Mathieu Mangeot
email: mathieu.mangeot@imag.fr

Chantal Enguehard
email: chantal.enguehard@univ-nantes.fr

Dictionaries for Under-Resourced Languages: from Published Files to Standardized Resources Available on the Web

Keywords: Dictionar., lexical database, Jibiki platform, XML, LMF, Bambara, Khmer, Wolof, Niger, National Language

Most work in the feld of natural language processing focuses on well-resourced languages.

However, much remains to be done on under-resourced ones: there are few dictionaries, parsers, etc. Nevertheless, when published dictionaries are available, it is sometimes possible to fnd the data fles used to print the dictionar. (usuall. in Word format). A conversion process can then be applied to these fles in order to obtain standardized XML lexical data.

Attention must be paid to specifc problems such as a lack of standardization in the alphabets or the use of hacked fonts for displa.ing specifc characters. Next, the standardized XML data can be imported into an online lexical resources management platform. It is then available online for lookup and editing. A fnal step can also be performed to automaticall. export the data into interchange formats such as Lexical Markup Framework or lemon in order to produce linked data.

Introduction

In the feld of natural language processing (NLP), most work focuses on wellresourced languages (English, French, German, Japanese, etc.): there are lexicons, dictionaries, corpora, sophisticated tools such as lemmatizers or parsers, etc. and one can fnd a lot of online resources. However, much remains to be done on underresourced languages: there are few dictionaries, parsers, etc. (and their qualit. is often ver. low) even when some have a large number of speakers (there are, for example, 250 million Bengalis, 30 million Haoussas).

Being a speaker of a poorl. endowed language means limited or no access to the linguistic resources of this language: dictionaries, but also textbooks, literar., media, etc. These unmet needs affect man. aspects of life: web, education, health, culture, etc. [START_REF] Osborn | Les langues africaines à l'ère du numerique[END_REF]. This diffcult access to the resources compromises the capacit.

to express one's thoughts: freedom of expression is at stake. In addition, it negativel. affects development with respect to several dimensions: the econom., culture, technolog., public health, etc.

NLP also suffers from this shortage because it is ver. diffcult to develop NLP tools or research without an. linguistic resources or with limited resources. Underresourced languages remain terra incognita for NLP.

The lack of qualit. and sustainable resources for under-resourced languages is a bottleneck that creates a vicious circle: the lack of resources discourages research in NLP, prevents the development of populations (including in education), resulting in a low level of education and a lack of "language workers" (linguists, lexicologists, novelists, reporters, etc.). Finall. there are not enough linguists and lexicologists to produce good qualit. resources... The United Nations Educational, Scientifc and Cultural Organization (UNESCO) has mentioned several times this dimension and the richness of linguistic diversit.. It has called upon Member States "to promote the preservation and protection of all languages used by peoples of the world". In 2005, during the conference organized in Bamako (Mali), it added that language is a critical factor in the abilit. to communicate.

Finall., the access to linguistic resources appears as an ethical issue. Promoting and creating linguistics resources for under-resourced languages meets this need.

Thus, we consider that there are two major reasons for NLP to develop research and tools which help in the creation and promotion of resources for under-resourced languages: the human development of the populations and the scientifc issues of NLP.

When printed dictionaries for these languages are available, it is sometimes possible to fnd the data fles used to print them (usuall. in Word format). A conversion process can then be applied to these fles in order to obtain standardized XML lexical data that is next put online for lookup and editing or exported into interchange formats such as Lexical Markup Framework (LMF) or lemon, in order to produce linked data.

If the data fles cannot be found either because the. were lost or non-existent (in the case of old dictionaries), it is also possible to perform an optical character recognition process on the scanned fles from the printed books. The result of the OCR process is then saved into Word or ODF format and processed as with the previous data fles. In order to cope with the remaining OCR errors, it is possible to use a lemmatiser if it exists for the processed language, like in the Japanese-French Jibiki.fr project 1 [START_REF] Mangeot | Collaborative Construction of a Good Qualit., Broad Coverage and Cop.right Free Japanese-French Dictionar[END_REF].

In the frst section of this article, specifc issues are tackled concerning available dictionaries for under-resourced languages, and the resources to which the conversion methodolog. was applied are presented. The following section details technical problems such as the lack of standardization in the alphabets or the misuse of unicode characters with hacked fonts. The third section focuses on the conversion process of a published dictionar. into a standardized XML fle with a discussion about the choice of the standard format, the description of the process itself and the different steps it involves. The last section describes the use of Jibiki, an online lexical resources management platform for lookup and editing of the previousl. converted dictionaries.

Dictionaries for under-resourced languages

2.1 SPECIFIC ISSUES OF UNDER-RESOURCED LANGUAGES Languages are more or less well-resourced in terms of their support b. tools: adapted ke.board, spell-checker, speech s.nthesis, machine translation, etc. A classifcation based on the estimation of the electronic resources and tools defnes three classes: well-resourced languages or τ-languages (eg: English, French), moderatel.-resourced languages or μ-languages (eg: Portuguese or Swedish), and under-resourced languages or π-languages (eg: Bambara, Kanuri or Khmer) [START_REF] Berment | Methodes pour informatiser des langues et des groupes de langues «g peu dotees[END_REF].

The term under-resourced languages covers contrasting situations. We mention here three of them:

-it is the offcial language of a countr., as is Irish (or Irish Gaelic) in Ireland. It is also the case for languages spoken b. the majorit. of the population such as Khmer in Cambodia.

-it is a language without offcial status, that became a regional language: for example Basque and Breton in France; Ladin in Ital., Cornish in the United Kingdom.

-it is a national language of a countr. whose offcial language (used at school, or to write the laws) is different and often comes from a former colonizer state [START_REF] Calvet | Les politiques linguistiques[END_REF]. This is the case of African languages on which we have worked and that are spoken in Niger, Mali and Burkina Faso. In these three countries, the offcial language is French.

The dictionaries presented in this article concern Khmer, the offcial language of Cambodia and also eight African languages from countries where French is the offcial language: Bambara, Fulfulde, Hausa, Kanuri, Tamajaq, Wolof and Zarma.

The. are under-resourced languages whose socio-economic context is characterized b. limited resources:

-there are few linguists who have an under-resourced language as their mother tongue and who exercise their professional activit. in that language.

-the budget for the development of linguistic resources is low.

The governmental investment dedicated to language planning and, in particular, the development of electronic language resources is therefore ver. limited. The few studies that are conducted are characterized b. a discontinuit. in the time and spatial spread, which affects their sustainabilit. and reuse [START_REF] Streiter | Implementing NLP projects for non-central languages: Instructions for funding bodies, strategies for developers[END_REF].

Because of the scarcit. of linguistic research, descriptions of these languages are incomplete and man. questions remain.

Developing lexical resources from scratch requires substantial budgets, qualifed and available people, and the abilit. to lead a project for several .ears, conditions that cannot be met in man. countries where there are few dictionaries which are generall. not compiled b. professional lexicographers. Therefore, the dictionaries on which we have worked contain numerous errors or incompleteness and are likel. to evolve. This contrasts sharpl. with the published dictionaries of well-resourced languages like French or English. For example, Larousse or Harrap's are frms emplo.ing dozens of professionals who regularl. review their dictionaries over several decades. However, there are some published dictionaries (often bilingual) which can be reused to achieve in onl. a few weeks, at low cost, a frst version of an electronic resource.

Collecting the digital fles constitutes an important advance. However, in their absence, the dictionar. can be ke.ed in again when onl. a printed cop. has been collected.

Whatever its format (electronic or print), a dictionar. represents a sum of important knowledge that can be recovered and reused. In all cases the authors or publisher of the initial dictionar. should be involved in the project in order to obtain their agreement that the lexical resource that will be produced can be widel. distributed in electronic form, visible on the Internet.

DICTIONARIES WRITTEN BY A SINGLE AUTHOR

Man. of the dictionaries written b. a single author are bilingual because their author, originall. from a τ-language, aims to promote a π-language. Some were written b. clerics in charge of the evangelism of populations in colonized countries ("pères blancs" in Africa, Portuguese Jesuits in Asia).

There are also dictionaries developed b. literate people, often linguists, wishing to serve their mother tongue. This is the case of the elementar. Hausa-French dictionar. written b. Abdou Minjinguini (Minjinguini, 2003) and the monolingual Zarma dictionar. written b. Issouf Alzouma Oumarou (Oumarou, 1997).

