@graphy/content.ttl.write patch

The @graphy/content.ttl.write module of the graphy.js libraries generates Turtle serialization of an RDF graph represented by a concise JSON object.

In the generated Turtle code, the first predicate-objects pair of every subject is on one line with this subject, and any predicate-objects pair is written in one line. When an RDF graph contains long object lists, the generated Turtle code is difficult to read.

For example, in the following Turtle code, the objects of the skos:hasTopConcept predicate don't fit to the window:

<http://example.com/my-concept-scheme> rdf:type skos:Concept, lime:Lexicon ;
	rdfs:label "My concept scheme"@en, "Mi esquema de conceptos"@es, "Моя концептуальная схема"@ru ;
	dc:language "en" ;
	dc:creator <http://example.com/john-smith> ;
	skos:hasTopConcept <http://example.com/my-concept-scheme/concept1>, <http://example.com/my-concept-scheme/concept2>, <http://example.com/my-concept-scheme/concept3>, <http://example.com/my-concept-scheme/concept4>, <http://example.com/my-concept-scheme/concept5> .

This code will be more readable, if it is formatted e.g. as follows:

<http://example.com/my-concept-scheme> 
	rdf:type 
		skos:Concept, 
		lime:Lexicon ;
	rdfs:label 
		"My concept scheme"@en, 
		"Mi esquema de conceptos"@es, 
		"Моя концептуальная схема"@ru ;
	dc:language "en" ;
	dc:creator 
		<http://example.com/john-smith> ;
	skos:hasTopConcept 
		<http://example.com/my-concept-scheme/concept1>, 
		<http://example.com/my-concept-scheme/concept2>, 
		<http://example.com/my-concept-scheme/concept3>, 
		<http://example.com/my-concept-scheme/concept4>, 
		<http://example.com/my-concept-scheme/concept5> .

This patch for the @graphy/content.ttl.write module makes it possible by adding the option to configure indentation style of the produced Turtle code.

Indentation options

Indentation style is defined by the following new properties of the style configuration object:

toStartFirstPredicateOnNewLine : boolean = false – whether the first predicate of a subject must start on a new line by default;
firstPredicatesStartingOnNewLine : Array <string> = [] – predicates, that when being the first predicates of a subject, must start on a new line;
firstPredicatesNotStartingOnNewLine : Array <string> = [] – predicates, that when being the first predicates of a subject, must not start on a new line;
toStartObjectsOnNewLineInObjectLists : boolean = false – whether objects in object lists (i.e. objects separated by ,) must start on a new line by default;
predicatesWhoseObjectsStartOnNewLineInObjectLists : Array <string> = [] – predicates whose objects in object lists must start on a new line;
predicatesWhoseObjectsDontStartOnNewLineInObjectLists : Array <string> = [] – predicate whose objects in object lists must not start on a new line.

By default (i.e. when the aforementioned properties are not specified), the indentation style is the same as in the original @graphy/content.ttl.write module.

Examples

Let objConcGraph object be a concise representation of some RDF graph. Turtle serialization of this graph is generated by the following code:

const graphy = require('graphy');
const ttlWrite = require('./main.js');

//Config object for customizing style of the generated Turtle serialization
let objStyle = {};

//Concise JSON representation of the RDF graph
let objConcGraph =
  {
  ">http://example.com/my-concept-scheme":
    {
      //this first predicate of the <http://example.com/my-concept-scheme> subject (i.e. "rdf:type")
      //will start on a new line
      //when objStyle.toStartFirstPredicateOnNewLine = true
      //and it is not in objStyle.firstPredicatesNotStartingOnNewLine,
      //or when it is in objStyle.firstPredicatesStartingOnNewLine
      "rdf:type":
        [
        "skos:Concept",
        "lime:Lexicon"
        ],
      "rdfs:label":
        //these objects will start from a new line
        //when objStyle.toStartObjectsOnNewLineInObjectLists = true
        //and their rdfs:label predicate is not in objStyle.predicatesWhoseObjectsDontStartOnNewLineInObjectLists,
        //or when this predicate is in objStyle.predicatesWhoseObjectsStartOnNewLineInObjectLists
        [
        '@en"My concept scheme',
        '@es"Mi esquema de conceptos',
        '@ru"Моя концептуальная схема',
        ],
      "dc:language":
        //this object will never start on a new line because it is not in an object list (i.e. in an array)
        '"en',
      "dc:creator":
        //put this object in an objects list represented by a one-element array
        //for it will start on a new line when the aforementioned properties of objStyle are set
        [">http://example.com/john-smith"],
      "skos:hasTopConcept":
        [
        ">http://example.com/my-concept-scheme/concept1",
        ">http://example.com/my-concept-scheme/concept2",
        ">http://example.com/my-concept-scheme/concept3",
        ">http://example.com/my-concept-scheme/concept4",
        ">http://example.com/my-concept-scheme/concept5"
        ]
    },
  ">http://example.com/john-smith":
    {
    "rdfs:label":
      [
      '@en"John Smith',
      '@ru"Джон Смит',
      ]
    }
  };

let objPrefixes =
  {
  rdf: 'http://www.w3.org/1999/02/22-rdf-syntax-ns#',
  rdfs: 'http://www.w3.org/2000/01/rdf-schema#',
  owl: 'http://www.w3.org/2002/07/owl#',
  skos: 'http://www.w3.org/2004/02/skos/core#',
  lime: 'http://www.w3.org/ns/lemon/lime#',
  dc: "http://purl.org/dc/elements/1.1/",
  };

let streemWriter = ttlWrite
  ({
  prefixes: objPrefixes,
  style: objStyle
  });

streemWriter.pipe (process.stdout);

streemWriter.write
  ({
  type: "c3",
  value: objConcGraph
  });

The objStyle object is used to customize the style of the generated Turtle.

Example 1

Default style:

let objStyle = {};

The generated Turtle serialization (hereinafter the prefixes are omitted):

#@prefix ...

<http://example.com/my-concept-scheme> rdf:type skos:Concept, lime:Lexicon ;
	rdfs:label "My concept scheme"@en, "Mi esquema de conceptos"@es, "Моя концептуальная схема"@ru ;
	dc:language "en" ;
	dc:creator <http://example.com/john-smith> ;
	skos:hasTopConcept <http://example.com/my-concept-scheme/concept1>, <http://example.com/my-concept-scheme/concept2>, <http://example.com/my-concept-scheme/concept3>, <http://example.com/my-concept-scheme/concept4>, <http://example.com/my-concept-scheme/concept5> .

<http://example.com/john-smith> rdfs:label "John Smith"@en, "Джон Смит"@ru .