Pierre Godard
email: godard@limsi.fr

Laurent Besacier
email: laurent.besacier@univ-grenoble-alpes.frmartine.adda-decker

François Yvon
email: yvon@limsi.fr

Martine Adda-Decker

Gilles Adda
email: gadda@limsi.fr

Hélène Maynard

Annie Rialland
email: annie.rialland@univ-paris3.fr

Adaptor Grammars for the Linguist: Word Segmentation Experiments for Very Low-Resource Languages

Computational Language Documentation attempts to make the most recent research in speech and language technologies available to linguists working on language preservation and documentation. In this paper, we pursue two main goals along these lines. The first is to improve upon a strong baseline for the unsupervised word discovery task on two very lowresource Bantu languages, taking advantage of the expertise of linguists on these particular languages. The second consists in exploring the Adaptor Grammar framework as a decision and prediction tool for linguists studying a new language. We experiment 162 grammar configurations for each language and show that using Adaptor Grammars for word segmentation enables us to test hypotheses about a language. Specializing a generic grammar with language specific knowledge leads to great improvements for the word discovery task, ultimately achieving a leap of about 30% token F-score from the results of a strong baseline.

Introduction

A large number of the world's languages are expected to go extinct during this century -as much as half of them according to [START_REF] Crystal | Language Death[END_REF] and [START_REF] Janson | Speak: A Short History of Languages[END_REF]. Such predictions have subsequently fostered a growing interest for a new field, Computational Language Documentation (CLD), as it is now clear that traditional field linguistics alone will not meet the challenge of preserving and documenting all of these languages.

CLD attempts to make the most recent research in speech and language technologies available to linguists working on language preservation and documentation (e.g. [START_REF] Anastasopoulos | A case study on using speech-to-translation alignments for language documentation[END_REF][START_REF] Adams | Phonemic transcription of low-resource tonal languages[END_REF]). A remarkable effort in this direction has improved the data collection tools to be used on the field [START_REF] Bird | Aikuma: A mobile app for collaborative language documentation[END_REF][START_REF] Blachon | Parallel speech collection for under-resourced language studies using the LIG-Aikuma mobile device app[END_REF], enabling to collect corpora for several endangered languages [START_REF] Adda | Breaking the unwritten language barrier: The Bulb project[END_REF]. In parallel, the language technology community is investing more efforts to design methodologies tailored for the new challenges posed by the analysis of such linguistic material: the extreme variability of the orthographic representation, the scarcity of annotated data (both written and oral), as well as the modeling of complex tonal systems.

This effort could greatly benefit from a tighter collaboration between the two main research communities involved in this endeavor, which often struggle to cooperate efficiently. Knowledge background differs between linguists and computer scientists; the definition of why a problem is interesting or not may not be the same for the two communities, theoretical and experimental platforms do not intersect much, etc. Consequently, for lack of investing enough energy working on the same problems with the same tools and towards the same goals, we might not achieve the efficiency that is needed, as time is running out for many languages. This view constitutes the underlying motivation of the work reported here.

We pursue two main goals in this spirit. The first one is to improve upon a strong baseline [START_REF] Goldwater | A Bayesian framework for word segmentation: Exploring the effects of context[END_REF] for the unsupervised word discovery task 1 on two low-resource languages, by teaming up with linguist experts. A natural idea to achieve this goal is to engage them in formalizing their linguistic knowledge regarding the languages or language families under study, in the hope that it will compensate for the small amount of available data. In our case, this expertise corresponds to morphological and phonotactic constraints for two Bantu languages displaying very similar structures (see Section 3). For one language, we were also able to elicit a list of prefixes and some additional knowledge regarding the consonantal system. Such expert knowledge can readily be integrated in grammar rules using the framework of Adaptor Grammars (see Section 6). Another interesting property of this framework is its compatibility with two strategies that are usually thought as being mutually exclusive: rule-based learning, still in wide use inside the linguistics community, and statistical learning, prevalent in natural language processing circles.

Our second goal is to study ways to help linguists explore language data when little expert knowledge is available. Our proposal is to complement the grammatical description activity with task-oriented search procedures, that will speed up the exploration of competing hypotheses. The intuition is that better grammars should not only truthfully match the empirical data, but also improve the quality of automatic analysis processes. The word discovery task considered below should thus be viewed as an extrinsic validation procedure, rather than a goal in and of itself. This process might also yield new linguistic insights regarding the language(s) under focus.

To sum up, the main contribution of this paper is a methodology for systematically exploring (a subpart of) the space of possible grammars, refining grammar rules (from the most generic to the most language specific) at four levels of description (see Section 4). This results in a comparison of 162 alternative accounts of the grammar for two languages. Our results (analyzed in Section 5) show that enriching grammar rules with language specific knowledge has a consistent positive impact in performance for the segmentation task. They validate our hypotheses that (a) improved grammatical descriptions actually correlate with better automatic analysis; (b) Adaptor Grammars provide a framework around which linguists and computer scientists can effectively collaborate, with tangible results for both communities.

2 Adaptor Grammars for Word Discovery

Adaptor Grammars

Formal grammars, and notably Context-Free Grammars (CFGs), are a cornerstone of linguistic description and provide a model for the structural description of linguistic objects. Our grammars capture simple aspects of the syntax and some less trivial aspects of the morphological and phonological structures. As discussed below, both levels of descriptions are useful for word discovery.

A CFG is a 4-tuple G = (N, W, R, S) where N and W are respectively the non-terminal and terminal symbols, R a finite set of rules of the form A → β, with A ∈ N and β ∈ (N ∪ W ) * , and S ∈ N the start symbol. Our grammars will be used to analyze the structure of complete utterances and the start symbol S will always correspond to the sentence top-level. Assuming that S, Words, and Word belong to N , the top level rules will typically look like: S → Words; Words → Word Words; Words → Word, the last two rules abbreviated as Words → Word +.

Probabilistic CFGs (PCFGs) [START_REF] Johnson | PCFG models of linguistic tree representations[END_REF]) extend this model by associating each rule with a scalar value θ A→β , such that for each A ∈ N , β θ A→β = 1. Under some technical conditions [START_REF] Zhiyi | Statistical properties of probabilistic context-free grammars[END_REF], PCFGs define probability distributions over the set of parse trees, where the probability of a tree is a product of the probability of the rules it contains. PCFGs can be learned in a supervised way from treebanks or in a unsupervised manner using, for instance, the EM algorithm (Lari and Young, 1990).

PCFGs make unrealistic independence assumptions between the different subparts of a tree, an observation that has yielded many subsequent variations and extensions. Adaptor grammars (AGs) (Johnson et al., 2007) define a powerful mechanism to manipulate PCFG distributions to better match the occurrences of trees and subtrees observed in actual corpora. Informally, an AG is a CFG where non-terminals have the possibility to be adapted: when non-terminal A is adapted, all subtrees rooted in A are "reified", meaning that they are no-longer viewed only as decomposable objects, but can also be manipulated and stored as a whole. In our grammars below, adapted non-terminals are underlined, and optional non-terminals appear between brackets. Following (Johnson et al., 2007), we only adapt non-recursive non-terminals. 2AGs define a framework to implement Bayesian nonparametric learning of grammars, and are usually trained in an unsupervised manner using sampling techniques (Monte-Carlo Markov Chain, MCMC). A typical run will produce, for each sentence, a distribution of possible parses under the grammar, from which we can then retain the most frequent one as the "best" possible analysis.3

Word Segmentation using AGs

In this work, we are interested in the word segmentation task: from an unsegmented stream of symbols, the system must output delimited sequences corresponding to actual words in the language. For this, we assume a linguistic grammar G, which parses sequences of letters (or phones) as being organized into Words, which themselves recursively decompose into smaller units such as Morphs, Syllables, etc. To induce word segmentation from parse trees, we will consider that each span covered by the non-terminal symbol Word defines a linguistic word, even though in a fully unsupervised setting, this non-terminal might actually correspond to larger or smaller linguistic units. Figure 2 illustrates this on two example parses.

Likewise, when examining the output of the training process, we are in a position to collect sets of word types (or morph types, syllable types, etc.) and will do so based only on the identity of the root symbol, i.e. without any certainty regarding the linguistic status of the collected sequences.