The conversion methodolog. (described in section 4) has been applied successfull. to the following two dictionaries.

The French-Khmer dictionar.

The French-Khmer dictionar. 2 project [START_REF] Richer | Dictionnaire Français-Khmer (en phonetique)[END_REF] The Bambara-French dictionar. 3 of Father Charles Bailleul (1996 edition) includes more than 10,000 entries. This dictionar. is primaril. intended for French speakers wishing to improve Bambara but it is also a resource for Bambara speakers. In the 7 Figure 1: Excerpt from the French-Khmer dictionar. in Word format words of the author himself, the dictionar. "pla.s the role of a working tool for literac., education and Bambara culture." To date, it can be considered as the most comprehensive dictionar. of the language. It is also used b. specialists of other varieties of this language such as D.ula (Burkina Faso, Côte d'Ivoire) and Malinké (Guinea, Gambia, Sierra Leone, Liberia, etc.).

DICTIONARIES BUILT BY PROJECTS

Dictionaries built b. projects have several authors. The group of authors usuall.

defnes some principles about the structure and the defnition of closed lists of values such as grammatical classes.

The most recent dictionaries of this t.pe are built with lexicograph. tools such as Linguist Shoebox/Toolbox 4 [START_REF] Buseman | The linguist's shoebox: tutorial and user's guide: integrated data management and analysis for the field linguist[END_REF] and FieldWorks Language Explorer (FLEx) 5 of the Summer Institute of Linguistics (SIL) or TshwaneLex (TLex) 6 .

Even if these tools are able to export content to an XML structure, it is often the case that this operation has not been performed or the fles produced b. the lexicographical tools are not available. Onl. Word fles can be used for printing.

The conversion methodolog. (described in section 4) has been applied successfull. to the following six dictionaries.

The Niger SouTeBa dictionaries

In the DiLAF project 2 [START_REF] Enguehard | Computerization of African languages-French dictionaries Proceedings of Collaboration and Computing for Under Resourced Languages in the Linked Open Data Era (CCURL)[END_REF], we worked on fve dictionaries written in fve national languages of Niger and French. The. have been produced b. the Soutéba project (a program to support basic education) with funding from German cooperation and the support of the European Union. The software used for building these dictionaries is the SIL toolbox. The. have a simple structure because the. were designed for children in primar. school classes in a bilingual school (education is given there in a national language and in French). Most terms of lexicolog., such as lexical labels, parts-of-speech, s.non.ms, anton.ms, genres, dialectal variations, etc. are noted in the language in question in the dictionar., contributing to forge and disseminate a meta-language in the local language, a specialized terminolog.. The entries are listed in alphabetical order, even for Tamajaq (although it is usual for this language to sort entries based on lexical roots) because the vowels are written explicitl. (this mode of classifcation was preferred because it is well known b. children).

The Fulfulde-French dictionary 7 includes 4,305 entries. The orthographic form of the entr. is followed b. a part-of-speech. Next, follows a defnition and an example in Fulfulde. Some grammatical information is mentioned, such as the plural form (mbahdi). The entr. ends with a French gloss (far). Here is an example: saabi jokk. helmere jokkondiroore konngi ngam hollude hujja. saabi o sooda ngawri waɗi o soonni nga'ari makko. mbahdi : saabi. far : à cause de.

The conversion of this dictionar. was particularl. diffcult because the original word fles disappeared and the dictionar. was re-ke.ed in b. hand from a printed version.

Thus man. structuring errors could be found.

The Hausa-French dictionary 2 includes 7,823 entries. The orthographic form of the headword is followed b. the pronunciation (tones are marked with diacritics placed on vowels) and part-of-speech. On the semantic level, there is a defnition in Hausa, a usage example (identifed b. the use of italics), and the equivalent in French. Here is an example: jaki [jàakíi] s. babbar dabbar gida mai kamar doki, wadda ba ta kai tsawon doki ba amma ta fi shi dogayen kunnuwa. Ya aza wa jaki kaya za ya tafi kasuwa. Jin.: n. Sg.: jaka. Jam.: jakai, jakuna. Far.: âne The Kanuri-French dictionary 2 includes 5,994 entries. The orthographic form of the entr. is followed b. an indication of pronunciation relating to tones. The part-ofspeech is shown in italics, followed b. a defnition, a usage example, a French translation and meaning in French. Additional information ma. appear as variants.

Here is an example:

The Tamajaq-French dictionary 2 includes 5,205 entries. The orthographic form of the entr. is followed b. the part-of-speech and a gloss in French displa.ed in italics.

For nouns, morphological information about the state of annexation is often included, the plural and gender are also explicitl. stated. A defnition and an example of usage follow. Other information ma. appear as variants, s.non.ms, etc. As Tamajaq is not a tonal language, phonetics does not appear. Here is an example:

The Zarma-French dictionary 2 includes 6,916 entries. Each entr. has an orthographic form followed b. a phonetic transcription in which the tones are rated according to the conventions alread. set for the Kanuri. The part-of-speech specifes explicitl. the transitivit. or intransitivit. of verbs. For some entries, anton.ms, s.non.ms and references are indicated. A gloss in French, a defnition and an example end the entr.. Here is an example:

The Wolof database

The Wolof database [START_REF] Cissé | Le dictionnaire électronique unilingue wolof et bilingue wolof-français : une création continuée, Repères DoRiF n.3 -Projets de recherche sur le multi / plurilinguisme et alentours[END_REF]) is a multifunctional lexical database from which it is possible to extract a monolingual Wolof dictionar. as well as a bilingual Wolof-French dictionar.. Each word sense has its own entr. in the database. Pol.semic words will then have several entries. The database was built with the SIL Toolbox tool. Each entr. has several administrative felds (or meta-information): status of the entr., comments, author of the entr..

Technical difficulties

LANGUAGES WRITTEN BUT POORLY STANDARDIZED

While the fact that a language is under-resourced has been defned solel. in terms of its equipment in IT tools and resources, the linguistic knowledge of this language is often scarce: there are few studies on the language, the. are inaccessible because the.

are not published in journals or conference proceedings, and the. are not available online. Moreover, these languages are also not ver. present in schools, either as a subject of stud. or as a teaching language. However, some exceptions are worth mentioning:

In Niger, experimental schools were established in the 1980s. The teaching is entirel. delivered in a national language in the frst half of the primar. c.cle. During the second half of the c.cle, French appears and the national language is studied as a subject. In the fnal .ear, the teaching takes place in French onl.. It will be the same for the rest of school: middle school, high school and higher education (Programme Décennal du Développement de l 'Éducation, 2003).

In Ecuador, the Shuar people (called improperl. Jivaro) was structured in a Federation of Shuar Centres in 1964. In the 1970s the Federation organized, among other initiatives, the establishment of primar. schools in villages with support through radio programs. These schools are bilingual. Instruction is provided almost entirel. in Shuar in the frst two .ears to move towards parit. in education in Shuar and Spanish in the fnal .ear [START_REF] Calvet | La guerre des langues[END_REF].

Be.ond the success of these approaches to children's literac., the creation of a school curriculum promotes the writing and editing of textbooks which constitute text corpora written b. language specialists, sometimes linguists, with a good knowledge of the written language. Such corpora could be exploited b. linguists to build lexical resources. Their size remains small. Other national language texts emerge. The. are written b. journalists and authors (of stories, novels, etc), who have mostl. no access to language resources. Therefore, these texts are written in a somewhat standardized language with particularl. man. spelling variations. These corpora thus cannot be used as a data source to automaticall. build lexical resources.

In this context of deprivation, the reuse of a published dictionar. is a frst step that will accelerate the creation of usable resources for natural language processing applications. In some dictionaries, word spelling is standardized and complies with linguistic studies; in others, such as [START_REF] Bailleul | Dictionnaire bambara-français[END_REF], variants are explicitl. marked and located geographicall., while the offcial spelling is reported in addition to the usual spellings. Furthermore, the defnitions and examples of use are a corpus of sentences and man. entries are accompanied b. morphological information for calculating the different forms of the same entr..

