So-Called “Prepositions” inSomali are Not Prepositions
A Linguistic Approach for Somali POS Tagging

Chihiro Taguchi, Taro Watanabe{taguchi.chihiro.td0, taro}@is.naist.jp
Nara Institute of Science and Technology (NAIST)NLP2021

無限の可能性、ここが最先端 －Outgrow your limits－

1 Introduction●●

4 lexemes in Somali are to be discussed○ u, ku, ka, la (“UKKL” henceforth)
Inconsistency in their linguistic status○ prepositions (Puglielli 1981, Saeed 1993, Morgan 2020)○ prepositional indicators (El-Solami-Mewis 1987)○ adpositional verbal particles (Mansur 1988)○ verbal adpositions (Saeed 1999)

This study provides:● Linguistic finding: they are best analyzed as preverbal applicative particles● Proposal to NLP: more consistency in the universal POS tagging based on linguistics

1NLP2021

無限の可能性、ここが最先端 －Outgrow your limits－

2 Overview: Somali
●

●●

●

2Bio:
○ Somali < Cushitic < Afroasiatic■ cf. Arabic, Hebrew, Amharic (Ethiopia)○ approx. 15 million speakers
Syntax:○ SOV with scrambling○ Rigid word order of VP
Distribution of Somali speakers
Source: Wikimedia CommonsMorphology:○ Nominal: number, gender, case, definiteness○ Verbal: person, number, gender, tense, aspect, mood, polarity, focus
Information structure:○ Focus

NLP2021

無限の可能性、ここが最先端 －Outgrow your limits－

2 Overview: Focus in Somali
cf. Japanese -ga: “Dare-ga kita?” — “Taroo-ga/*wa kita”● Focus by auxiliaries:○ ayaa, baa: focus on the preceding noun
■ Maxamed (baa|ayaa) bariis
cunay.
M.
FOC
rice
ate
“Mohammed ate rice.”○ waxa: focus on the noun after the inflected verb
■ BariiswaxacunayMaxamed.
riceFOC
ate
M.
“Mohammed ate rice” (or “It is Mohammed who ate rice”)● No focus:○ waa■ Maxamed bariis wuu
cunay.
M.
rice AUX.3SG.M
ate3

NLP2021

無限の可能性、ここが最先端 －Outgrow your limits－

2 Overview: u, ku, ka, la●u, ku, ka, la:“for” (benefactive), “in” (locative), “from” (elative), “with” (comitative) respectively●UKKL and the verb must not be intervened:○ Maxamed baa ka yimi Soomaaliya.
M.
FOC from came Somalia○ Maxamed baa Soomaaliyaka yimi.
M.
FOC Somaliafrom came
○ Soomaaliya
Maxamed baaka yimi.
SomaliaM.
FOCfrom came
“Mohammed came from Somalia.”○4

roughly the same meaning*Maxamed baa ka Soomaaliyayimi.
M.
FOC from Somalia
cameungrammatical (intended: “Mohammed came from Somalia.”)
NLP2021

無限の可能性、ここが最先端 －Outgrow your limits－

2 Overview: Ambiguities caused by UKKLs

5●The position of UKKLs’ argument is free as long as it is grammatical○ UKKLs select their argument based on context information●Ambiguity may emerge:○ Cali baa Maxamed i-uA.
FOC M.
me-for“Ali hit Mohammed for me.”“Ali hit me for Mohammed.”

dilay.
hit.

NLP2021

無限の可能性、ここが最先端 －Outgrow your limits－

3.1 UKKLs are not adpositions

6●●Prepositions ⊂ Adpositions
Consider:○ Maxamed baa ka yimi Soomaaliya.
M.
FOC from came Somalia“Mohammed came from Somalia.”●

ka “from” and Soomaaliya “Somalia” are intervened by the verb yimi “he came”○ Produces a crossing tree

NLP2021

無限の可能性、ここが最先端 －Outgrow your limits－

3.2 UKKLs are Applicatives
●
●

●

●

7Applicative: one of verbal voices○ Voices in Japanese: passive (-sareru), middle (Hokkaido dialect -rasaru) , etc.
Applicative promotes an oblique argument to an object (core argument)○ Widely reported in Bantu languages (Africa), etc.
Somali UKKLs play a role of augmenting an object with a particular semantic role
○ u: benefactive (“for”)○ ku: locative (“in”)○ ka: source, elative (“from”)○ la: comitative (“with”)
Example:○ yimi “came”:
monovalent verb, requiring only its subject○ ka yimi “came from”: divalent verb, requiring its subject and source object