3 Linguistic material

Mboshi and Myene

We experiment with two Northwestern Bantu Languages: Mboshi (Bantu C25), a language spoken in Congo-Brazzaville, and Myene (B10, Gabon), a cluster of six mutually intelligible varieties (Adyumba, Enenga, Galwa, Mpongwe, Nkomi and Orungu) spoken at the coastal areas and around the town of Lambarene in Gabon. 4 Unlike southern Bantu relatives such as Swahili, Sotho or Zulu, Mboshi and Myene are scarcely studied, protected, and resourced. We briefly describe the main aspects related to phonetics, phonology, morphology, and tonology of these languages.

Phonetics and phonology. Mboshi and Myene both have a seven vowel system (i, e, E, a, O, o, u). Mboshi has an opposition between long and short vowels, which does not exist in Myene. Mboshi consonantal system includes the following phonemes : p, t, k, b, d, B, l, r, m, n, ñ, mb, nd, ndz, ng, mbv, f, s, G, pf, bv, ts, dz, w, j. It has a set of prenasalized consonants (mb, nd, ndz, ng, mbv) which is common in Bantu languages [START_REF] Martial | Processus segmentaux et tonals en Mbondzi -(variété de la langue embosi C25)[END_REF]Kouarata, 2014). Myene includes the following phonemes: p, t, k, b, d, B, l, r, m, n, f, s, g, y, v, ŋ, w, z -many of them with variants of realization. Prenasalized consonants exist also in Myene [START_REF] Ambouroue | Éléments de description de l'orungu, langue bantu du Gabon (B11b)[END_REF].

While both languages can be considered as rarely written, linguists have nonetheless defined a non-standard graphemic form for them, considered to be close to the language phonology. Affricates and prenasalized plosives are coded using multiple symbols (e.g. two symbols for dz, three for mbv). For Mboshi, long and short vowels are coded respectively as V and as VV. In Myene, the transcription of the corpus involves not only the phoneme set, but also the main variants (ñ, tS, dz) and some marginal sounds found in loanwords.

Both languages display a complex set of phonological rules. The deletion of a vowel before another vowel in particular, common in Bantu languages, occurs at 40% of word junctions in Mboshi (Rialland et al., 2015). This tends to obscure word segmentation and introduces an additional challenge for automatic processing.

Morphology. Words are composed of roots and affixes, and almost always include at least one prefix, while the presence of several prefixes and one suffix is also very common. The suffix structure mostly consists of a single vowel V (e.g. -a or -i) whereas the prefix structure may be both CV or V (or CVV in Mboshi). The most common syllable structures are V and CV in both languages. CVC also occurs in Myene, and CVV in Mboshi. 5The noun class prefix system is another feature typical of Bantu languages. For both languages, the structure of the verbs, also common in Bantu languages, is as follows: Subject Marker -Tense/Mood Marker -Root-derivative Extensions -Final Vowel. A verb can be very short or quite long, depending on the markers involved.

Tonology. Prosodic systems for both Mboshi and Myene involve tones, but the transcribed data used for this work do not encode tone markers. Experiments to assess the usability of tonal information for word segmentation were conducted in (Godard et al., 2018b Corpora for Mboshi and Myene were collected following a real language documentation scenario, using a mobile app dedicated to fieldwork language documentation [START_REF] Blachon | Parallel speech collection for under-resourced language studies using the LIG-Aikuma mobile device app[END_REF]. These corpora contain manual transcriptions in the form of a non-standard graphemic form close to the languages' phonology. The correct word segmentations for these transcripts were also annotated by linguists. Basic statistics are in Table 1.

The Mboshi corpus is more comprehensively described in (Godard et al., 2018a).6

4 Grammars

Structuring Grammar Sets

Our starting point is the set of grammars used in [START_REF] Goldwater | A Bayesian framework for word segmentation: Exploring the effects of context[END_REF]) and (Eskander et al., 2016) which we progressively specialize through an iterative refinement process involving both field linguists and computer scientists. As we wish to evaluate specific linguistic hypotheses, the initial space of interesting grammars has been generalized in a modular, systematic, and hierarchical way as follows. We distinguish four sections in each grammar: sentence, word, syllable, character. For each section, we test multiple hypotheses, gradually incorporating more linguistic structure. Every hypothesis inside a given section can be combined with every hypothesis of any other section, 7 thereby allowing us to explore a large quantity of grammars and to analyze the contribution of each particular hypothesis.

The Full Grammar Landscape

All the grammar sections (sentence, word, syllable, character) experimented in this paper are detailed in Figure 1. We describe below the way each section was designed.

• sentence level: we model 3 different hierarchies of words. We introduce first the flat variety with two rules generating rightbranching parse trees. colloc adds a single level of word collocation, aimed to capture recurrent local word associations (such as frequent bigrams); colloc3 displays a deeper hierarchical structure with three levels of collocations. Exploring more realistic syntactic structures is left for future work.

• word level: here we propose 6 competing hypotheses. flat is similar to previous sentence variety but at the word level instead of the sentence level. generic corresponds to a more structured version of flat, as the specification of a sequence of 5 adapted morphemes allows, in principle, the Adaptor Grammar to learn some morphotactics. bantu defines a generic morphology for Bantu languages. basaa implements the morphology of a well-studied Bantu language, Basaa (A43 [START_REF] Hamlaoui | Focus marking and the unavailability of inversion structures in the Bantu language Bàsàá[END_REF]). mboshi/myene corresponds to a somewhat crude morphology of Mboshi, also applicable to Myene. Last mboshi/myene_NV refines mboshi/myene with a specification of the morphology of nouns and verbs. Additionally, for basaa, mboshi/myene and mboshi/myene_NV which introduce a notion of prefix, we also test a variant (called respectively basaa+, mboshi/myene+ and mboshi/myene_NV+) containing an explicit list of prefixes in Mboshi.

• syllable level: we contrast 3 hypotheses : flat is similar to previous sentence and word varieties but at the syllable level, defining the syllable as a mere sequence of characters. generic/basaa is a generic set of rules modeling phonotactics applicable to a wide scope of languages (including Basaa mentioned in the preceding level). bantu/mboshi/myene displays a set of rules more specific to Mboshi and Myene.8

• character level: rules in the chars set simply rewrite the characters (terminals) ob- A3B5C2D1+, "moro amii obe" (correct word segmentation)

Figure 2: Examples of parses -some non-terminals have been omitted for readability -obtained with two grammars, and the corresponding word segmentation for Mboshi sentence "Moro a-mii o-be". (CL1.man 3SG-swallow.PST CL14-bad; since Moro is an irregular noun, the prefix and the stem are difficult to separate, which is signaled by a dot, following the Leipzig glossing rules.) served in our data. chars+ adds rules to capture the digraphs or trigraphs occurring in Mboshi (see details in Section 3).

Experiments and Discussion

We now experiment along the methodology presented in Section 4. We report word segmentation performance using precision, recall, and Fmeasure on tokens (WP, WR, WF), and types (LP, LR, LF). We also report the exact-match (X) metric which calculates the proportion of correctly segmented utterances. 9

In all the figures, and in this section, we use the following compact names for grammatical hypotheses at each level:

• A1 (flat), A2 (colloc), A3 (colloc3),
• B1 (flat), B2 (generic), B3 (bantu), B4 (basaa), B5 (mboshi/myene), B6 additional "+" variants for B4, B5, and B6 when a list of prefixes is provided, for instance B6+ (mboshi/myene_NV+),

• C1 (flat), C2 (generic/basaa), C3

(bantu/mboshi/myene),

• D1 (chars), D1+ (chars+).

For each language, we evaluate our 162 grammar configurations using Mark Johnson's code, 10 collecting parses after 2,000 sampling steps. 11 We adapt all non-recursive non-terminals and use a Dirichlet prior to estimate the rule probabilities. We place a uniform Beta prior on the discount parameter of the Pitman-Yor process, and a vague Gamma prior on the concentration parameter.

Figure 3 presents token metrics (WP, WR, WF) and type metrics (LP, LR, LF), as well as sentence exact-match (X) for both corpora on all grammars.

