当某些字母发生变化时，如何在复数中找到单数？ 最好的方法是什么？

Question

How can I find the singular in the plural when some letters change?

Following situation:

• The German word Schließfach is a lockbox.
• The plural is Schließfächer.

As you see, the letter a has changed in ä . For this reason, the first word is not a substring of the second one anymore, they are "regex-technically" different.

Maybe I'm not in the right corner with my chosen tags below. Maybe Regex is not the right tool for me. I've seen naturaljs ( natural.NounIflector() ) provides this functionality out of the box for English words. Maybe there are also solutions for the German language in the same way?

What is the best approach, how can I find singular in the plural in German?

Answer 1

I once had to build a text processor that parsed many languages, including very casual to very formal. One of the things to identify was if certain words were related (like a noun in the title which was related to a list of things - sometimes labeled with a plural form.)

IIRC, 70-90% of singular & plural word forms across all languages we supported had a "Levenshtein distance" of less than 3 or 4. (Eventually several dictionaries were added to improve accuracy because "distance" alone produced many false positives.) Another interesting find was that the longer the words, the more likely a distance of 3 or fewer meant a relationship in meaning.

Here's an example of the libraries we used:

const fastLevenshtein = require('fast-levenshtein');

console.log('Deburred Distances:')
console.log('Score 1:', fastLevenshtein.get('Schließfächer', 'Schließfach'));
// -> 3
console.log('Score 2:', fastLevenshtein.get('Blumtach', 'Blumtächer'));
// -> 3
console.log('Score 3:', fastLevenshtein.get('schließfächer', 'Schliessfaech'));
// -> 7
console.log('Score 4:', fastLevenshtein.get('not-it', 'Schliessfaech'));
// -> 12
console.log('Score 5:', fastLevenshtein.get('not-it', 'Schiesse'));
// -> 8


/**
 * Additional strategy for dealing with other various languages:
 *   "Deburr" the strings to omit diacritics before checking the distance:
 */

const deburr = require('lodash.deburr');
console.log('Deburred Distances:')
console.log('Score 1:', deburr(fastLevenshtein.get('Schließfächer', 'Schließfach')));
// -> 3
console.log('Score 2:', deburr(fastLevenshtein.get('Blumtach', 'Blumtächer')));
// -> 3
console.log('Score 3:', deburr(fastLevenshtein.get('schließfächer', 'Schliessfaech')));
// -> 7


// Same in this case, but helpful in other similar use cases.

Answer 2

You can use a stemmer (which is in fact a lemmatizer) from the nlp.js library, which has models for 40 languages.

const { StemmerDe } = require('@nlpjs/lang-de');

const stemmer = new StemmerDe();
console.log(stemmer.stemWord('Schließfach'));
console.log(stemmer.stemWord('Schließfächer'));