Susana Santos

Ellis Voerman

Pilar Amiano

Henrique Barros

Lawrence J Beilin

Anna Bergström

Marie-Aline Charles

Leda Chatzi

Cécile Chevrier

George P Chrousos

Eva Corpeleijn

Olga Costa

Nathalie Costet

Sarah Crozier

Graham Devereux

Myriam Doyon

Merete Eggesbø

Maria Pia Fantini

Sara Farchi

Francesco Forastiere

Vagelis Georgiu

Keith M Godfrey

Davide Gori

Veit Grote

Wojciech Hanke

Irva Hertz-Picciotto

Barbara Heude

Marie-France Hivert

Daniel Hryhorczuk

Rae-Chi Huang

Hazel Inskip

Anne M Karvonen

Louise C Kenny

Berthold Koletzko

Leanne K Küpers

Hanna Lagström

Irina Lehmann

Renata Majewska

Johanna Mäkelä

Yannis Manios

Fionnuala M Mcauliffe

Sheila W Mcdonald

John Mehegan

Erik Melén

Monique Mommers

Camilla S Morgen

George Moschonis

Deirdre Murray

Carol Ní Chaoimh

Ellen A Nohr

Anne-Marie Nybo Andersen

Emily Oken

Adriëtte J J M Oostvogels

Agnieszka Pac

Eleni Papadopoulou

Juha Pekkanen

Costanza Pizzi

Kinga Polanska

Daniela Porta

Lorenzo Richiardi

Sheryl L Rifas-Shiman

Nel Roeleveld

Luca Ronfani

Ana C Santos

Marie Standl

Hein Stigum

Camilla Stoltenberg

Elisabeth Thiering

Carel Thijs

Maties Torrent

Suzanne C Tough

Tomas Trnovec

Steve Turner

Marleen M H J Van Gelder

Lenie Van Rossem

Andrea Von Berg

Martine Vrijheid

Tanja G M Vrijkotte

Jane West

Alet H Wijga

John Wright

Oleksandr Zvinchuk

I A Thorkild

Sørensen

Debbie A Lawlor

Romy Gaillard

MD Vincent W V Jaddoe
email: v.jaddoe@erasmusmc.nl

Impact of maternal body mass index and gestational weight gain on pregnancy complications: An individual participant data meta-analysis of European, North American and Australian cohorts

Keywords: Setting: Europe, North America and Oceania. Population: 265, 270 births weight gain, body mass index, pregnancy complications, preterm birth, birth weight Tweetable

à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

INTRODUCTION

Obesity among women of reproductive age is increasing in prevalence worldwide. 1 A metaanalysis of published data of 38 cohorts reported that not only maternal obesity but also

Accepted Article

modest increases in maternal body mass index (BMI) were associated with an increased risk of fetal and infant death. For women with a BMI of 30 kg/m 2 , absolute risks per 10,000 pregnancies were 102 and 43 fetal and infant deaths, respectively. 2 Maternal overweight and obesity are also associated with increased risks of more common pregnancy complications, such as gestational hypertensive disorders, gestational diabetes, preterm birth and large size for gestational age at birth. [3][4][5] Next to maternal pre-pregnancy BMI, excessive gestational weight gain, defined by the US Institute of Medicine (IOM) criteria, is associated with increased risks of pregnancy complications. [6][7][8][9] However, most previous studies have lacked power to robustly assess whether differences in risk are also present for modest changes in maternal pre-pregnancy BMI and gestational weight gain and by severity of obesity.

Although the associations of maternal obesity and excessive weight gain with pregnancy complications have been extensively studied, less is known on the population disease burden attributable to these conditions. [10][11][12] Gaining insight into the population attributable risks will allow the development of future population preventive strategies designed to reduce the risks of common pregnancy complications. Furthermore, a meta-analysis of individual participant data (IPD) on this topic, in contrast to the previously performed meta-analyses of published results, 4, 9 allows more powerful and flexible analyses, better harmonization of the data, consistent adjustment for potential confounders and leads to a reduced risk of publication bias.

Therefore, we conducted a meta-analysis of IPD among 265,270 singleton births from 39 American, European and Oceania pregnancy and birth cohorts to assess the associations of maternal pre-pregnancy BMI and gestational weight gain with the risks of gestational hypertension, pre-eclampsia, gestational diabetes, preterm birth, and small and large size for gestational age at birth and to assess their population impact.

METHODS

Inclusion criteria and participating cohorts

We used data from an existing international collaboration on maternal obesity and childhood outcomes. Pregnancy and birth cohort studies were eligible if they included mothers with singleton live-born children born from 1989 onwards, had information available on maternal pre-or early-pregnancy BMI and at least one offspring measurement (birth weight or childhood BMI) and were approved by their local institutional review boards. We invited 50 cohorts from Europe, North America and Oceania selected from existing collaborations on childhood health (EarlyNutrition Project, CHICOS Project, www.birthcohorts.net assessed until July 2014), of which 39 agreed to participate, providing data of 277,042 singleton births.

Of those, information on maternal pre-or early-pregnancy BMI and at least one pregnancy complication was available for 265,270 singleton births (flowchart in Figure S1).

Anonymized datasets were stored on a single central secured data server with access for the main analysts (SS, EV). A description of the eligibility criteria and the references of the study design and profile papers of each included cohort are given in Table S1. Participants were not involved in the development of the study.

Maternal anthropometrics

Maternal anthropometrics were measured, derived from clinical records or self-reported (cohort-specific information in Table S2). Maternal BMI before pregnancy, available in 96% of the study population, was used in the analyses. For participants without information on pre-pregnancy BMI, BMI obtained before 20 weeks of gestation was used. Maternal BMI was categorized into underweight (<18.5 kg/m 2 ), normal weight (18.5-24.9 kg/m 2 ), overweight (25.0-29.9 kg/m 2 ), obesity grade 1 (30.0-34.9 kg/m 2 ), obesity grade 2 (35.0-39.9 kg/m 2 ), and obesity grade 3 (≥40.0 kg/m 2 ), 13 and into 11 groups with a range of 2.5 kg/m 2 Accepted Article each. Information on total gestational weight gain, defined as the difference between the latest weight before delivery and pre-pregnancy weight, was provided by the cohorts and was classified as inadequate, adequate, or excessive weight gain in relation to maternal prepregnancy BMI according to the IOM guidelines. 14 We calculated weight gain until 20 weeks of gestation as the difference between a weight obtained until median 15.4 weeks (95% range 10.0, 19.3) and pre-pregnancy weight. We calculated maternal pre-pregnancy BMI specific weight gain for gestational age z-scores based on reference charts created using data from this collaboration (Appendix S1). 15 These z-scores were categorized into 6 categories (<-2.0 standard deviation (SD), -2.0 to -1.1 SD, -1.0 to -0.1 SD, 0 to 0.9 SD, 1.0 to 1.9 SD and ≥2.0 SD) and into low (≤-1.1 SD), medium (-1.0 to 0.9 SD) and high (≥1.0 SD) weight gain.

Pregnancy complications

Information on gestational hypertension, pre-eclampsia, gestational diabetes, gestational age at birth and birth weight was measured, derived from clinical records or reported (cohortspecific information in Table S2). Preterm birth was defined as <37 weeks of gestation. 16 We created sex-and gestational age-adjusted birth weight SD scores based on a North-European reference chart. 17 Small and large size for gestational age at birth were defined per cohort as sex-and gestational age-adjusted birth weight below the 10 th percentile and above the 90 th percentile, respectively. Any pregnancy complication was defined as at least one of the pregnancy complications. A core outcome set was not used in this study.

Covariates

Information on covariates was assessed by questionnaires and provided by the cohorts as categorical covariates: educational level (low, medium, high), parity (nulliparous, multiparous), smoking habits during pregnancy (yes, no), and child's sex. Maternal age was

Accepted Article

categorized based on data availability as <25.0, 25.0-29.9, 30.0-34.9, and ≥35.0 years. As part of the analysis plan, covariates were selected based on the graphical criteria for confounding and data availability in the cohorts. 18 Maternal ethnicity was not included due to the fact that most cohorts were largely Caucasian and a high percentage of missings in ethnic specific information. Cohort-specific information is given in Table S3.

Statistical analysis

We conducted one-stage IPD meta-analysis by analyzing individual level data from all cohorts simultaneously in a multilevel model. Our model followed a two-level hierarchical structure with participants (level 1) nested within cohorts (level 2). 19 We used generalized linear mixed models with a binomial distribution and logit link. We defined the models assuming a random intercept at cohort level to allow variation in the baseline risk for each cohort. We used these models to examine the separate and combined associations of maternal pre-pregnancy BMI and gestational weight gain, in clinical categories and across the full range, with the risks of pregnancy complications. We only examined the associations of gestational weight gain clinical categories with the risks of small and large size for gestational age at birth due to the possibility of reverse causality for the other outcomes. The associations of excessive weight gain with gestational hypertensive disorders might be partly explained by pathologic fluid retention as part of the disease. Women diagnosed with gestational diabetes might try to improve their diet and restrict their total weight gain.