Word Segmentation Results

Impact of sentence level variants We can see in Figure 3 that A2 and A3 hypotheses globally yield better results than A1 in both languages. For 9 The exact-match metric includes single-word utterances. 10 http://web.science.mq.edu.au/ ~mjohnson/Software.htm 11 The large number of experiments we are dealing with did not allow us to average over several runs. Stable results were obtained on a subset of grammars. Two particular configurations in Mboshi (A3-B6-C3-D1+ and A1-B6-C1-D1) did not reach 2,000 iterations within the maximum wall clock time allowed by the cluster used for these experiments (2 weeks), and are left out of the discussion.

Mboshi, the benefit of A3 vs. A2 appears especially on token metrics (WP, WR, WF), but this contrast is less clear on Myene. For both languages, however, our results confirm that modeling collocation-like word groups at the sentence level is important. These word dependencies seem indeed related to a universal linguistic property.

Impact of word level variants

If we now focus solely on the A3 hypothesis for Myene in Figure 3, we observe a general trend upwards for all metrics. The benefit of gradually using more languagespecific grammars, from B1 to B6+, is clear. While this trend is also observed for Mboshi, the less specific B3 hypothesis yields the strongest results on token metrics (WP, WR, WF). Precision on types (LP) with B3 is also the strongest, but B6+ achieves better performance on type recall and F-measure (LR and LF). The contrast between B1 and B2 for all metrics on both languages (keeping a focus on A3, but this can also be seen for A1 and A2) highlights the benefit of modeling some morphotactics inside the word-level hypotheses, which seems to correspond to another universal linguistic property (the dependency between morphemes inside a word).

Impact of syllable level variants

It is difficult to see a clear trend for the impact of syllable-level variants in Figure 3. Importantly, the syllable level will only be effective when combined with word level variants B4, B5 and B6 (and their "+" versions) which model the concept of syllable: when combined with B1, B2 or B3, each C level hypothesis will default to its "Chars → Char +" rule. Figure 4 illustrates the impact of C1, C2, and C3 by averaging type and token F-measures (LF and WF) over all grammar sections with a syllable non-terminal (B4, B4+, B5, B5+, B6, and B6+). The benefit of C2/C3 vs. C1 appears more clearly, especially on type F-measures and on Myene.12 Nevertheless, the impact of the syllable level, and the capacity to incorporate phonotactics in our models, seems of less significance for word segmentation than choices made at the word and sentence levels.

Impact of character level variants

In Figure 3, it is also hard to see if there is any benefit in using D1+ over D1, i.e. adding digraphs or trigraphs to the consonant inventory. Averaging over all hypotheses at the A, B, and C levels do not exhibit any clearer impact. It is likely that refined models at the syllable level (C) compensate for a less accurate consonant inventory through the adaptation of their non-terminals, and do learn some phonotactics. This would explain the weak contribution of D1+. To test this hypothesis, we set the sentence level to A3 (the best compromise for Mboshi and Myene) and the word level to B1, B2, or B3 (levels without a Syllable non-terminal, which cancels the effect of the syllable level C). The token and type F-measures averaged over the considered hypotheses are shown Figure 5. We do observe a benefit in using the D1+ character variant in Mboshi, but not in Myene. This is not surprising, as the digraph and trigraph rules added by the D1+ variant are specific to Mboshi and do not cover the inventory for Myene.

Stronger results in Myene Segmentation performance is globally superior in Myene. This can probably be explained by corpus statistics (see Table 1), as the average number of words per sentence is 3.94 in Myene, and 5.96 in Mboshi. Since sentence boundaries are also word boundaries, the proportion of already known word boundaries is higher in Myene, which makes word segmentation a harder task in Mboshi. Figure 3 also reveals an interesting contrast: token results are higher than type results in Myene, while the converse is true in Mboshi. The token/type ratio (5.75 tokens for one type in Mboshi, and 4.30 in Myene) indicates a higher lexical diversity in Myene, which might explain weaker results on types. Strong results on types for Mboshi, on the other hand, show the ca- Comparison to an existing baseline Overall, our best performing grammars are A3-B3-C3-D1+ for Mboshi (64.78% token F-measure) and A3-B6+-C2-D1 for Myene (72.62% token Fmeasure). This result is about 30 points higher than a strong Bayesian baseline, the Dirichlet process-based bigram word segmentation system of [START_REF] Goldwater | Contextual Dependencies in Unsupervised Word Segmentation[END_REF][START_REF] Goldwater | A Bayesian framework for word segmentation: Exploring the effects of context[END_REF], 13 which yields 34.34% token F-score on Mboshi and 44.48% on Myene.

How Can This Help a Linguist?

Our second goal is to understand more precisely how such experiments can be useful for linguists, beyond the benefit of having access to better automatic word segmentation tools for their data.

Phonological status of complex consonants In the analysis of the results (Section 5.1 above) we showed the benefit of integrating digraphs or trigraphs in the consonants inventory for Mboshi. This result is of special interest for linguists, since it is in line with the most recent phonological analyses of Mboshi [START_REF] Martial | Processus segmentaux et tonals en Mbondzi -(variété de la langue embosi C25)[END_REF]Kouarata, 2014;Amboulou, 1998) which agree in recognizing complex consonants (represented by digraphs or trigraphs) in the phonological inventory of this language. The analysis of complex consonants, in particular prenasalized consonants, generated many debates in Bantu linguistics (Odden, 2015;[START_REF] Herbert | Language Universals, Markedness Theory, and Natural Phonetic Processes[END_REF][START_REF] Downing | On the ambiguous segmental status of nasals in homorganic NC sequences[END_REF]. The present experiments provide more substance to support the integration of complex consonants in the phonological inventory of Mboshi.

Learning prefixes without supervision Since parses are produced to segment sentences into words, it is possible to extract the most frequent prefixes or suffixes (for B variants introducing such a concept). The precision on the 20 most frequently found prefixes for grammars without prefix-supervision (B3, B4, B5 and B6) 14 reaches 58.21% in Mboshi, and 61.21% in Myene. The capacity of AGs to learn true prefixes without supervision could thus help linguists in the process of documenting a new language. On the supervised variants (B4+, B5+, and B6+), the precision achieved in Mboshi is 61.11%, and 63.07% in Myene: the benefit of the supervision is limited; token measures for Mboshi with these variants (Figure 3) nevertheless indicate a benefit for word segmentation.

Related Work

AGs have been used to infer the structure of unsegmented sequences of symbols, offering a plausible modeling of language acquisition (Johnson, 2008b;[START_REF] Goldwater | A Bayesian framework for word segmentation: Exploring the effects of context[END_REF]; they have also been used for the unsupervised discovery of word structure, applied to the Sesotho language by Johnson (2008a). One notable outcome of this latter study was to demonstrate the effectiveness of having an explicit hierarchical model of word internal structure ; an observation that was one of our primary motivations for using AGs in our language documentation work. In this series of studies, AGs are shown to generalize models of unsupervised word segmentations such as the Bayesian nonparametric model of [START_REF] Goldwater | Nonparametric Bayesian Models of Lexical Acquisition[END_REF], delivering hierarchical (rather than flat) decompositions for words or sentences.

While AGs are essentially viewed as an unsupervised grammatical inference tool, several authors have also tried to better inform grammar inference with external knowledge sources. This is the case of Sirts and Goldwater (2013), who study a semi-supervised learning scheme combining annotated data (parse trees) with raw sentences. The linguistic knowledge considered in [START_REF] Börschinger | Exploring the Role of Stress in Bayesian Word Segmentation using Adaptor Grammars[END_REF] aims to better model function words in a 14 We include B3 variant, interpreting its non-terminal Prefixes as a prefix. language acquisition setting: explicitly representing the occurrence of these short (typically monosyllabic) tokens in front of content-bearing words was shown to improve the resulting word segmentations. The work of [START_REF] Eskander | Extending the Use of Adaptor Grammars for Unsupervised Morphological Segmentation of Unseen Languages[END_REF] considers the use of additional dictionaries, storing partial lists of prefixes or suffixes collected either on the Internet, or discovered during a first round of training. We study similar complementary information, which are collected in close collaboration with linguistic experts.

