Philippe Wanlin

Holli Schauber

The development of primary and secondary pre-service teachers' beliefs about constructivist and transmission-oriented teaching

Keywords: Constructivism, Transmissive teaching, Beliefs profiles, Measurement scale, Development Le développement des conceptions d'enseignants en formation pour le

The development of primary and secondary pre-service teachers' beliefs about constructivist and transmission-oriented teaching

Introduction

La littérature récente oppose les approches constructivistes et transmissives de l'enseignement.

Les programmes de formation des enseignants contemporains considèrent que l'enseignement constructiviste est la meilleure voie à suivre pour favoriser l'apprentissage des élèves.

Objectif

Cet article examine si les enseignants en formation se positionnent à l'identique par rapport à ces aspects : opposer les approches d'enseignement constructivistes et transmissives et considérer que les approches constructivistes sont supérieures en termes de gains d'apprentissage.

Méthode

Nous nous référons à plusieurs instruments de mesure issus de la littérature en sciences de l'éducation Anglophone et germanophone. Nous en extrayons des items que nous avons traduits en français et que nous avons soumis à 228 enseignants en formation. Ils devaient donner leur degré d'adhésion à ces affirmations sur une échelle Likert à 6 modalités de réponse.

Resultats

Les analyses factorielles aboutissent à un modèle présentant de bonnes qualités psychométriques. Les résultats montrent que les enseignants en formation détiennent des conceptions nettement moins binaires que ce que suggère la littérature et que l'adhésion au constructivisme dépend du programme ou de la filière de formation à l'enseignement suivi(e).

Conclusion

Vu que les conceptions constructiviste et transmissive coexistent dans les cognitions des enseignants en formation, nous discutons d'implications pour la recherche et la formation des enseignants.

Mots clés : Constructivisme; Enseignement transmissif; Profiles de conceptions; Echelle de mesure; Développement

The development of primary and secondary pre-service teachers' beliefs about constructivist and transmission-oriented teaching

Philippe Wanlin & Holli Schauber, University of Geneva

Introduction

Recent research reveals some contradictory evidence about the effectiveness of constructivist teaching approaches. On the one hand, the research indicates that constructivist teachers provide enhanced learning environments (e.g. [START_REF] Staub | The nature of teachers' pedagogical content beliefs maters for students' achievement gains: Quasi-experimental evidence from elementary mathematics[END_REF] and generate better student learning than traditional teaching strategies (e.g. [START_REF] Voss | Überzeugungen von Mathematiklehrkräften[END_REF]. The opposing view is that constructivist teaching is only effective if it is undertaken with behaviorist teaching principles (e.g. Alfieri, Brooks, Aldrich, & Tenenbaum, 2011). This view also suggests that teachers holding constructivist beliefs don't implement different practices than their transmission-oriented colleagues (e.g. [START_REF] Leuchter | Zusammenhänge zwischen unterrichtsbezogenen Kognitionen und Handlungen von Lehrpersonen[END_REF].

Most current teacher training programs provide a strong emphasis on constructivist teaching approaches; as is the case in Geneva, Switzerland. Drawing on this premise, our main objective is to analyze pre-service teachers' opinions on constructivist and transmissionoriented teaching approaches. We aim to analyze the development of the beliefs they hold about the best teaching principles and practices throughout the duration of the training program. Our purpose is also to analyze if there are differences in these developments related to the school level and the content area for which they are being prepared.

In order to pursue this research objective, we first reviewed the literature to develop a questionnaire with general, non-content-oriented statements about constructivist and transmission-oriented teaching approaches. Then, we validated this instrument with a sample of 228 pre-service teachers being trained for elementary or secondary education to permit a robust description of their beliefs and of the possible differences one can observe between the years of the training program or the levels for which the pre-service teachers are being prepared. This led us to interesting findings which we discuss in terms of possible sources of developmental differences and in terms of implications for research and teacher education.

Theoretical background

Assessing teachers' beliefs about constructivist and transmission-oriented teaching approaches

There are many texts on teachers' beliefs about constructivist and transmission-oriented teaching approaches but most of them rely on the same instrument developed by [START_REF] Fennema | Teacher beliefs scale: cognitively guided instruction project[END_REF] see also Fennema & Carpenter, 1990). This instrument is designed to measure mathematics teachers' beliefs on the best way to teach mathematics. It contrasts constructivist student-centered approaches with a teacher-centered direct transmissive instructional approach. It was first used by [START_REF] Peterson | Teachers' pedagogical content beliefs in mathematics[END_REF] but the most commonly cited paper using this instrument is that of [START_REF] Staub | The nature of teachers' pedagogical content beliefs maters for students' achievement gains: Quasi-experimental evidence from elementary mathematics[END_REF]. Both of these papers conclude that teachers with constructivist beliefs obtain higher student performance than those with transmission-oriented beliefs. 1 They also conclude that constructivist teachers provide better and richer learning environments than their behaviorist colleagues. There are plenty of studies that have used this instrument [START_REF] Capraro | Construct validation and a more parsimonious mathematics beliefs scales[END_REF][START_REF] Dubberke | Lerntheoretische Überzeugungen von Mathematiklehrkräften: Einflüsse auf die Unterrichtsgestaltung und den Lernerfolg von Schülerinnen und Schülern[END_REF][START_REF] Hess | Lehren zwischen Belehrung und Lernbegleitung : Didaktische Hintergründe und empirische Untersuchung zum Lehrverständnis und dessen Umsetzung im mathematischen Erstunterricht[END_REF]OECD, 2009;[START_REF] Rakoczy | Befragungsinstrumente[END_REF][START_REF] Voss | Assessing teacher candidates' general pedagogical/psychological knowledge: test construction and validation[END_REF]. For example, Voss et al. (2011) showed a positive association between constructivist teacher beliefs and students' math performance and 1 Note that both papers also concluded that students' prior achievement is a better predictor of students' learning gains than teachers' beliefs orientations.

a negative link between transmission-oriented teacher beliefs and student's achievement in secondary math. [START_REF] Kunter | Professional competence of teachers: effects on instructional quality and student development[END_REF] also provide an interesting study about the effects of teacher Pedagogical Content Knowledge (PCK), including among others, teachers' orientations towards constructivism, assessed with a part of the instrument developed by Fennema et al. (1990), on students' performance and motivation. They show that constructivist beliefs, when taken independently, are positively associated with students' motivation and achievement. This univariate effect was not found in the analysis taking into account all other teacher characteristics measured in their study. They conclude that "all other teacher attributes being equal, teachers who endorse constructivist beliefs showed no advantage in cognitive activation or student support, and even scored lower on classroom management" (Kunter et al., 2013, p. 816). Note that, [START_REF] Leuchter | Zusammenhänge zwischen unterrichtsbezogenen Kognitionen und Handlungen von Lehrpersonen[END_REF] could not demonstrate that constructivist or transmission-oriented teachers differ in their teaching practices.

It is important to underline that our reading of all papers using this instrument led us to the following finding: little evidence was available on the reliability and the psychometric quality of this instrument before the work of Mareike Kunter and Jürgen Baumert (e.g. Kunter et al., 2011). The German research team provides two interesting insights. Firstly, teachers can hold both kinds of beliefswith a preferred orientationso that constructivist and transmission-oriented beliefs are not seen as two extremes of the same continuum but rather as a bi-dimensional interrelated system (Voss et al., 2011). Even if some researchers highlight that elementary school teachers prefer transmissive teaching [START_REF] Demant | Primary teachers' attitudes toward the direct instruction construct[END_REF] or that teachers can adopt one orientation and not the other [START_REF] Tsai | Nested epistemologies: science teachers' beliefs of teaching, learning and science[END_REF], research shows that secondary physics teachers hold both kinds of beliefs in an interrelated system consisting of contentoriented and student-oriented beliefs and that teachers agree with the importance of both teacher-regulated and student-regulated learning (Belo, van Driel, van Veen, & Verloop, 2014). [START_REF] Schuh | Learner-centered principles in teacher-centered practices[END_REF] discusses results adopting the same interrelated beliefs system as her elementary school teacher used principles of learner-centered teaching embedded within a traditional teacher-centered environment. Secondly, they provide an indication about the high quality of their 44 item instrument (4 point likert scale): χ 2 (13) = 21.62 p<0,05, CFI = .988, RMSEA = .045 with factor loadings ranging between .46 and .91 and Cronbach's alphas ranging from .67 to .88. Unfortunately, most of these papers do not provide the entirety of the instruments' itemswith the exception of [START_REF] Hess | Lehren zwischen Belehrung und Lernbegleitung : Didaktische Hintergründe und empirische Untersuchung zum Lehrverständnis und dessen Umsetzung im mathematischen Erstunterricht[END_REF] and [START_REF] Capraro | Construct validation and a more parsimonious mathematics beliefs scales[END_REF] and all of the items are dedicated to mathematics instruction so that it is not designed to assess the beliefs of generalist teachers working for example in elementary schools or the beliefs of secondary school practitioners teaching different subjects.