Preterm birth shortens the gestation and thus women are less likely to gain excessive gestational weight. The proportion of pregnancy complications at a population-level attributable to each maternal pre-pregnancy BMI and gestational weight gain clinical category was estimated by calculation of population attributable risk fractions. For this, we used the adjusted Odds Ratio (OR) and the prevalence of the exposure category in the

Accepted Article

population. 20 To study the effects of weight gain across the full range on gestational hypertension, pre-eclampsia and gestational diabetes, we used weight gain z-scores until 20 weeks of gestation to avoid reverse causality. For the models using maternal pre-pregnancy BMI and gestational weight gain z-scores continuously, the inclusion of quadratic terms did not improve the fit. We did not observe statistical interactions between both maternal BMI and gestational weight gain with child's sex. All models were adjusted for maternal age, educational level, parity, and smoking habits during pregnancy. Models for birth complications were additionally adjusted for child's sex. Models for weight gain across the full range were also adjusted for maternal pre-pregnancy BMI. As sensitivity analyses, we conducted two-stage IPD meta-analyses and tested for heterogeneity between the cohorts estimates. 19,21 We used missing values in covariates as an additional group to prevent exclusion of non-complete cases. We performed statistical analyses using the Statistical

RESULTS

Participants' characteristics

Table S4 shows cohort-specific information on maternal anthropometrics and pregnancy complications. Overall, the median maternal pre/early-pregnancy BMI and total gestational weight gain were 22.7 kg/m 2 (95% range: 18.1-34.7 kg/m 2 ), and 14.0 kg (95% range: 3.9-27.0 kg), respectively.

Accepted Article

Maternal pre-pregnancy BMI and risks of pregnancy complications

Table 1 shows that, as compared to normal weight mothers, underweight, overweight and obesity grades 1 to 3 mothers had higher risks of any pregnancy complication (all p-values<0.05). The highest risk of any pregnancy complication was observed for obesity grade 3 mothers (OR 2.99 (95% Confidence Interval (CI) 2.68, 3.34)). Mothers with obesity grade 3 had also the highest risks of gestational hypertension (OR 5.40 (95% CI 4.47, 6.51)), preeclampsia (OR 6.50 (95% CI 5.48, 7.73)), gestational diabetes (OR 7.59 (95% CI 6.14, 9.38)), preterm birth (OR 1.52 (95% CI 1.24, 1.87)) and large size for gestational age at birth (OR 3.06 (95% CI 2.69, 3.49)). We estimated that 23.9% of any pregnancy complication, and specifically, 35.6% of gestational hypertension, 34.6% of pre-eclampsia, 42.8% of gestational diabetes, 3.9% of preterm birth and 20.6% of large size for gestational age at birth were attributable to maternal overweight and obesity (Table 1).

Figure 1 shows that higher maternal pre-pregnancy BMI was across the full range associated with higher risks of gestational hypertensive disorders, gestational diabetes and large size for gestational age at birth and with a lower risk of small size for gestational age at birth (p-values<0.05). Both lower and higher maternal pre-pregnancy BMI were associated with a higher risk of preterm birth (p-values<0.05). Similar results were observed in the unadjusted models (Table S5 andFigure S2

Gestational weight gain and risks of pregnancy complications

Table 1 shows that, as compared to mothers with adequate gestational weight gain, mothers with excessive gestational weight gain had a lower risk of small size for gestational age at birth (OR 0.62 (95% CI 0.60, 0.65)) and a higher risk of large size for gestational age at birth Accepted Article (OR 2.11 (95% CI 2.04, 2.18)). We estimated that 11.0% of small size for gestational age at birth and 31.6% of large size for gestational age at birth were attributable to inadequate and excessive gestational weight gain, respectively.

Figure 2 shows that higher weight gain z-scores until 20 weeks of gestation were associated with higher risks of gestational hypertension, pre-eclampsia and gestational diabetes. Both lower and higher total gestational weight gain z-scores were associated with a higher risk of preterm birth (p-values<0.05). Higher total gestational weight gain z-scores were, across the full range, associated with a lower risk of small size for gestational age at birth and a higher risk of large size for gestational age at birth (p-values<0.05). Similar results were observed in the unadjusted models (Table S5 andFigure S4 Similar results were observed in two-stage IPD meta-analysis (Figure S5).

Maternal pre-pregnancy BMI and gestational weight gain and risks of pregnancy complications

Table 2 shows that, as compared to normal weight mothers with medium gestational weight gain, overweight and obese mothers had higher risks of any pregnancy complication, independent of their gestational weight gain (p-values<0.05). The highest risk of any pregnancy complication was observed for obese mothers with high weight gain (OR 2.51 (95% CI 2.31, 2.74)). Low and high gestational weight gain were also, among normal weight mothers, associated with a higher risk of any pregnancy complication (p-values<0.05). Obese mothers with high gestational weight gain had the highest risks of gestational hypertension (OR 4.52 (95% CI 3.86, 5.31)), pre-eclampsia (OR 4.58 (95% CI 3.90, 5.37)), gestational diabetes (OR 7.84 (95% CI 6.38, 9.62)), preterm birth (OR 2.14 (95% CI 1.86, 2.46)) and

Accepted Article

large size for gestational age at birth (OR 4.77 (95% CI 4.35, 5.22)). Underweight mothers with low gestational weight gain had the highest risk of small size for gestational age at birth (OR 3.12 (95% CI 2.75, 3.54)). Similar results were observed in the unadjusted models (Table S6).

DISCUSSION

Main findings

In this IPD meta-analysis, higher maternal pre-pregnancy BMI and gestational weight gain were, across the full range, associated with higher risks of gestational hypertensive disorders, gestational diabetes and large size for gestational age at birth. Preterm birth risk was higher at both BMI and weight gain extremes. Obese mothers with high gestational weight gain had the highest risk of any pregnancy complication. We estimated that up to 24% of any pregnancy complication could be attributed to maternal overweight and obesity, whereas up to 32% of large size for gestational age infants could be attributed to excessive gestational weight gain. However, the estimated population attributable risks should be carefully interpreted since the causality of the observed associations remains unknown.

Strengths and limitations

We performed a large meta-analysis of IPD from many cohorts. As part of an international collaboration between pregnancy and birth cohort studies, we invited all cohorts from Europe, North America, and Oceania that we were able to identify from existing large international collaborations on childhood health and that met the inclusion criteria. Therefore, we believe this meta-analysis covers a large proportion of individual participant data available on this topic. However, we cannot disregard the possibility of data missing from other cohorts, especially recent cohorts, that were not included. We did not rely on published

Interpretation

Maternal obesity is a major public health concern. 24 A meta-analysis of published cohort studies showed that maternal obesity is associated with a higher risk of fetal and infant death. 2 Maternal obesity is also associated with increased risks of more common pregnancy complications, such as gestational hypertensive disorders, gestational diabetes, preterm birth and large size for gestational age at birth, [3][4][5] which are important risk factors for both maternal and neonatal morbidity and mortality. [25][26][27][28] In line with these previous studies, we observed that maternal pre-pregnancy overweight and obesity are related to increased risks of any of these pregnancy complications. Mothers with obesity grade 3 showed the highest risks.

Importantly, we estimated that over 40% of gestational hypertensive and diabetic disorders could be attributed to maternal overweight and obesity. Smaller but yet considerable risk fractions attributable to maternal overweight/obesity were observed for preterm birth (3.9%) and large size for gestational age at birth (20.6%). Overall, 23.9% of any pregnancy complication was estimated to be attributable to maternal pre-pregnancy overweight/obesity, which underlines their major public health implications and the possibility to substantially reduce pregnancy complications by optimizing maternal BMI.

The associations of maternal BMI with pregnancy complications were also present across the full range. Even modest increases of maternal pre-pregnancy BMI were associated with higher risks of gestational hypertensive disorders, gestational diabetes and large size for gestational age at birth. The association of maternal pre-pregnancy BMI with the risk of preterm birth tended to be U-shaped. Thus, our findings suggest that mothers do not necessarily need to become overweight or obese to be at risk of pregnancy complications, since higher risks of pregnancy complications were already observed for an increase in BMI within the healthy range.

Accepted Article

Next to pre-pregnancy BMI, excessive gestational weight gain may affect the risks of pregnancy complications. [6][7][8][9] We observed gradually higher risks of gestational hypertension, pre-eclampsia and gestational diabetes over the full range of weight gain. Similar to the association of maternal BMI, the association of total gestational weight gain z-scores with preterm birth tended to be U-shaped. We also observed that not only excessive weight gain but also higher weight gain across the full range was associated with a higher risk of large size for gestational age at birth. At the population level, 31.6% of large size for gestational age infants could be attributed to excessive weight gain. Altogether, these findings suggest that gradual increases in gestational weight gain, and not only excessive weight gain, are associated with higher risks of pregnancy complications.

We also assessed the combined effects of pre-pregnancy BMI and gestational weight gain on pregnancy complications. Previous studies showed that mothers with both high BMI and gestational weight gain had the highest risk of large size for gestational age. The risk of preterm birth was increased at both extremes. [29][30][31][32][33] In line with these previous studies, we observed that obese mothers with high weight gain were at the highest risk of any pregnancy complication. Importantly, we also observed that overweight and obese mothers are at risk of these complications, regardless how much weight they gain during pregnancy. These findings show the importance of promoting a healthy weight status before and during pregnancy.

The mechanisms underlying the associations of maternal adiposity and pregnancy complications are not fully understood yet, but might include insulin resistance, endothelial dysfunction, oxidative stress, lipotoxicity, inflammation, and infection. 3,4,34 The associations of maternal adiposity with large size for gestational age infants might be explained by fetal over-nutrition, since an increased placental transfer of nutrients to the fetus might lead to an Accepted Article increased synthesis of insulin and insulin-like growth factors, both of which are growthpromoting hormones. 35 The causal role of glucose is also suggested in a large Mendelian randomization study. 36 Gestational weight gain reflects fat storage during pregnancy, but also reflects fetus growth, amniotic fluid, placenta, uterine and mammary tissue expansion, increased blood volume, and extracellular fluid. 37 These factors may all have different roles in the associations with pregnancy complications. From the current observational data, we cannot drive conclusions on the mechanisms underlying the observed associations.

