Jacques Durand

Typhanie Prince

Laurie Buscail

Philip Carr

Marie-Hélène Côté

Chantal Lyche

Cécile Sylvain Navarro

Phonological markedness, acquisition and language pathology: what is left of the Jakobsonian legacy?

Keywords: phonology, acquisition, aphasia, Broca, Wernicke, conduction, markedness, distinctive feature, binary features, single-valued features, elements, dependency phonology, government phonology, syllable, syllabic constituent

This chapter looks at some of the phonological theses put forward by Roman Jakobson (1941/1968) concerning language acquisition and language impairment. We argue, with special reference to the French language and on the basis of aphasiological data, that the notion of markedness, which played a central role in Jakobson's work, is still relevant. If built into our representational machinery, markedness can provide an insightful account of the development of phonology and its destructuring and restructuring in various types of aphasia.

INTRODUCTION

Roman Jakobson's work has been extensively discussed in the literature for its attempt to apply key concepts of structural linguistics, and particularly the notion of markedness, to the study of language acquisition and language impairment. [START_REF] Jakobson | Child Language, Aphasia and Phonological Universals, The Hague: Mouton[END_REF]Jakobson ( /1968) put forward the thesis that the distinctive sounds of a language (i.e., phonemes) are acquired in an order that reflects their structural complexity, in terms of feature composition and basic syllabic structure, and lost in the reverse order in certain types of aphasia. Moreover, he claimed that the complexity of segments that can be laid bare in the development and loss of language corresponds to universal or near-universal laws that govern the sound systems of the world. We argue, with special reference to French and on the basis of aphasiological data collected by one of us (TP), that despite criticisms of the Jakobsonian programme, the notion of markedness is still relevant and, if built into our representational machinery, can provide an insightful account of some of the attested patterns in the development of phonology or its destructuring in aphasia. 1 [START_REF] Jakobson | Child Language, Aphasia and Phonological Universals, The Hague: Mouton[END_REF]Jakobson's ( /1968) main theses concerning the acquisition of phonology have no doubt been presented before, but need to be summarized succinctly to set the scene for our own developments and our own evaluation of his overall contribution (see, too, the reassessment in Jakobson and Waugh, 1979: 165-176).

JAKOBSON AND ACQUISITION

A brief overview of Jakobson's position

The central assumption is that phonological development needs to be accounted for in linguistic terms, as it is not simply derivable from physical, perceptual or conceptual limitations in children.

The first stage is one of babbling, during which a vast gamut of sounds is produced, often unrelated to the ambient language (e.g., clicks or obstruent liquids for a French learner). This can be seen as a preliminary tuning up of the articulatory system. A major discontinuous change then occurs, during which sounds are put to the service of meaning, thus allowing for the emergence of distinctive oppositions between words. Jakobson claimed that 'the relative chronological order of development remains everywhere and at all times the same ' (1968: 46), although the pace of development was acknowledged to vary tremendously across children. For instance, at a given stage of development, 'the Swedish child says tata for "kaka", the German child topf for "kopf", the English child tut for "cut", and the Japanese child also changes /k/ to /t/ (ibid: 47)'. The point at which velar plosives are acquired may vary enormously between children, but it seems a universal fact that velar stops appear after dental ones (hereafter coronals, since dental appears to be used by Jakobson as an umbrella term for sounds that can equally well be alveolar).

In this scenario, all children start with the combination of an open or low vowel of the [a] type and a single consonant that is a forward articulated stop, usually a labial ([p]). This CV structure constitutes the basic syllabic template on which more complicated sequences will be based.

Thereafter, the initial stop is split into orals versus nasals (/p/ vs. /m/), followed by the opposition between labials and coronals (/p/ vs. /t/). Cross-cutting the acquisition of consonant manner and place of articulation, one needs to consider voicing (leaving aside the question of tenseness).

