Saga Lemmatize stage uses a dictionary file to identify words and reduce them to their basic form. For example it will identify that "running" is a verb form (gerund) and will reduce it to its base infinitive form "run".

The Lemmatizer will also expand the word to its synonyms in case there are synonyms available in the dictionary. It could also expand antonyms, alternative forms, etc.

An important note here is that Saga Lemmatizer Stage code is agnostic to what reductions or expansions it uses. The set of reductions and expansions (Relationship Types) to use are defined in the dictionary file and in the Lemmatize Stage configuration. 

This means that when creating the dictionary file for each language, we need to be careful to understand which relationship types we want the lemmatizer to use and make sure to include them in the dictionary file.

In order to produce the dictionary file an internal tool called "Wiktionary Dump Parser" is used.  This tool uses an open source library called "Java Wiktionary Library" (JWKTL) that makes the parser of the Wiktionary dump file much easier.

In the following diagram you can see different components and different stages the tool uses to produce a dictionary file:

Wiktionary dump parser tool will:

Stage 1:  using JWKL, parse the language specific Wiktionary dump file and produce an index in Oracle Berkeley DB format.

Stage 2:  read the contents of the index, transform them and store entries in a Mongo DB collection.

Stage 3:  read and parse entries stored in Mongo DB then produce a file in a JSON entry per line format that SAGA lemmatizer can use.

On following steps you will know where to get Wiktionary dump files, what code you need to add/modify to support an additional language and how to test your new generated dictionary file.

Step-by-step guide

Step 1: Download Wiktionary dump file

Dump files are periodically generated as a back up in the Wikimedia site. You can see a list of all Wiki backups including Wiktionary for each language at this URL: https://dumps.wikimedia.org/backup-index.html

In order to find your language, use the ISO 2 letter language code plus the word 'wiktionary'. So for example:

For English: enwiktionary

For Spanish: eswiktionary

For German: dewiktionary

And so on...

Here a useful list of language codes: https://www.loc.gov/standards/iso639-2/php/code_list.php

For Spanish you should see something like this:

Once you know it exists, click on the link to load a landing page for the language or simply go directly to the file list page using this URL: https://dumps.wikimedia.org/eswiktionary/latest/

Note the word 'eswiktionary' is used in the URL, you can change that for you desired language. For example 'dewiktionary' in case you want German.

When the page loads, look for a file that ends in "-latest-pages-articles.xml.bz2" and download it. For example, the Spanish file name is "eswiktionary-latest-pages-articles.xml.bz2"

Once downloaded just unzip it and you are ready to go.

Step 2: Get familiar with Wiktionary format and specific templates for you language

As you may already know, Wiktionary is an multilingual project to create free content dictionary of all words in all languages.

Each word you find in Wiktionary is called a page/article/entry and it is manually added by volunteers around the globe.

Obviously, languages are different, communities contributing are different, therefore format used to write these entries varies a lot between languages. They could even change between entries in the same language, depending on who did it and how old the entry is.

This means that before implementing a new language for SAGA Lemmatize Stage, it is a good idea to get familiar with the specifics of the language.

2.1 Inspecting an Entry

First step is to load wiktionary in your browser: https://www.wiktionary.org/

Then choose your desired language, for this guide we'll use the Spanish one as example: https://es.wiktionary.org/wiki/Wikcionario:Portada

Then look for a word, for example: 'casa' (spanish for home). Once the word page is displayed, click on the Edit tab:

You should see the entry definition, like this:

In general, for all languages:

• Portions that appear enclosed in curly brackets are called templates. Templates have a name and usually none to N parameters which can be named parameters or numbered parameters (have no name but need to appear in order)
• When there is a sequence of  2 to 4 equal characters, it usually means it is the start of a new section. In the image above the section Word Sense is started with === sustantivo femenino|es ===. This section defines the word form (a noun in this case) and all different meanings the word has.

2.2 Learning more about Wiktionary

For more information on templates use the Help in the Wiktionary site. For example:

1. English help: https://en.wiktionary.org/wiki/Help:Contents
2. English templates: https://en.wiktionary.org/wiki/Wiktionary:Templates
3. Spanish help: https://es.wiktionary.org/wiki/Wikcionario:Ayuda
4. Spanish template listing: https://es.wiktionary.org/wiki/Especial:Todas?from=es.v.conj&to=&namespace=10

Step 3: Get familiar with JWKTL and add support for your language

Related articles

• Page:
  How to Add a New Language to the Lemmatizer