We observed that a high percentage of pregnancy complications is attributable to suboptimal maternal BMI and gestational weight gain, which suggests the potential for prevention of pregnancy complications by optimizing these maternal measures. Thus far, randomized trials focused on lifestyle interventions to improve gestational weight gain and subsequent pregnancy complications are disappointing. An IPD meta-analysis from randomized trials focused on lifestyle interventions in pregnancy showed a reduction in gestational weight gain but no effects on gestational hypertensive and diabetic disorders, preterm birth and size for gestational age. 38 Strategies to improve body mass index before pregnancy rather than during pregnancy may be more effective in prevention of pregnancy complications.

CONCLUSION

Maternal pre-pregnancy BMI and gestational weight gain are, across the full range, associated with the risks of pregnancy complications. Obese mothers with high gestational weight gain are at the highest risk of pregnancy complications. Up to 30% of any pregnancy complication is estimated to be attributable to overweight/obesity or excessive gestational weight gain. Our findings provide evidence for advocating a healthy BMI in women who are

Accepted Article

planning to become pregnant and an adequate weight gain during pregnancy to reduce the burden of obstetric and neonatal morbidity.

Accepted Article

DETAILS OF ETHICS APPROVAL

Cohorts were approved by their local institutional review boards and consent to participate was obtained from participants.

REFERENCES TABLES TITLES/LEGENDS

Table 1. Maternal pre-pregnancy body mass index and gestational weight gain clinical categories and the risks of pregnancy complications a a n cases/total represent the number of cases for each pregnancy complication in each clinical category/the population in each clinical category. Values are odds ratios (95% confidence intervals) from multilevel binary logistic regression models that reflect the risk of pregnancy complications per prepregnancy body mass index and gestational weight gain clinical category compared with the reference group (normal weight and adequate weight gain). Mothers diagnosed with pre-eclampsia were excluded from the models for gestational hypertension. The reference group for the analyses on preeclampsia comprises the mothers without both pre-eclampsia and gestational hypertension. The reference group for the analyses on small and large size for gestational age at birth is appropriate size for gestational age at birth. Models are adjusted for maternal age, educational level, parity, and smoking habits during pregnancy. Models for birth complications are additionally adjusted for child's sex. *P-value<0.05; **P-value<0.001. PAR is the population attributable risk fraction in percentage that reflect the proportion of pregnancy complications at a population-level attributable to each maternal pre-pregnancy body mass index and gestational weight gain clinical category. NA, not applicable. b PAR calculated based on preterm birth and small size for gestational age at birth. c PAR calculated based on gestational hypertension, pre-eclampsia, gestational diabetes, preterm birth and large size for gestational age at birth. Table 2. Maternal pre-pregnancy body mass index and gestational weight gain categories and the risks of pregnancy complications a a n cases/total represent the number of cases for each pregnancy complication in each group/the population in each group. Values are odds ratios (95% confidence intervals) from multilevel binary logistic regression models that reflect the risk of pregnancy complications per combined pre-pregnancy body mass index and gestational weight gain categories compared with the reference group (normal weight and medium weight gain). For any pregnancy complication, gestational hypertension, pre-eclampsia and gestational diabetes, weight gain z-scores until 20 weeks of gestation were used and for preterm birth, and small and large size for gestational age at birth, total gestational weight gain z-scores were used. Mothers diagnosed with pre-eclampsia were excluded from the models for gestational hypertension. The reference group for the analyses on pre-eclampsia comprises the mothers without both pre-eclampsia and gestational hypertension. The reference group for the analyses on small and large size for gestational age at birth is appropriate size for gestational age at birth. Models are adjusted for maternal age, educational level, parity, and smoking habits during pregnancy. Models for birth complications are additionally adjusted for child's sex. *P-value<0.05; **P-value<0.001. Significant interaction terms were present (p-values<0.05) for preterm birth, and small and large size for gestational age at birth.

FIGURES TITLES/LEGENDS

Figure 1. Maternal pre-pregnancy body mass index and the risks of pregnancy complications a a Values are odds ratios (95% confidence intervals) on a log scale from multilevel binary logistic regression models that reflect the risk of pregnancy complications per pre-pregnancy body mass index group compared with the reference group (largest group, 20.0-22.4 kg/m 2 ). The bars represent the percentage of each pregnancy complication per body mass index group. Mothers diagnosed with preeclampsia were excluded from the models for gestational hypertension. The reference group for the analyses on pre-eclampsia comprises the mothers without both pre-eclampsia and gestational hypertension. The reference group for the analyses on small and large size for gestational age at birth is appropriate size for gestational age at birth. Models are adjusted for maternal age, educational level, parity, and smoking habits during pregnancy. Models for birth complications are additionally adjusted for child's sex. Excel's trendline function was used to fit the curve to the data. The risks of pregnancy complications per kg/m 2 were: gestational hypertension OR 1.11 (95% CI: 1.11, 1.12), pre-eclampsia OR 1.11 (95% CI: 1.11, 1.12), gestational diabetes OR 1.12 (95% CI: 1.12, 1.13), preterm birth OR 1.02 (95% CI: 1.01, 1.02), small size for gestational age at birth OR 0.96 (95% CI: 0.95, 0.96), and large size for gestational age at birth: OR 1.08 (95% CI 1.08, 1.08).

Figure 2.

Gestational weight gain and the risks of pregnancy complications a a Values are odds ratios (95% confidence intervals) on a log scale from multilevel binary logistic regression models that reflect the risk of pregnancy complications per gestational weight gain group compared with the reference group (largest group, -1.0 to -0.1 SD). The bars represent the percentage of each pregnancy complication per gestational weight gain group. Mothers diagnosed with preeclampsia were excluded from the models for gestational hypertension. The reference group for the analyses on pre-eclampsia comprises the mothers without both pre-eclampsia and gestational hypertension. The reference group for the analyses on small and large size for gestational age at birth is appropriate size for gestational age at birth. Models are adjusted for maternal age, educational level, parity, smoking habits during pregnancy and maternal pre-pregnancy body mass index. Models for birth complications are additionally adjusted for child's sex. Excel's trendline function was used to fit the curve to the data. The risks of pregnancy complications per SD increase in gestational weight gain were: gestational hypertension OR 1.12 (95% CI: 1.09, 1.14), pre-eclampsia OR 1.07 (95% CI: 1.05, 1.10), gestational diabetes OR 1.14 (95% CI: 1.10, 1.18), preterm birth OR 1.09 (95% CI: 1.07, 1.11), small size for gestational age at birth OR 0.73 (95% CI: 0.72, 0.74), and large size for gestational age at birth OR 1.53 (95% CI 1.51, 1.55).

ccepted Article

  Package of Social Sciences version 21.0 for Windows (SPSS Inc, Chicago, IL, USA) and Review Manager (RevMan) version 5.3 of the Cochrane Collaboration (The Nordic Cochrane Centre, Copenhagen, Denmark).

  ). The risks of pregnancy complications per kg/m 2 are given in the footnotes of Figure1 and Figure S2. Similar results were observed in two-stage IPD meta-analysis (FigureS3).

  ). The risks of pregnancy complications per SD increase in gestational weight gain are given in the footnotes of Figure 2 and Figure S4.

  LC, CC, GPC, EC, OC, NC, SC, GD, MD, ME, MPF, SF, FF, VG, KMG, DG, VG, WH, IHP, BH, MFH, DH, RCH, HI, AMK, LCK, BK, LKK, HL, IL, PM, RM, JM, YM, FMM, SWM, JM, EM, MM, CSM, GM, DM, CNC, EAN, AMNA, EO, AJJMO, AP, EP, JP, CP, KP, DP, LR, SLRS, NR, LR, ACS, MS, HS, CS, ET, CT, MT, SCT, TT, ST, MMHJG, LR, AB, MV, TGMV, JW, AHW, JW, OZ, TIAS, DAL participated in the acquisition of data, performed a critical revision of the manuscript for important intellectual content, approved the version to be published and take responsibility for the accuracy and integrity of the work.

Table 1 . Pregnancy complications Odds Ratio (95% Confidence Interval) and Population Attributable Risk Fractions (PAR), % Any pregnancy complication Gestational hypertension Pre-eclampsia Gestational diabetes Preterm birth Small size for gestational age Large size for gestational age Pre-pregnancy body mass index

 1

		1.08 (1.03, 1.13)*	0.63 (0.55, 0.73)**	0.67 (0.57, 0.78)**	0.66 (0.53, 0.82)**	1.20 (1.10, 1.31)**	1.67 (1.58, 1.76)**	0.45 (0.41, 0.50)**
	Underweight
		PAR 2.3 b	NA	NA	NA	PAR 0.8	PAR 2.7	NA
	(<18.5 kg/m 2 )
		n cases/total =3079/9586	n cases/total =216/9416	n cases/total =168/9368	n cases/total =85/10449	n cases/total =599/10455	n cases/total =1900/10382	n cases/total =383/8865
	Normal weight	Reference	Reference	Reference	Reference	Reference	Reference	Reference
	(18.5-24.9 kg/m 2 )	n cases/total =46774/159983	n cases/total =5066/155612	n cases/total =4100/154646	n cases/total =1857/168117	n cases/total =7852/172123	n cases/total =18185/159778 n cases/total =14674/156267
		1.35 (1.32, 1.38)**	2.04 (1.94, 2.15)**	1.96 (1.86, 2.07)**	2.22 (2.06, 2.40)**	1.06 (1.01, 1.11)*	0.79 (0.76, 0.82)**	1.61 (1.56, 1.66)**
	Overweight
		PAR 11.4 c	PAR 17.1	PAR 16.0	PAR 19.4	PAR 1.2	NA	PAR 10.8
	(25.0-29.9 kg/m 2 )

Table 2 .