SPECIAL CHARACTERS

Set up in the 1960s, long before Unicode, the alphabets of most African languages use special characters which were absent from the standard character tables at that time. Although the alphabets of languages on which we have worked [START_REF] Enguehard | Les langues d'Afrique de l'ouest : de l'imprimante au traitement automatique des langues[END_REF] are mainl. of Latin origin, new characters needed to note specifc sounds in some languages with a single character have been adopted b. linguists in a series of meetings. Thus, each of the alphabets of the African languages we have worked on includes at least one of these special characters: ǝ ŋ . The character b ɓ ɗ ɛ ɣ ƙ ɲ ɔ ƴ with hook ( , ) appears in the Hausa alphabet (République du Niger, 1999a) while ɓ Ɓ the character eng (velar n) (ŋ, Ŋ) appears in the Bambara, Tamajaq (République du Niger, 1999c) and Soŋai-Zarma (République du Niger, 1999d) alphabets. Characters composed of a Latin character and a diacritical mark have also been created (such as â, ă, ã, ḍ, ǧ or š).

Targeted primaril. for printing texts on paper, fonts displa.ing these special characters have been created b. redrawing the gl.phs of certain characters [START_REF] Chanard | Encodage informatique multilingue : application au contexte du Niger[END_REF]). These fonts have for decades allowed texts to be published in national languages, but the. prohibit natural language processing on these texts [START_REF] Enguehard | Les langues d'Afrique de l'ouest : de l'imprimante au traitement automatique des langues[END_REF]. The habit of using them is being installed, and the source fles of the dictionaries we have collected use such fonts. It is therefore necessar. to convert them to Unicode so that the character encoding meets the international standards.

CHARACTER CONVERSION TO UNICODE

Establishing replacement characters can be trick. if the original fonts are not available, which is the most common situation. In this case, it is preferable to have a printed version to be sure to establish proper conversions. This step can be more subtle when the same character is used to displa. different gl.phs. For example, the Table 1 shows part of the list for Zarma. There is no automatic method that will detect these problematic characters. It is imperative to look at the data.

Origin Unicode § ã $ ɲ ù ŋ £ Ɲ
Table 1: Partial view of the Unicode correspondence table for Zarma.

Figure 2 shows two entries. In their original version, special characters initiall.

entered with a hacked font are not readable. In the Unicode version these special characters have been transformed to compl. with Unicode. Digraphs can be easil. t.ped using two characters but their use changes the sort order which determines the lexicographic presentation of dictionar. entries. Thus, for

Hausa and Kanuri, the digraph 'sh' is located after the letter 's'. So, in the Hausa dictionar., the word "sha" (drink) is located after the word "su.a" (fried), and, in Kanuri, the word "suwuttu" (undo) precedes the noun "shadda" (basin). It would be necessar. to complete the Unicode standard with digraphs of Hausa and Kanuri alphabets in their various letter cases. Certain characters with diacritics are included in Unicode as a unique sign, whereas others can onl. be obtained b. composition.

Thus, vowels with tilde 'a', 'i', 'o' and 'u' can be found in Unicode in their lowercase and uppercase forms while the 'e' with a tilde is missing and must be composed with the character 'e' or 'E' followed b. the tilde accent (U+303), which can cause renderings which are different from other letters with tilde when viewing or printing (tilde at a different height for example).

Letter j with caron exists in Unicode as a sign ǰ (U+1F0), but its capitalized form Jm ust be composed with the letter J and the caron sign (U+30C).

The characters e, and J̌ should be added to the Unicode standard.

Concerning letter case change, word processors usually provide this functionality, but

do not always realize it in the correct way. Thus, we have found during our work that  The microstructure is sometimes slightl. modifed according to the dictionar..

Traditional lexicograph. distinguishes two vocables as homographs if the. have no clear semantic link with each other [START_REF] Polguère | Enseignement bilingue[END_REF]. But in practice, it frequentl.

happens that dictionaries of the same languages follow a division into different homograph vocables.

We believe that this distinction is actuall. arbitrar.. To our knowledge, there are also no specifc criteria to evaluate a semantic link between two words that can be implemented easil. with NLP tools, let alone for under-resourced languages. When it is possible, we have therefore chosen to group homograph vocables into a single entr.. However, we distinguish entries with different parts-of-speech. The combination of a lemma and a part-of-speech therefore constitutes a single entr..

For lexical databases generated from retrieved data (such as the MotÀMot project, see the target format below), the Jibiki platform allows great freedom in the defnition of the macrostructure (ref paper links). It is possible to design complex macrostructures composed of several la.ers of volumes related to each other (see PiVAX [START_REF] Ngu | PIVAX, an online contributive lexical database for heterogeneous MT systems using a lexical pivot[END_REF] or proAxie [START_REF] Zhang | Gestion des terminologies riches : L'exemple des acron.mes Procs of TALN-RECITAL[END_REF] macrostructures). However, the foundations of a Jibiki structure are based on a traditional approach to designing dictionaries, the onomasiological approach: from the lexical unit to the word meanings and gathering word meanings into interlingual links (axies) at the interlingual pivot level. Axies are not concepts, although the. tend to become ones.

The OntoLex W3C working group, and more generall. linked data and lemon projects are based on a semasiological approach (from the concept to the word meaning). As stated in the frst point of the OntoLex declaration: "The mission of the Ontolog.-Lexicon communit. group is to develop models for the representation of lexica […] relative to ontologies. These lexicon models are intended to represent lexical entries containing information about how ontolog. elements […] are realized in multiple languages. It is certainl. possible to defne a macro-structure based on a semasiological approach with Jibiki, but the tool has not been designed for that and it has not .et been experimented. For a more detailed discussion, see [START_REF] Zhang | Jibiki-LINKS: a tool between traditional dictionaries and lexical networks for modeling lexical resources[END_REF].

Another difference between these two approaches is that, for the onomasiological one, the aim is to build consistent and high-qualit. resources. This can be done onl.

if thorough verifcations are carried out on the nomenclature (choice of entries) and the data. Several possibilities exist: to indicate for each entr. a qualit. level, to show the histor. of the origin of the data, to establish a process of revision / validation, etc.

For the semasiological approach, the main goal is to obtain the broadest coverage in terms of quantit. of entries and number of languages. That said, we believe that in the future these two approaches, complementar., should become closer or even merge.

CHOICE OF THE STANDARD

Our goal is to convert published dictionaries to make them available to the natural language processing (NLP) scientifc communit.. Thus, the fnal format must be based on standards. We studied two main standards: The Text Encoding Initiative and the Lexical Markup Framework.

The Text Encoding Initiative

The TEI is led b. a consortium gathering American and European public research organizations. Its goal is to defne an exchange format for exchanging, creating and storing annotated texts with a standardized tagset. The latest version is P5, published in 2007. Each TEI encoded document must begin with a header described in chapter 2.

Chapter 9 focuses on dictionaries. To address the problem of the structuring of entries, the TEI provides a binar. solution: an article can be represented b. a <entry> element whose structure is ver. rigid and codifed; the element <entryFree> ma. be preferred because it admits the insertion of an. elements in an. order in the entr..

In practice, the <entry> is too burdensome to use. [START_REF] Francopoulo | Multilingual resources for NLP in the Lexical Markup Framework (LMF)[END_REF].

We would draw the reader's attention to the fact that LMF is separated into two parts.

The normative part describes the meta-model but does not specif. the data representation scheme (which elements and attribute names to use). This is described in the informative part of LMF, which is not included in the standard itself. Thus, it is possible to obtain a resource using its own elements and attributes names but still following the normative part of LMF. Some people enjo. that freedom (and we are among them), while others would have preferred the informative part to be included in the standard in order for all LMF resources to follow the same s.ntax.

Lexical Markup Framework: the informative part

The informative parts of LMF give precise information as to how to encode a lexical resource in XML: the structure that must be followed and the elements and attributes that must be used. As it can be suitable for an interchange format, we prefer not to use it as a working format for the following reasons:

 The name of the elements are in English. While it can be understood b. the majorit. of the researchers in the world, it can be diffcult to understand for the people working directl. on the dictionar.. When developing a resource, the. are the most important people to take into consideration!

 Objects of different nature can be put at the same level. We think that, in order to be clearl. understandable, an XML format should avoid putting objects of different nature at the same indentation level. The siblings of an element must be of the same nature. The LMF format does not respect this principle. The object <GlobalInformation> which isa meta-information about the lexicon is a sibling of the object <Lexicon>, which is the resource itself.

 Free text is stored in attribute values. In XML, it is customar. to include items from closed lists as attribute values, and frame the free texts b. using markup tags. This general principle is not respected in the informative part of LMF since all the information is stored in textual attributes. This choice has the effect of prohibiting the minimal information displa. via a browser for example.