Basically, voiceless obstruents are acquired before voiced ones, but the child may well vacillate between voiceless and voiced realizations according to the context. As far as vowels are concerned, the single initial vowel /a/ gives rise to an initial split between a low (/a/) vowel and a high one (/i/), creating the opposition between compact and diffuse vowels, to use Jakobson's terms. This opposition can lead to a linear system with three degrees of vowel height, but in most cases it gives rise to systems based on the vocalic triangle /i, a, u/. In the beginning, as Jakobson stresses, the child possesses 'only those sounds which are common to all the languages of the world, while those phonemes which distinguish the mother tongue from the other languages of the world appear only later ' (1968: 50).

A further thesis defended by Jakobson is that identical laws operate in the phonological development of child language and in the synchronic structure of the world's languages. Thus, the acquisition of fricatives presupposes the acquisition of stops, in the same way as, in the languages of the world, the former cannot exist without the latter. Equally, the class of liquids is claimed to be acquired after obstruents, reflecting its typological distribution. Furthermore, '[t]he currency of a single liquid among the sense-discriminative elements in the word's languages [...] is paralleled by the fact that, as has been observed repeatedly, in the experience of children the second liquid, usually some kind of "r" sound, belongs to their last acquisitions' (Jakobson and Waugh 1979: 161).

Finally, and this is the topic of the section on speech pathology from a phonological perspective, the implicational laws that unite language acquisition and typology find confirmation in the study of aphasia, which is claimed to provide a mirror image of the developmental sequence of language acquisition. Thus, the sounds that are acquired last, because of their inherent complexity, their markedness (see 'Distinctive features and markedness section') are affected first.

Evaluating Jakobson's claims regarding acquisition

Jakobson's position is usually acknowledged as having given a major impetus to the study of phonological acquisition by children. Over the years, however, a number of corrections or objections have been formulated. First of all, the discontinuity hypothesis at the core of Jakobson's account, which flags first a babbling stage, then an initial stage divorced from the ultimate system, has been found wanting, and babbling itself is generally split into two stages (e.g., Vihman 1985, forthcoming;[START_REF] Fikkert | Acquiring phonology[END_REF]. We now know that the foetus is already an active perceiver of sounds (particularly the mother's productions) and that babbling is not limited to a tuning up of the vocal system, but is already shaped by the ambient language (e.g., [START_REF] Boysson-Bardies | Comment la parole vient aux enfants. De la naissance jusqu'à deux ans[END_REF]. Second, while Jakobson's hypothesis on the relevance of features drew support from the idea that our speech abilities are in some sense special and innate, in that they are based on uniquely human mechanisms for production and/or perception, there is now a substantial body of work questioning this assumption. Thus, Chomsky himself in collaboration with other researchers (see [START_REF] Hauser | The faculty of language: what is it? and how did it evolve?[END_REF]others 2002: 1574) argue that there appears to be a stronger continuity between animals and humans with respect to speech than previously believed. For them, 'the continuity hypothesis thus deserves the status of a null hypothesis'. In our opinion, though, this does not necessarily challenge the postulation of a universal network of distinctive features (or elements, as we refer to them below).

Third, it has been argued that the order of acquisition of sounds by children does not necessarily match the Jakobsonian scenarios, and that children may work in a very different way, starting out by producing sounds or sound sequences that would be classified as complex in Jakobsonian terms, then using these as a template for generating other sounds or sound sequences. Along with this idea, the role of frequency and usage is often cited in support of the idea that statistical regularities in the input are far more relevant than the feature classifications proposed in the Jakobsonian tradition (e.g. [START_REF] Beckman | Language-specific and language-universal aspects of lingual obstruent productions in Japanese-acquiring children[END_REF][START_REF] Carr | Individual variability in the acquisition of English phonetics and phonology: the role of the richness of the input[END_REF]Vihman 1993, forthcoming).

A proper review of the literature is far beyond the scope of this chapter. On the question of variability, [START_REF] Jakobson | The Sound Shape of Language[END_REF] agree that a detailed analysis of the idiosyncratic paths that particular children follow to learn their language is essential but, as they point out, such variation need not be incompatible with overall patterns of invariance and, indeed, successive expansions of the domain of invariance 'can reduce the dominion of variance to tractable proportions' (ibid: 158).