Various other extensions or applications of AGs are worth mentioning, such as O'Donnell et al. (2009), which generalizes AGs so as to adapt fragments of subtrees (rather than entire subtrees). [START_REF] Botha | Adaptor Grammars for Learning Non-Concatenative Morphology[END_REF] consider the adaptation of grammars from a more general class than context-free grammars (mildly context-sensitive grammars), in order to model discontinuous fragments in non-concatenative morphology. Finally, [START_REF] Börschinger | Exploring the Role of Stress in Bayesian Word Segmentation using Adaptor Grammars[END_REF] propose to model the role of stress cues in language learning.

Conclusion

This paper had two main goals: (1) improve upon a strong baseline for the unsupervised discovery of words in two very low-resource Bantu languages;

(2) explore the Adaptor Grammar framework as an analysis and prediction tool for linguists studying a new language.

Systematic experiments with 162 grammar configurations for each language have shown that using AGs for word segmentation is a way to test linguistic hypotheses during a language documentation process. Conversely, we have also shown that specializing a generic grammar with language specific knowledge greatly improves word segmentation performance. In addition, our paper reports word segmentation results that are way higher than a Bayesian baseline. These results invite us to further this collaboration, and to analyze more thoroughly the usability of output parses in speeding up the documentation process.

Figure 1 :

 1 Figure 1: Grammar rules for all the hypotheses presented in Section 4.

Figure 3 :

 3 Figure 3: Word segmentation performance evaluated with token metrics (WP, WR, WF), type metrics (LP, LR, LF), and sentence exact-match (X) for Mboshi (top) and Myene (bottom). All grammars are broken down by A, B, C, and D levels (D1 shown before D1+).

Figure 4 :

 4 Figure 4: Impact of C variants on Mboshi and Myene. Token F-measure (WF) and type Fmeasure (LF) are averaged over hypotheses B4, B4+, B5, B5+, B6, and B6+.

Figure 5 :

 5 Figure 5: Impact of D variants on Mboshi and Myene. Token F-measure (WF) and type Fmeasure (LF) are averaged over hypotheses with A level set to A3 and B level set to B1, B2, or B3.

  ).

	language #sent #tokens #types avg. token length
	Mboshi	5130	30,556	5,312	4.19
	Myene	4,579	18,047	4,190	4.72
		Table 1: Corpora Statistics
	3.2 Corpora for Mboshi and Myene

We indifferently use the terms word discovery and word segmentation to denote the task defined in Section

2.2.

A non-terminal A is recursive if R contains a rule where A appears both in the left and right-hand sides.

In practice, we will retain the most frequent segmentation rather than the most frequent parse (see Section 2.2).

 4 Our Myene data correspond to the Orungu variant.

CCV may also arise due to the presence of affricates and prenasalized plosives mentioned in this section.

This dataset has already been used in several studies targeting endangered languages and is available at http://www.islrn.org/resources/

747-055-093-447-8/.7 Note that if a non-terminal is absent from a hypothesis (e.g. Syllable in a word level hypothesis), the corresponding non-terminal in the subsequent hypotheses (e.g. at the syllable level) will be ignored.

In theory, we should not include a coda in this last hypothesis, but loanwords and proper names in our data made the Adaptor Grammar fail to parse without a coda. To decrease the impact of this rule, we chose not to adapt the corresponding non-terminal, in contrast to generic/basaa.

The differences between C3 and C2, two very similar hypotheses, are hardly significant.

https://homepages.inf.ed.ac.uk/ sgwater/resources.html.

Acknowledgments

We thank the anonymous reviewers for their insightful comments. We also thank Ramy Eskander for his help in the early stages of this research. This work was partly funded by French ANR and German DFG under grant ANR-14-CE35-0002 (BULB project).

Sentence level (A)

Words → Word+ flat(A1)

Character level (D)


Lydia Coudroy

Housing Cooperatives in Poland. The Origins of a Deadlock

Keywords: housing, housing cooperatives, co-ownership, privatization, eastern and central Europe, People's Republic of Poland, Poland

Housing cooperatives in Poland have a long history, which began at the end of the nineteenth century. The cooperative movement proposed innovative solutions for housing, as far as the architectural and the social dimensions are concerned especially in the interwar period, and became in the 1960s the most important actor in the housing system in Poland, until the end of the 1980s. Nevertheless, this dominant position contained the roots of a decline of cooperatives which is on-going. Today, 17% of the housing stock belongs to the cooperative sector, but less than 3 % of new dwellings are built by cooperatives. This article analyzes the growth and decline of Polish housing cooperatives during the twentieth century and why we consider that they have reached a deadlock in the neoliberal Poland.

Introduction

Co-housing has become very popular in the 2000s in Western Europe, and is often associated to an emergent issue of affordable and self-managed housing. But it was not always the case, and in Poland, it is not at all "fashionable". Generations of people born after the war very often lived in a housing cooperative (spółdzielnia mieszkaniowa), and this experience was not the result of a choice, but almost the only way for urban dwellers to get a flat. Generally, people now associate cooperatives to bureaucratic 'monsters' and to prefabricated blocks in the outskirt of the city. The stereotype view of cooperative blocks is based on this vision. Housing cooperatives are present everywhere in the country, especially in big cities. They also often occupy the public debate, because in the 1990s and especially in the 2000s, their future has been publicly discussed, engaging more than 5 millions of Poles. This article aims to analyse the long term position of housing cooperatives in the Polish housing system.

Today, co-housing experiences are clearly bottom-up and considered to be empowerment strategies from citizens who try to solve the issue of housing at the very local scale [START_REF] Bacqué | L'habitat alternatif : quoi de neuf ? Territoires[END_REF][START_REF] Marchand | Le Village vertical : la longue marche d'une coopérative d'habitants à Villeurbanne[END_REF], outside state housing policies or even against them. But this was not always the case, especially in Poland. What was actually the relationship between the cooperative sector and the state? How could a model of self-managed housing become paradoxically the mainspring of the housing system in a people's democracy in the post-war period? A wide reflection is taking place in Europe, about new forms of affordable housing: do the national economic and political conditions offer the possibility for cooperatives to play this role in Poland?

To answer these questions, I will focus on the relationship between the state and the housing cooperative sector, because it is the key to understanding the present difficulties of housing cooperatives. I will first present the origins of Polish housing cooperatives; then I will analyze the state policies towards them during the People's Republic of Poland, and its consequences in the housing system; finally, I will explain how the neo-liberal policies have been forcing cooperatives into a difficult process of adaptation, leading them to a turning point for their survival in a deadlocked situation.

2.Origins and development of housing cooperatives in Poland

Polish housing cooperatives without Poland

The first cooperatives in Poland are attributed to Stanisław Stazic (1755Stazic ( -1826) ) who created in 1826 the first 'agricultural society'. The word 'cooperative' did not exist then, it appeared at the beginning of the nineteenth century. It comes from the verb spółdziałać or współdziałać which is made of the prefix with (spół) and the verb to act (działać). Housing cooperatives were founded at the end of the nineteenth century, at a time when Poland had been crossed off Europe's map to the benefit of the empires of the Partition: Russia, Prussia and Austria. While the former polish territory did not belong to the most industrialized parts of Europe at the time, urban growth was still very high, especially in Greater Poland, under Prussian domination. For example, the population of Wrocław grew from 87,000 inhabitants in 1825 to 422,000 in 1900 and in Warsaw (in the Russian zone of partition) from 150,000 circa 1795 to 885,000 in 1914 [START_REF] Drozdowski | Warszawa w latach 1914-1939[END_REF]). Urban infrastructures did not match this growth, and housing availability thus was very low. The typical urban form of housing during this period of growth was the dom koszarny (tenement barracks), a tenement house with high densities offering a low quality accommodation. The 'housing issue', analysed in Friedrich Engels' essay [START_REF] Engels | La question du logement[END_REF][START_REF] Engels | La question du logement[END_REF]) relying on the examples of England and Germany was also very acute in Polish territories: 22% of dwellings in Wrocław in 1916 consisted of only one room [START_REF] Maleczyński | Wrocław. Rozwój urbanistyczny[END_REF]. In this context of difficult housing conditions, the first housing cooperative, named "Help" (Pomoc) was created in the city of Posen (today Poznań). It was an owner-occupancy form of cooperative: members contributed towards financing the houses and became owners after the payment of installments over several years or decades. In Silesia, situated in the southern-western part of the present territory, which also belonged to Prussia before the First World War, other housing cooperatives appeared at the turn of the nineteenth and the twentieth, on a rent-occupancy model. The background of urban growth, the lack of dwellings, but also this political context explain the development of housing cooperatives: in the absence of a Polish state, and against policies of germanization provided by Prussian authorities, cooperatives offered the Polish people a model of self-management and selfeducation which was encouraged by Staszic. The same factors had already occurred during the nineteenth century and explained the development of agricultural cooperatives in the Prussian partition zone, but also in Galicia (in Austria), and in the Poland of Congress (in the Russian part) where the cooperative movement inspired socialist parties (Janczyk 1980).