PRESENTATION OF THE METHODOLOGY

The conversion process

The conversion methodolog. proceeds in several steps and requires successive transformations of the published dictionar. to several XML fles called cop., central, target and export formats. We also take into account the fact that lexicographers will revise and develop the produced resources. conceive these programs the. get the opportunit. to detect new errors and inconsistencies that are reported for subsequent correction.

The methodolog. is simple and based exclusivel. on freel. available tools such as Open/Libre Offce, NotePad++ and FireFox. In the following parts, we will brief.

present the necessar. steps of the methodolog. to transform one format to another.

For more information, it is possible to refer to the technical manual stored on the DiLAF website (see the "Méthodologie" section of the "Projet" page). In the following section, the methodolog. steps necessar. in order to obtain each format will also be explained.

The cop. format

The cop. format is a structural cop. of the published dictionar. in a valid XML format: the nature of each information part is identifed and pieces of information are bracketed b. XML markups according to this nature: it could be a part-of-speech, a defnition, an example, etc. The transformation of the published dictionar. to the cop. format is performed b. lexicographers with the support of NLP experts. This step requires the resolution of man. problems, including the conversion of special characters to Unicode, the identifcation of each information part, the defnition of a set of markup tags and fnall. the explicit tagging of information b. adding tags (Mangeot & Enguehard, 2013).

In order to bracket each information part composing an entr. (defnition, lexical label, phonetic, s.non.ms, translations, etc...), a set of elements must be chosen. This raises the question of the choice of the language used for the elements. English, the international language of research ma. be favoured. But in man. cases, it is not present in the dictionaries. Furthermore, it is not mastered b. all linguists working on the project. In the case of under-resourced language computerization projects, it is important to encourage partners to use terms in their own language (or mother tongue) to defne the names of the elements. This ma. eventuall. lead to the creation of new terms that did not exist in these languages and contribute to the transfer of knowledge and ideas and, consequentl., to scientifc and technological development [START_REF] Diki-Kidiri | Multilinguisme et politiques linguistiques en Afrique. Colloque Developpement durable, leçons et perspectives[END_REF]. From a political point of view, it participates in moving awa.

from a post-colonial vision of the social status of these languages and contributes to their valorization.

For example, Table 3 shows the element names chosen for the Kanuri-French dictionar. (Programme de soutien à l'éducation de base, 2004) in the DiLAF project: The basic unit constituting an article ma. var. from one dictionar. to another: the lexeme (lemmatised surface form without part-of-speech), the vocable, etc. When the basic unit is the vocable, homon.m vocables have multiple entries. It is necessar. to distinguish these entries in order to indicate possible links (s.non.m., homon.ms, etc.) between them. It is also necessar. to identif. each word sense of an article. It is therefore necessar. to build a unique identifer for each article and each word sense in an article. When the nomenclature choices have not been respected throughout the dictionar., it is sometimes also necessar. to perform certain changes in the nomenclature: merging two articles, for example when word senses of the same vocable have been described in two different articles; splitting an article into two, for example when an article includes two different parts-of-speech, etc. Finall., within the microstructure, restructuring is sometimes required, such as moving morphological information described in a semantic block to the form block.

These treatments are performed b. perl programs. Markup tag names are preserved from the cop. format.

Depending on the goals of the project, especiall. if there is a target format, the central format can be frozen and proposed for download without further modifcation. It represents the standardized electronic version of the published dictionar..

A detailed example of a Kanuri entr. in central format is available in Annex 2.

The target format

The target format is specifc to each project. Each target format is defned from the needs of a project. The central format is then converted automaticall. into the target format.

The resources in central formats are electronic versions of printed dictionaries, mainl. monolingual or bilingual. The use of computers has helped to overcome the constraints of the paper form. The impossibilit. of inverting bilingual dictionaries led to a model having a "pivot" consisting of an axis (interlingual meanings). This leads to the defnition of new macrostructures based on this pivot such as Papillon [START_REF] Mangeot | Construction collaborative de données lexicales multilingues, le projet Papillon. (Papillon, a project for collaborative building of multilingual lexical resources)[END_REF] and Pivax macrostructures [START_REF] Zhang | Jibiki-LINKS: a tool between traditional dictionaries and lexical networks for modeling lexical resources[END_REF]. Several lexical resources can be used and merged to enhance the qualit. and add information that is not available in the converted resource. The result is a new resource that will then be corrected and completed online b. voluntar. or paid contributors.

For example, in the case of the French-Khmer dictionar. of the MotÀMot project [START_REF] Mangeot | MotàMot project: conversion of a French-Khmer published dictionar. for building a multilingual lexical s[END_REF], the French volume has been completed with information from two other existing resources: the pronunciation of the entries was taken from the FeM dictionar. and the list of French entries from the GDEF dictionar. (taken from the Morphalou lexicon, taken from the TLFi).

In the future, the target format will be the onl. one to evolve. It can then be uploaded onto an online lexical resource management platform in order to be readable and editable online b. lexicographers who will be able to correct and enhance it directl. Nevertheless, there is still an important issue: the data categories. In order to be 100% compliant with the LMF standard, the data categories such as the list of parts-ofspeech must follow the ISOcat Data Categor. Registr. (DCR) 8 . We encountered parts of speech that are missing such as "ideophone", appearing in the list of parts of speech in Hausa and Kanuri dictionaries. Thus, it appears necessary to enrich this list or to allow a modular definition of this list with a sublist for each language.

A detailed example of a Kanuri entry in LMF syntax format is available in Annex 3.

Linked data is a set of strongl. interconnected graphs. In the case of data coming from dictionaries, the graphs are lexical networks where nodes represent the lexemes of one or more languages, and links represent the relationships between these lexemes (translation, s.non.m., etc.). A lexical network can be monolingual or multilingual.

Although lexical networks have man. advantages, the. are not suitable for all usages.

Usuall., the. are not browsable in alphabetical order. But we need that possibilit. to have an idea of the content of a lexical repositor., whatever its nature. On the other hand, in a lexical network, the concept of volume is missing, which prevents the creation of a resource in a simple wa. when stud.ing a new language. When importing previousl. existing dictionar. data into a lexical network, the editorial responsibilit. of the dictionar. editors is also lost. Most of the time, there is no guarantee of qualit., nor a clear view of which entr. should be in the network or not.

Once again, while it is important to produce linked data in order to provide machines with eas. access to our data, this should not be directl. used as a working format.

In order to produce linked data, the ideal export format is the lemon model 9 . It is very close to LMF [START_REF] Eckle-Kohler | lemonUb. -a large, interlinked s.ntacticall.-rich lexical resource for ontologies[END_REF]. Apart from slight modifications for some element names, the biggest difference is the word senses. In LMF, there is a fixed set of senses whereas in lemon, each word sense is linked to an ontology concept. In the case of LMF, the semasiologic (from word to meaning) approach has been chosen whereas in the case of lemon, the onomasiologic one (from concept to word) has been chosen. In the case of bilingual dictionaries or multilingual databases, we prefer to follow the semasiologic approach and use axes (interlingual acceptions) instead of concepts in order to link word senses of different languages [START_REF] Mangeot | Construction collaborative de données lexicales multilingues, le projet Papillon. (Papillon, a project for collaborative building of multilingual lexical resources)[END_REF]. This is the choice adopted by dbnary 10 (Sérasset, 2014), the team database for linked data.

5 Web access via a resource management platform

DESCRIPTION OF THE PLATFORM

Jibiki [START_REF] Mangeot | Dictionar. building with the Jibiki platform: the GDEF case[END_REF][START_REF] Mangeot | Dictionar. Building with the Jibiki Platform. Software Demonstration[END_REF] is a generic platform for handling online lexical resources with user and group management. It was originally developed for the Papillon Project. The platform is programmed entirely in Java based on the "Enhydra" environment. All data is stored in XML format in a Postgres database.

This website mainly offers two services: a unified interface for simultaneous access to many heterogeneous resources (monolingual or bilingual dictionaries, multilingual databases, etc.) and a specific editing interface for contributing directly to the dictionaries available on the platform.

Several lexical resource construction projects are using this platform successfully for consultation or edition (DiLAF 2 , GDEF 11 , Jibiki.fr 12 , MotÀMot 1 , Papillon 6 , Pivax 13 ).

The source code for this platform is freely available for download from github 14 . A docker image is also available 15 . In order to import a resource into the Jibiki platform, it has to be described in XML metadata fles. The dictionar. metadata (authors, dates, licence, etc.) and macrostructure (languages, volumes, links between volumes) are described in the dictionar. metadata fle. Each volume and microstructure is described in a separate volume metadata fle.