They also point out that 'even where the claims of universality appear to be overstated and the alleged universality is demoted to the status of a near-universal, the importance of rules with probability near 1.0 remains highly relevant to the question of general linguistic laws' (ibid: 157)'.

As far as French is concerned, we note with interest that a body of fairly recent work on the emergence of phonology has yielded results which that are, by and large, in agreement with a number of Jakobsonian predictions (cf., [START_REF] Demuth | The acquisition of word-final clusters in French[END_REF][START_REF] Demuth | The longitudinal development of clusters in French[END_REF][START_REF] Rose | French speech acquisition[END_REF][START_REF] Yamaguchi | Parcours d'acquisition des sons du langage chez deux enfants francophones[END_REF]. Thus, Rose and Wauquier-Gravelines (2007: 374) show that, in French, plosives are acquired before fricatives and nasals, which in turn precede the stable use of liquids. Voiceless plosives are also acquired before voiced ones, a pattern that has often been observed across languages of the world and which is also characteristic of many aphasic participants (especially those suffering from Broca's aphasia). As far as the liquids are concerned, [START_REF] Rose | French speech acquisition[END_REF], Dos [START_REF] Santos | Développement phonologique en français langue maternelle: une étude de cas[END_REF], Kehoe and others (2008) and [START_REF] Yamaguchi | Parcours d'acquisition des sons du langage chez deux enfants francophones[END_REF] all agree that in the acquisition of the French phonology, a single liquid is initially present, and of the two liquids, /ʁ/ is acquired later than /l/. Other authors, such as [START_REF] Vihman | Variable paths to early word productions[END_REF] and Beckman and others (2003), report results for English that contradict Jakobson's claims and emphasize the role of frequency and usage. While some of their examples are persuasive, it can be argued that in French, the later acquisition of /ʁ/ in relation to /l/, for example, cannot be due to frequency, given that /ʁ/ is more frequent than /l/. Assuming, however, that such observations are correct (and they are reinforced by our observations on aphasia in the section on speech pathology), we believe it is interesting to examine what phonology can tell us about the complexity of certain sounds, that is, their markedness in terms of feature composition.

Distinctive features and markedness

As is well known, Jakobson, in the wake of [START_REF] Trubetzkoy | Grundzüge der Phonologie[END_REF], played a major role in placing distinctiveness and the reduction of redundancies at the core of phonology and in putting forward a universal set of distinctive features that are part of our cognitive make-up. We believe that he was correct in doing so, and while some research has questioned this assumption, it is not clear to us how one can really proceed if distinctiveness is to fall by the wayside. We note that some of the research in question is often ambiguous, sometimes acknowledging distinctiveness and other times not (see Anderson 2011: 78). We will assume here that phonological systems make crucial use of distinctive features, and adopt the term elements to separate our own approach from the Jakobsonian tradition.

Jakobson's work is associated with the idea that, as far as phonology is concerned, distinctive features are binary -a hypothesis articulated in depth in Jakobson and others (1952) and taken further by [START_REF] Chomsky | The Sound Pattern of English[END_REF]. Carrying on where Trubetzkoy left off, Jakobson also stressed the importance of markedness, the idea that within the values of a feature, one of the poles is, so to speak, more basic and less complex than the other. Thus, we know from the study of vowel systems throughout the world that nasal vowels are rarer than oral vowels, that the presence of nasal vowels within a system presupposes that of oral vowels, and that the set of nasal vowels is never larger than the set of oral vowels. From an acoustic standpoint, nasal vowels are indeed more complex than oral vowels, since they involve a supplementary resonator (the nasal cavity), and experimental work has often acknowledged the complexity of the acoustic signature of nasality in vowels. 2 The + value for the [nasal] attribute can therefore be regarded as marked. It should, however, be noted that the binary hypothesis as defended in the Jakobsonian tradition does not directly reflect markedness. For instance, the [±strident] feature could just as well be expressed as

[±mellow] (i.e., its opposite), without any consequences for the formulation of phonological generalizations. In what follows, we make a different assumption.