Two other instruments used to assess teachers beliefs about constructivist and transmission-oriented teaching approaches exist. Both are similarly designed to assess constructivist and transmission-oriented beliefs from a non-subject specific perspective. The first one was developed by [START_REF] Woolley | Construct validity of a self-report measure of teacher beliefs related to constructivist and traditional approaches to teaching and learning[END_REF] and stems from their findings resulting from teacher interviews. Their instrument, a 34 item (short version 21) 6 point likert scale, leads to a three-factor solution for their validation study using a sample of 856 pre-service teachers: traditional management (α=.52), traditional teaching (α=.78), and constructivist teaching (α=.73). The psychometric qualities of this instrument are relatively low (χ2 (186) = 753.79 p<0.00, CFI = .81 NFI = .76 NNFI = .78 GFI = .91 AGFI = .88 RMSEA = .066). Unfortunately, these researchers do not provide the factor loadings of the 21 items in their respective factors using a confirmatory factor analysis. The second instrument was developed in an identical way by [START_REF] Hermans | Development of the Beliefs about Primary Education Scale: Distinguishing a developmental and transmissive dimension[END_REF] [START_REF] Brown | Confirmatory factor analysis for applied research[END_REF][START_REF] Furr | Scale construction and psychometrics for social and personality psychology[END_REF][START_REF] Muthén | MPlus Statistical analysis with latent variables : user's guide[END_REF]. Other instruments were used by Belo et al. (2014) and [START_REF] Könings | Differences between students' and teachers' perceptions of education: profiles to describe congruence and friction[END_REF] that we didn't use as they were not published yet when we constructed our pool of items. But by checking our items afterwards with those available in the item sample provided by the authors of these texts, one can say that they are relatively close.

As the quality of the mathematics-oriented measurement scale is better than the generaloriented instruments, it might be interesting to convert the items of the instrument developed by Fennema et al. (1990) into global non content-oriented statements. In addition, it is important to keep some of the items of the more generalist-oriented instrument scales, those with the better factor loadings.

Effectiveness of constructivist teaching: some insights

As noted before, evidence of an effect of constructivist beliefs on student performance and motivation has led to opposite findings. One body of research provides evidence of a direct effect, while evidence from competing studies suggest that constructivist beliefs are a part of teachers PCK and do not influence the positive effect of high quality PCK on student development. Studies also show that constructivist teachers provide better learning environments but also that there is no difference in the teaching process of teachers holding constructivist beliefs versus teachers holding transmission-oriented beliefs. These contrasting results led us to the following question: what empirically-based evidence exists on the efficacy of constructivist strategies?

Within the last decade, many concerns have emerged about the effectiveness of constructivist teaching approaches [START_REF] Kirschner | Why minimal guidance during instruction does not work: an analysis of the failure of constructivist, discovery, problem-based, experiential, and inquiry-based teaching[END_REF][START_REF] Mayer | Should there be a three-strikes rule against pure discovery learning? The case for guided methods of instruction[END_REF][START_REF] Sweller | Why minimally guided teaching techniques do not work: a reply to commentaries[END_REF][START_REF] Tobias | Constructivist instruction: success or failure?[END_REF]. For example, Alfieri, Brooks, Aldrich, and Tenenbaum ( 2011) provide two interesting meta-analyses of 164 studies about the effectiveness of constructivist teaching approachesi.e. unassisted and enhanced discovery learningcontrasted with transmission-oriented teaching or other teaching methods. Their results are unambiguous: explicit teaching outperforms unassisted constructivist teaching and enhanced discovery teaching has a more positive but small effect on students' learning than do other types of instructional methods. Their overall conclusion is that unassisted discovery learning does not benefit learners. They write that the most important contributions to students' learning are feedback, worked examples, scaffolding, and elicited explanations. They also found that domain and subjects' age are significant moderators of these overall results. Verbal and social learning tasks favor explicit instruction and enhanced discovery learning followed next by problem solving, science, and math. Children and adolescents were found to benefit significantly more from explicit instruction than did adults who also do not benefit from unassisted discovery. In the case of enhanced discovery, adults benefit more from this method than children do. That is, adolescents tend to benefit least and adults tend to benefit most from both unassisted and enhanced discovery tasks.

Examining the effectiveness of a variety of teaching strategies in the area of science teaching, [START_REF] Schroeder | A meta-analysis of national research: effects of teaching strategies on student achievement in science in the United States[END_REF] 2012) also suggest that transmissionoriented teaching is associated with significant higher student achievement. [START_REF] Furtak | Experimental and quasiexperimental studies of inquiry-based science teaching: a meta-analysis[END_REF] show that studies of inquiry-based science teaching involving teacher-led activities combining procedural, epistemic and social goals had mean effect sizes about .40 larger than those with student-led conditions.

Additional support for teacher led teaching strategies is found in Hattie's well known work [START_REF] Hattie | Visible learning: A synthesis of over 800 meta-analyses relating to achievement[END_REF][START_REF] Hattie | Visible learning for teachers: Maximizing impact on learning[END_REF]) that suggests i.e., that providing "dollops of feedback" is one of the most important contributions to student learning [START_REF] Hattie | Instruction based on feedback[END_REF][START_REF] Hattie | The power of feedback[END_REF]). Hattie's conclusions are interesting in two ways. First, he shows that almost all teaching strategies contribute to students' learning outcomes but that their effectiveness is not equally strong; the strongest are globally teacher led. Secondly, he suggests that variation in teaching strategies might be a strong influence on students' learning gains. Such a view is close to the position of the aptitude-treatment interaction paradigm [START_REF] Cronbach | Aptitudes and instructional mathods: A handbook for reasearch on interactions[END_REF]. According to this paradigm, students with different characteristics benefit from different teaching procedures. [START_REF] Mayer | Should there be a three-strikes rule against pure discovery learning? The case for guided methods of instruction[END_REF] has a similar opinion. His results show that guided discovery appears to offer the best method for promoting constructivist learning. He suggests therefore that what counts in promoting students' learning gains by guided discovery is to know how much and what kind of guidance to provide. [START_REF] Helmke | Interactional effects of instructional quality and teacher jugement accuracy on achievement[END_REF] showed that the teachers who do best in adapting the amount and kind of guidance are those with the best diagnostic competences of their students' needs. Thus, [START_REF] Brunner | Diagnostische Fähigkeiten von Mathematiklehrkräften[END_REF] showed that the quality of diagnostic competences has a positive effect on students' achievement in secondary math.

Research questions

According to the literature, effective teaching combines both transmission-oriented To analyze this objective, we need a reliable scale, but as mentioned above, an instrument measuring constructivist and transmission-oriented teacher beliefs from a nonsubject specific perspective containing high psychometric properties does not exist. The second purpose of this article is therefore to provide such an instrument combining statements from older measurement scales.

Method

Sample

A

Instrument

Appendix 1 provides the instrument we used to assess teacher's beliefs about constructivist and transmission-oriented teaching approaches. We took all of the questions from Fennema and Carpenter's (1990) questionnaire and adapted them in two ways: first, as Geneva is part of the French speaking community of Switzerland, all items were translated into French.

Secondly, all of the references to mathematics were eliminated. That led to the observation that the questionnaire was redundant so we retained only 20 of the 48 items of Fennema and Carpenter's (1990) instrument. As the balance between constructivist and transmission -oriented items was not optimal (respectively, 8 items vs. 12 items), we completed our pool of items with 10 items from the scale developed by [START_REF] Hermans | Development of the Beliefs about Primary Education Scale: Distinguishing a developmental and transmissive dimension[END_REF] because it provides better psychometric qualities than the scale provided by [START_REF] Woolley | Construct validity of a self-report measure of teacher beliefs related to constructivist and traditional approaches to teaching and learning[END_REF]. We chose the 10 remaining items according to the following selection criteria: they had to explicitly involve teaching strategies 2 . This led to a pool of 30 items, 14 are supposed to be linked to a constructivist orientation of teaching and 16 to a more transmission-oriented approach. Preservice teachers had to rate their degree of agreement with all statements on a 6 point likert scale from "strongly agree" to "strongly disagree".

