "2024-06-09T11:06:35+10:00"^^xsd:dateTime ] ;
  fhir:signature [
    fhir:when [ fhir:v "2024-06-09T11:06:35+10:00"^^xsd:dateTime ] ;
    fhir:who  [ fhir:reference [ fhir:v "Organization/ig-publisher" ] ] ;
    fhir:sigFormat [ fhir:v "application/jose" ] ;
    fhir:data  [ fhir:v "eyJhbGciOiJSUzI1NiIsImI2NCI6ZmFsc2UsImNyaXQiOlsiYjY0Il19..stub" ]
  ] .

After topoWrite + reindent + expandLiterals:

@prefix fhir: <http://hl7.org/fhir/>.
@prefix xsd: <http://www.w3.org/2001/XMLSchema#>.

<http://something4> a fhir:Provenance;
  fhir:id [ fhir:v "prov1" ];
  fhir:target [
    fhir:reference [ fhir:v "Bundle/signed" ]
  ];
  fhir:recorded [ fhir:v "2024-06-09T11:06:35+10:00"^^xsd:dateTime ];
  fhir:signature [
    fhir:when [ fhir:v "2024-06-09T11:06:35+10:00"^^xsd:dateTime ];
    fhir:who [
      fhir:reference [ fhir:v "Organization/ig-publisher" ]
    ];
    fhir:sigFormat [ fhir:v "application/jose" ];
    fhir:data [ fhir:v "eyJhbGciOiJSUzI1NiIsImI2NCI6ZmFsc2UsImNyaXQiOlsiYjY0Il19..stub" ]
  ].

topoWrite(writer, quads)

Blank nodes that appear as an object exactly once are inlined as [ ] blocks. Blank nodes used more than once, or with no outgoing triples, fall back to _:label references. Duplicate quads (e.g. from a SPARQL CONSTRUCT) are silently deduplicated.

Input quads can be any iterable of RDFJS-compatible quads (n3, graphy, etc.).

reindent(turtle, step = ' ')

n3.Writer hard-codes 4 spaces for predicate-continuation lines and 2 spaces inside [ ] blocks. reindent normalises this so each additional nesting level adds exactly one step:

# before                          # after (step = '  ')
<ex:s> ex:p1 "a" ;                <ex:s> ex:p1 "a" ;
    ex:p2 [                         ex:p2 [
      ex:q "v"                          ex:q "v"
    ] .                             ] .

expandLiterals(turtle)

Converts \n escape sequences inside double-quoted literals to real newlines using triple-quoted form:

"line1\nline2"  →  """line1
                   line2"""

Falls back to the original form if the expanded content would contain """.

TypeScript

The package ships with declarations. The TurtleWriter interface is structural, so it matches n3.Writer without importing n3 as a type dependency:

import type { TurtleWriter, RdfQuad } from 'n3writer-wrapper';

License

MIT