From tradition to modernity

But the cooperative movement came to enjoy its real boom once the Polish state recovered its sovereignty and encouraged it, through a fund and a law [START_REF] Andrzejewski | Polityka mieszkaniow[END_REF]). Among other elements of a new housing policy, the National Fund for Reconstruction, created in 1919, aimed to support the efforts of housing reconstruction after the war destructions, since in these new boundaries, about 650.000 dwellings had been destroyed. The law of October 1920 authorized housing cooperatives in Poland, among which housing cooperatives. They could get subsidies fom the National Fund for Reconstruction up to 95% of the final cost of construction. The architectural style of these first cooperatives belonged to the "New Manor" (nowy dwór) tradition, typical for this time of new sovereignty: even in urban context, architects used to build houses which looked like polish lords' country houses, with such elements like white walls, columns, a pediment. Symbolically, the manor used to be one of the refuges of the national identity during the times of Partitions [START_REF] Piwińska | Pologne : le manoir, un conservatoire de l'idée nationale[END_REF]) and for this reason was still very popular after 1918 (Figure 1). The most famous housing cooperatives created thanks to the 1920 law was the Warsaw Housing Cooperative, the WSM (Warszawska Spółdzielnia Mieszkaniowa), created in 1921 by the founder of Polish town planning (Tadeusz Tołwiński), and militants from the Socialist Polish Party (Stanisław Szwalbe, Teodor Toeplitz). According to its statutes, the WSM wished to 'provide and rent to its members convenient and affordable dwellings thanks to mutual help' [START_REF] Turowski | Existe-t-il un art en Europe de l'est ? Paris[END_REF]). In the 1930s, the cooperative movement became the main vector of spreading for modern architecture and town planning (author 2004). The residential cooperative estates of this decade, especially in Warsaw, expressed the convergence of the social, artistic and architectural avant-garde trends [START_REF] Leśnikowski | Functionalism in polish architecture[END_REF]. The most famous architects of the interwar period worked for the WSM, like Barbara Brukalska and Stanisław Brukalski (estate Żoliborz, Warsaw), Helena and Szymon Syrkus (estate Rakowiec, Warsaw); they also belonged to the group of modern artists and architects Praesens, founded in 1926 and participated in the artistic and intellectual movements of Central Europe (Germany, Austria, etc.), to the CIAM. Barbara Brukalska had also a theoretical approach to housing and defended the ideas of 'social housing estates' (osiedle społeczne) and of Minimalwohnung, close to Gropius. Thus, the cooperative housing estates of that time were social and urban entities, for about 3000 to 5000 inhabitants made of small houses with three or four levels, placed in a linear fashion to ensure exposure to sun-shine, and built with modern materials (Figure 2). The dwellings were small (from 11 m² to 47 m² in Brukalska's houses for instance), but inhabitants could share collective amenities such as leisure rooms, day nursery and a laundry. In the Żoliborz WSM estate, there is also a cinema, a theatre. Like in the first generation of the nineteenth century, the members of cooperatives could own or rent their flat. The historical impact of this generation of cooperatives is very important; nevertheless, one should not forget that in the interwar period, most of dwellings were built from private funds: the quantitative contribution of cooperatives to the dwelling completion remained very low: about 230 cooperatives were registered in 1938 in Poland, with a population of about 30,000 inhabitants [START_REF] Andrzejewski | Polityka mieszkaniow[END_REF]. The most famous cooperative housing estates realized before the war by the WSM are Rakowiec (1931Rakowiec ( -36), Żoliborz (1929-32)-32); some others were started in the 1930s but finished a few years after the Second World War.

2.3.Continuity through the War

Indeed, the Second World War did not represent a very relevant break in the history of the Polish theoretical approach to housing and urban planning. First, because architects and town planners secretly went on working and teaching during the Nazi occupation. Second, because the political atmosphere between 1945 and 1948 was still ambiguous, allowing some pre-war experiences and policies to continue. This was the case for housing: the minister of reconstruction Michał Kaczorowski announced that the housing issue had to be cared for by the private, the public, and the cooperative sectors, just like before the war. The cooperatives resumed unfinished projects in all major cities (Koło II in 1947, Praga I in 1948 in Warsaw), following the same modernist principles that existed before 1939. But this continuity suddenly stopped at the end of 1948, for political reasons. The socialist and the communist polish parties merged and formed the Polish Unified Worker's Party (PUWP), directed by its First Secretary Bolesław Bierut. This event marked the beginning of the transformation of the country into the 'People's Republic' of Poland. Politically, it means the introduction of Stalinist principles in the state's policy, including housing. The Three Year Plan emphasized the necessity of industrialization, not of housing expenditures; State funds for Reconstruction were concentrated in regions having priority for economic or political reasons: the capital city, and the industrial conurbation of Upper Silesia. From 1948, the cooperative movement, which originally and by definition expresses the capacity of the society to manage itself, became suspicious. Cooperatives were not disbanded, but they activity was limited to the maintenance of the existing stock and some historical militants were removed. In addition, the state created the Department for Workers' Housing (Zaklad Osiedli Robotniczych), which was in charge of investing in public dwellings for the working class. Parallel to the centralization of the housing economy, during the period 1949-55, socialist realism came to dominate in the fields of arts, architecture and town planning. This anti-modern aesthetic policy produced in the urban landscapes new classical, monumental buildings and estates, especially in Warsaw, but also in new districts (Nowa Huta in Cracow) or new towns (Nowe Tychy in Upper Silesia). The contrast with the urban creations of the 1930s is startling [START_REF] Aman | Architecture and ideology in Eastern Europe during the stalin era : an aspect of Cold War History[END_REF][START_REF] Aman | Architecture and ideology in Eastern Europe during the stalin era : an aspect of Cold War History[END_REF]; Włodarczyk 1991). Thus, the activity of housing cooperatives was put in brackets in the first half of the 1950s. Their subsequent come back was possible by several events: first the death of Stalin in March 1953, then Khrushchev's and Bulganin's Resolution of November 1955 titled "On the renewal of exaggerations in planning and building", and at last, in March 1956 the death of Bolesław Bierut under strange circumstances in Moscow, shortly after the 20 th Congress of the Communist Party of the Soviet Union dominated by Khruschchev's 'Secret Speech'.

3.Cooperatives in the People's Republic of Poland: come back, power and ruin

3.1.From an ideological come back to a pragmatic power

After the period of socialist realism, housing cooperatives could again work normally under three forms : rental cooperatives, owner-occupancy cooperatives1 , and cooperative associations of individual houses2 . The new First Secretary of the PUWP Władysław Gomułka asserted in his 'new housing policy' that the housing situation required a huge effort, and that it should be shared by various actors: the state, but also the private sector (that is to say individuals only), and the cooperatives. This was confirmed by the law 'about cooperative and their unions' in 1961 [START_REF] Pietrzykowski | Spółdzielczość w Polsce Ludowej[END_REF]. A new system of financing was set up for the cooperatives: every citizen could open a savings bank-book with an initial installment -a part of the construction cost of the dwelling that was necessary to be a cooperative member. The rest of the building cost was covered by members' contributions after moving in, plus state subsidies allocated to cooperatives. The housing cooperatives entered what is seen in their history as a second 'golden age', since they were again supported by the state, which assumed the largest part of the building costs. In state policies, cooperatives appeared then as a pragmatic issue to solve the lack of housing due to the war destructions and to the stress put on industry in public investments (Coudroy de Lille 2004b). As a result, they had to fit with the interests of the central and regional planification and entered a phase of concentration and centralization: the number of cooperatives was stabilized at about 1000 until 1981, whereas the number of people affiliated to them continuously increased -cooperatives accounted on average 175 members in 1960, but 2000 in 1980. In addition,the Central Union of Building and Housing Cooperatives created in 1961 aimed to coordinate and control the activity of all housing cooperatives. Concentration also affected the building process when house-building industry adopted prefabrication technology.