We consider here that phonological elements are single valued, or unary, and that this gives us a direct measure of complexity. 3 The more elements a sound possesses the more complex it is. Thus, using Jakobsonian features for the moment, a system containing three oral vowels /i a u/ would (as a very first approximation) entail simple characterizations as follows: /i/ = {diffuse} (= high), /u/ = {flat} (= round) and /a/ = {compact} (= low). These three vowels would have the same degree of complexity (i.e., 1). By contrast, if these vowels had nasal counterparts, the latter would come out as more complex, as they would include the |nasal| element,4 as with, /a/ = {compact, nasal} (where the elements are not ordered and are, in fact, simultaneous, as in a traditional feature matrix). A simple formal consequence of considering that a segment is a set of elements is the possibility of having an empty set (i.e., a segment that is empty either for all elements or else for a particular subbundle of elements). For example, if /a/ were taken as unmarked in relation to /i/ and /u/, it could be treated as containing no element { }. We will set this possibility aside for the time being, so as not to complicate matters, but return to the idea of underspecification or nonspecification later on.

The main point at this stage is to realize that, while Jakobson stressed the role of markedness, the notational apparatus he used did not reflect this. Markedness constitutes a dimension that is external to formalization, an approach that also characterizes Chomsky and Halle's The Sound Pattern of English (1968) and many of its descendants.

SPEECH PATHOLOGY FROM A PHONOLOGICAL PERSPECTIVE

Relatively few studies have been specifically devoted to the phonology of aphasias, particularly as far as French is concerned. Nevertheless, a number of aphasiology specialists have acknowledged the existence of strategies favouring simplification within certain types of aphasia (e.g., [START_REF] Béland | Contraintes syllabiques sur les erreurs phonologiques dans l'aphasie[END_REF][START_REF] Béland | Les perturbations phonétiques et phonémiques: nouvelles perspectives[END_REF][START_REF] Moreau | Apport de la "théorie des contraintes et des stratégies de réparation" à l'étude des paraphasies phonémiques dans l'aphasie[END_REF][START_REF] Nespoulous | Segmental errors in aphasia as (psycho)linguistic evidence of the nature of phonological representations[END_REF][START_REF] Valdois | Les erreurs d'addition et d'omission dans l'aphasie: rôle du gouvernement phonologique[END_REF]; among others). As in the ideal Jakobsonian scenario, the literature presents cases that seem to be the mirror image of the order attested in acquisition. One well known example is that of patients with Broca's aphasia, who produce, voiceless instead of voiced obstruents (e.g., brosse (brush) /bʁɔs/ → /pʁɔs/). 5 We have already noted that for obstruents in the initial or final position, voicelessness is the unmarked value. Such substitutions may be the result of phonetic disorders arising from motor impairments (more or less pronounced, according to the type of patient), but can still reflect a clear systematicity. We note in passing that, even if participants with Broca's aphasia exhibit deficiencies of an articulatory nature, this does not mean that they do not also suffer from phonological deficiencies. Thus, Prince (2011) provides as a very concrete example the substitution of /t/ for /k/ in words such as crocodile (crocodile): /kʁokodil/ → /tʁotodil/, crapaud (toad): /kʁapo/ → /tʁapo/ and casquette (cap): /kaskɛt/ → /tastɛt/, among many others. We discuss this preference for coronal segment over the velar place of articulation below.

It should, however, be stressed that not all types of aphasia exhibit transformations in the direction of less marked structures. On the contrary, there are examples where the data reveal multiple transformations that appear at first sight quite chaotic, although deeper explanations may well exist.