IMPORTING

The entr. microstructure of each volume is described using common pointers identif.ing the same kind of information (entr., entr. id, headword, pronunciation, part-of-speech, defnition, domain, word sense, translation, translation link, example, etc.). These CDM pointers use the XPath standard. The. allow the resource to be handled without an. format conversion that would involve a loss of information.

An HMTL interface simplifes the creation of the metadata fles. The dictionar. the user via an HTML interface.

When the metadata fles are read., the resource can be automaticall. imported into the Jibiki platform. It is then instantl. accessible for lookup and editing.

ONLINE LOOKUP AND EDITING

Lookup interfaces

Three different interfaces are available to the user:

-the generic lookup allows the user to look up a word or a prefx of a word in all the dictionaries available on the platform. The language of the word must be specifed.

-the volume lookup allows the user to look up a word or prefx on a specifc volume.

In the left hand part of the result window, the volume headwords are displa.ed, sorted in lexicographical (alphabetical) order. An infnite scroll allows the user to browse the entire volume. In the right hand part of the window, the entries previousl.

selected on the left are displa.ed.

-the advanced lookup is available for complex multi-criteria queries. For example, it is possible to look up an entr. with a specifc part-of-speech, and created b. a specifc author. On the left of the result window, the headwords of the matching entries are displa.ed, sorted in alphabetical order. A scroll bar allows the user to browse all the matching entries. On the right, the entries previousl. selected on the left are displa.ed.

Editing process

The editing module [START_REF] Mangeot | Online Generic Editing of Heterogeneous Dictionar[END_REF]) is based on an HTML interface model instantiated with the lexical entr. to be published. The model is generated automaticall. from an XML schema describing the entr. structure. It can then be modifed to improve the rendering on the screen. Therefore, it is possible to edit an.

t.pe of dictionar. entr. provided that it is encoded in XML.

THE DILAF METHODOLOGY AND WEBSITE

Until now, we have focussed this article on the conversion methodolog., but the DiLAF methodolog. is not limited to these technical subjects. It also includes the constitution of some documentation concerning each dictionar. (a minima: origin of the dictionar., alphabet, parts of speech list, markup list) and the chosen licence. This documentation and the publication of our methodolog. is central to the scientifc qualit. of the dictionaries.

We have applied our methodolog. to several dictionaries. It appears that the best results are obtained when a linguist and a computer scientist cooperate closel.. This multidisciplinar. work leads to scientifc questioning and discussions and is also a good opportunit. to detect inconsistencies that ma. occur in dictionaries. With such a team a dictionar. can be converted and documented within one month of work. We stress that this methodolog. has been successful in converting entire dictionaries.

For the moment, the DiLAF website available at dilaf.org presents fve dictionaries and their documentation: Bambara, Hausa, Kanuri, Tamajaq, Zarma. These dictionaries were downloaded 260 times between Januar. 2014 and September 2015.

Two additional ones are in progress (Wolof and Fulfulde).

The website is based on the Jibiki platform. People can have a look at the dictionaries or download them (in central format). It has been designed in accordance with our African partners: the interface is simple, free and designed to be used without an.

technical skills. We can see in Figure 4 that the website displa.s all the entries of the dictionar. on the left hand side in order to incite the user to discover words s/he does not know, as a person usuall. does when leafng through a paper dictionar..

Conclusion

Faced with the lack of online, free, and good qualit. resources for under-resourced languages, we searched for an approach to help to transform the vicious circle caused b. this shortage into a virtuous one.

We found that some good qualit. dictionaries are produced b. local linguists or lexicographers, but that this knowledge usuall. remains unavailable online. We decided to carr. out some research that could meet two objectives. First, we developed a methodolog. to transform a good qualit. dictionar. (linguisticall.

speaking) into an online resource that could be useful to both NLP specialists and populations. This methodolog. was designed to use onl. free tools and limited knowledge and to be off line. It is written simpl. (in French), in order to achieve the second goal: to make it possible for non-NLP specialists to put new dictionaries online. In addition, b. following this methodolog., people would learn new pieces of knowledge the. are not familiar with: using regular expressions, designing a DTD for an XML document, checking and correcting some non Unicode characters, etc.

In a context of povert. where speakers often have never seen a dictionar. of their language, but where access to the Web is improving, the benefts for the population are considerable. Furthermore, the visibilit. of the results is an additional motivation for those involved in the conversion process.

The converted dictionaries are incomplete, and corrections are needed. However, the. Structuring elements in red were added during conversion from cop. format.

Appendix 3: Kanuri entry bannadu (2) in LMF syntax

<LexicalEntry id="bannadu2"> <Lemma> <feat att="writtenForm" val="bannadu"/> <feat att="phoneticForm" val="bànnàd̠ ú"/> </Lemma> <feat att="partOfSpeech" val="kkye3."/> <Sense id="1"> <Equivalent> <feat att="language" val="fra"/> article with identifier written form phonetic part of speech equivalent in French <feat att="writtenForm" val="éduquer(mal)"/> </Equivalent> <Definition> <feat att="writtenForm" val="Diwiro yal alamdu."/> </Definition> <Context> <TextRepresentation> <feat att="language" val="kau"/> <feat att="writtenForm" val="Gǝnanjun bannaje, ku tadanju rakce kǝlanju rojiwawo."/></TextRepresentation> <TextRepresentation> <feat att="language" val="fra"/> <feat att="writtenForm" val="Durant son jeune âge il l'a mal éduqué, aujourd'hui son fils n'arrive pas à se prendre en charge."/> </TextRepresentation> </Context> <SenseRelation targets="là̠ nd̠ ú"> <feat att="type" val="synonym"/> </SenseRelation> </Sense> </LexicalEntry>

  , started in the late 1990s, was completed in 2006 b. a small group of computer scientists gathered in the "Pa.s Perdu" NPO created b. Denis Richer, a French ethnolinguist established in Siem Reap (Cambodia). This frst version of the dictionar. was published in spring 2007 and has 13,249 entries. Each entr. is composed of a French headword, in some cases a part-of-speech and a list of word senses. Each word sense has a gloss in French and a translation in Khmer. The Khmer translation is noted in International Phonetic Alphabet and not in Khmer writing. The dictionar. was originall. encoded in Word format. An example of the original fle can be seen in Figure 1. 2.2.2 The Bambara-French dictionar.

  ampersand & is redrawn as t with a dot below ṭ of the Tamajaq alphabet in the 'Albasa Tamjq' font, as d with a hook of the Hausa alphabet in the ɗ 'AlbasaRockwellhau' and 'Hausa' fonts and as open e of the Bambara alphabet in the ɛ 'Times New Bambara' and 'Arial Bambara' fonts. It ma. also happen that different fonts have identical names. Finall., the same character ma. be used within the same document to displa. different gl.phs. For example in the Tamajaq-French bilingual dictionar. (Programme de soutien à l'éducation de base, 2007), the p lowercase character (U+0070) was used as such in the parts of the entries in French, and redesigned as a schwa ə in the 'Tamajaq Literac.2 TT20.4 SILSop' font for the Tamajaq parts.

Figure 2 :

 2 Figure 2: Tamajaq lexical entry "ǎṣaruf" in published format then in Unicode format

  These subtle differences can hardl. be processed b. software and require that digraphs appear as a proper sign in the Unicode repertoire. Some used b. other languages are alread. there, sometimes under their different letter cases: 'DZ' (U+01F1), 'Dz' (U+01F2), 'dz' (U+01F3) are used in Slovak; 'NJ' (U+01CA), 'Nj' (U+01BC), 'nj' (U+01CC) in Croatian and for transcribing the letter " Њ " of the Serbian C.rillic alphabet, etc.

the

  OpenOffice Writer software (3.2.1 version) fails in transforming 'ɍ' to 'Ɍ' from lowercase to uppercase or vice versa (the character remains unchanged) while Notepad++(5.8.6 version) fails in transforming 'ǰ' to 'J'.4 Conversion process into a standardized format4.1 LEXICOGRAPHIC FOUNDATIONSFor recovered dictionaries (such as the DiLAF project, see the central format below), we do not know exactl. which lexicographical choices led to the nomenclature and microstructure. In the DiLAF project, the aim is to make existing resources available to the public. The initial lexicographical choices of the authors are therefore virtuall.unchanged. Lexicographical order is implemented b. a specifc function directl. on the database following the orders defned b. the alphabets of the concerned languages; The macrostructure is not altered: each paper volume is represented b. an electronic volume;

Figure 3 :

 3 Figure 3: Conversion process

3.