2

It is for that same reason that we didn't refer to the questionnaire developed by [START_REF] Chan | Relational analysis of personal epistemology and conceptions about teaching and learning[END_REF]. We didn't include items of [START_REF] Chen | Teachers' conceptions of excellent teaching and its relationship to self-reported teaching practices[END_REF] because our research team thought it could be problematic for the Swiss teachers in terms of social desirability.

Results

Instrument validation

Pre-service teachers' responses on the 30 items were analyzed first using an exploratory factor analysis [EFA] within MPlus 7.1 [START_REF] Muthén | MPlus Statistical analysis with latent variables : user's guide[END_REF]. Data were analyzed using the weighted least-squares within mean and variance (WLSMV) estimation procedure with an oblique CF-Equamax rotation. The WLSMV procedure was chosen because it is the best way to analyze categorical ordinal data and is robust for non-normal data distributions [START_REF] Brown | Confirmatory factor analysis for applied research[END_REF][START_REF] Muthén | MPlus Statistical analysis with latent variables : user's guide[END_REF]. The CF-Equamax rotation was used because it combines the Quartimax and Varimax criteria and simplifies both variable and factor complexity by spreading the variances more equally across the factors [START_REF] Brown | Confirmatory factor analysis for applied research[END_REF]. Although the percent of missing data was minimal (< 1.5%), all missing data were treated using the FIML estimation procedure by default in MPlus. The same estimators were used for the confirmatory factor analysis [CFA].

The statistics employed to evaluate model fit for EFA and CFA were the following:

-Tucker-Lewis Index [TLI] and Comparative Fit Index [CFI] with values less than .90 for a suspect model that has to be rejected, between .90 and .95 for a model with an acceptable fit, and from .95 and greater for a model with excellent fit [START_REF] Brown | Confirmatory factor analysis for applied research[END_REF].

-Root Mean Square Residual [RMSEA] with values higher than .10 for a model with poor fit, between .10 and .08 for a model with acceptable fit, and from .06, or better less than .05, for models with excellent fit [START_REF] Brown | Confirmatory factor analysis for applied research[END_REF].

- [START_REF] Brown | Confirmatory factor analysis for applied research[END_REF][START_REF] Muthén | MPlus Statistical analysis with latent variables : user's guide[END_REF][START_REF] Wang | Structural equation modeling : applications using MPlus[END_REF].

Note that less emphasis was placed on the χ 2 statistic compared to the above mentioned statistics because it varies as a function of the sample size. This is in line with the suggestions provided in [START_REF] Brown | Confirmatory factor analysis for applied research[END_REF] and [START_REF] Furr | Scale construction and psychometrics for social and personality psychology[END_REF]. There is also no clear agreement about the cut-off of the WRMR [START_REF] Muthén | MPlus Statistical analysis with latent variables : user's guide[END_REF]vs. Wang & Wang, 2012) so that we would be less strict with this statistic.

Appendix 1 shows the factor loadings of the two EFA we applied to our data. The first EFA was performed including all 30 statements of our pool of items. It led to satisfying psychometric qualities with the extraction of two factors according to our theoretical model (χ 2 (435) = 2868.909, p < 0.001; CFI = 0.853; TLI = 0.830; RMSEA = 0.065 (90 % CI = 0.050 -0.071); SRMR = 0.070). In order to shorten our instrument's size and to improve the psychometric qualities of our instrument, we used the following rules: removing items (1) loading on the incorrect factor, (2) possessing a higher cross-loading on another factor (factor loading >.30), and (3) having a small estimated factor loading on the theorized factor (<.40).

We then removed the items which had the lowest factor loading on their theorized factor to get an equilibrated balance between the number of constructivist and transmission-oriented items.

We get an excellent model fit by using this procedure (χ 2 (66) = 1506.783, p<0,001; CFI = 0.950; TLI = 0.923; RMSEA = 0.086 (90 % CI = 0.067 -0.105); SRMR = 0.050).

We kept a 12 item short version including 6 items to assess constructivist beliefs and 6 items to assess the transmission-oriented beliefs. CFA showed an excellent model fit for this solution (χ 2 (66) = 1506.783, p<0,001 ; CFI = 0.965 ; TLI = 0.957 ; RMSEA = 0.064 (90 % CI = 0.046 -0.083) ; WRMR = 0.831). MPlus suggested a correlation between the residuals of two pairs of items to improve model fit: a22c with a13c, and a16c with a06c. These correlations are theoretically significant as both items a22c and a13c deal with cooperation between students, and items a06c and a16c deal with individualized problem solving. This model, shown in figure 1, gets excellent model fit indices (χ 2 (66) = 1506.783, p<0,001; CFI = 0.989; TLI = 0.986; RMSEA = 0.036 (90 % CI = 0.000 -0.059); WRMR = 0.631) that appear to be statistically better than the solution without correlations between residuals (DIFFTEST: χ 2 (2) = 37,022 ; p<.001). Factor loadings range from .458 to .799 for the constructivist sub-scale and from .533

to .819 for the transmission-oriented sub-scale. These values are good and close to those obtained by other researchers [START_REF] Voss | Überzeugungen von Mathematiklehrkräften[END_REF]. We used this last model to generate the factor scores we would use later in this paper. There is a small but significant negative correlation between the constructivist and the transmission-oriented beliefs. This suggests that these two approaches are somehow a bit opposite but that they can't be seen as extremes of a same continuum. This observation is supported by MPlus analysis fixing the correlation between both belief orientations at 1 or force a 1 dimensional solution. In both cases the fit indices decrease (e.g. RMSEA = .284 and CFI = .337 for the fixed correlation model).

Internal consistency is acceptable to strong. Cronbach's alpha for the constructivist subscale is .75 and it is .83 for the transmission-oriented sub-scale. [START_REF] Furr | Scale construction and psychometrics for social and personality psychology[END_REF] and [START_REF] Brown | Confirmatory factor analysis for applied research[END_REF], wrote that Cronbach's coefficient alpha is a misestimation of the scale reliability of a multicomponent measuring instrument like for example multi-item questionnaires. We used the estimated reliability formula provided by Furr (2011, p. 105): (∑λi) 2 / ((∑λi) 2 + ∑θii +2∑θij).

The estimated reliability for both sub-scales ranges from good to strong (Constr.: .70; Transm.:

.83). These values are close to the reliability values obtained by other researchers in the domain of mathematics [START_REF] Dubberke | Lerntheoretische Überzeugungen von Mathematiklehrkräften: Einflüsse auf die Unterrichtsgestaltung und den Lernerfolg von Schülerinnen und Schülern[END_REF].

Discussion

As seen earlier in this paper, the literature raises much concern about the efficiency of constructivist beliefs and about the implementation of constructivist teaching strategies in the classroom. Some research shows that teachers holding constructivist beliefs offer better learning opportunities for their students and obtain better results in terms of student achievement (e.g. [START_REF] Staub | The nature of teachers' pedagogical content beliefs maters for students' achievement gains: Quasi-experimental evidence from elementary mathematics[END_REF]Voss et al., 2011). [START_REF] Kunter | Professional competence of teachers: effects on instructional quality and student development[END_REF] showed that the (0,59) link between constructivist beliefs and students' motivation and performance is more complex.

Their results show that what determines learning gains and motivation is the broader concept of PCK and especially teacher enthusiasm. Even if, in their study, teachers with the highest PCK hold especially strong constructivist beliefs, all other teacher attributes being equal, the latter do not influence student outcomes and motivation in math.

Research on the efficacy of teaching strategies showed significant importance for keeping some kind of behaviorist strategies such as feedback, practice, etc. to ensure some positive impact on students' learning when teachers use constructivist teaching approaches. 3 Effectively, results show that providing problem solving tasks to students that have to resolve them individually or in collaboration with peers without providing guidance is counterproductive (e.g. Alfieri et al., 2011). Research also supports the idea that the teacher should identify students' needs and adapt the nature and amount of guidance they provide to their students according to their diagnosis (e.g. [START_REF] Helmke | Interactional effects of instructional quality and teacher jugement accuracy on achievement[END_REF], and that this adaptation should depend on students' characteristics (e.g. [START_REF] Cronbach | Aptitudes and instructional mathods: A handbook for reasearch on interactions[END_REF].