NLP2021

無限の可能性、ここが最先端 －Outgrow your limits－3.3 UKKLs are Particles●●●8Linguistic status of UKKLs:○ Verbal prefix, clitic, particle?
Theoretical linguistics may prefer them as verbal prefixes○ Phonogically they are pronounced together
In NLP, it is better to treat them as particles○ one token needs one POS tag○ no POS tag for verbal prefixes, because they are a part of verb
○ yields an uncrossing tree

NLP2021

無限の可能性、ここが最先端 －Outgrow your limits－

4 Universal POS Tags and Dependency Tree9●Universal Dependency (UD):○ universal framework for annotation of grammatical information in different languages○ covers more than 120 languages (as of 2020)○ ongoing project○ Somali is not included●We propose a way of annotating UKKLs in UD based on our linguistic findings

NLP2021

無限の可能性、ここが最先端 －Outgrow your limits－

4 Universal POS Tags and Dependency Tree●

10Example of a manual POS Tagging below:○ PART is tagged to the UKKL ku “in”

NLP2021

無限の可能性、ここが最先端 －Outgrow your limits－

4 Universal POS Tags and Dependency Tree●

11Example of a manually drawn dependency tree below:○ The relation of the predicate (noolyihiin) and the UKKL (ku) is aux○ The feature of the UKKL (ku) is specified as PartType=Loc

NLP2021

無限の可能性、ここが最先端 －Outgrow your limits－

4 Universal POS Tags and Dependency Tree●

12Two new features:○ Valency: specifies the number of the predicate’s core arguments (cf. Senuma&Aizawa 2017)○ Focus: specifies that the token introduces focus■ Its syntactic relation is specified by the arrow

NLP2021

無限の可能性、ここが最先端 －Outgrow your limits－

5 Conclusion
This study has shown:● Linguistic findings:○ u, ku, ka, la are not prepositions (nor adpositions!)○ u, ku, ka, la are either prefix, clitic, or particle, which functions as applicative○ the best candidate is particle for the sake of NLP●

13Proposals:○ for relatively minor languages, UD heavily relies on descriptive linguists○ an example of the Somali UD based on the linguistic findings

NLP2021

無限の可能性、ここが最先端 －Outgrow your limits－

References
●
●
●
●
●
●
●
●
●
●
●
●13Catherine El-Solami-Mewis. Lehrbuch des Somali. Verlag Enzyklopädie, 1987.
Ethnologue, 2019.
Abdalla O. Mansur. Le lingue Cuscitiche e il Somalo. Ministero AA. EE., 1988.
Morgan Nilsson. Beginner’s Somali grammar. 2020. Available at: http://morgannilsson.se.
Martin Orwin. Colloquial Somali. Routledge, 1995.
David A. Peterson. Applicative constructions. Oxford University Press, 2007.
Annarita Puglielli. Sintassi della lingua somala. Ministero AA. EE., 1981.
John I. Saeed. Somali reference grammar (2nd ed.). Dunwoody Press, 1993.
John I. Saeed. Somali. John Benjamins B.V., 1999.
Daisuke Shinagawa. A grammatical sketch of Chaga-Rombo (Bantu E623). Research Institutefor Languages and Cultures of Asia and Africa, 2014.
Universal POS Tags, 2020. https://universaldependencies.org/pos.
Arnold M. Zwicky. Clitics and particles. Language, 63(2):283–305, 1985.

NLP2021

無限の可能性、ここが最先端 －Outgrow your limits－

To Do
●
●
●
●
●

●
●
●
●
●
NLP2021

ページ番号の挿入
発表者名（自分の名前）をボールドで示すなどしてわかりやすく
Overview: どの言語に近いのかを示すとわかりやすいかも強調の仕方（ボールド、色分け）に一貫性を持たせる
Focus をわかりやすく説明（日本語では …？）○ 誰が鹿を見ましたか。
■ *太郎は見ました。 / 太郎が見ました。 (focus)
三つの文（scrambling）が permutation のみで同じ意味を示していることを明確にする○ 波カッコを用いるなどCrossing に関して質問が出るかも
NLPではParticleで分析されるべきであることを強調する○ 言語学のツリーとの比較、など
UD, POS では kuの位置をboldにするなどしてわかりやすくする
図のどこに言及しているかをわかりやすくする
無限の可能性、ここが最先端 －Outgrow your limits－