But soon, in the Five Year plan of 'socialist accumulation ' (1961-65), the share of public investment in housing fell, and the priority was to build very large housing estates as cheap as possible, including in the city centre (Figure 3). The quality of construction did not improve at all: the generation of dwellings of the 1960s is made of very small flats, according to a decree that set the average useful surface at 11 m² per person. The average surface of dwellings built in the socialized sector (made of cooperative and municipal building) went from 50 m² in 1958 to 42 m² in 1965, including very often a blind kitchen. Furthermore, needs of housing grew up in the 1970s because the second generation of the post-war baby-boom arrived on the 'market'. In this context, The First Secretary of the Party Edward Gierek in 1972 entrusted the cooperatives to answer this demand in his long-term program for housing, which they did. As a result, the great majority of urban landscape from the socialist period is made of large housing estates built by cooperatives, especially in the big cities: in Warsaw for example, cooperative construction accounted for more than 80 % of all the newly built housing units from the mid 1960s to the mid 1980s (Figure 4). About half of those cooperative dwellings were rental, the others being owner-occupancy dwellings at the end of the 1980s. In the case of cooperative tenancy, 10 % of the final cost of dwellings had to be covered by down payment, whereas it reached 20 % for owner-occupancy. Repayments times for the members could run for fourty years with low interest rates. But in his new 1972 housing policy, Edward Gierek allowed for repayment periods up to sixty years. This is why the share of housing expenses in household incomes remained very low during the whole socialist period, below 1 % of the average salary until 1980, and still below 5 % until the mid 1980s [START_REF] Kozłowski | The housin system in Poland[END_REF]).

The price of fame

The position of cooperatives with regards to the state was ambiguous and brought them power but also paralysis: on the one hand, they occupied a dominant position in the housing economy (concerning urban areas at least), and received high state subsidies. On the other hand, they were in competition with stronger actors at the local level, whose interests were constantly supported by the state, such as industrial complexes or local administrations. Both of these actors were also involved in housing construction: they used to finance and manage houses for their employees, and until 1965, half of the new dwellings were built by local state authorities and companies. But this share fell in tandem with the growing role of cooperatives. When this occurred, local administrations and companies could get a part of the new dwellings built by cooperatives and transfer them to their workers. Thus, cooperatives provided more and more dwellings for these powerful local actors to the detriment of their own members. In 1980, at a time when the state had stopped building for residential needs, cooperatives could allocate to their members only 30 % of the new dwellings in the socialized sector, whereas they used to build 75 % of them. But of course, not every cooperative member waiting for a flat was employed in a local administration or in a big factory plant: the majority of them had to wait during long years in the cooperative queue. The housing cooperative system was thus definitely part of the 'economics of shortage' [START_REF] Tadeusz | Spółdzielczość w Polsce Ludowej[END_REF]. Although the volume of construction grew continuously up to the end of the 1970s, it did not cover the housing shortage, and thus produced its own roundabouts to avoid the general queue. A widespread feeling of injustice and inequality ensued (Figure 5). 1 9 5 0 1 9 5 3 1 9 5 6 1 9 5 9 1 9 6 2 1 9 6 5 1 9 6 8 1 9 7 1 1 9 7 4 1 9 7 7 1 9 8 0 1 9 8 3 1 9 8 6 1 9 8 This dominant position in the economy of housing had also deep consequences for the nature of cooperatives: far from the social and architectural ideal of small housing estates called 'social estates' (osiedle społeczne) theorized by the architect Barbara Brukalska [START_REF] Brukalska | Zasady społeczne projektowania osiedli mieszkaniowych[END_REF], cooperatives of the 1970s had reached huge dimensions, up to 30,000 or 40,000 dwellings. The centralization was incompatible with the earlier principle of selfmanagement. On the contrary, the cooperative council in each of the buildings was supposed to provide and diffuse a 'socialist way of life', rather than self-organizing or a sense of community [START_REF] Madej | Spółdzielczość mieszkaniowa. Władze PRL wobec niezależnej inicjatywy spółdzielczej[END_REF].

This 'cooperative way of life' actually began very often at birth: parents registered their child to the 'general cooperative queue' and began to gather the deposit waiting for membership in one cooperative or another. Candidates would eventually form part of a cooperative queue, of which they became members waiting for a dwelling. From 1978 (which is the peak of housing building for the post-war Poland) to 1990, the number of citizens waiting for a cooperative dwelling (inside or at the gate of the cooperative system) has been almost always exceeded the number of cooperative members having a dwelling (Fig. 6). All in all, considering that the rate of available dwellings never exceeded 8 per 1000 inhabitants, and that a significant part of dwellings was excluded from the cooperative queue to the benefit of companies or local authorities, candidates had to wait up to 15 years after the becoming adults. For example, in Warsaw, in 1988, 245,000 persons were registered in the queue, waiting to become member of a cooperative (from which 115,000 had already gathered the deposit, and 48,000 were minors); 42,100 were already registered in a cooperative, waiting for a flat [START_REF] Gaudray | Funkcjonowanie małych spółdzielni mieszkaniowych w aglomeracji warszawskiej[END_REF].

The cooperative institution tried in the 1980s to recover some sort of autonomy from the state at the local and at the national level. From 1981, the state encouraged the development of new 'small cooperatives', presented as a return to the roots, and a way to solve the housing shortage. Many of them were created by companies, others brought together members of 'old' cooperatives waiting in vain for a flat, who decided to shift to self-building cooperatives. Between 1981Between and 1987Between , 1793 new small cooperatives were born, out of which 1107 did build about 21,000 dwellings. This represents only 1.5 % of the construction in this period: small cooperatives suffered mainly from a difficult access to plots and materials (Godziejewska 1991).

At the end of the socialist period, the state of paralysis of the cooperative sector was total: to incentivize its reduction, registering new candidates in the queue was forbidden, but at the same time, housing construction fell down to 4 newly built dwellings per 1000 inhabitants (Figure 5). The housing shortage in Poland was estimated to 1.4 million dwellings, and a major part of this burden was attributed to the cooperative sector. Thus, when the socialist regime fell, the cooperative sector was in a very critical situation and had lost people's trust, which was the result of its trajectory since the 1960s. This legacy raises the question of its adaptability in market economy conditions.