These observations led us to the hypothesis that an optimal teacher should teach using both kinds of belief orientations. In accordance with that hypothesis, an optimal teacher training program should prepare its students to value both kinds of beliefs. So our purpose was to describe how pre-service teachers in the teacher training program at the University of Geneva develop their beliefs about constructivist or transmission-oriented teaching approaches.

Drawing on that perspective, we developed an instrument to assess these beliefs without reference to a specific content or domain. Our measurement scale possesses robust 3 Some will counter this assertion by saying that certain types of feedback are wholly constructivist acts [START_REF] Hmelo-Silver | Scaffolding and achievement in problem-based and inquiry learning: a response to Kirschner, Sweller, and Clark[END_REF]. This position has been criticized by [START_REF] Sweller | Why minimally guided teaching techniques do not work: a reply to commentaries[END_REF]. See these texts for a detailed review.

psychometric qualities. Comparisons show that developmental paths are different for elementary school pre-service teachers than for secondary school pre-service teachers.

Secondary school pre-service teachers favor transmission-oriented beliefs and reject the constructivist beliefs and maintain this belief profile throughout the teacher training program.

Elementary school pre-service teachers enter the training program with the same profile as their colleagues graduating in the secondary school program. But from the third year on, they highly value constructivist beliefs and are strongly opposed to transmission-oriented beliefs.

Implications for teacher training

Three issues grow out of these findings. The first issue is linked to the impact of the teacher training programs in Geneva on the beliefs of pre-service teachers. Secondary school pre-service teachers keep their beliefs orientation stable throughout the training. Thus, the influence of this program on teacher beliefs is not visible in our data or it is not strong enough to impact their beliefs significantly. It might be that this stability is because these pre-service teachers all hold at least a Master's degree in a discipline such as math or English. They are content-oriented and maybe this influences their teaching beliefs in such a way that they want to transmit their knowledge and expertise of a specific content. Another explanation could be their year-long transmissive lecture experiences during their training at the university. Maybe this influences their view about how to best teach their content [START_REF] Lortie | Schoolteacher[END_REF]. A third reason could be due to their employment in the field. For most of them, it is their early encounter with adolescents and with the realm of teaching and managing a class. It is well known that the first induction phase is a difficult period for beginning teachers as they struggle with self-oriented concerns while developing their teacher identity (e.g. [START_REF] Fuller | Becoming a teacher[END_REF][START_REF] Fuller | Concerns of teachers: A developmental conceptualisation[END_REF][START_REF] Ryan | The induction of new teachers[END_REF]. This phase includes concerns about how to discipline a group of students, one of the tasks pre-service teachers struggle with the most (e.g. [START_REF] Lasley | Problems of early field experience students of teaching[END_REF]. During this induction phase it might be possible that they experience that classroom management and constructivist teaching represent mutually exclusive paradigms of instruction [START_REF] Brophy | Perspectives of classroom management: Yesterday, today, and tomorrow[END_REF].

Maybe they experience that it is important to monitor or direct students' behavior with principles like, for example, those developed by [START_REF] Kounin | Discipline and group management in classrooms[END_REF]. It might also be that in doing so pre-service teachers experience some incompatibility between these principles and student self-directed learning common to the constructivist approaches (cf. [START_REF] Tobias | Constructivist instruction: success or failure?[END_REF]. It might also be that they need to guide students learning to achieve better content mastery according to research findings showing that enhanced learning is more effective than nonguided discovery (Alfieri et al., 2011;[START_REF] Kirschner | Why minimal guidance during instruction does not work: an analysis of the failure of constructivist, discovery, problem-based, experiential, and inquiry-based teaching[END_REF][START_REF] Mayer | Should there be a three-strikes rule against pure discovery learning? The case for guided methods of instruction[END_REF][START_REF] Sweller | Why minimally guided teaching techniques do not work: a reply to commentaries[END_REF].

The profile of elementary school pre-service teachers differs from their secondary colleagues perhaps because they come directly from secondary school when entering teacher education. Their belief profiles change radically so that they reject transmission and value constructivism. Elementary teacher education has a strong influence on the development of preservice teachers' beliefs about the constructivist and transmission-oriented practices.

Unfortunately, our study could not find reasons explaining this strong influence. Among the possible factors one could probably consider is that (1) these pre-service teachers come directly from secondary schools without experiencing many transmissive lectures at universities, (2) they are not oriented towards the transmission of specific content knowledge, (3) the elementary teacher education curriculum is built in such a way that it favors a strong beliefs transformation in line with constructivist principles, and (4) their teaching experiences are divided into periods of a few weeks spread over the duration of their training program through internships. They experience many reflective seminars and are not as challenged by the urgencies of every day practice as those pre-service teachers who prepare for secondary education. This may provide them with the opportunity to experience the idea that active participation of students in constructivist approaches and classroom management can be successfully combined despite the challenges this poses (e.g. [START_REF] Evertson | Support for managing learning-centered classrooms: the classroom organization and management program[END_REF][START_REF] Weinstein | Reflections on best practices and promissing programs[END_REF].

The second issue is more linked to the kind of desired teacher profile. According to research results underlining the importance of embedding behaviorist principles into constructivist teaching strategies (cf. Alfieri et al., 2011), is it desirable for teachers to reject one kind of belief system (e.g. constructivist beliefs) and value another set of beliefs (e.g.

transmission-oriented beliefs) ? More explicitly, is the development observed for the elementary school pre-service teachers an appropriate one when the goal is to favor student learning and motivation or to ensure an optimal classroom environment? Unfortunately, our research design does not permit any speculation on this crucial issue. But according to the findings of previous research, it might be that the most effective teachers hold both kinds of belief orientations with equal strength and that they rely on one or the other kind of belief in response to contextual demands and student characteristics, etc. (e.g. [START_REF] Cronbach | Aptitudes and instructional mathods: A handbook for reasearch on interactions[END_REF][START_REF] Karst | Kompetenzmodellierung des diagnostischen Urteils von Grundschullehrern[END_REF]. This has an important implication for teacher education. Teacher training programs should probably provide pre-service teachers with opportunities to learn different kinds of teaching strategies that are not only associated with a constructivist orientation but also with behaviorist principles (e.g. [START_REF] Schauber | A pluripedagogical and dual-language approach to teacher education[END_REF]. [START_REF] Schauber | A pluripedagogical and dual-language approach to teacher education[END_REF] argues that teacher education presents a natural instructional and mentoring opportunity for the consideration of pluripedagogical values wherein multiple pedagogical orientations (culled from exposure to diverse global educational perspectives) serve as instructional resources that are mobilized in response to local contextual demands. Moreover, the selection of a constructivist or transmission-oriented approach may well depend on the student's orientations and not on the teacher's. She claims that denying pre-and in-service practitioners with access to a pluripedagogical orientation may limit the kinds of instructional decisions they can ultimately make and therefore the kinds and range of learning opportunities their students can experience.

The third issue is linked to students' transition between elementary and secondary school. Our results show two contrasting ways to conceptualize teaching depending on the school level for which pre-service teachers are being professionally prepared. Elementary school pre-service teachers are convinced constructivists, while, secondary school pre-service teachers are convinced transmitters. This absence of harmony between the two school levels is surprising and might generate some student difficulties during the transition between elementary and secondary school. It might be interesting to develop programs to help students grapple with both kinds of profiles when they move from primary to secondary school.

Implications for Future Research

The implications for follow up research are numerous and diverse. We only mention four in this paper as we do not have enough space to treat more. Firstly, an analysis of different belief profiles would be interesting as we saw that beliefs about constructivist and transmissionoriented teaching approaches are not extremes of the same continuum. It seems possible that beliefs about teaching approaches spread out in a bi-dimensional space. It might be that teachers can be categorized into this bi-dimensional space. This categorization should lead to a hypothetical four profile system of non-constructivist-transmissive, non-constructivist-non-

Limitations of the Research

Beyond the fact that our sample size is reasonable but contains an unequal number of subjects by years and levels of teacher education, one important limitation of our research is its cross-sectional design. This may limit the impact of our analysis of pre-service teachers' conceptual change towards their training program. Some longitudinal research is needed to broadly analyze the development of pre-service teachers' personal epistemologies and the evolution of their beliefs about the best teaching approaches to favor students' learning.