 2

	Pregnancy complications
	Odds Ratio (95% Confidence Interval)

n cases/total =16817/47825 n cases/total =2531/45509 n cases/total =2202/45180 n cases/total =1156/49203 n cases/total =2433/50852 n cases/total =4074/44476 n cases/total =6837/47239

n cases/total =734/1345 n cases/total =139/1151 n cases/total =164/1176 n cases/total =113/1357 n cases/total =99/1429 n cases/total =114/1109 n cases/total =316/1311

n cases/total =5632/70709 n cases/total =11994/77071

n cases/total =1098/2323 n cases/total =202/2074 n cases/total =194/2066 n cases/total =134/2374 n cases/total =230/2820 n cases/total =165/2085 n cases/total =732/2652

Acknowledgements

Cohort-specific information is given in the Appendix S2.

Keith M. Godfrey has received reimbursement for speaking at conferences sponsored by companies selling nutritional products, and is part of an academic consortium that has received research funding from Abbott Nutrition, Nestec and Danone. Debbie A. Lawlor has received support from Roche Diagnostics and Medtronic in relation to biomarker research that is not related to the research presented in this paper. Andrea von Berg has received reimbursement for speaking at symposia sponsored by Nestlé and Mead Johnson, who partly financially supported the 15 yrs follow-up examination of the GINIplus study.

Funding

Accepted Article

data, limiting any potential publication bias and enabling a consistent definition of exposures, confounders and outcomes. The large sample size enabled us to study the risks of pregnancy complications in relatively rare conditions, such as severe obesity. We did not consider additional levels, such as country and continent, in our multilevel modelling due to the high computational complexity required for this approach and the likely minimal influence of this on the findings. We performed two-stage meta-analyses as sensitivity analyses, which gave similar results and showed moderate-to-high heterogeneity between the cohorts estimates.

Missing values of covariates were used as an additional group. This approach, although commonly used in large IPD meta-analyses due to the constraints in applying more advanced imputation strategies, might lead to bias. 22 However, in the current study, bias is unlikely considering the small percentage of missings and the similar findings between unadjusted and adjusted models. We relied on weights obtained partly by self-report, which might be a source of error. However, a large systematic review showed that reporting error did not bias associations between pregnancy-related weight and birth outcomes. 23 We used maternal prepregnancy BMI specific weight gain for gestational age z-scores, which classify weight gain independently of gestational age. 15 This approach allows assessing the unbiased associations between gestational weight gain and pregnancy outcomes that are highly correlated with gestational age at birth. This method is needed because the absolute value related to the zscore changes across pregnancy. However, the use of z-scores might complicate the clinical interpretation of the observed associations. Some cohorts relied on self-reporting to obtain information on gestational hypertensive and diabetic disorders. If misclassification of women occurred, our associations might be attenuated. As in any observational study, residual confounding by unmeasured lifestyle related variables may be an issue.


Andrey Sadovykh
email: andrey.sadovykh@softeam.fr

Dragos Truscan
email: dragos.truscan@abo.fi

Wasif Afzal
email: wasif.afzal@mdh.se

Hugo Bruneliere
email: hugo.bruneliere@imt-atlantique.fr

Adnan Ashraf
email: adnan.ashraf@abo.fi

Abel Gómez

Alexandra Espinosa
email: alexandra.espinosa.hortelano@mdh.se

Gunnar Widforss
email: gunnar.widforss@mdh.se

Pierluigi Pierini
email: pierluigi.pierini@intecs.it

Elizabeta Fourneret
email: elizabeta.fourneret@smartesting.com

Alessandra Bagnato
email: alessandra.bagnato@softeam.fr

MegaM@Rt2 Project: Mega-Modelling at Runtime -Intermediate Results and Research Challenges

Keywords: Cyber-Physical Systems, Model-Driven Engineering, Runtime Analysis, Tools, Mega-Modelling, Traceability, ECSEL

de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

Electronic systems are becoming more and more complex and software intensive. This situation calls for modern software and systems engineering practices in order to keep high productivity and quality levels. In the last decade, the ecosystem around Model-Driven Engineering (MDE) has flourished, providing developers with a plethora of tools. However, these tools need to be further developed to scale up for real-world industrial applications. They also need to be enhanced in order to provide advantages at runtime as well. This represents a real opportunity for achieving a complete continuous systems engineering lifecycle, thus connecting together the design and runtime phases [START_REF] Bagnato | The MegaM@Rt2 ECSEL project: MegaModelling at Runtime -Scalable model-based framework for continuous development and runtime validation of complex systems[END_REF] [START_REF] Sadovykh | Model-Based System Engineering in Practice: Document Generation-MegaM@Rt2 Project Experience[END_REF] . The MegaM@Rt 2 project's main goal is to create a framework incorporating methods and tools for the continuous development and runtime support of complex software-intensive systems. Our current architecture vision and development over the MegaM@Rt 2 framework integrate three main complementary big capabilities: systems design engineering, runtime analysis, and global model & traceability management. The project is organized around the research work and related technical developments concerning the tool sets supporting those capabilities.

The research topics include holistic Systems Engineering covering design, verification and validation; Runtime Analysis dealing with monitoring, online testing and verification as well as models@runtime techniques; and so-called Mega-Modelling, i.e. large-scale model and traceability management. The framework is under evaluation by 9 industrial case studies ranging from transportation -avionics, railway, automotive, traffic monitoring; and telecommunications -short range communications, base transceiver stations; to logistics -indoor positioning, smart warehouses domains. Among the partners providing use cases in the project, we can cite Thales, Volvo Construction Equipment, Bombardier Transportation and Nokia. These organizations have different product management and engineering practices, as well as regulatory and legal constraints. This results in a large and complex catalog of requirements to be realized by the architecture building blocks at different levels of abstraction. Thus, the development of the MegaM@Rt 2 framework is based on a feature-intensive architecture and on a related implementation roadmap that is kept up-to-date. A comprehensive set of the project information, as well as the published deliverables, are all publicly available from the project web site [START_REF]MegaMart2 -MegaModelling at Runtime[END_REF] .

In this paper, we present the main project research and technological results after two years, and outline the outstanding challenges and further work. To this intent, the rest of the paper is structured as follows. Section 2 briefly describes the MegaM@Rt2 overall approach. Then Section 3 focuses on the three complementary tools sets that are designed and developed in the project to support this MegaM@Rt2 approach in practice. We notably insist on the main related research achievements we obtained so far, as well as on still open research and technical challenges. Finally, Section 4 concludes by summarizing the main results from this first phase of MegaM@Rt2 and by opening on some future work to come during the second phase of the project.

Description of the Overall Approach

As stated in the Electronic Components and Systems for European Leadership program's Multi-Annual Strategic Plan [START_REF]ECSEL's Multi-Annual Strategic Plan[END_REF] , design methods and related technologies should fully support the constant technology push and corresponding new user/society demands of products/services based on more and more complex Electronic Components and Systems (ECS). This is particularly true in the context of the involved software components relying on hardware configurations and their interactions e.g. with their underlying environment, being very often numerous, complex, heterogeneous and strongly interrelated. In the past, Model-Based Engineering principles and techniques have already shown promising capabilities that have been experimented in such context. However, they have generally failed in terms of 1) scalability to support real-world scenarios implied by the full deployment and use of complex ECS and 2) efficient traceability, integration and communication between two fundamental system levels which are design time and runtime, notably as far as non-functional properties and their verification & validation aspects are concerned.

As a consequence, the overall idea of MegaM@Rt2 is to scale up the use of model-based techniques by offering scalable methods and related tools interacting between both design time and runtime, as well as to validate the designed and developed approach in concrete industrial cases involving complex ECS. To this intent, MegaM@Rt 2 proposes an overall model-based approach combining existing techniques to be enhanced when relevant, and novel ones to be developed when needed. A fundamental challenge notably resides in providing efficient traceability support between the two levels i.e. from design models to runtime ones and back. In parallel to these, modern large-scale industrial software engineering processes require thorough configuration and model governance to provide the promised productivity gains. Thus, a scalable mega-modelling approach is being designed and will be deployed to manage all the involved artifacts e.g. the many different models, corresponding workflows, configurations, etc. and to better tackle their large diversity in terms of nature, number, size, complexity, etc.

To cover all these topics and deal with the complete value chain, MegaM@Rt 2 brings together prominent tool developers and vendors and research organisations with state-of-the-art methods and tools that are validated in highly relevant European industry case studies. The end users from the space, naval, railway, smart grid, smart warehouse and telecom industry domains are driving the project by providing real-world requirements and case studies as well as by validating and endorsing the MegaM@Rt 2 results.

Fig. 1 provides an overview of the MegaM@Rt 2 global approach and emphasizes its key principles and concepts. Industries apply a set of current engineering practices based on SysML, AADL, EAST_ADL, but also Matlab/Simulink, and Method B, each one producing specific design models, requirement specifications and resulting software and hardware artefacts. MegaM@Rt 2 suggests to integrate those artefacts into a global system model providing a complete view of the Cyber-Physical System (CPS), and detailing the component, behaviour and desired quality properties of the system. These properties are then an object of exhaustive continuous testing and monitoring in the runtime environment to detect deviations in real-time, thanks to the configuration of the target platform and the injection of probes in the software. The detected deviations plus all the traces information collected in the process are analyzed to detect the impacted components in the integrated view of system models. When possible, automatic repairing suggestions are provided to correct the issue and reconfigure or redeploy the system to start the next iteration of the continuous integration process. This approach was further developed in [START_REF] Sadovykh | A Tool-Supported Approach for Building the Architecture and Roadmap in MegaM@Rt2 Project[END_REF] where we defined the specific tool sets -their requirements and features as well as outlined integration means. The methods and tools provided by MegaM@Rt 2 are evaluated and applied in several industrial case studies. Each individual case study defines a set of key performance indicators (KPIs) that are used to evaluate the improvement that the new technologies provide. The case study specific KPIs are aggregated into project level KPIs which provide a quantitative evaluation of the project goals.

