beacon-links

beacon-links.js

JavaScript implementation of BEACON link dump format. The beacon-links package provides for:

• Parsing BEACON link dump format
• Writing BEACON link dump format
• RDF Mapping BEACON link dumps
• Storage of BEACON link dumps in memory
• command line client for processing BEACON link dumps

Installation

Requires at least node.js 6.4. Install the npm package:

$ npm install beacon-links

Introduction

BEACON is a data interchange format for large numbers of uniform links. A BEACON link dump consists of a set of links and a set of describing metadata fields. Link dumps can be serialized in a condense text format that utilizes common patterns for abbreviation. Link dumps can further be mapped to and from RDF with minor limitations. The most popular use case of BEACON link dumps is collection of resources related to entities identified in authority files.

For example this link dump in BEACON format consists two links from authors, identified by their Integrated Authority File URI (GND), to reviews in the German literary magazine "Perlentaucher":

#PREFIX: http://d-nb.info/gnd/
#TARGET: http://www.perlentaucher.de/autor/
#TARGETSET: http://www.wikidata.org/entity/Q2071388
#NAME: Perlentaucher
#TIMESTAMP: 2017-11-24

118757261|Dylan Thomas|dylan-thomas.html
128915706|Shirin Ebadi|shirin-ebadi.html

The links can be mapped to RDF triples:

<http://d-nb.info/gnd/118757261> <http://www.w3.org/2000/01/rdf-schema#seeAlso> <http://www.perlentaucher.de/autor/dylan-thomas.html> .
<http://d-nb.info/gnd/128915706> <http://www.w3.org/2000/01/rdf-schema#seeAlso> <http://www.perlentaucher.de/autor/shirin-ebadi.html> .

The beacon-links package and its command line client provide methods to parse, serialize and map BEACON link dumps:

const { MetaFields } = require('beacon-links')
 
var meta = MetaFields({
  PREFIX: 'http://d-nb.info/gnd/',
  TARGET: 'http://www.perlentaucher.de/autor/',
  TARGETSET: 'http://www.wikidata.org/entity/Q2071388',
  NAME: 'Perlentaucher',
  TIMESTAMP: '2017-11-24'
})
 
var link = meta.constructLink('118757261', 'Dylan Thomas', 'dylan-thomas.html')

Command line client

$ beaconlinks -h

Usage: beaconlinks [options] [file]

Parse and serialize BEACON link dumps.

Options:

  -h, --help             show usage information
  -b, --brief            omit meta fields having default values
  -l, --links            only write links
  -m, --meta             only read and write meta fields
  -f, --format <format>  output format (txt|json|rdf)
  -c, --color            enable color output
  -C, --no-color         disable color output

Try for instance beaconlinks -f rdf test/perlentaucher.txt to map the sample link dump to RDF.

Parsing

A Parser reads BEACON format from strings or streams. Method parse returns a with the whole link dump on success or an Error otherwise. The link dump is an object with properties meta (a MetaFields) and links (an array of Link). Parsing errors come with properties number for the line number and line for the faulty line.

var parser = beacon.Parser()
var input = fs.createReadStream('beacon-file.txt')
 
parser.parse(input)
  .then(dump => {
    console.log('Read %d links', dump.links.length)
  ))
  .catch(error => {
    console.error('%s at line %d: %s', error.message, error.number, error.line)
  })

For more details and large data sets the parser should better be used on streams. Parsing emits:

• a meta event for all meta fields combined (a MetaFields)
• a tokens event for each non-empty link line, passed as non-normalized array of tokens
• a data event for each constructed link (a Link)
• a error event on parsing errors

var parser = beacon.Parser()
fs.createReadStream('beacon-file.txt')
  .pipe(parser)
  .on('meta', metaFields => ... )
  .on('tokens', tokens => ... )
  .on('data', link => ... )
  .on('error', error => ... )
  .on('end', () => ... ) // called after successful parsing

Writing

A Writer writes BEACON format to strings:

writer = beacon.Writer(options)
writer.writeMeta(metaFields)
writer.writeTokens(source, annotation, target)
process.stdout.write(writer.output)

or to streams:

writer = beacon.Writer(process.stdout, options)
writer.writeMeta(metaFields)
writer.writeTokens(source, annotation, target)

Writer options include:

• omitDefaults to omit meta fields with default values (false by default)
• omitEmptyLine to omit the empty line after meta fields
• highlight: optional object with functions to highlight
  • delimiter (delimiter characters)
  • field (meta field name)
  • value (meta field value)
  • source (source token)
  • annotation (annotation token)
  • target (target token)

RDF Mapping

BEACON link dumps can be mapped to RDF with RDFMapper. The constructor can be configured with an instance of the JavaScript RDF Interfaces DataFactory interface. By default N3 triples representation is used.

interface RDFMapper {
  Object *metaTriples(MetaFields meta);
  Object *linkTriples(Link link, String annotation);
  Object *countTriples();
  Object *allTriples(MetaFields meta, Link* links);
}

const { RDFMapper } = require('beacon-links')
 
var mapper = RDFMapper(dataFactory)
for (let triple of mapper.allTriples(linkDump)) {
  // ...
}

API

MetaFields

BEACON meta fields are implemented as object with properties for each meta field:

interface MetaFields {
  attribute URIPattern PREFIX;
  attribute URIPattern TARGET;
  attribute string MESSAGE;
  attribute URI|URIPattern RELATION;
  attribute URI ANNOTATION;
  attribute string DESCRIPTION;
  attribute string CREATOR;
  attribute string CONTACT;
  attribute URL HOMEPAGE;
  attribute URL FEED;
  attribute string TIMESTAMP;
  attribute string UPDATE;
  attribute URI SOURCESET;
  attribute URI TARGETSET;
  attribute string NAME;
  attribute string INSTITUTION;

  string getValues(bool brief);

  Link constructLink(string source, string annotation, string target);
  array constructTokens(Link link);
}

Property values PREFIX, TARGET, and RELATION can be URIPattern objects. URIs and URLs are stored as plain strings. Additional constraints apply on property TIMESTAMP and UPDATE. Empty fields are set to the empty string. A new MetaFields object can be created with function MetaFields:

meta = beacon.MetaFields({INSTITUTION: 'ACME'})
console.log(meta.RELATION) // default value "http://www.w3.org/2000/01/rdf-schema#seeAlso"

Method getValues returns a plain object with flat field values, optionally omitting default values.

Link

BEACON links are implemented as object with four properties:

interface Link {
  attribute string source;
  attribute string target;
  attribute string relation;
  attribute string annotation;
}

Links can be constructed from meta fields and link tokens:

meta = MetaFields({
  PREFIX: 'http://example.org/',
  TARGET: 'http://example.com/',
  MESSAGE: 'Hello World!'
})
link = meta.constructLink('foo')

URIPattern

Implements BEACON link dumps

interface URIPattern {
  string expand(string ID);
  attribute string uriSpace;
  attribute string uriRegexPattern;  // not implemented yet
  string toString();
  string match(string);
  boolean isDefault();
}

The match method can be used to abbreviate a URI to a token. Method isDefault return whether the pattern is {+ID}.

Storage

An experimental TokenIndex is included to efficiently store and query links in memory.

To index a BEACON link dump:

var input = fs.createReadStream('beacon-file.txt')
var index = beacon.TokenIndex()
 
index.parse(stream, (error) => {
  // called on success or error
})
.on('meta', metaFields => { ... }) // optional

Contribution

Bug reports and fixes are welcome!

Clone this project from github

git clone https://github.com/gbv/beacon-js.git