A further limitation of the research is that our instrument was not created to reveal the factors influencing pre-service teachers' development through constructivist and transmissionoriented teaching. That means that our discussion about the impact of early education, teacher training program or field experience is hypothetical. Similarly, our suggestion about the context-, task-or student-oriented choices of teaching approaches should be tested for example with a vignette study design.

We hope our paper provides some stimulation for further research.

Alfieri, L., Brooks, P. J., Aldrich, N.

  teaching strategies and constructivist teaching methods. Pure discovery methods are ineffective on their own. In contrast, enhanced discovery learning including feedback, demonstration, worked examples, explanations, etc. are the most effective means to ensure students' learning gains. In other words, constructivist teaching strategies have to be provided through behaviorist teaching principles in order to have positive effects on students' achievement. Yet, most of today's curricula favor constructivist teaching strategies. The purpose of this article is to investigate how constructivist teaching approaches are imparted in pre-service teacher education programs. We want to analyze the effects of the initial teacher training program at the Institute of Teacher Education of the University of Geneva on the development of these beliefs. Our hypothesis is that pre-service teachers should demonstrate equally strong beliefs on constructivist and transmission-oriented beliefs. This profile might be linked to their adaptation competence to their students' heterogeneous learning profiles and levels. So it might be that adopting strong beliefs on both teaching orientations would be favorable to teaching effectiveness.

  sample was taken of 228 pre-service teachers from the Institute for Teacher Training at the University of Geneva in Switzerland. Most of them are preparing for elementary school certification (n=138) while the remaining 90 are training to become secondary school teachers. Elementary school pre-service teachers are from the three last years of training. As the first year of elementary teacher training is a general track for individuals who want to become a teacher and those who want to become social scientists, psychologists and speech pathologists; first year students were excluded from this study. Teaching experience of the elementary school preservice teachers is limited at the beginning of the second year of training and increases in importance in the third and fourth years of the program when a practicum is included in the training. This subsample of elementary pre-service school teachers includes 84 second year students (ET2), 38 third year students (ET3), and 16 fourth year students (ET4). The secondary school training program takes two years. Our sample focuses on 21 first year students (ST1) and 69 second year teachers (ST2). An important feature of the secondary teacher training program is that first year students have no practicum and therefore limited access to teaching experience; second year students divide their time equally between a teaching post and courses in the teacher training program. These teachers who enter the program with a Master's degree come from varying content areas: social sciences (n=26), sciences (n=28), languages (n=13), sports (n=14), and 9 missing data. Most of the participants are female (n=158) and are registered in the primary school training program (n=110).

Figure 1 Figure 2

 12 Figure 1Structural model for pre-service teachers' beliefs about teaching approaches -standardized values

  transmissive, constructivist non-transmissive, and constructivist-transmissive beliefs. Research should also foster interest in analyzing which belief profiles generate the best student achievement and motivation and in which circumstances. Another interesting research orientation would be to analyze if teachers adopt different belief profiles according to student or task characteristics. Finally, other research should analyze whether the belief profiles we found remain stable over time, especially when pre-service teachers are employed in a school and experience the reality of a class during their first induction phase.

  J., & Tenenbaum, H. R. (2011). Does discovery-based instruction enhance learning? Journal of Educational Psychology, 103(1), 1-18. doi: 10.1037/a0021017

  obtained similar results. Their meta-analysis of 61 studies indicates the following effectiveness results for eight strategies (effect sizes in parentheses): enhanced context strategies where the teacher refers to students' prior knowledge and beliefs (1.48); collaborative learning strategies where the teacher arranges

	students in flexible groups (0.95); questioning strategies where the teacher varies timing,
	positioning, or cognitive levels for questions (0.74), inquiry strategies where the teacher uses
	student-centered instruction that is less step-by-step and teacher-oriented than traditional
	instruction (0.65); manipulation strategies where the teacher provides the students with
	opportunities to work or practice with physical objects (0.57); assessment strategies where the

teacher changes the frequency, purpose, or cognitive levels of testing and evaluation (0.51); instructional technology strategies (0.48); and enhanced material strategies i.e. teacher's modification and transformation of existing instructional material (0.29).

[START_REF] Schwerdt | Is traditional teaching really all that bad? A within-student between-subject approach[END_REF]

as well as

Castonguay and Gauthier (

  .08 or .07. This statistic is not provides for the CFA. For CFA, the Weighted Root Mean Square Residual [WRMR] is computed. Models with values of approximately 1 would be a good model fit

Two other indicators were used. The first one is the Standardized Root Mean Square Residual [SRMR] which is computed for the EFA and that has to reach values equal or less than


Keywords: engine management, real time, integration, dynamic architecture, scheduling, data consistency

This dynamic facet is characterized by sporadic events, time events in a range of 1 millisecond (ms) to 1 second (s), and angular events in a range of 0.5ms to 100ms depending on engine configuration and speed. The EMS functions have to be called from these events, and in addition to their recurrence, they may have phasing, sequencing, and also deadline constraints.

Typical problems in the dynamic behavior are infinite loops, wrong initializations of pointers, stack overflows, recursivity, wrong calculation sequences, data inconsistencies, and deadline misses. Whereas some of these errors are intrinsic to SW-components (SW-C), others are related to their integration within the project. In other words, the same SW-C may show a correct behavior in one project, but an incorrect behavior in another project, because of integration failure, or different integration contexts.

After an overall description of the EMS context, we will describe in this paper the most common integration failures with impact on dynamic behavior, and means to avoid them. We will also show the importance of the architecture and integration activities in the specific area of engine management, in particular due to the above mentioned constraint of strong coupling.

Engine management software dynamic architecture versus integration

D. Claraz 1 , M. Niemetz [START_REF] Claraz | Fiabilité des logiciels embarqués, exemple architecture dynamique logicielle d'un contrôle moteur[END_REF] 1: Continental Automotive France SAS, 1, av. Paul Ourliac, BP 1149, Toulouse -France 2: Continental Automotive Germany AG, Siemensstr.12, Regensburg -Germany

Abstract

Variability, hard real time, increasing functional complexity (due to emissions and driveability standards), limited hardware (HW) resources : these are some of the -sometimes antagonisticconstraints a modern Engine Management Software (EMS) has to deal with. In addition, to face the price reductions in the automotive electronics industry, an intensive reuse strategy is deployed, based on a platform architecture and a component based development, despite the high functional coupling between those components, characteristic to the engine management area. To respond to these constraints, a static (or functional) architecture defines the split of the software (SW) into compilation units: modules or aggregations of modules. This static architecture mostly focuses on reuse and decoupling of functions. It is in general well managed, documented, and supported by tools.

In parallel to this static facet, to respond to the real time requirements, the dynamic architecture defines the split of the SW into execution units: functions, tasks, interruptions. This part of the architecture is often underestimated, poorly documented, and insufficiently supported by tools.

Context of Engine Management Software

A high end Electronic Control Unit (ECU) may have up to 200 connectors, 250.000 lines of code, and around 1000 functions to control all sensors and actuators needed to manage the combustion process of the engine.

Fig. 2: Gasoline direct injection system

The architecture of the software is mostly impacted by the following constraints:

Coupling between EMS functions:

An EMS is a system with a high functional cohesion.

There are only few functions mapped to an EMS, which could be exported to another ECU of the vehicle. These functions interact together either directly or through the engine and the components they control, and thus can hardly be managed independently.

Fig. 3: All sensors and actuators managed by EMS are involved in the same physical process For instance, misfire, injection and ignition functions depend on each other and participate all to the same combustion process. They are interacting together, and thus communicate by exchanging data. In the following figure, we give an overview of the coupling of the main EMS functions on a typical high end project.

Fig. 4: Coupling between main EMS functions

On this graphic, each dot represents interfaces (links) between the functions. In particular, we see that there is nearly no 1:1 link between functions, and that most of the functions are linked to many other ones. To be more concrete, typical variables of the system like engine speed, coolant temperature, ignition key, ... are needed in more than 100 modules, spread in around 50 functions. This strong coupling between functions creates one of the most important constraints on the architecture, and is specific to Engine Management Systems.

Variability:

Due to the reuse objectives, the configurability of the EMS SW is a key issue, in order to avoid parallel branches, expensive to maintain. EMS applications are similar, but have also a big level of variability, due to different engine architectures, sensor and actuator positions or electrical characteristics. This variability is much higher at the supplier side than the OEM side, due to a multi-customer and multiengine orientation.