The project has set challenging goals in terms of KPIs such as:

• Reduction of design time/design effort in the range of 10%-50% by design artefacts reuse. • Reduction of validation effort in the range of 10%-30% by automated trace collection and analysis. • Reduction 10%-50% in time/effort required for managing and handling all the involved models (e.g. time for model retrieval and access). • Reduction 10%-50% in time/effort required for tracing and handling all the involved models at design and runtime levels (e.g. creation of and access to relations between system and traces models). The above-mentioned KPIs are measured through out the project industrial case studies. At the current stage the first evaluation phase has finished. The next sections present the preliminary results.

Results of the First Evaluation Phase and Outstanding Research Challenges

At the time of writing this paper, the MegaM@Rt 2 project has entered its second half.

In the following sections, we provide an overview of the current achievements of the project by focusing on research work and the corresponding results that we have already obtained.

The MegaM@Rt2 System Engineering Tool Set

This tool set aims to support system design activities. It has been architected around three main topics: i) requirements analysis & specification, ii) system modeling and iii) model verification & validation. The approach integrates up to 20 different open source tools, mainly Eclipse-based, such as Modelio, developed by the consortium research partners. These tools support a variety of current engineering practices based on standard modelling languages, profiles and extensions like: UML, SysML, MARTE, AADL, EAST_ADL, etc. The framework is designed to integrate additional "external" tools like Matlab/Simulink, AUTOSAR, Modelica and others, based on specific needs of the industrial partners. Different techniques have been adopted to ensure the correctness of system models, either in terms of verification of languages syntactic paradigms (e.g. using SAT-and CP-solver technologies) and in terms of functional and non-functional validation of system artefacts with respect of given requirements (e.g. through model simulation, model testing, machine learning technique, etc.). For example, [START_REF] Pérez | Reasoning about UML/OCL class diagrams using constraint logic programming and formula[END_REF] proposes a framework to reason about the satisfiability of class models described using the Unified Modeling Language (UML). It allows to identify possible design flaws as early as possible in the software development cycle, by annotating UML Class Diagrams with Object Constraint Language (OCL) invariants. Then, the Constraint Logic Programming (CLP) paradigm allows to reason about UML Class Diagrams modeling foundations thanks to a translation to Formula.

Several other research areas have been investigating. For instance, the current trend on Internet-of-Things Systems of Systems (IoT-SoS) implies significant evolution of modeling, analysis and design approaches [START_REF] Villar | Model-Driven Analysis and Design of IoT Systems[END_REF] .

Separation of concerns is one of the fundamental principles allowing to build well-structured software and improving its maintainability/evolutivity. Executable models are good candidates to capture the behavior of a software-intensive system using separation of concerns approach. In [START_REF] Cariou | A generic solution for weaving business code into executable models[END_REF] , Domains Specific Languages (DSL) have been exploited to create executable models when business operations are tied to specific technological platforms. This method is applied both at design-time for creation of executable models with EMF and at run-time by monitoring operation calls from the deployed execution engine.

Another aspect investigated in [START_REF] Muttillo | Design Space Exploration for Mixed-Criticality Embedded Systems Considering Hypervisor-Based SW Partitions[END_REF] [10] is the availability of platform-independent SW models and HW synthesis tools able to automatically produce efficient implementations based on performance predictions of the system model and this on many different distributed and parallel computing resources.

Safety critical systems, e.g. as proposed by Bombardier Transportation and ClearSy in the project, require specific support for safety analysis, assessment and certification. The contract-based approach is adopted by some of the framework tools and is presented and discussed in [START_REF] Wiik | A Contract-Based Approach to Scheduling and Verification of Dynamic Dataflow Networks[END_REF] . It is based on finding static schedules relying on contracts and using this information in the verification process to reduce the number of invariant annotations needed. Moreover, contracts can be used to make compile-time scheduling decisions, improving runtime performance.

A complementary research area is related to the application of the Aspect-Oriented Methodologies focusing on the reduction of the modeling and verification effort by applying aspect-oriented principles in model construction [START_REF] Vain | On the benefits of using aspect-orientation in UPPAAL timed automata[END_REF] . The industrial partners have a preference for more classical and consolidated methodologies. However, such capabilities are still available for possible future applications in case needed.

In the general case, a main achievement is the ongoing contribution to the MARTE standard, as presented in [START_REF] Medina | Towards MARTE++: an enhanced UML-based language to Model and Analyse Real-Time and Embedded Systems for the IoT age[END_REF] and responding to the Request for Information issued by the OMG for a new MARTE 2.0. Partners proposals have been collected in an initial survey, then an answer to the RFI has been prepared and sent back.

Finally, the last project period will focus on the exploitation, at design time, of the runtime trace collection and analysis capability, in order to address possible model refinements in the context of feedback loops. To this intent, the most promising approach is the one provided by PADRE tool on performance anti-pattern detection and model refactoring [START_REF] Arcelli | Automating Performance Antipattern Detection and Software Refactoring in UML Models[END_REF] [START_REF] Arcelli | Exploiting Architecture/Runtime Model-Driven Traceability for Performance Improvement[END_REF] . Finally, as a part of an effort to automate system engineering, [START_REF] Nybom | A Systematic Mapping Study on API Documentation Generation Approaches[END_REF] provides a systematic mapping study on published tools and approaches that can be used for generating API documentation, or for assisting in the API documentation process. the paper presents an overview of what kind of tools have been developed, what kind of documentation they generate, and what sources the documentation approaches require.

The MegaM@Rt2 Runtime (Trace) Analysis Tool Set

This tool set aims to define new methods and tools for creating and managing models at runtime verification and testing, including automated runtime testing and monitoring as well as a model-based log collection and analysis infrastructure supported by tools such as PauWare or CertifyIt. This runtime tool set integrates 24 tools that further propose automated code generation, model execution as a part of a system, runtime verification and online testing, such as CompleteTest, JTL, PauWare, Smartesting tools, AIPHS, Comformiq Designer, Modelio, etc. These tools within the MegaM@Rt 2 approach integrate with the analysis tools. The main ongoing activity is related to establishing a smooth connection with the analysis tools, that will allow user-friendly and simple inclusion within the continuous development process, addressed in MegaM@Rt 2 .

Several results have been published. In the context of testing and test generation several papers address test generation using UPPAAL model checker and its extensions. For instance, [START_REF] Marinescu | An Energy-aware Mutation Testing Framework for EAST-ADL Architectural Models[END_REF] outlines a method for testing energy consumption in embedded systems using energy-related mutants for EAST-ADL architectural models, which are converted to UPPAAL Timed Automata and used for test generation UPPAAL Statistical Model Checker (SMC). A complementary approach is presented in [START_REF] Marinescu | Automatic Test Generation for Energy Consumption of Embedded Systems Modeled in EAST-ADL[END_REF] , where we show how architectural models described in the EAST-ADL architectural language can also be used for testing the energy consumption of embedded systems, after transforming them into networks of formal models called priced timed automata. A mutation testing approach for UPPAAL TA has been proposed in [START_REF] Siavashi | Vulnerability Assessment of Web Services with Model-Based Mutation Testing[END_REF] to mutate UPPAAL-TA models and use them for generating tests used for evaluating security vulnerabilities of web services. Last but not least, in order to enable the analysis of failed traces and quick fault localization, [START_REF] Iqbal | Reconstructing timed symbolic traces from rtioco-based timed test sequences using backward-induction[END_REF] proposes an approach that converts concrete test sequences generated and executed by Uppaal Tron against the system under test into symbolic traces that can be imported in the Uppaal tool and visualized in the Uppaal simulator.

In the same context of testing, [START_REF] Stratis | A Practical Approach Towards Validating HIL Simulation of a Safety-Critical System[END_REF] presents an approach for testing of software intensive safety-critical products to validate the hardware-in-the-loop simulation of a safety-critical system, by executing test cases both in the control setting (lab) and on the real product (train). The process is intended to be used when certifying the simulation which is a necessary step in order to certify the complete system. In addition, in [START_REF] Bergstrom | Using Timed Base-Choice Coverage Criterion for Testing Industrial Control Software[END_REF] , the authors propose an extension of base-choice criterion used for testing software-based on its nominal choice of input parameters, which takes into account time as another parameter when generating and executing tests by defining the timed base-choice coverage criterion. In [START_REF] Enoiu | A Comparative Study of Manual and Automated Testing for Industrial Control Software[END_REF] , the authors conducted a comparative study on the cost and effectiveness of tests that are manually written versus those that are automatically generated in the field of industrial control software, where strict requirements on both specification-based testing and code coverage typically are met with rigorous manual testing.

In order to explore the performance of deployed systems at runtime, [START_REF] Ahmad | Identifying worst-case user scenarios for performance testing of web applications using Markov-chain workload models[END_REF] suggests a performance space exploration approach for inferring the worst-case user scenario in a given workload model. The goal of this work is to detect which configuration of the load model has the potential to create the highest resource utilization on the system under test with respect to a given resource so that performance tests can be run with that configuration. An exact and an approximate method are suggested and compared.