4.Housing cooperatives in the market economy

From cooperatives to co-ownerships

Housing in Poland since 1990 has become market oriented, and the structures of housing economy have turned to a disengagement of the state from it at least at the beginning of the decade. Actually, it was already the case in construction itself since the end of the 1970s since the state could take from the cooperative housing stock for its needs at the local scale. The process of housing privatization in Eastern Europe has been widely described in the literature [START_REF] Andrusz | Cities after socialism[END_REF]Barks, O'Leary, and Rabenhorst 1996;Clapham and Murice 1996;[START_REF] Dawidson | Geographic impacts of the political : dealing with nationalised housing in Romania[END_REF][START_REF] Enyedi | Social change and urban restructuring in eastern and central Europe[END_REF][START_REF] Hegedüs | Transition of the housing sector in the East central European Studies[END_REF][START_REF] Hegedüs | Towards new models of the housing system[END_REF][START_REF] Lowe | Housing Change in East and Central Europe[END_REF][START_REF] Lux | Social Housing in the Czech Republic, Poland and Slovakia[END_REF]Lux , 2003)). It contains the introduction of market principles in housing financing, including bank credits, access to materials and the management of the housing stock. The state stopped to subsidy housing construction directly, and like in other countries from the former socialist Europe, the housing issue was decentralized to the municipalities which were now responsible for the allocating funds or designating plots, as well as for social issues for their poorest inhabitants. But unlike neighboring countries, Poland had to find means to solve the specific issue of housing cooperatives. The major change for cooperatives were the introduction of privatization of dwellings, and the end of the financial support from the state (Kozłowski 1996[START_REF] Kozłowski | The housin system in Poland[END_REF]. The cooperative movement ceased to be an auxiliary of state housing policy, and had to adapt itself to the market economy. The Housing Ownership Act of 1994 introduced co-ownership in the Polish Law; and the 2000 Act for Cooperatives instituted the conditions under which they can be privatized and transformed into co-ownerships. If the majority of members decided, they could buy the dwellings. But there were two ways for cooperative tenants to buy their flat. Either they would get a 'separate ownership' (concerning only the flat itself), which cancelled their link to the cooperative. Or they could shift to a 'cooperative ownership' as in the traditional framework, and remained still members of the cooperative. Both types of ownership are marketable and inheritable but in the case of separate ownership, the buyer has to cover the notary's fees, and becomes owner of a part of the real estate. In the second case, the cooperative remains the owner of the real estate. Very often people did not have the choice: if the building was standing on a plot whose cooperative was neither the full owner nor the perpetual usufruct, then the cooperative ownership remained obligatory. Actually this was very often the case, because during the socialist period, cooperatives were allocated huge plots without legal regularization, without notarial deed. This is why the share of cooperative dwellings in the housing stock has first increased from 1988 to 2002 (some cooperative buildings were completed after the 1990 turn) and is slowly decreasing from 2002 to 2011 (table 1). But inside the cooperative housing stock, about 70 % of dwellings are now in owner occupancy, whereas during the socialist period, the proportion was stabilized at the half of it.

Table1. Share of cooperative dwellings in the polish housing stock from 1988 to 2011 The figures clearly show that the cooperative housing stock is a declining legacy in the housing system, but still important in cities. The cooperative issue concerns every region, especially the most urbanized and industrialized voivodeships like Lodz, Masovian, Silesian (Fig. 7). In this unstable legal situation, what can be the social, economical or political future of housing cooperatives?

Do cooperatives contribute to the supply of affordable housing?

The number of cooperative dwellings in Poland will probably continue to decrease. Although some of them are in bad conditions, Polish housing policy does not up to now include programs of demolition/reconstruction, such as in France or in Germany [START_REF] Roth | Les « villes rétrécissantes » en Allemagne[END_REF][START_REF] Epstein | La rénovation urbaine. Démolition-reconstruction de l'Etat[END_REF]) because of a general context of housing shortage. One million of dwellings are still missing in Poland, when considering the difference between the number of households and the number of dwellings (GUS, 2011), and 13% of Poles in 2010 suffered from severe housing deprivation in contrast with 5,7 % of the population in the European Union (Eurostat). But the cooperative sector is not anymore supposed to resolve to the housing shortage, as it was in the 1960s and in the 1970s. The renewal of the cooperative housing stock is now very low, because a very few of them go on building: only 3500 cooperative dwellings were completed in 2013, which represent 2.4% on a total of 145,000 completed dwellings in the country. Thus they are not able to resolve the housing shortage, just from a quantitative point of view. Furthermore, they cannot either take up the challenge of affordable housing: cooperative dwellings, even rental, were never a type of 'social' housing in the socialist period. Insterad, they used to provide dwellings for the largest sectors of society. Although the architecture of cooperative housing estates is reminiscent of social housing estates elsewhere in Western countries, they never had (except in theory in the pre-war period) and still do not have this role. Social housing has always been the matter of local authorities, occupying old buildings generally situated in the inner city. In 1995 the Social Building Societies (Towarzystwo Budownictwa Społecznego, TBS) were created by the law. They provide social housing just like municipalities, and own about 80 000 dwellings. They could apply for credits from the National Housing Fund, just like cooperatives building rental dwellings. But this fund was cancelled in 2009: the offer of non-profit rental dwellings is thus dramatically low today. Altogether, the rental housing stock (owned by companies, municipalities, TBS or cooperatives) has shifted from 58 % in 1988 to 20 % in 2011 (GUS).

In the current housing market, it is hard to compare the price of rental cooperative flats to other rental dwellings (Table 2). The rent itself is much lower in cooperatives, but since the fees for water and energy is now estimated within each dwelling, the total rent may be much more expensive than in the rest of the tenant housing stock (Instytut Rozwoju Miast 2011). The chances for a renewal of the cooperative sector in the future are weak, for economical and social reasons. The political context since 1990 has been creating very unstable and difficult conditions of work for cooperatives: the fall of cooperative share in house building to less than 3 % reflects this evolution. The most common way to get a dwelling now is to buy one from a developer or to build as an individual (Figure 8). Cooperatives, municipalities, TBS and companies together built 7500 dwellings in 2013, that is to say 5 % of the new dwellings. But in addition, all of these institutions -even TBS-lost a part of their stock in recent years because they were encouraged to practise the 'right to buy'. And the private market does not fill this gap. Thus the opportunities to enter the housing market renting a flat are decreasing, especially for the middle class. 1 9 9 1 1 9 9 2 1 9 9 3 1 9 9 4 1 9 9 5 1 9 9 6 1 9 9 7 1 9 9 8 1 9 9 9 2 0 0 0 2 0 0 1 2 0 0 2 2 0 0 3 2 0 0 4 2 0 0 5 2 0 0 6 2 0 0 7 2 0 0 8 2 0 0 9 2 0 1 0 2 0 1 1 Cooperatives Others (Municipalities, TBS, Companies) Private Persons Developers Furthermore, for generations of Poles, cooperatives are associated to long years in the cooperative housing queue, to a generally poor quality of building and of architecture, and to a heavy bureaucracy. They are definitely perceived as a legacy from the socialist times. During decades of housing shortage, the cooperative way of housing was the only one for urban population, and the majority of it endured frustration because of the unequal and nontransparent allocation of flats. This is why in the popular language, cooperatives are often named 'moloch', from the Ammonite god Moloch evoking a monster who requires costly sacrifices. The dictionary of Polish language also defines a moloch like 'a big, overwhelming, unfriendly city, housing estate or a faulty institution'3 .

Nevertheless, in the 2000s, a new cooperative model is arising, undertaken by a new generation, that is highlighting the critical effects of the new housing market, dominated by private actors, especially developers. Some of them are organizing projects of so called "micro-cooperatives" [START_REF] Czeredys | Mikrospółdzielnia[END_REF]. The idea of these, often young architects is to provide a bottom-up model of housing that could change the city itself through small cooperatives (less than 20 dwellings) including houses in ownership and tenant dwellings. This young generation of activists refers to examples from Austria, Germany, Sweden or the Netherlands, but also to polish historical experiences of cooperatives like WSM in Warsaw.

5.Conclusion

The cooperative movement is thus represented today by two very different trends. On the one hand, young architects are connected to other European experiences and networks; they do not ignore the past, and would like to take from the history the cooperative spirit of the 1930s. On the other hand, organizations of the cooperative traditional sector are still alive, and apart from managing its stock, they participate in the political debate, supported mainly by the post-communist party (SLD) and the peasants party (PSL).The first newly emerging movement and the second one, which is well established, both retain nostalgia for the inter-war period of cooperatives, but this is the only connecting point between them; they do not share any common actions or objectives.

Nevertheless, both are concerned by the transformation of the legal framework of cooperatives. It has been threatened since 2011 by a bill proposed by the liberal party Civic Platform according to which cooperatives would be obliged to shift to co-ownerships. Either the Cooperative Act of 2000 will be once again amended, or a new act will be written. Millions of persons are concerned, and have to make their opinion, but they are probably lost because the debate is very confusing and longlasting. Anyway, the unregulated status of many plots on which cooperative estates stand makes the implementation of any reform difficult. But the cooperative issue does have great political magnitude in some regions where one quarter of the dwelling stock still belongs do cooperatives (fig. 7).