As an example, the figure below shows the diversity of camshaft target profiles that have to be handled by the same SW. EGCP 250 12 490 5 0 11 3 14 0 3 2 5 2 1 0 1 13 3 0 1 0 2 0 1 1 3 0 6 0 1 0 0 0 0 0 0 0 0 0 INSY 80 337 0 6 15 17 11 7 0 2 2 3 0 1 2 1 1 0 0 1 0 1 0 0 1 0 0 0 0 0 0 0 0 0 0 0 2 0 1 CHRG 80 28 0 5 298 9 0 0 0 1 0 0 1 1 1 4 0 0 0 0 0 0 0 2 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 ERRM 243 31 21 6 5 11 8 16 2 11 6 4 1 2 1 0 3 6 3 2 0 8 5 0 3 5 2 2 0 1 0 2 0 1 0 0 2 0 0 EGTR 240 10 14 4 0 11 1 11 0 3 2 3 2 0 0 0 101 3 0 1 0 1 0 1 1 2 0 0 0 1 0 0 0 0 0 0 0 0 0 VVLI 43 9 2 10 0 0 200 5 0 1 7 1 0 5 0 1 0 1 1 0 0 0 0 1 2 0 0 0 1 0 0 0 0 0 0 0 0 0 0 ECM2 6 3 1 4 0 11 1 3 190 3 2 0 6 5 11 4 0 0 16 1 18 2 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 EVAM 144 12 0 2 0 8 2 3 0 2 2 5 1 0 0 0 0 0 2 101 0 0 0 1 1 0 0 0 0 1 0 0 0 0 0 0 0 0 0 ENSD 40 0 0 208 0 0 0 0 0 0 4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 LACO 11 12 16 6 0 3 1 164 0 3 3 9 3 0 2 0 5 3 0 4 0 1 0 1 1 1 0 1 0 1 0 0 0 0 0 0 0 0 0 VVTI 28 4 0 6 0 8 7 0 0 2 165 0 0 3 0 1 0 0 0 0 0 0 0 1 0 0 1 0 1 0 0 0 0 0 0 0 0 0 1 ENSC 72 6 0 8 0 13 0 2 0 3 2 1 0 0 1 3 1 0 86 1 0 0 0 3 1 0 0 1 2 1 0 0 0 0 0 0 0 0 0 AIRT 67 12 0 5 4 0 4 0 0 4 0 0 0 0 0 1 0 0 0 0 0 0 105 0 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 EVAC 4 9 5 3 0 2 0 12 0 2 2 141 2 2 4 1 1 1 0 6 0 3 0 0 1 0 0 0 0 1 0 0 0 0 0 0 0 0 0 THRO 19 7 0 2 0 162 2 0 1 2 0 0 0 1 0 0 0 0 0 0 4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 INJR 6 2 0 10 0 1 5 0 1 2 0 0 126 1 17 1 1 2 0 0 5 2 0 4 6 0 0 2 2 1 0 0 0 1 0 0 0 0 0 TQSP 6 3 0 3 1 5 4 0 5 2 0 1 1 27 1 85 0 0 9 0 0 5 0 7 1 1 1 0 7 0 0 0 0 1 1 0 0 0 0 ENTE 41 9 0 4 0 0 0 0 0 115 0 0 0 0 0 1 0 0 0 1 0 0 3 0 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 FMSP 0 9 0 6 0 2 8 3 0 4 1 0 6 1 103 2 0 0 1 1 0 3 0 6 10 0 0 0 0 1 0 0 0 1 0 0 0 0 0 MISF 23 3 2 6 0 4 2 0 0 2 1 0 5 3 0 0 0 96 0 1 0 0 0 1 1 1 0 0 0 3 0 0 0 0 0 0 0 0 0 FUSL 21 0 2 4 0 0 1 6 0 4 0 2 3 1 2 2 1 2 0 2 0 87 0 5 7 0 0 0 0 0 0 0 0 0 0 0 1 0 0 TQDR 0 9 0 4 0 1 3 0 0 2 0 0 2 91 0 14 0 0 4 0 0 0 0 1 0 0 1 0 0 1 0 0 1 1 0 0 0 0 0 KNCK 22 4 0 8 0 3 1 0 0 2 0 0 1 0 0 0 0 0 0 0 0 0 0 0 1 0 86 0 1 1 0 0 0 0 0 0 0 0 0 EXTD 23 2 2 1 1 0 1 0 0 4 0 0 2 1 2 0 1 0 0 0 0 0 0 0 2 83 0 0 0 0 0 0 0 0 0 0 0 0 0 EXTC 1 8 0 4 1 3 1 2 0 3 2 0 2 3 2 4 1 1 0 1 0 1 0 72 1 5 0 0 1 1 0 0 0 0 0 0 0 0 0 ALAM 1 2 4 3 0 0 0 16 0 1 2 2 1 0 0 1 0 2 0 0 0 0 0 2 0 1 0 67 0 0 0 0 0 0 0 0 0 0 0 ECM3 4 0 0 0 0 0 0 0 5 0 0 0 0 0 0 0 0 0 0 0 95 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 IGRE 27 2 0 9 0 1 0 0 0 1 0 0 1 0 0 1 0 1 0 0 0 0 0 0 2 0 0 0 0 55 0 0 0 0 0 0 0 0 0 DRVB 0 0 0 4 0 0 1 0 0 1 0 0 1 1 0 4 0 0 3 0 0 0 0 0 0 0 0 0 61 0 0 0 0 0 0 0 0 0 0 ENRD 8 2 0 9 0 4 0 0 0 1 0 0 1 0 0 0 0 4 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ENSS 6 0 0 3 0 0 0 0 0 2 0 0 2 0 1 0 1 0 0 0 0 1 0 0 48 0 0 0 0 0 0 0 0 0 0 0 0 0 0 IGSP 0 3 0 3 0 0 9 0 0 1 0 0 0 3 4 1 0 0 0 0 0 0 0 1 3 0 1 0 0 0 0 0 24 0 0 0 0 0 0 DRRQ 16 0 0 2 0 0 0 0 1 0 0 0 0 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 31 0 0 0 0 0 0 0 FUTL 8 0 0 1 0 0 0 0 0 0 0 0 0 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 35 0 0 0 0 0 0 0 0 TQLO 1 4 0 2 0 2 2 2 1 4 2 0 1 0 1 0 0 1 3 1 0 1 0 0 0 0 0 0 0 1 0 0 0 15 0 0 0 0 0 ENSL 0 0 0 5 0 3 1 0 2 1 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 11 0 0 0 0 LASP 0 1 2 1 0 0 0 0 0 2 0 0 0 3 0 1 2 0 0 0 0 0 0 4 0 0 0 0 0 0 0 0 0 0 0 0 0 7 0 AVIM 6 3 0 3 0 0 0 0 0 1 0 0 0 1 0 1 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 3 EGPR 0 3 0 1 4 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 9 0 0 0 AEFP 7 0 0 2 0 0 0 0 0 2 0 0 0 0 0 0 0 0 0 0 0 1 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 In total, more than 160 points of configuration are needed to configure the acquisition of engine position and speed, depending on the shape of the crankshaft, the type and position of sensors, the type of diagnosis, etc... For a complete application, more than 10.000 points of configuration are used.

Real time:

As the physical process in a combustion engine is fast and repetitive, an EMS is a fast system: Acquisitions, diagnosis, treatments, and corrections on control strategies are done very often. To reach new emission regulations, new functionalities require multiple acquisitions of the same parameter and multiple actuations of the same output within one same combustion cycle. Engine synchronous calculations may have a recurrence of 2.5 ms on 8 cylinder systems, and fast time bases like 5 ms are widely used. As a result, around 80% of the calculations are executed within a 10ms (or faster) time frame. In addition to this speed, the complexity of an EMS is due to the mixture between sporadic events (like for instance an ignition key transition), time periodic events, and angle periodic events. For instance, many calculations are synchronous to the crankshaft position. Their recurrence is variable, and can range from 100ms at low engine speed to 5ms at high engine speed, for a 4 cylinders engine. In total, around 70 different events are needed with sometimes precise phasing or deadlines needs.

Fig. 7: Time and Angle based events

Reuse:

As mentioned, reuse is a key driver of the architecture, in order to reach productivity objectives inherent to the automotive electronics industry. This reuse impacts mostly the static architecture, i.e. the split into functional bricks. The decoupling of functionalities is done using a top-down approach and an aggregate concept already described in ERTS2004 [1]. This is done through a better and formalized management of interfaces, and through an application of abstraction principle, in order to define sub-packages (aggregates) with a high internal coherency.