Finally, in [START_REF] Diaz | Short and long distance marker detection technique in outdoor and indoor environments for embedded systems[END_REF] we propose a marker design and an algorithm to detect the markers under different ambient conditions, with a long range to be executed on embedded systems with low computational requirements. The proposed method reduces the existing problems in the state-of-the-art related to the use of different environments and conditions such as different distances or different illumination.

The MegaM@Rt2 Model and Traceability Management (MTM) Tool Set

The Model and Traceability Management (MTM) tool set aims at providing generic global model management and traceability capabilities, with a focus on the dedicated support for creating and using feedback loops between design-time and runtime models in the context of complex CPSs engineering. To this intent, the MTM tool set is composed of 5 different complementary tools supporting the Eclipse [START_REF] Gronback | Eclipse Modeling Project | The Eclipse Foundation[END_REF] and Modelio [START_REF]Modelio Open Source -UML and BPMN modeling tool[END_REF] technical modeling environments. These tools provide support for storing and handling large EMF models (NeoEMF) [START_REF] Daniel | NeoEMF: A multi-database model persistence framework for very large models[END_REF] , building and handling views integrating different EMF models (EMF Views) [START_REF] Bruneliere | EMF Views: A View Mechanism for Integrating Heterogeneous Models[END_REF] , keeping consistency and traceability between different EMF models (JTL) [START_REF] Cicchetti | JTL: A Bidirectional and Change Propagating Transformation Language[END_REF] , detecting and refactoring performance antipatterns (PADRE) [START_REF] Arcelli | Automating Performance Antipattern Detection and Software Refactoring in UML Models[END_REF] or organizing and managing Modelio-based models and their relationships (Modelio Constellation) [START_REF] Desfray | Model repositories at the enterprises and systems scale: the Modelio Constellation solution[END_REF] . In all cases, their main objective is notably to leverage the different kinds of models resulting from the System Engineering and Runtime Analysis tool sets, in order to handle and reuse these models altogether in a coherent way as part of the continuous CPS engineering approach promoted by MegaM@Rt2. During the first phase of the MegaM@Rt2 project, a significant research effort has been conducted by the involved partners in order to provide these fundamental capabilities via the various tools of the MTM tool set. We summarize significant related research achievements in what follows.

On one hand, we have worked on improving the general support for backward traceability and change propagation between different kinds of models thanks to the JTL tool [START_REF] Eramo | Enhancing the JTL tool for bidirectional transformations[END_REF] . We then used such a support in order to provide change propagation capabilities at architectural (design) model-level, and illustrated it in a software availability context [START_REF] Cortellessa | Availability-Driven Architectural Change Propagation Through Bidirectional Model Transformations Between UML and Petri Net Models[END_REF] . We also used this same support in order to automate performance improvements via the detection of architectural antipatterns using PADRE and thanks to traceability with corresponding runtime data [START_REF] Arcelli | Exploiting Architecture/Runtime Model-Driven Traceability for Performance Improvement[END_REF] (cf. also Section 3.1).

On the other hand, we have obtained interesting results in the model view area [START_REF] Bruneliere | A Feature-based Survey of Model View Approaches[END_REF] . Notably, we have worked on supporting the creation and handling of scalable model views combining different large-scale models together (including design and runtime ones) via traceability links [START_REF] Bruneliere | Towards Scalable Model Views on Heterogeneous Model Resources[END_REF] . To this intent, we worked on providing the required infrastructure to store, handle and trace efficiently very large models. This has been implemented in practice by leveraging the EMF Views and NeoEMF tools from the MTM tool set. This was a required achievement in order to be able to implement runtime-to-design time feedback loops, which is one of the longer-term objectives of MegaM@Rt2.

Interestingly, based on the two complementary efforts above-mentioned, we have then been able to apply our model view approach -EMF Views, in combination with our traceability capabilities in JTL, in order to provide a first concrete instantiation of the MegaM@Rt2 runtime-to-design feedback loop in the context of a safety-critical system from our partner ClearSy [START_REF] Eramo | Model-driven Design-Runtime Interaction in Safety Critical System Development: an Experience Report[END_REF] . In the second phase of the project, we plan to work on more practical instantiations of such a feedback loop by relying on tools from the MTM tool set.

Nevertheless, there are still open challenges in these promising research areas. We have already been able to discuss that within the Modeling community when organizing and running the first edition of the International Workshop on Model-Driven Engineering for Design-Runtime Interaction in Complex Systems (MDE@DeRun 2018), co-located with STAF 2018 in Toulouse, France [START_REF] Bruneliere | Model-Driven Engineering for Design-Runtime Interaction in Complex Systems: Scientific Challenges and Roadmap[END_REF] . Notably, we identified challenges related to the particularities of design-runtime traceability: e.g. which semantics has to be given to the traceability information, in which contexts and how? We also identified questions related to the analysis of the traced runtime information: e.g. what kind of runtime data is actually needed, in which contexts and how to collect it properly? Finally, we identified issues related to the overall objectives of such a design-runtime traceability: e.g. which engineering purposes or activities do we intend to address or cover thanks to such feedback loops?

Case Study Evaluation

A total of nine industrial case studies are used in the project in order to evaluate the MegaM@Rt 2 framework in practice. To provide measurable evidence on the extent to which the framework fits and provides benefits to the industrial development process, each case study defined a set of Key Performance Indicators (KPIs) that have been measured at baseline (i.e. when the project started) and have been / will be measured again after each of the two development phases of the project (i.e. at month 24 and month 36 respectively). At the time of writing this paper, the first evaluation phase has recently finished (at month 24).

During Phase 1, the case study providers have evaluated different scenarios using the tools and technologies offered by the different tool sets previously presented in this Section 3. The evaluation in terms of scenarios has put the focus on the benefits that MegaM@Rt2 is expected to bring: 1) They allow to better understand the aspects that the case study providers found most important for their industrial activities and 2) They structure and organize the tools' verification and validation, which are based on the requirements and the KPIs defined by MegaM@Rt2. The case study providers made some changes in the choice of the best scenario to validate a tool/technology and, conversely, in the judgement of the best way for using a tool in a certain scenario; many problems were encountered but solved thanks to the collaboration that the tool providers fully offered.

The details on the case study results are provided in deliverable D5.5 as available from the project website [START_REF]Deliverables -MegaMart2 -MegaModelling at Runtime[END_REF] . It is important to mention that case studies measure differently the KPIs depending on their respective contexts and designed experiments. Nevertheless, it is noteworthy to point out that the case studies succeeded to demonstrate improvements significantly above targets, in particular, in:

• Time required for identification of design problems;

• Time/effort for requirements validation;

• Productivity improvements;

• Cost savings for development and maintenance of large complex systems. The project has also already demonstrated values close to the targets for the following set of KPIs:

• Reduction of validation effort by automated trace collection and analysis;

• Reduction in time/effort required for tracing and handling all involved models at design and runtime levels; • Quality improvement by improving predictability and conformance to specifications.

Conclusions and Future Work

With a total of 40 deliverables and multiple tools provided via three complementary tool sets [START_REF]MegaM@Rt2 tool box[END_REF] , MegaM@Rt 2 aims at improving the productivity and quality of the system development and at reducing the time-to-market for complex systems, as well as to reinforce the European scientific and technological leadership and competitiveness of the European market. The project has already delivered a significant number of research approaches, technical tools and methods spanning from system-level modeling to runtime analysis and global traceability and model management. While the results are globally evaluated as substantial, we face several open challenges towards our goal for scalable and traceable model-driven engineering applicable to a variety of industrial domains. The first phase of the project put in place the baseline methods that were assessed in the industrial settings. We demonstrated the opportunities brought by the global traceability and model management technologies resulting from research activities. In the meantime, we identified several further challenges. One of them is the need for a common runtime trace format, i.e. a shared representation for different types of runtime (meta)data. Another challenge is the need for more automated inference methods that could systematically relate these runtime traces (uniformly represented/modeled) to the corresponding system design artifacts.

Therefore, during its last period, the project plans to concentrate on those open areas by scheduling dedicated activities such as hackathons, demonstration session and workshops. We would like to engage the project community, both case study providers and technology providers to focus on a common agenda that would push the state-of-the-art further (in these areas, but also in others of interest to the project). Moreover, we plan activities to create awareness about the approaches and technologies developed in the project, which have already been adopted and endorsed by the industrial partners. Finally, an important aspect is about planning and preparing for the sustainability of the project results by creating an ecosystem for all the tools and methods composing the MegaM@Rt 2 framework.

Fig. 1 .

 1 Fig. 1. Overall conceptual architecture of the MegaM@Rt project.

Acknowledgement. This project has received funding from the Electronic Component Systems for European Leadership Joint Undertaking under grant agreement No. 737494. This Joint Undertaking receives support from the European Union's Horizon 2020 research and innovation program and from Sweden, France, Spain, Italy, Finland and Czech Republic.


Claire Scopsi
email: claire.scopsi@lecnam.net

The documentality of memory in the post-truth era

Keywords: memory, narratives, document theory, post-truth

This article compares the definitions of the document, produced by the document theorists and the arguments advanced by the French historical epistemology of the twentieth century in order to set what is a reliable documentary source. In the context of digital post-truth, the former criteria, based on the paradigm of truth and authenticity guaranteed by institutions and scientists, can be questioned. We suggest to consider the production of historical narratives as a design process, and to evaluate the truthfulness of a source according to their three regimes of documentality: textualization, auctorialisation and documentarisation.