Thus, the range of allophones for what is a phoneme in the ambient language may go well beyond what is normally attested (e.g., /k/ realized as [t], [k], [p], [ɡ] or even as a fricative), what is a single sound in the unimpaired language may result in clusters, and there may well be insertions that once again depart from normal usage (e.g,. [START_REF] Béland | Les perturbations phonétiques et phonémiques: nouvelles perspectives[END_REF]. These questions demand that we go beyond purely segmental phonology, since as Moreau (1993: 62) reminds us, 'A repair can account for a less complex structure locally, but may well engender a greater degree of complexity for the word as a whole' (our translation). This is the perspective we adopt to understand some of the mechanisms involved in aphasic productions.

One important question in aphasiology relates to the nature of transformations across different types of aphasia. For instance, there is an ongoing debate as to whether fluent and dysfluent aphasias lead to the same processes of transformation. [START_REF] Nespoulous | Le langage et les processus cérébraux: apport de la linguistique et de la psycholinguistique à l'aphasiologie et à la neuropsycholinguistique cognitive du XXème siècle[END_REF] and Nespoulous and others (1987) anarthria.

reach the conclusion that the transformations do indeed differ from one type of aphasia to another, especially as far as Broca's aphasia and conduction aphasia are concerned: the first is characterized by a phonetic deficit, and the second by a phonemic deficit. However, this result is true only of substitutions, and other types of transformation still need investigating. By contrast, Valdois' thesis (1987) was specifically concerned with insertions and deletions, and argued that the transformations due to aphasia do not differ from one type of impairment to another. Of course, some participants with aphasia exhibit different strategies, but the same phonological processes and constraints are involved. The only strategy that differentiates between them is the use of metathesis, which Valdois claims to be characteristic only of conduction aphasia.

As far as segmental transformations are concerned, [START_REF] Béland | On the special status of coronals in aphasia[END_REF] conclude on the basis of a study of 29 participants with aphasia (7 Broca's, 10 Wernicke's, 6 conduction, and 6 mixed) that labials are replaced by coronals in 56.25 per cent of cases, and the same type of substitution also applies to velar sounds. (Coronals themselves are replaced in 50 per cent of cases by other coronals). Nespoulous and others (1987) also point out that coronality is maximally used in substitutions. However, [START_REF] Béland | On the special status of coronals in aphasia[END_REF] go further: while they confirm that coronals are the default substitute for other sounds, they also note that they are the least resistant in the initial and intervocalic positions, in that they are often deleted, they are the only segments to be clearly transparent in processes of vocalic harmony, and lastly they are the most frequent epenthetic consonants (Béland and Favreau 1991: 213). We explore below one solution that consists in treating them as empty elements in terms of place features. In the ensuing section ('Beyond segments'), we stress the need to go beyond purely segmental phonology.

The special status of coronals

Ongoing collaborative work by one of the authors of this paper has confirmed the special status of coronals (cf., Prince andTifrit 2012, 2013). The first study was based on a sample of 15 participants with aphasia (6 Broca's, 7 Wernicke's, 2 conduction aphasia). These were recorded from Day 1 to Day 15 at the stroke unit of Nantes University Hospital (CHU).6 All these participants had aphasia caused by lesions resulting from brain damage. An experimental protocol composed of 40 items with clusters was tested using a naming and repetition task. Data revealed that substitutions followed a variety of routes, with some appearing quite chaotic at first sight (see Table 1):

Substitutions affecting place of articulation

Labial

Velar Coronal Source P7 K T Lab. serpent (snake): /sɛʁpɑ/ Table 1. Some examples of substitutions in participants with aphasia On closer examination, it turns out that the substitutions followed an organized pattern, which is explored in terms of frequency below. Most of the time, a member of the velar class K was substituted by a member of the coronal class T, as in (1), where we first give the expected pronunciation.

( Looking at all the within-category substitutions, we can see that the coronal place of articulation was the preferred target of a substitution even for the coronals themselves (51.16 per cent versus 10.47 per cent of labial substitutions and 38.37 per cent of velar substitutions). The above observations confirm the Jakobsonian prediction that velars are the most affected sound class (44.18 per cent), mostly by coronals (81.40 per cent,). Coronals constitute the major target of substitution (68.84 per cent), while labials are in between coronals and velars. Why should this be? What might be special about coronals from a phonological point of view?