  Tagging each information part b. converting the XML with regular expressions. This part is the most important one and takes up most of the conversion time. One must recognize how each information part is tagged and replace those tags b. the new tag set defned previousl..4.Checking the validit. of the result fle. First, the well-formedness of the XML fle must be checked. A simple web browser can be used for this task, as long as it gives the line numbers where the errors are located. Once the fle is well formed, the structural validit. can be checked. Before this step, it is necessar. to specif. the structure of the cop. format (either with a Document T.pe Defnition or an XML schema). Then an XML parser is used to check the validit.. Annex 1 shows the result of the conversion process from the published format to the cop. format for a Kanuri entr.. When a frst valid version of the cop. format is available, various checks are made using programs (counting the number of occurrences of each tag, checking the embeddedness of the markups, counting the number of closed list values such as parts of speech, etc.) and errors are reported to lexicographers, who can make the corrections. The cop. format does not alter the structure nor the order of the information of the original format, but improves readabilit. b. explicitl. labelling ever. information part. Finall., it is designed to disappear in favor of the other formats.4.3.3 The central formatThe central format respects the normative core of LMF. Consequentl. the original order of the information (that was still kept in the cop. format) is changed. The structure of the entries follows the LMF meta-model but the tag names do not necessaril. follow the informative part of LMF. It is obtained b. appl.ing an XSLT program that performs structural changes on the cop. format. During this step, it is sometimes necessar. to clarif. the nomenclature.

  (b. adding new lexical entries, adding various information, translations, examples, etc..). It would then be eas. to generate a new export format dictionar. b. processing again the appropriate program on the target format dictionar.. 4.3.5 Export formats Export formats depend also on the needs of each project. But, as the central format respects the LMF normative part, it is eas. to generate a format that follows the s.ntax of the informative part of the LMF standard. It is obtained b. processing the central format with an XSLT program. The transformations are limited to changing the name of an element, to add an additional level with a child element, and to convert a text node into an attribute value.

  metadata fle is flled in b. hand. The volume metadata fles are automaticall. generated b. a program that anal.ses the XML data and produces several description fles (number of entries, CDM pointers, XML schema of an entr., XSL st.lesheet, XML template for an empt. entr., etc.). The information can then be corrected b.

Figure 4 :

 4 Figure 4: The entr. "bannadu" on the DiLAF website

Table 2 :

 2 Hausa and Kanuri digraphs missing in Unicode 3.5 CHARACTERS WITH DIACRITICS

  Therefore, lexicographers prefer to use the <entryFree>, but it is too loose to allow effective standardization and exchange of data encoded using the TEI.TEI has had real success in encoding corpora. This is unfortunatel. not the case for

dictionaries. The proposed solution (dichotom. between the <entry> and <entryFree>) is not satisfactor.. As a consequence, ver. few dictionaries are encoded with TEI.

4.2.2 Lexical Markup Framework: the normative part

Lexical Markup Framework

[START_REF] Romar | Standards going concrete: from LMF to Morphalou[END_REF]

is a meta-model separating the lexical parts, grammatical and semantic. The main class is a Lexical Resource. It contains a class that describes the meta-information on the lexicon Global Information and one or more Lexicons. The lexicon contains one or more Lexical Entries. A lexical entr. contains one or more Forms of the entr. and one or more Senses. The forms contain spelling variants Form representations. The senses can in turn contain other senses recursivel.. The. can contain Definitions that contain Text Representations and narrative descriptions or Statements. The Representation class allows one to link different Form Representations and their occurrences in a Text Representation. This meta-model became an ISO standard under the number 24613:2008 in November 2008

Name of the element in Kanuri English equivalent

	bowodu_gade	variant
	mane	cross-reference
	kalma	headword
	bowodu	pronunciation
	naptu_curo_nahauyen	part-of-speech
	maana	definition
	misal	example
	kalakta	translation
	maana_tiloa	synonym
	fǝrǝm	antonym

Table 3 :

 3 Element names chosen for the Kanuri-French dictionar.. The conversion process from the published format to the cop. format consists of four main steps: 1. Retrieving the published format in XML format (either Open Document Format or OpenXML from Microsoft). A text document in Open Document format (.odt) or Open XML (.docx) is in fact a zip archive containing several fles and folders. The core document containing the text must be extracted from the zip archive. For a .odt document, the fle is called content.xml; for a .docx document, the fle is word/document.xml.

2.

Appl.ing an XSL st.lesheet to simplif. the XML. The ODF or OpenXML formats are ver. verbose and diffcult to read. Furthermore, much of the information concerning st.les is not useful for the conversion process.

Therefore, a frst simplifcation of the XML can be made with an XSL st.lesheet. More precisel., the "text:p" elements are replaced b. "p" elements, and "text:span" elements are replaced b. the value of the "text:st.le-name attributes; headers, sections, columns breaks and page breaks are removed.

  A RESOURCE ON THE PLATFORMThe Jibiki lexical resource management platform is able to handle an. resource provided that it is encoded in XML. Indeed, a s.stem of common pointers in heterogeneous structures can manipulate the resources without changing their structure. Each pointer is indexed in a database and can perform a quick search. This s.stem is called Common Markup Dictionar. (CDM). There are predefned common pointers for lexical items that are commonl. found in most dictionaries. It is also possible to defne specifc pointers for a resource.

Therefore, dictionaries in man. formats can be imported (cop., central, target or LMF formats). It ma. be a structured dictionar. following the recommendations of the TEI, such as the LMF standard, etc.

  are a stepping stone to other developments: bilingual corpus construction; development of morphological anal.zers; etc. The availabilit. of these resources can motivate new researchers, and thus increase the potential for research.Informative elements in green were added during conversion from published format.

	<bowodu>[bànnàd̠ ú]</bowodu> <naptu_curo_nahauyen>kkye3.</naptu_curo_nahauyen> <maana>Diwiro yal alamdu.</maana> <misal> <version tǝlam="ka">Gǝnanjun bannaje, ku tadanju rakce kǝlanju rojiwawo.</version> <version tǝlam="fa">Durant son jeune âge il l'a mal éduqué, aujourd'hui son fils n'arrive pas à se prendre en charge.</version> </misal> <maana_tiloa>là̠ nd̠ ú</maana_tiloa> <kalakta tǝlam="fa">éduquer (mal)</kalakta> </article>	phonetic part of speech definition example example in Kanuri equivalent of example in French synonym equivalent in French	the
	Appendix 2: Kanuri entry bannadu (2) in central format
	<article id="bannadu2"> <bloc-vedette> <kalma lamba="2">bannadu</kalma> <bowodu>bànnàd̠ ú</bowodu> </bloc-vedette> <naptu_curo_nahauyen>kkye3.</naptu_curo_nahauyen> <bloc-semantique id="bannadu2.1"> <kalakta tǝlam="fra">éduquer(mal)</kalakta> <maana>Diwiro yal alamdu.</maana> <misal> <version tǝlam="kau">Gǝnanjun bannaje, ku tadanju rakce kǝlanju rojiwawo.</version> <version tǝlam="fra">Durant son jeune âge il l'a mal éduqué, aujourd'hui son fils n'arrive pas à se prendre en charge.</version> </misal> <maana_tiloa>là̠ nd̠ ú</maana_tiloa> </bloc-semantique> </article>	article with identifier lexical entry number 2 phonetic part of speech equivalent in French definition example example in Kanuri equivalent of the example in French synonym

Acknowledgements

The MotÀMot project that produced the French-Khmer dictionar. has been partl. funded b. the Agence Universitaire de la Francophonie. We thank especiall. Vanra Ieng.

The DiLAF project that produced the Bambara-French, Hausa-French, Kanuri-French, Tamajaq-French and Zarma-French dictionaries has been funded b. the Fonds Francophone des Inforoutes of the International Organization of Francophonie.

We thank especiall. Soumana Kané, Issouf Modi, Michel Maï Moussa Maï, Mahamou Raji Adamou, Rakiatou Rabé, Mamadou Lamine Sanogo.

The ALFFA project that produced the Fulfulde-French dictionar. is funded b. the French National Agenc. for Research (ANR). We thank especiall. Mariam Barr. and Alicia Boucard.

We would like to stress here the fact that although Jibiki provides all the tools necessar. for a correction/revision/validation process of the data online, it is completel. illusor. to imagine that the qualit. of a dictionar. will be improved b. allowing potential voluntar. contributors to act alone.