The documentality of memory in the post-truth era

Claire Scopsi

Dicen-idf Cnam Paris, claire.scopsi@lecnam.net Politics, environment and economy are affected by the phenomenon of post truth. So is history. Revisionism, politicized or racialized memories, and collective memories of small groups are opposed to the works of historians. The paradigm of truth, which historians of the twentieth century have put in the center of historical knowledge, is weakening and scientific institutions are no longer sufficient to impose their visions of the past, facing storytelling. The documentality, according to Bernd Frohmann (2012), is a power or a force which is given to a thing by special arrangements with other things1 . And, according to Maurizio Ferraris, documentality is the relation with the social object, instituted with the registered acts (2013,247). Both are referring to a special agency, which is given to objects by the documents.

Because the production of historical knowledge is directly concerned with documents (Buckland), we propose to analyze the documentality of memories. In order to analyze memory and history, the documentary nature of the memories makes it possible to identify other paradigms than the paradigm of truth.

I will first present some of the main points of the document theory. Then I will show that the relation of historians to the document since the 20th century is led by the paradigm of truth. I will quickly recall what the recent concept of post-truth is and how it undermines the role of historians as a guarantee of truth. In a third part, I will refer to the work of Manuel Zacklad on the design of information. I will propose three regimes of existence of memories (mediality, indiciality, auctoriality) and I will also propose to take them as criteria in order to evaluate the reliability of memories.

Memory and history in the light of the document theory

In the epistemology of history, authors apply the term of memory to various ways to evoke the past: museums of history, heritage, traditions, national commemorations, and oral history narratives. They share the fact of not being scientific productions and of rather addressing the general public.

In this work, I will try to encompass under the term of memory, historians' scientific works, and narratives produced by amateurs. But I admit it is a heresy from the point of view of historical epistemology. The criteria proposed by the twentieth century's historians in order to set the frontier between history and memory are deeply linked to the notion of the historical sources, that are the documents on which this science is based. Therefore the document theory is very useful for us in order to understand the arguments of historians.

Niels Lünd (2009) and Mickael Buckland (2015[START_REF] Buckland | Document Theory (IEKO)[END_REF] produced relevant syntheses of the emergence of the document theory and the evolution of its concepts and issues. I will quickly recall them. Lünd recalls the etymological definition of the document which refers to its function. In Latin, "documentum", and its root "doc" are related to teaching, to examples, to demonstration. In French, we find a new meaning "evidence and information" linked to the birth of bureaucracy and written law. The functions of the documents are to carry and transmit knowledge or to produce a reliable trace of the reality of a fact. Lünd suggested this definition of the term document: "written, true knowledge 2 " (Lünd, 2009).

The document started with writing and remained for a long time synonymous of a book or bundles of paper. But in the 1930s, with photography and phonography as professional practices, Paul [START_REF] Otlet | Mons, Editiones Mundaneum[END_REF] proposed a simple definition of the document as signs on a medium3 . Robert Pagès (1948) and Suzanne Briet (1951) replaced the term "sign" with the term "evidence" 4 , thus encompassing in the definition, the objects and the living beings. It is no longer the shape which defines a document, but the function which is assigned to an object in order to represent a set of knowledge. The importance of use 5 is reinforced by Jean [START_REF] Meyriat | Document, Documentation, Documentologie[END_REF] who made a difference between a document by destination, which is a 2 "Here a document is a piece of writing that tells you something. These three characteristics can be merged into one central phenomenon in modern society: written, true knowledge." (Lünd, 2009,3).

document voluntarily produced to be the trace of a fact, and a document by use, produced in another intention and used as evidence of facts or knowledge.

In 1997, Mickael Buckland renewed the question, "what is a document", within the digital context. And a few years later, in the early 2000s, the collective project R.T. Pedauque, coordinated by Jean Michel Salaün, proposed a global approach in three dimensions for the study of documents, their actors and their economy. These dimensions are the physical perception (SEEN = (medium + inscription), the intellectual effort (READ = decoding + representations), the mediation (KNOWN = memory + transaction) [START_REF] Salaün | Les Architectes de l'information Face à l'oligopole Du Web[END_REF].

All these works led Mickael Buckland (2017,3) to identify three statuses of the document according to their origin:  a conventional view that is a document created as a document, ordinarily producing an inscription on a flat surface,  a functional view that is objects made into or presented as documents,  a semiotic view that is objects regarded as documents by a perceiver, whether or not they were produced with this purpose.

We will now consider the paradigm of truth.

Memory vs History: the paradigm of truth

At different periods of the twentieth and twenty-first centuries, many historians have presented their reluctance as concerns the memory and particularly the testimony. They often perceive memory as an instrument of power, manipulated by social groups, or states, in order to serve their struggles and interests 6 . (Le Goff, 1986). Memory, as a narrative of past facts, does not fit with the paradigm of history, that is the search for authenticity: authenticity of sources and truth of facts.

According to Paul [START_REF] Ricoeur | La mémoire, l'histoire, l'oubli[END_REF] the orthos logos of memory is the "requête de vérité" (a search for truth). Something occurred, and someone tries to remember it as precisely as possible 7 . But some characteristics of the memory-as-a-narrative, take away from the truth and pervert it. These characteristics are:  Orality. The memory is oral thus, it is moving. According to Ricoeur, the declared memory, (that is the testimony), is reliable if stable, and if the witness is able to repeat 6 "Collective memory is one of the major stakes of developed societies, and of developing societies, ruling classes and dominated classes, fighting for power or for life, for survival and for promotion. " Jacques Le Goff, Histoire et mémoire, Gallimard, 1986, p. 174, 177. (trans. By author).

7

"It is in the moment of recognition, upon which the recall effort ends, that this search for truth declares itself. We feel and know then that something happened, that something has taken place, that involved us as agents, as patients, as witnesses. Let's call fidelity this request for truth." Paul Ricoeur, La mémoire, l'histoire, l'oubli, 2003, 66) (trans. by author).

it without modifying it. And it is all the more trustworthy that it can be subject to controversy and confronted to other testimonies.

 The memory is embodied. Thus, it is emotional. The testimony carries the emotion of its author and communicates it to others. According to Ricoeur the testimonies of survivors of the Holocaust are the most difficult to receive in the paradigm of authenticity, because the emotion we feel faced to the horror and the respect of the suffering of the witness do not make it possible to evaluate the reliability of the story.

 Testimony is voluntary. As said Marc Bloch, the witness is a prisoner of his own prejudices, and of the prejudices of his time, which lead him to misrepresent the truth.

Therefore, the declared memory can not be history. But it can be a source, provided that some technologies are implemented. Such as:

-inscription, which set the declared memory in the shape of a verbatim, and "removes it from its narrator" (Ricoeur, 2003, 209) -a critical method, practised by professional historians, which is a mechanism to sort out "what people can believe to be true or false; or more exactly, to be probably true or probably false". (Bloch, 2006, 831).

We can say that the historians ask in their own way, and with their own conclusions, the same questions as do the theoreticians of the document.

The first question is "what is a document"? The answers of the historians sometimes meet the answers of the document theory. Like Briet and Pagès, Bloch accepted all types of evidence: object (such as remains), inscribed signs, parts of the body like bones (Bloch did not tell about living animals, but he evoked the Plesiosaurus.). Ricoeur evoked non-verbal and non-narrative evidence: fingerprints, photographic archives, or traces (Ricoeur, 2003, 220). But he advised us to use them in addition to a testimony and not as a single clue.

Can an oral source be a document? Marc Bloch considered that idiomatic expressions or linguistic traits, can be evidence. But he didn't specify whether these words should be written in a text or whether they would survive in the language itself. In the same period Paul Otlet (Otlet, 1934, 366), included oral literatures and tradition within the global class of documents.

But Paul Ricoeur firmly rejected the oral forms. He accepted them as evidence only once recorded on a medium, and even more so, written in order to become invariable and removed from the emotion of the witness. But is a verbatim good evidence? The verbatim sets a reference version of a story, but is it truer than another version? A lie, or a false testimony does not become true once it is transcribed.

Oral and written documents are not as different as they seem to be, fora testimony can only exist if it is delivered to somebody. A memory is always a sort of text, because it is always a sort of inscription, if only in the mind of its receivers. Pierre [START_REF] Nora | Les Lieux de Mémoire[END_REF] stated that there is no more memory, but only history, because there are no more traditional societies in which memory is embodied, in the gestures and rituals 8 . According to him, the contemporary memory is an archival-memory for it always puts the past into texts whether they are verbal or not. Therefore, in our "requête de vérité" the document no longer matters as a physical medium but as a substitute of the tradition-memory.

The second question is about the document by destination and the document by use. The documents by use are "involuntary witnesses" [START_REF] Ricoeur | La mémoire, l'histoire, l'oubli[END_REF](Ricoeur, , 2015) ) like remains or written records produced for other purposes and diverted into historical sources such as charters, minutes of a trial and administrative documents. The documents by destination are the voluntaries testimonies (narratives), or the memoirs. Bloch said that history should rather trust sources by use (2006[1949], 892). Ricoeur accepted voluntary testimonies only when they are officially registered as archives and used by readers other than those that they tried to convince first. Because this slightly turns them into a sort of document by use.

The third question refers to the three dimensions of the document: it is the question of the critical method of historians, as exposed by Marc Bloch. Bloch referred to De re diplomatica which Jean Mabillon wrote at the end of the 17th century in order to expose his method to authenticate documents. Diplomatic studies analyse the shape of a document, its process of design and the way it is transmitted. Diplomatics do not concern the core of the discourse but the shape and the layout of the writing and the chemical characteristics of the paper. They evaluate if the elements of presentation are consistent with the conventions of the time and the place in which the document is said to have been produced, and if the document "is what it claims to be". All those points are about the SEEN.