One avenue that we wish to explore briefly is the use of single-valued features, or elements as we have called them above, investigating the possibility that some segments are underspecified or unspecified. 9 Thus, let us assume (along with research within the unary frameworks cited in As the representations stand, the first result is that the K class comes out as more complex than the P and T classes. If the partial destructuring in aphasia reflected complexity, then we would expect the more complex class K to be affected before its two congeners. Furthermore, although we have repeatedly observed that the T class is special in that it is the main target of substitution, our representation in (4) ranks P and T as equal in terms of complexity. Moreover, other studies of 9 Concerning the elements used here, we refer the reader to Footnote 3 above. For the postulation of underspecified or unspecified segments within a framework, see, for example, Anderson and Durand (1988) on Nez Perce and Durand (1988) on southern French.

French-speaking participants with aphasia have argued that the T class proves transparent to harmonic processes. T therefore behaves as though it had no articulatory content. Independently of these observations, if we look at the representations in (4), we can see that they do not maximize contrastivity. That is, not all the elements mentioned are needed to separate the P, T and K classes.

Jakobson always made the important point that distinctive features are inherently relational. They do not label phonetic classes independently of the language one is dealing with. Applying this idea to the categories in (4), we now formulate them as in ( 5) and (5'), where the coronals have no place features. 10 The idea of underspecifying phonemes is by no means new. It has been articulated in various frameworks, and coronals, as we saw in connection with the work of [START_REF] Béland | On the special status of coronals in aphasia[END_REF], have indeed been argued by many specialists to be the most unmarked of the consonantal segments 11 (e.g., [START_REF] Paradis | Phonetics and Phonology. The Special Status of Coronals. Internal and External Evidence[END_REF]Prunet 1991, Rice 2009).We submit that theories of elements provide a natural way of expressing this. It should be observed that, on totally independent grounds, [START_REF] Durand | Les phénomènes de nasalité en français du Midi: phonologie de dépendance et sous-spécification[END_REF], in his analysis of nasality phenomena in Midi French, argued that the coronal /n/ was unspecified for articulatory features (in relation to /m/ and /ɲ/), and provided a full analysis in terms of single-valued elements.

Beyond segments

10 One of our readers correctly points out that nothing then would separate a /t/ from a glottal stop. A proper debate on this issue would require an examination of phonation features in opposition to place features, and would go beyond the scope of this chapter. In any case, it should be noted that the glottal stop does not belong to the inventory of contrastive phonological segments in French, which are the subject under discussion here.

One of the possible criticisms that can be levelled at Jakobson's work is its over-emphasis on phonemic units and the lack of a deeper reflection on units larger than segments and prosodic phenomena in general (the prosodic hierarchy from the syllable upwards, the role of stress, tone, intonation, as well as harmonic processes). In this paper, we examine just one of these issues, namely the need for a theory of syllabic constituents if one wants to deal appropriately with a number of phenomena linked to aphasia. Despite the impetus given by Blumstein and others (1977), there are still comparatively few essays on the relevance and structure of syllabic constituents for the analysis of data from different types of aphasia. Nevertheless, contributions by authors such as [START_REF] Béland | Contraintes syllabiques sur les erreurs phonologiques dans l'aphasie[END_REF], [START_REF] Valdois | Les erreurs d'addition et d'omission dans l'aphasie: rôle du gouvernement phonologique[END_REF], [START_REF] Béland | Les perturbations phonétiques et phonémiques: nouvelles perspectives[END_REF] and [START_REF] Nespoulous | Repair strategies and consonantal cluster production in Broca's production[END_REF] seem to converge on the idea that paraphasias are governed by different phonological processes, and that epentheses and syncopes can often be seen as repair strategies helping participants to cope with structures that are proving costly at a given stage. In particular, patients are often observed to find syllabic clusters problematic, but more attention needs to be paid to the solutions they find as the simplifications can vary in nature. For example, setting epentheses aside, initial CCV clusters are regularly simplified to CV clusters. Moreover, when in an initial CC cluster is made up of Obstruent + Liquid (e.g., (e.g. /pʁ-/, /tʁ-/, / ɡl-/), it is overwhelmingly the liquid that is dropped, leaving the obstruent as the sole onset of the syllable onset. Thus, Nespoulous and Moreau (1997: 76) observed that it is always C 2 that is omitted within initial /fricative + liquid/ clusters, whereas it is C 1 with clusters of the form /s/ + obstruent. In a study examining 15 participants with aphasia (6 Broca's, 7