First, a real project must be defned with a communit. animator, a group of editors and validators must be selected based on their skills, and especiall. contributors must be motivated.

Second, the success of Wikipedia might lead us to think that the same can be obtained for the construction of a qualit. dictionar., but various experiences have shown us that it is not the case.

We also quote Larr. Sender, founder of Wikipedia on the subject: "To tr. to develop a dictionar. b. collaboration among random Internet users, particularl. in a completel. uncontrolled wiki format, now strikes me as a nonstarter."

Each Wikipedia article can be written b. a specialist in his or her feld, but for a general dictionar., it is not possible to fnd a specialist for some articles onl.. Onl. linguists who are specialists in the language as a whole can reall. help (after being trained in lexicograph.). Moreover, in the case of under-resourced languages, linguists who are specialists in these languages are few and far between. The. are often ver. bus. and cannot work on a project if not fnanced.

Remote access via an API

Once dictionaries are uploaded onto the Jibiki server, the. can be accessed via a REST API. Lookup commands are available for quer.ing indexed information: headword, pronunciation, part-of-speech, domain, example, idiom, translation, etc.

The API can also be used for editing entries. The user must be previousl. registered on the website.

Appendix

Appendix 1: Kanuri entry bannadu (2) in copy format <article> <kalma lamba="2">bannadu</kalma> lexical entry number 2


Hadrien Tournaire

Franck Renaud

Jean-Luc Dion

A REDUCTION METHODOLOGY USING FREE-FREE COMPONENT EIGENMODES AND ARNOLDI ENRICHMENT

In order to perform faster simulations, the model reduction is nowadays used in industrial contexts to solve large and complex problems. However, the efficiency of such an approach is sometimes cut by the interface size of the reduced model and its reusability.

In this article, we focus on the development of a reduction methodology for the build of modal analysis oriented and updatable reduced order model whose size is not linked to their contacting interface. In order to allow latter model readjusting, we impose the use of eigenmodes in the reduction basis. Eventually, the method introduced is coupled to an Arnoldi based enrichment algorithm in order to improve the accuracy of the reduced model produced.

In the last section the proposed methodology is discussed and compared to the Craig and Bampton reduction method. During this comparison we observed that even when not enriched, our work enables us to recover the Craig and Bampton accuracy with partially updatable and smaller reduced order model.

INTRODUCTION

The iterative design of a system involves several validation simulations that may slow its conception process. Moreover, in such a context, the required accuracy and detail level is expected to provide a model whose significant size leads to time consuming simulations.

Nowadays substructuring and reduction methods like the superelements or the Craig and Bampton method as instances are industrially used to solve large and complex structural dynamic problems and to cut simulation time.

In a design context, the Mac Neal and Rubin reduction methods are particularly interesting since they use substructures eigenmodes. Indeed, the use of free-free component modes enables to evaluate the contribution of each part into the global dynamics of a system. This may contain interesting information for the design of a system in terms of dynamic behavior. Furthermore, using eigenmodes enables to build updatable models that do not have to be entirely rebuilt when the relative position of a component is changed. Eventually, the use of these modes also allows to perform model readjusting.

Despite their numerous qualities, the Mac Neal and Rubin methods such as Craig and Bampton are facing limitations since they lead to reduced models whose size depends on the substructures contacting interfaces. As a results, this can lower the interest of a reduction approach when working on heavy models.

Several researches have been led to overcome these weaknesses. As an example, methodologies to improve the reusability of the Craig end Bampton basis by enrichment were performed [START_REF] Ellenbroek | A hybrid design optimization method using enriched Craig Bampton approach[END_REF], [START_REF] Cogan | Component mode synthesis (CMS) based on an enriched Ritz approach for efficient structural optimization[END_REF]. Rixen proposed a dual Craig and Bampon method using free-free eigenmodes [START_REF] Daniel | A dual Craig and Bampton method for dynamic substructuring[END_REF] and an additional contribution that aimed at reducing the number of interface mode [START_REF] Daniel | Interface Reduction in the Dual Craig-Bampton method based[END_REF].

We suggest here an alternative methodology providing reduced order model whose size is not linked to the contacting interface. The research of reusability for the reduced order model and the use of free-free eigenmodes in the reduction basis are conjointly performed. In a last stage, an Arnoldi based enrichment algorithm for a selective improvement of the model solutions is used.

NOMENCLATURE

Quality criterion of a reduced order model

The quality estimation of a reduced order model can be done thanks to several tools, some of them are summarized in [START_REF] Bobillot | Méthodes de réduction pour le recalage, application au cas d'Ariane 5[END_REF]. The selection of the quality criterion should be done in regard to the aim of the simulation.

Here the reduction is performed to faster the modal analysis of a structure, so that the Modal Assurance Criterion (MAC) is favored. Indeed, this indicator is geometric and enables to quantify the collinearity of two vectors. When dealing with vectors families U = [u 1 … u n ] and V = [v 1 … v m ] the terms of the associated MAC matrix of dimension n × m are defined as:

MAC i,j = mac(u i , v j ) = |u i T * v j | 2 u i T * u i ̅ * v j T * v j ̅
Where u ̅ is the conjugate of a vector u. Thus the quality of each solution of the reduced model is estimated by a MAC comparison with corresponding solutions of the non-reduced model.

Reduction methodology

Let us consider a system Σ made of two components Σ 1 and Σ 2 tied to each other on their contacting interfaces Γ 1 and Γ 2 of the two components. For the sake of simplicity the two meshes of the contacting interfaces are taken as coherent and the interfaces DoF j 1 and j 2 are sorted so that they exactly match in both FE characteristic matrix. The interior DoF of the components are noted i 1 and i 2 .

In order to get coherent displacement fields on the contacting interface the first step of our work consists in primarily assemble both components so that the deformation continuity is imposed in a strong manner. Indeed, dual assemblies rely on the force continuity that may cause displacement jumps on the contacting interfaces. The dynamic stiffness of the assembled system Z(ω) can be split into an elastic dynamic stiffness Z E (ω) that is block diagonal and an interaction stiffness matrix Z I (ω) that is mostly sparse so that:

Z(ω) = Z E + Z I Z(ω) = [ Z 1,ii Z 1,ij Z 1,ji Z 1,jj 0 0 0 0 0 0 0 0 Z 2,ii Z 2,ij Z 2,ji Z 2,jj] + [ 0 0 0 Z 2,jj 0 0 Z 2,ji 0 0 0 Z 1,ji 0 0 0 0 Z 1,jj]
The reduction of such a model with a basis ϕ f only made of free-free eigenmodes ϕ 1 and ϕ 2 lead to reduced model exclusively working for very low frequencies [START_REF] Vermot | Frequency and time simulation of squeal instabilities[END_REF]. Thus, additional reduction vectors ϕ c called coupling vectors have to be taken into account to enable recovering the system behavior on a more spread frequency bandwidth. From now, the hunted reduction basis T have the following structure:

T = [ϕ f ϕ c ]
In order to increase the numerical conditioning of the reduced order model the coupling deformations ϕ c are orthogonalized to the free-free eigenmodes ϕ f using a Gram-Schmidt algorithm.

Interface reduction using the eigenmodes interface deformations

In the previous section the use free-free eigenmodes ϕ f to reduce the model was not satisfying, indeed this involves no global deformation of Σ 1 and Σ 2 simultaneously. Moreover, this projection of the coupled components on an uncoupled deformation basis may lead to interface discontinuities. In order to improve the displacement field accuracy on the interface a first method consist in imposing to each component the interface displacement field that are contained in the eigenmodes of the other component. The deformation of a k-component Σ k whose contacting interface Γ k is submitted to the deformations of a pcomponent Σ p are written Θ k/p :

T = [ ϕ 1,i 0 ϕ 1,j 0 Θ 1/2,i 0 Θ 1/2,j 0 0 ϕ 2,i 0 ϕ 2,j 0 Θ 2/1,i 0 Θ 2/1,j]
Where the deformations Θ k/p,j are in fact equal to the interface deformation found in the eigenmodes of the pcomponent ϕ p,j . The deformations on the interior DoF of the components are computed using:

{ Θ 1/2,i = -Z 1,ii -1 * Z 1,ij * ϕ 2,j Θ 1/2,i = -Z 2,ii -1 * Z 2,ij * ϕ 1,j
In order to improve validity of the reduced order model it is interesting to use several coupling deformations computed for different given circular frequencies ω 1 , ω 2 ,…,ω n . In spite of this, the size of the basis T may fast increase and its conditioning may collapse, especially if the circular frequencies ω 1 , ω 2 ,…,ω n are closed.