But documentary authenticity is not the historical truth. Authentic documents can lie. And fake documents can tell the truth. The understanding of the text and the overlaps with other sources allow the historians to detect the inconsistencies and contradictions that reveal a lie or an error. They have to cross the "intelligibility gap", and the "cultural readability" (Bachimont, 2017, 100), and deliver a story of the past as fair as possible. This point is about the READ).

What about the KNEW? With the question of the post-truth, we are getting nearer to the paradigm of the documentary truth in its socio-medial dimension, which is the KNEW approach. The recent concept of post-truth refers to a new relationship to the truth that is particularly observed around political debates in newspapers and social networks. The term 8 "Modern memory is, above all, archival. It relies entirely on the materiality of the trace, the immediacy of the recording, the visibility of the image". Pierre Nora, Entre mémoire et histoire, la problématique des lieux, 1997[1984],26.(trans.;by Marc Roudebush) has recently emerged in the Anglo-Saxon press, but the origin of the concept is granted to the philosopher Harry Frankfurt, in his essay "On bullshit" (1986, republished in 2005). He makes a difference between the lie, which is the opposite of the truth, and the bullshit, which makes no reference to the truth. While the liar makes an audience believe his lie, the bullshitter tries to give a certain image of himself whatever the truth of his words. Of course the debates of opinion, and the statements that can not be checked particularly suit the bullshitter.

What moves the bullshit from rhetoric to the social field, is its generalization. The other initiator of the concept, Ralph [START_REF] Keyes | The Post-Truth Era: Dishonesty and Deception in Contemporary Life[END_REF], points out the generalization of the "spin job". It is a communication which aims at manipulating, and in which the effect matters more than the truth. Keyes identifies the root of the phenomenon in the practices of narrative psychology, in which the patient's well-being overrules the sincerity of his story. Storytelling in corporate communication, postmodernism and linguistic turn, are also related to post-truth.

Post-truth is a "hyper-communication" (Tanquerel, 2017, 11). His paradigm is not the truth of the message, but the efficiency of the perlocution. It leads to two contradictory behaviors among the receivers: they trust those who comfort their beliefs, and they are suspicious of those who contradict them. Too much doubt here, not enough there... Thus, who can guarantee the truth in our society? According to Bloch, it is, without doubt, the professional, that is, the librarian, the historian, the teacher or the journalist. But in postmodern society, they are suspected, of manipulating the past according to their own beliefs and producing not a historical truth, but certainly a discourse on the past.

Antoine Prost (2014[START_REF] Prost | Douze leçons sur l'histoire[END_REF],284) attributed what he called the demystifying posture to the aftermath of the events of May '68 and the influence of Michel Foucault and the linguistic turn. The semiological approach, according to him, reduced the historical narrative to a text, devoid of its relation to the real. It is no more than a simple literary product, which no longer reflects the preliminary work of critical analysis of the sources. Ricoeur also wrote a few pages in "La mémoire, l'histoire, l'oubli" 9 about his controversy over Roland Barthes' "Discours de l'histoire" and Haydn White's Metahistory. He considered these approaches as aporetic, because the historic knowledge can not be reduced to its only discursive dimension. The history must be analyzed according to a "triple membrure" 10 : the documentary evidence, the causal/final explanation and the literary formatting (Ricoeur, 2003, 323). 9 Memory, History, Forgetting", Paul Ricoeur, Translated by Kathleen Blamey and David Pellauer, University of Chicago Press, 2006, 624p. 10 "a triple timber" (trad. by the author).

We can see that Ricoeur admitted the communicative character of historiography. The historian's narratives are not pure documents, (as are the involuntary sources), neither are they pure works of communication in the meaning of the post-truth (as are the voluntary testimonies). They are communicative-documents, which prove AND produce effects. We will examine Ricoeur's "triple membrure" and compare it to the three dimensions of R. T.

Pedauque, in a more communicative perspective. For this we will refer to Manual Zacklad works.

Analyzing memory in its documentary and communicative dimensions

Social networks which mix all the publishing systems reinforce the post-modern phenomenon. If the scientists stay among their peers, in their own traditional publishing networks, they can not reach the general public. But, publishing on the web, in the same networks as the general public, they may lose their authority and have to face the "invasion of idiots" according to the formula of Umberto Eco 11 . However, Ulrich Beck noted that they are also confronted with the "enlightened citizen" because the difference between an amateur and an expert is blurry. Even worse, in order to be heard, scientists must play the game of hyper-communication. It is no longer sufficient for them to prove the relevance of a discovery, they now have to introduce themselves and be convincing. (Beck, 2003, 368). As we can not accept to give up la requête de vérité, what criteria should be used instead of authority? Traditional methods of authentication by the shape of the medium still exist, but methods of evaluating the intent of the author and the use of the receiver should be added.

So we have to get into the communicative dimension of the historical memory and study it, not isolated as a medium of knowledge, but in its social dimension as an interaction of productions and receptions. (Which makes memory being a cooperative transaction).

Manuel Zacklad noted that information design is too often approached from the point of view of graphic processing or information architecture. He recommends, not only to consider the final semiotic unit (a website, a newspaper, a poster...) which is the result of informational design, but to consider also, what are the impulses and the devices which led a production to this result. These devices encompass heterogeneous elements: the actors who are involved in the process and their modes of coordination, the editing plans and the structures of the semiotic fragments, the tools and the mediums (which can be plural in the case of a transmedia communication). All these elements can be reduced to three main 11 "The social media give the right to speak to legions of idiots who spoke only at the bar after a glass of wine, without damaging the community. They were immediately silenced, while now they have the same right to speak as a Nobel Prize. It is the invasion of idiots ". Umberto Ecco, interview, la Stampa, 11juin 2015 (trans. by author) interdependent activities, which are the "moteurs" of the whole design of an information system: textualization, auctorialisation and documentarisation. (2018,18).

• The textualization aims at producing a media content with a narrative or argumentative logic. It concerns the text in its rhetorical dimension.

• The documentarisation / éditorialisation (which is documentarisation of digital contents for the web) structures and makes a content visible in its medium. In the digital context, it corresponds to a semiotic and technical arrangement of dispersed elements (codes and files) which leads to an understandable element, like a web page.

• The auctorialisation concerns the signature, the intellectual property, the rights of access to a platform and everything which makes it possible to guarantee the identity of the producers and the beneficiaries of the information.

Since history is textual and documentary, and has a communicative logic, we can apply this dispositive approach to all memory productions, whether or not they are scientific. It is possible to forget the paradigm of authenticity, which separates memory from history, and to consider memory, from the point of view of its dynamics of production. The question of the truth will not be left aside but will be integrated into all the documentary characteristics. The three impulses of the information design allow us to propose a grid which can be applied to the analysis of all types of memory productions and to classify them according to the results of this analysis. All the memorial productions, whatever the status of their authors, are made of these three components, but the intensity of their investment in each regime makes it possible to sort out and classify them.

-

The regime of mediation is the way in which memory productions are invested in perlocution, that is in its capability to produce an effect on the receivers.

This is textualization because it is about the processes of argumentation which makes it possible to convince an audience, to move them and to capture their -

The regime of indiciality is the way in which the memorial productions mobilize techniques to make a fact of the past exist in the present. On the one hand, there are the processes of inscription on a medium, which give a permanence to the past, and make us access to traces. On the other hand, indiciality is also all the processes of documentarisation, the designations, the classifications, the sortings which allow the receiver to refer to a specific moment of the past (as an index refers to a specific page of a book) and to have mental representations of it. Oral archives collections, and all the memories registrated in archival collections, heritage lists, chronologies, maps and timelines, Wikipedia pages and Wikimedia collections are some examples of these devices of the regime of indiciality.

-

The regime of evidence is the way in which memorial productions try to guarantee the reliability of a trace of the past, and the truthfulness of a story. We find here, of course, diplomatics, bibliographies, the references of sources, and signatures. When the productions are collective, or participatory, the regime of evidence is shown by the rules which are fixed to the participants (for example how they are identified). Evidence is an important part of the work of historians, archivists, or heritage institutions, but collaborative platforms also show many processes of authorship. The fact that crowds can react and report errors or can participate in an authentication collective work is an emerging process of the regime of evidence.

So, there is no true or doubtful memory in itself. Each memory has three dimensions. The works of historians always have an important regime of auctoriality, for it is the basis of their method. But some historians aim to have an effect on their readers, because their research

  attention. The work of the mediators in museums and memorials, historical performances in heritage sites, national celebrations, historical programs and films and, in general, productions aimed at a general public, are examples of memorial activities which mainly invest in mediation. Minority memories and militant memories are other examples. They are performative because they build up the identity of a social group and make it exist in the eyes of others. The devices of the regime of mediation are life storytelling, testimonies, pictures, and artistic practices such as theatre or contemporary installations.

"I intend documentality to denote a property of a specific thing or phenomenon: is power or force. This fourth aspect of documentality refers to a thing's agency, which is exercised in its arrangements with other things. (Frohmann,

2012, 174)

"The most general definition that can be given of the Book and the Document is this: a support of a certain material and dimension, possibly of a certain folding or winding on which are shown signs representative of certain intellectual data.(Paul Otlet, Traité de Documentation, Editiones Mundaneum, 1934,

43) (trans. by author).4 "Any concrete or symbolic index preserved or recorded in order to represent, reconstruct or prove a physical or intellectual phenomenon (Suzanne Briet, Qu'est-ce que la documentation, EDIT,1951, 1) (trans. by author).5"The desire to obtain information is therefore a necessary element for an object to be considered as a document, while the will of its creator may have been other. The desire to obtain information is therefore a necessary element for an object to be considered as a document, while the will of its creator may have been other.Jean Meyriat, ' " Document, Documentation, Documentologie .', in Schéma et Schématisation, 1981, 51- 63. (trans. by author).