Time Events

Hardware resources:

In order to minimize the ECU price, the RAM, ROM and CPU load consumptions have to be limited. The balance has to be done between the economy of HW resources and the typical objectives of maintainability, testability, and in particular reusability. In the simple example shown below, a calculation done every top dead center (tdc) depends on interpolations on input variables with different dynamics. Some of them change every tdc, but some other only every 100ms or every 1s. To ease the integration (testability and maintainability) of such a function, a monolithic calculation every tdc would be the best choice. But this would cost approximately twice the CPU load as a calculation optimized according to the input variables dynamics.

Business model:

With the introduction of OSEK in 2001, a fundamental change of the business process has been initiated: before that date, the complete SW embedded in the ECU was developed by the supplier (based on own, or on OEM specifications). Today, a complete project is -and will be more and more -built from individual SW-C coming from the OEMs, suppliers, tool vendors, and even competitors. The formats of the SW-C to be integrated are disparate (C, obj, libraries, MDL, XML), and have increasing impact on the architecture. For instance, a non-negligible part of the CPU, RAM, ROM is dedicated to interface adaptation.

Different views on an EMS architecture

According to the above constraints, the EMS architecture is split into different facets (or areas), corresponding to different types of problems. Architectural choices and mechanisms are defined in each of these areas, and may apply either to a complete platform (or product line, or project family), to a single project, or finally to a single function. The Static architecture , or functional architecture, aims to split the system into functional abstractions, with an objective of decoupling functionalities. These functional abstractions will be either modules (i.e. compilation units, SW-Cs), or groups of SW-Cs. These SW-Cs will be the base for reuse, or for distributed development [START_REF] Claraz | Reuse Strategy at Siemens VDO Automotive : The EMS 2 Powertrain Platform Architecture[END_REF] .

Typical topics of static architecture are: -In which SW-C to locate the torque correction due to air conditioning? -Is it possible to exchange calibration data between SW-Cs? Which kind of exchange is allowed? Why? The Layer architecture defines the split into hardware abstractions, with an objective of independence from microcontroller, hardware, or [START_REF] Claraz | Reuse Strategy at Siemens VDO Automotive : The EMS 2 Powertrain Platform Architecture[END_REF] With increasing size and complexity of applications, a good partitioning is becoming essential to reduce coupling, allow work split between teams, and ease further integration. The "Configurational" architecture focuses on the management of the variability, with an objective of reducing its impact on development effort and hardware resources. Once integrated in a project, a SW-C designed to be "configurable" will then become "configured". This configuration can be done either at "build time" (same source code, different executables), at "runtime" (same source code, same executable, different parameters), or both.

Examples of topics related to this facet are:

-How to decouple the ignition functionality from the number of cylinders? -How to encapsulate the diversity? How to handle its impact on the interfaces?

The Dynamic architecture, finally, aims to split the system into execution units (i.e. tasks), with an objective of schedulability and efficiency. This facet is described in the following chapter.

Dynamic architecture of an EMS

As described before, an EMS is stimulated by around 70 sporadic, periodic, or angular events, mostly represented by Operating System tasks. The phasing between these events is sometimes important, and for one same recurrence, there might be different events with different phasing. For instance, in order to be precise in the combustion cycle, different events are necessary between 2 tdc of the same cylinder. So, the first dynamic architecture choice, when designing, and integrating a control strategy, is the selection of the adequate event(s), out of a list of around 60. The below figure shows the functions split on some events and puts in focus that the EMS functions are not monolithic in term of dynamics, but use various events (for functional or HW resources optimization reasons).

Fig. 13: Functions vs. events mapping Consequently, in addition to the static data flow described in Fig. 4, a dynamic data flow can be displayed, corresponding to the exchange between events, or tasks: A variable is modified by one (or more) event, and read by one (or more) other event. The above matrix shows the data flow between some producing and consuming tasks.

A comparison between the static data flow (between SW-Cs) and the dynamic data flow (between tasks)

shows that the static one is much better controlled than the dynamic one: The static flow is easy to formalize and to encapsulate. In general, there is only one single producer for various consumers, and the access to external data can be protected using special mechanisms. Finally, a failure of the static flow can hardly generate a failure at run time, but rather at build time. Which means that it is much easier to detect. None of these characteristics apply to the dynamic flow: formalization and encapsulation are difficult; there is often more than only one producer-task; and no simple mechanism permits reducing the access to a data from a single task. And finally, a failure here will hardly be detected at build time, and will be difficult to identify at run time.

Due to this huge "dynamic flow" (like the static one, a particularity of EMS systems), data consistency issues will be more difficult to handle, in particular in case of preemptive scheduling. This is a second aspect of the dynamic architecture.

Another consequence of the coupling between functions is the importance of the calculation sequence between them: When a new function is added, it has to be inserted at the right place in the program flow corresponding to one event. Different criteria are defined by the dynamic architecture, to ensure a correct and reproducible sequencing (the same combination of functions should be integrated in the same way on different applications). Another important parameter of a function is its deadline, or maximum allowed response time. The response time is the delay between the activation of a function and its completion. For instance, the time elapsed between the decision to update the injection time (detection of the tdc), and the point in time it actually is updated. The intrinsic duration of the function is included in its response time, but also the delay introduced by the other functions and events of higher priority. All these information depend on the integration platform, and a correct behavior has to be ensured on the slowest one.

Exceeding deadlines:

Depending on the functionality, a missed deadline can be destructive (e.g. injection update), or have such a light consequence that it is better to simply skip the calculation (e.g. coolant temperature acquisition). An EMS system uses a mixture of hard and soft deadlines, typically in the range of 1ms to 1 sec. In general, defining the deadline of a functionality is not a simple issue, and requires a good system knowledge. Violating deadlines is a typical problem of integration, as the response time of one function is mostly impacted by the other functions sharing the same CPU: The response time of a function integrated since a while can be impacted by the introduction of a new one. In order to fulfill the deadlines, priorities are assigned to tasks, based on a standard scheduling policy and task priority scheme. Standard priority orders ensure consistent response times between projects.

Fig. 19: Standardization of priority scheme

To verify deadlines, advanced techniques can be used, like schedulability prediction, simulation of the dynamic behavior, or simply measurements. These techniques need a very good understanding of the dynamic behavior and are used by architects. To define the correct sequence between functions of the same event, one of the criteria which can be used is the data flow criterion. A function producing a variable should be located before all the functions that consume this data, in the program flow. Otherwise, the consuming functions will work with an old (or, even worst, non initialized) value. It is also preferable, in general, that all the consumers get a consistent value for the variable, which means that all consumers should be either before, but preferably after the producer module. Furthermore, in some cases, enlacing between functions is required: a function has to be inserted between 2 parts of another one Thus, defining the right sequence of functions connected to the same event can be a complex job: the below figure shows the amount of direct (produced, then consumed) and reverse (consumed, then produced) data flow in a typical task. Note here that one green or red arrow may encapsulate more than one variable. The amount of arrows (links) here is an additional testimony of the high coupling between EMS functions. Finally, the correct sequence of functions within a task is verified by a static analysis tool, based on data production and consumption order. Due to the big number of links between functions, finding the right precedence order may be a complicated job. Because of algebraic loops, the solution to the precedence problem is not always obvious, and needs some system choices. For the sequence flow across tasks (when defined), the same kind of analysis can be conducted.

Inconsistency of data:

The modification, by a high priority task, of a variable during its use in a low priority task, corrupts the behavior of the low priority functionality 4 , as its 2 parts work with different values for the same variable. This standard problem of real time software is particularly important in EMS context due to the big coupling (and data flow) between functions and between tasks.

4 This also applies across different functions which need to work with the same input values. For instance, misfiring, ignition, injection functions are strongly coupled together. The data consistency problem can also be analyzed statically by a tool, by checking the data flow between tasks ("dynamic flow"). Identifying this flow between the tasks is the first step for a better control.

Fig. 25: Shared data between tasks of different priorities and recurrences

Dynamically, it is nearly impossible to verify the consistence of data, as the occurrence of the critical case is very unlikely and difficult to reproduce. This is particularly the case in an EMS context, where regular time based tasks and engine angle based tasks can interact at any time.