Wernicke's and 2 conduction aphasia), [START_REF] Prince | Sur le comportement des attaques complexes /occlusive+ʁ/ dans l'aphasie: #Tʁ et .ʁT[END_REF], found that 37.8 per cent of transformations of an OL group involved the deletion of C 2 (e.g., prune /pʁyn/ → [pyn]). By contrast, only 3.7 per cent involved the deletion of C 1 (e.g., [bʁɔs] → [ʁɔs]).

Branching OL onsets (e.g., /tʁu/ trou) are, in a sense, puzzling. If we look at them in terms of the classic sonority curve, liquids are ideally placed between the obstruent and the vowel. In fact, in the early work on dependency phonology in the 'seventies (e.g., [START_REF] Anderson | Three theses concerning phonological representations[END_REF]Durand 1990: 279), a syllable such as trou was represented as in ( 6): But then, why should the liquid be preferentially deleted? It should be noted that the dependency representation in (6) embodies the idea that the liquid is the head of the initial CC structure, in the same way as the vowel labelled V here is the head of the whole construction. If the initial plosive /t/ were deleted, it would leave behind a perfectly well formed structure. The answer is that, contrary to (6), the plosive in such structures is actually the head, and that sonority in onsets is not the determining factor. Plosives provide an ideal onset, and other members of an initial onset are subordinated to the plosive as in ( 7):

(7) Revised dependency graph with the obstruent as head The structure in ( 7) is not put forward to deal with these data. It was independently argued for in Anderson (1986) and is related to the claim made in government phonology that within OL clusters, the obstruent is the governor and the liquid is a governed element (see Kaye and others 1985).

Heads are central to a given construction and, evidently, as governors, they prove more resistant to deletions than dependents.

Let us now turn briefly to C 1 C 2 onsets made up of /s/ + obstruent onsets. We pointed out earlier that Nespoulous and Moreau (1997: 76) argue that such onsets are characterized by the opposite pattern to the previous one. Thus, it is C 1 (i.e., the /s/) that is deleted -a result supported by [START_REF] Prince | Sur le comportement des attaques complexes /occlusive+ʁ/ dans l'aphasie: #Tʁ et .ʁT[END_REF] on aphasia and acquisition. Why should the target of deletion be C 1 now and not C 2 ? First, it should be noted that the presence of a fricative /s/ in such onsets is unusual in terms of sonority. The onsets of syllables normally respect the sonority curve (e.g., froid /fʁwa/), with an obstruent, a liquid and a glide preceding the vowel. Second, /s/ does not stand in opposition to other fricatives in the core vocabulary of French (no initial *#ft-, *#fk-, #ʃp-, *#ʃk, etc.). The initial /s/ in such clusters is isolated, and in terms of an approach inspired by [START_REF] Trubetzkoy | Grundzüge der Phonologie[END_REF], it would actually be an archiphoneme representing the neutralization of all voiceless fricatives in that position. Various solutions have been put forward in the literature to account for the special nature of this initial /s/. [START_REF] Kaye | Do you believe in magic? The story of s+C sequences[END_REF] treats it as, in some sense, extrametrical -part of a degenerate syllable with an empty vowel head reminding us that many words beginning with /s/ once had a vowel (e.g., spatule < OF espatule < Lat. espat(h)ula). Another possible solution is that, as in (7) above, the /s/ is part of the onset, but subordinate to the obstruent that is always the head of the onset (as in Anderson 1986).