The cooperative sector is thus a complex legacy in the history of Polish cities. First, it represents a social and ideological patrimony which has never ceased to be a positive reference for town planners, architects, even in the worst period for cooperatives, when they provided huge housing estates and were the major actor of the housing shortage in the 1980s. But this collective memory has not been extended to any wider social practices such as tours or urban museum that would show the shared nature of this patrimony even in the most famous cooperative estates. Second, cooperatives have given present generations 2,300,000 dwellings mostly built in prefabricated materials during the 1960s and the 1970s. Of course, a lot has already been done to maintain the structural soundess of this stock and to improve conditions of living in these buildings [START_REF] Chmielewski | Modernizacja osiedli mieszkaniowych[END_REF].

The cooperative experience of housing in Poland is a paradox: it went through a decline precisely when it had most power. From the 1970s onward, they received much from the state: plots, subsidies, and political power. But they did not receive enough means to resolve the housing issue, and were hostages in this relationship, losing their autonomy, their own dwellings, and their functional identity. Housing cooperatives let a huge material and legal legacy in the housing system, but their legal framework in particular is today being challenged. Who will take over the maintenance of the cooperative housing stock in the next decades? Is there a chance for a renewal of housing cooperatives on the roots of Polish long term experiences? It depends on the amendment of the law about cooperatives. Counter to the wider European context where, like the 2014 'participative housing' law passed in France, innovation in housing through cohousing, housing associations, and cooperatives in the third sector are being encouraged, the legal framework of cooperative in Poland is under threat. This potential cancelation raises the question of the emergence of cohousing or microcooperatives in the future.

Figure1.

  Figure1. Cooperative house for Officers in Łódź (Arch. Wacław Kowalewski, 1925) Source: Coudroy de Lille, 2009

Figure 2 .

 2 Figure 2. Cooperative estate WSM Żoliborz in Warsaw (arch. Barbara Brukalska and Stanisław Brukalski, 1927-32) Source: Coudroy de Lille, 2010.

Figure 3 .

 3 Figure 3. Za Żelazną Bramą, Warsaw, 1972 Source: Coudroy de Lille, 2010.

Figure 4 .

 4 Figure 4. The share of cooperatives in housing construction in Poland (1961 -1989) author, 2013. Sources: Grabowieska-Łaszek 1988; CZSBM 1987; GUS.

Figure 5 .

 5 Figure 5. Housing Construction and Housing Shortage in Poland (1960-1989). Coudroy de Lille, 2013. Source : GUS.

Fig. 6 .

 6 Fig.6. Candidates and members in housing cooperatives (1978-1990) Coudroy de Lille 2014. Source: GUS.

Figure 7 .

 7 Figure 7. Cooperative dwellings in the Polish regions in 2011

Figure 8 .

 8 Figure 8. Dwellings completed by sector in Poland from 1990 to 2011 Coudroy de Lille 2013. Source : GUS

  Coudroy de Lille 2013. Source : GUS.

	%	Total	Cities
	1988	24,3	36,7
	2002	28,6	40,8
	2007	24,4	35,7
	2011	17,5	26,2

Table 2 .

 2 Average rent for a 3 person's household in a 50 m² dwelling in 2010 (in złoty per month)

	Types of rental	Rent	Water, Energy, Garbage
	dwellings		Disposal
	Private	550	994
	TBS	426	662
	Municipal	291	655
	Cooperative	129	nd
	Source : Instytut Rozwoju Miast, 2011, Informacje o mieszkalnictwie.
	Note: The exchange rate is about 4 złoty per 1 euro.

The ownership was a limited one: the house belonged entirely to the cooperative. The so-called cooperative ownership was the right to occupy the dwelling. This right was marketable and inheritable.

These associations were seldom. The cooperative was created to build houses and disappeared once they were built. The ownership was thus transferred to their inhabitants.

'Duże, przytłaczające, nieprzyjazne ludziom miasto, osiedle; też: duża, niesprawna instytucja', Słownik Języka Polskiego, Państowe Wydawnictwo Naukowe, http://sjp.pwn.pl


Poher Yoann

Ponel Philippe

Guiter Frédéric

Tachikawa Kazuyo

Médail Frédéric

Impacts of sea-level rise and responses of Mediterranean coastal wetland biodiversity: lessons from fossil insect assemblages

come

Impacts of sea-level rise and responses of Mediterranean coastal wetland biodiversity: lessons from fossil insect assemblages

Coastal wetland-based archives have an exceptional scientific potential to observe past biodiversity changes and identify key thresholds for particular ecosystems facing relative sealevel rise. In this presentation, we focus on the multiproxy analyses (palaeoentomology, palynology and geochemistry) of two 14C-dated cores from Corsican back-barrier wetlands: the Grecu pond located on a low-laying island (S. Corsica) and the Cannuta marsh situated on a deltaic floodplain (N. Corsica).

The respectively 7000-and 5900-year sedimentary records from the two sites show contrasted ecosystem trajectories, stemming mainly from their different geomorphological features.

Regarding the Grecu pond, by comparing the beetle fauna present on the island today with fossil beetle assemblages, we find that 60% of past wetland beetle fauna became locally extinct because of the increase in salinity caused by marine intrusions. Most of this diversity loss occurred 3700 years ago, when relative sea-level reported in the region was at ~-1.5 meters.

Regarding the Cannuta marsh, fluctuations of calcium and sulphur (used as tracers of Gypsum), show evolution from a brackish lagoon to a freshwater environment. This transition, marked by a diversification of wetland beetle fauna 1000 years ago, is possibly due to relative sea-level stability and floodplain progradation. It is consistent with evidences of soil erosion (inferred from titanium abundance) and of pastoral practices in the watershed.

This retrospective approach provides a foreshadowing of potential future insect diversity changes along Mediterranean coastal lagoon ecosystems. We discuss the implications of these findings in terms of resilience and conservation strategies to minimise coastal wetland losses.


Poher Yoann

Ponel Philippe

Médail Frédéric

Tachikawa Kazuyo

Guiter Frédéric

Response of two Mediterranean coastal wetlands (Corsica, France) to Holocene relative sea-level rise and land-use changes revealed by fossil Coleoptera records

Response of two Mediterranean coastal wetlands (Corsica, France) to Holocene relative sea-level rise and land-use changes revealed by fossil Coleoptera records

POHER Yoann 1 , PONEL Philippe 1 , MÉDAIL Frédéric 1 , TACHIKAWA Kazuyo 2 , GUITER Coastal wetland-based archives have an exceptional scientific potential to observe past biodiversity changes and identify key thresholds for particular ecosystems facing relative sealevel rise (RSLR). In this presentation, we focus on the fossil Coleoptera analysissupplemented by pollen and geochemical dataof two 14C-dated cores from Corsican backbarrier wetlands: the Grecu pond located on a low-laying island (S. Corsica) and the Cannuta marsh situated on a deltaic floodplain (N. Corsica).

The respectively 7000-and 5900-year sedimentary records from the two sites show contrasted ecosystem trajectories, stemming mainly from their different geomorphological features.

Regarding the Grecu pond, by comparing the beetle fauna present on the island today with fossil beetle assemblages, we find that 60% of past wetland beetle fauna became locally extinct because of the increase in salinity caused by marine intrusions. Most of this diversity loss occurred 3700 years ago, when relative sea-level reported in the region was at ~-1.5 meters. These local extinctions have been exacerbated by the aggravation of human pressures over the last decades, with the artificial reduction of the wetland surface area. Regarding the Cannuta marsh, fluctuations of calcium and sulphur (used as tracers of Gypsum), show evolution from a brackish lagoon to a freshwater environment. This transition, marked by a diversification of wetland beetle fauna 1000 years ago, is possibly due to relative sea-level stability and floodplain progradation. It is consistent with evidences of soil erosion (inferred from titanium abundance) and of pastoral practices in the watershed.

We demonstrate the efficacy of fossil beetles for reconstructing the environmental changes in coastal lagoon ecosystems, their resilience, and their response to the Holocene RSLR in the western Mediterranea. This retrospective approach also provides a foreshadowing of potential future insect diversity changes along Mediterranean coastal lagoon ecosystems.