The coupling vectors presented below enable to get interesting results in terms of MAC but the associated reduced model may be consequent in terms of size, depending on the number of truncated modes in the basis ϕ 1 and ϕ 2 . In order to increase the compactness of the basis T we use the Rayleigh coefficient to filter the coupling deformations that are remote from the studied frequency bandwidth.

The Rayleigh coefficient root's r of a coupling deformation Θ k/p is computed using the characteristic matrix associated to the k-component, so that:

r = √ Θ k/p T K k Θ k/p Θ k/p T M k Θ k/p
Eventually, the coupling deformations are selected in regard to their Rayleigh coefficient. Indeed, the more a Rayleigh coefficient closed to the studied waveband is, the more the associated coupling vector is interesting for the model reduction.

Interface reduction using a singular value decomposition of the eigenmodes interface displacements (proposed methodology)

Another approach for the interface reduction consists in building a common interface displacement space T j for both components and simultaneously imposing these deformations to both components Θ T j . We suggest here the use of the singular value decomposition (SVD) for the build of the interface displacement basis:

T j = SVD(ϕ 1,j , ϕ 2,j )

Like in the previous method, the coupling deformations are computed for different circular frequencies using the analog formula:

{ Θ T j ,1 = -Z 1,ii -1 * Z 1,ij * T j Θ T j ,2 = -Z 2,ii -1 * Z 2,ij * T j
Once again, it is interesting to compute these deformations for several pulsations. Here the selection of the coupling deformations is performed according to the singular value associated to the interface deformations computed with the SVD. Indeed the higher singular values are associated to the deformations that best engender the interface deformations observed in the eigenmodes.

Estimators for the quality of reduce model solutions

Once built, the quality of a reduced order model has to be estimated. In our context the use of the MAC is not possible since we try to pass by the heavy computation of the high fidelity model (HFM) solutions.

Several indicators were developed for an a priori accuracy evaluation of a model solution, some of them are presented in the following works [START_REF] Balmès | Modèles expérimentaux complets et modèles analytiques réduits en dynamique des structures[END_REF], [START_REF] Bobillot | Méthodes de réduction pour le recalage, application au cas d'Ariane 5[END_REF]. In our case we decided to use the following force based indicators:

ε i = ‖R f (ϕ ̃i)‖ K 2 ‖Kϕ ̃i‖ K 2 using the scalar product ‖g‖ K = g T Kg
Where R f (ϕ ̃i) is the residual force associated to the i th solution couple (ω ̃i 2 , ϕ ̃i) of the considered reduced model. Indeed, contrary to the displacement based indicators, a timeexpensive inversion of the stiffness matrix K is avoided here.

Each solution ϕ ̃i whose indicators reach a given tolerance ε tol is considered as poor and then enriched by an Arnoldi based algorithm that leads to construction of the new basis T. Once enriched, the solutions of the newly reduced model are computed and their quality indicator are evaluated once again.

In practice, each poor solution is enriched using n Arnoldi vectors that may fast lead to consequent reduction basis. Thus, the evaluations of the model solutions are expected to slow since the size of the reduce models tend to increase. To avoid this we use a restart step that consists in using the model solution in addition to the Arnoldi vectors to reduce the model Figure . 1.

Eventually, the coupling vectors computed in the loop are orthogonalized to the free-free eigenmodes and added to them that gives the reduction basis T.

Update of the reduction basis

Unlike the Craig and Bampton method, the modification of the relative position of the contacting surface has a limited Figure 1.: Enrichment algorithm implementation impact on the reduction basis. Indeed, it only affects the coupling deformations. This explains why it is interesting to also build a database with containing both coupling and free-free deformations ϕ l , Θ k/p,j and/or Θ T j of the component in order to faster the rebuild of the initial reduction basis T and then enrich it.

It has however to be noticed that in the case of a structural modification of a component, the proposed methodology do not offer any advantage compared to the Craig and Bampton method.

Application of the reduction methodology

In order to support our purpose we apply the methodology previously described to a study case made of two simple parts. The parts of the model are linear and considers small deformations, their properties can be associated to those of a steel. The two parts are embedded and studied on a bandwidth Δf between 0 and 3000 Hertz that contains 41 eigenmodes. The two interface reduction methods are compared themselves and with the Craig and Bampton method since it is a common method often considered as a reference in substructuring and that is already implemented in industrial codes like NASTRAN or CODE_ASTER.

Application of the Craig and Bampton method

Here, the tied interface eigenmodes used are taken in the frequency range between [0; 4000] Hertz (54 modes) while the interface deformations are computed for a null pulsation (321 vectors).

Application of the interface reduction methods

For the interface reduction methods, the free-free eigenmodes considered are taken below 3000 Hertz (47 modes). In order to get a rich model we computed the coupling deformations at the start, middle and end of the bandwidth (0, 1500 and 3000 Hertz).

The coupling deformations obtained using the SVD are selected by associated singular value. On Figure 3, the plot of the singular values of the interface deformation led us to only consider the singular values equal or higher than 0.2, this eventually lead to 126 coupling deformations.

In order to get reduction basis of the same size for the two methods, only the coupling vectors associated to the 126 th smallest Rayleigh coefficients are taken into account for the firstly introduced interface reduction method.

As is it visible on Figure 4.b, the first interface reduction method provides rather good results for most of MAC but its conditioning is extremely poor that avoid to recover some of the high fidelity modes. This explains why its flexible MAC average collapses to 86.63% only. Indeed, the interface deformations observed in the eigenmodes of both components are rather similar. Moreover the pulsations taken for the computation of the coupling vectors are not remote enough to insure a good orthogonality between these vectors.

Nevertheless, we can observe on Figure 4.c that the method using the singular decomposition of the interface deformations provides very good results in terms of flexible MAC average and compactness. Indeed, compared to the Craig and Bampton method the compactness of the reduction basis is increase by 2 while the model accuracy is improved by 2.44% of MAC average. It can however be noticed that the conditioning of the reduction basis is higher (9069.67) than the one of the Craig and Bampton method (133.65). This loss is mostly brought by the computation of the coupling deformations for too closed frequencies (0, 1500 and 3000 Hz).

Conclusions

The proposed method enable us to get accurate reduction basis for the Arnoldi enrichment. Thus, we expect this enrichment to be quick. The reduced model we build is more compact than those obtained with Craig and Bampton that was one of our first goal.

Although the reduced order model provided by the proposed reduction model is efficient for modal analysis it has to be noticed that its spatial convergence is not guaranteed for forced response simulations, unlike the Craig and Bampton method.

Eventually, the topology of the reduction basis we created is favorable to update if the position of a component is changed.

  Σ k : Component k Γ k : Contacting surface of the k component j k : Junction DoF set of the k component i k : Interior DoF set of the k component k M k : Mass matrix of the k component K k : Stiffness matrix of the k component Z k : Dynamic stiffness of the k component ϕ : Eigenmodes basis (truncated or not) ϕ c : Basis of coupling vectors T : Reduction basis SVD : Singular Value Decomposition ε tol : Tolerance threshold r : Root of the Rayleigh coefficient

Figure 2 .

 2 Figure 2.: Case study used for the test of the proposed methodology. the contacting interface of the component is curved and own 109 nodes (321 DoF)

Figure 4 .

 4 Figure 4.a.: MAC comparison of the flexible model solutions of the HFM and Craig and Bampton reduced model. Number of DoF: 375, mac average: 93.98%. Reduction basis conditioning: 133.65.

Figure 3 .

 3 Figure 3.: Decrease of the singular values obtained by the SVD of the interface deformation observed in the eigenmodes.

Figure 4 .

 4 Figure 4.b. MAC comparison of the flexible model solutions of the HFM and reduced model using θ k/p,j as coupling deformations. Number of DoF: 173, MAC average: 86.63%. Reduction basis conditioning: 1.29e+15.

Figure 4 .

 4 Figure 4.c. MAC comparison of the flexible model solutions of the HFM and reduced model using θ t j as coupling deformations. Number of DoF: 173, mac average: 96.42%. Reduction basis conditioning: 9069.67.

ACKNOWLEDGMENTS

This research work has been carried out under the leadership of the Technological Research Institute SystemX, and therefore granted with public funds within the scope of the French Program "Investissements d'Avenir". In addition, we acknowledge the SNECMA and the LISMMA for their implication and cooperation on the current work.