Organization

In addition to the above measures, an adequate organization allows to control the dynamic architecture:

SW architects analyze new concepts, define standard methods and mechanisms, and support the projects in their deployment. SW integrators focus on their own project and ensure a correct integration of the reused functionalities. Both are well trained to the architecture mechanisms and constraints, and are highly skilled engineers. Developers of functions are specialists on their own functional scope and know perfectly how to develop a generic solution, portable on different system and HW configurations. They control the internal architecture of their function, in order to ease its maintainability and configurability.

Architecture and integration activities are budgeted, empowered, and considered in the early project planning, as major activities, particularly in a context of intensive reuse.

Architecture assessments are conducted by architecture specialists independent from the projects. They are done at an early phase of the project, to be able to take corrective or preventive actions.

Standardization

As seen in the above chapters, the frame a SW-C is plugged into has a major impact on its behavior, in particular in the EMS context of hard real time and high coupling between functions. For instance, a SW-C designed for a non-preemptive environment cannot simply be used in a preemptive one. Even in a given proprietary architecture, the behavior of a reused proprietary SW-C is not automatically the same, due to the different system and HW configurations.

With the trend to integrate more and more external SW-Cs, the need for adaptation layers increases, and consequently the need for HW resources. As long as the number of external SW-Cs is limited, such an integration can be managed. But with an increasing number, a standardization is necessary.

Ahead from the pure mechanisms (like interfacing mechanisms), a standardization of the architecture itself is necessary to build complete projects out of SW-Cs. Which events, which recurrences, which links between them (precedence, phasing, exclusion, ...) ? Which scheduling concept, which priorities, which deadlines for the functions, and how to ensure them? Which sequencing between components, and how to control it? Which data to be protected against concurrent accesses, and which mechanism to protect them, compatible with the HW resources constraints? These are some of the challenges to be solved by AUTOSAR or any standard willing to authorize porting of SW-Cs across different platforms.

Conclusion

Compared to other automotive areas like car body, an Engine Management System has specific constraints which make the integration of functions more difficult. High coupling between functions, hard and complex real time, and limited HW resources are the ones with major impact on the dynamic behavior. Combined with the strong reuse objectives inherent to the automotive business, these constraints increase the challenge of integration activities. Hidden part of the iceberg, the dynamic integration of a SW-C is certainly much more difficult to put under control than its static one. But there are nevertheless various techniques and means to reach this goal. Standardization will help in this direction, but has to be supported by efficient mechanisms and tools, and has to consider all the facets of the problem.

Fig. 1 :

 1 Fig. 1: Memory vs. price of EMS

Fig. 5 :

 5 Fig. 5: Same SW for different camshaft targets

Fig. 6 :

 6 Fig. 6: Relative weight of main recurrences

Fig. 8 :

 8 Fig. 8: Hierarchical architecture: packages of SW-Cs (Hood-like representation)Finally, a hierarchical architecture is defined, with different levels of interfaces.

Fig. 9 :

 9 Fig. 9: CPU load vs. dynamic architecture

Fig. 10 :

 10 Fig. 10: Facets and scope of architecture

Fig. 11 :

 11 Fig. 11: Static (or functional) architecture of EMS

  Fig. 12: Functional architecture plugged on layer architecture of EMS

Fig. 14 :

 14 Fig. 14: Data flow (coupling) between main tasks

Fig. 15 :

 15 Fig. 15: A task: sequence of functions

Fig. 16 :

 16 Fig. 16: Response time and deadline

Fig. 20 :

 20 Fig. 20: Response time verification by simulation

3 .Fig. 21 :

 321 Fig. 21: Correction of function sequence based on data flow

Fig. 22 :

 22 Fig. 22: Data flow between synchronous functions To reduce the coupling between functionalities and to better control the sequencing, standard sequence orders or ordering criteria are defined, and sequencing modules are used. Standard initialization mechanisms and standard task scheduling ensure that data are available at the right time.

Fig. 23 :

 23 Fig. 23: Intermediate scheduler reduces integration effort and risk of wrong sequence

Fig. 24 :

 24 Fig.24: Data inconsistent within 100ms functionality So, to reduce the risk of misuse of shared data, specific design patterns, atomic libraries, restrictions like controlled use of preemption, and encapsulation principles are applied. The data consistency problem can also be analyzed statically by a tool, by checking the data flow between tasks ("dynamic flow"). Identifying this flow between the tasks is the first step for a better control.

40 functions export... 40 functions import ...

														Fct_04	Fct_02	Fct_01	Fct_09	Fct_03	Fct_15	Fct_06	Fct_10	Fct_41	Fct_18	Fct_11	Fct_14	Fct_16	Fct_22	Fct_19	Fct_17	Fct_05	Fct_20	Fct_12	Fct_08	Fct_27	Fct_21	Fct_13	Fct_25	Fct_31	Fct_24	Fct_23	Fct_26	Fct_29	Fct_28	Fct_30	Fct_34	Fct_33	Fct_32	Fct_35	Fct_36	Fct_39	Fct_40	Fct_37	Fct_38
														Fct_01
														Fct_02
														Fct_03
														Fct_04
														Fct_05
														Fct_06
														Fct_07
														Fct_08
														Fct_09
														Fct_10
														Fct_11
														Fct_12
														Fct_13
														Fct_14
	Box Air Cleaner	Sensor with Mass Air Flow	Throttle Control Electronic	Recirculation Exhaust Gas	Manifold Composite	Absolute Pressure Manifold	Injection Piezo Piezo Direct	Ignition	Var. Dual Cont.	Position Camshaft	Fct_15 Fct_16
		Temp. Sensor Integrated		Valve (EGR)			Sensor		Injector		Cam Phaser	Sensor	Fct_18 Fct_17
														Fct_19
														Fct_20
											Exhaust			Fct_21
											T e			Fct_22 Fct_23
														Fct_24
														Fct_25
														Fct_26 Fct_27																											Number
										3-Way Catalyst	Lean NOx Trap Catalyst		Fct_28 Fct_29																											of links
														Fct_30
														Fct_31 Fct_32																											> 10
														Fct_33
														Fct_34 Fct_35																											6...10
														Fct_36
	Active Carbon Caniste												Fct_37 Fct_38 Fct_39																											< 6
														Fct_40
	Canister	Fuel Supply	High Pressure	Fuel Pressure	Engine	Active Crankshaft	Knock Sensor	Engine Coolant	Linear /	NOx
	Purge	Unit	Fuel Pump with	Sensor	Control	Position Sensor			Temperature	Binary
	Solenoid		Flow Control							Sensor	O2 Sensor
			Valve

It should be specified, here, what means "integrated in the same way", when the 2 integration frames are different. Indeed, integration instructions are dependant on the integrated object itself, but also on the integration environment, which is not portable. This is particularly true on the dynamic aspects.

At first sight, this seems to be a wrong architecture, but in reality, this may be a consequence of the static partitioning, which is mainly driven by reuse aspects..

Integration faults and how to avoid them

Like described in a previous document [2], dynamic architecture failures can be classified in 3 categories: intrinsic to the reused component, intrinsic to the frame it is plugged into, or finally failure due to an integration error or incompatibility.

In the first category are the typical problems of infinite loops, wrong pointer initializations, recursivity, interrupt disabling. They are independent of the integration environment, and a verification needs to be done only once on a SW-C, independently of its reuse level. A correct SW-C will be correct even if reused many times on different platforms. On the other side, a faulty SW-C will be faulty on any integration platform. These typical problems are detected by peer reviews, architecture mechanisms, unit testing, or static analysis tools generally available on the market.

The second category of problems refers to the behavior of the project the SW-C is plugged into. CPU overload, or stack overflow are generally detected by embedded mechanisms, by static analysis tools, or by a combination of those. Regular measurements are done along the complete project life, in order to react before the limits are exceeded.

In this paper, we will focus on the third category of problems, which concerns the behavior of a SW component once it is integrated in the complete project. As the integration environment changes (e.g. due to the influence of other SW components), the behavior may change: The same SW-C shows different behavior on 2 different projects, being or not integrated in the same way 2 . These problems are generally less tracked; their specification, formalization, and verification can be a cumbersome job. Their effect is not immediate, difficult to reproduce, and in extreme cases, can be destructive. These problems are:

Wrong recurrences:

A calculation is not executed with the right recurrence, or has an unexpected jitter. In general, this problem is due to an integration error, or to high CPU load conditions. By static analysis, consistency between expected recurrence and integration task or container can be checked. By regular measurements on bench, engine, or vehicle, and by simulation, the correct