Do we need to stress that, once again, the patterns of deletion favour segments whose nature and position are marked in relation to the unmarked CV syllable containing an obstruent and a vowel, as in the classic Jakobsonian picture?

CONCLUSION

Our aim in this chapter has been a modest one. On the basis of observations regarding the acquisition of phonology and its destructuring and restructuring in various types of aphasia, we have tried to show that phonological representations that have been defended on independent grounds can provide an insightful understanding of the attested patterns. Jakobson's hypotheses regarding binary features and markedness constitute a good starting point, although we have argued that better accounts are possible in terms of single-valued features (elements) and syllable structures that encode markedness in a direct manner. Moreover, while many of the details of Jakobson's hypotheses need to be revised, the data from aphasia that we have examined appear to provide a mirror image of the acquisition phenomena reported in some of the recent literature. We can therefore claim that Jakobson gave a major impetus to research into the acquisition of language and its destructuring in aphasia, and that the theoretical landscape he provided is still worth revisiting today. We can only concur with Nespoulous and Moreau's (1997: 71)

Footnote 3 )

 3 that all the plosives we have examined in this chapter have a feature specifying that they involve a closure of the articulators. Let us represent this feature by a single symbol, in this case[ʔ]. Now, let us further assume that the labials /p/ and /b/, the coronals /t/ and /d/, and the velars /k/ and /ɡ/ are analyzed as in (4), summarized with the class labels in (4'), which we remind the reader are not archiphonemes here: these representations, apart from |ʔ| which has already been defined, |u| is a feature corresponding closely to Jakobson's feature [grave], |v| stands for voice and |l| represents linguality, that is, the involvement of the body or blade/tip of the tongue (seeLass 1984: 285;[START_REF] Anderson | Principles of Dependency Phonology[END_REF].

  = {ʔ,u,v} /d/ = {ʔ,v} /ɡ/ = {ʔ,l,u,v} (5') P = {ʔ,u} T = {ʔ} K = {ʔ,l,u}

  observation that 'It was indeed the merit of Roman Jakobson to draw aphasiology away from the mere surface description of symptoms and to provide the first interpretations of aphasic language disturbances in a linguistically motivated way'. BIBLIOGRAPHY Anderson, J.M. (2011) Phonology-Syntax Analogies, Vol. 3 of The Substance of Language, Oxford: Oxford University Press. Anderson, J.M. (1986) 'Suprasegmental dependencies', in J. Durand (ed.) Dependency and Nonlinear Phonology, Beckenham: Croom Helm. Anderson, J.M. and Durand, J. (1988) 'Vowel harmony and non-specification in Nez Perce', in H. van der Hulst and N. Smith (eds) Features, Segmental Structure and Harmony Processes, Dordrecht: Foris.

Table 2 .

 2 Patterns of plosive substitution 8Chi-square test: χ2 = 45.568, df = 4, p-value < 0.01 Table2shows both the number of plosive substitutions for each source class and their frequency, expressed as a percentage (in brackets). Overall, labial sounds were substituted in 26.37 per cent of cases, coronals in 29.45 per cent and velars in 44.18 per cent. Velars were the most

		Substitutions affecting place of articulation
	Source	Labial P	Velar K	Coronal T	total
	[coronal] 9 (10.47%)	33 (38.37%) 44 (51.16%)	86 (29.45%)
	[labial]	18 (23.38%)	7 (9.09%)	52 (67.53%)	77 (26.37%)
	[velar]	14 (10.85%)	10 (7.75%) 105 (81.40%) 129 (44.18%)
	total	41 (14.04%)	50 (17.12%) 201 (68.84%) 292 (100%)

susceptible to change. This table also indicates that the coronal place of articulation (201 occurrences) was the most frequent result of a transformation, contrasting with just 41 occurrences for the labial place and 50 for the velar place. In Table

3

, we present the rate of substitutions (expressed as a percentage) for each class out of the total number of substitutions for the relevant class (e.g., [coronal] > [labial] / total substitutions [coronal]).

Table 3 .

 3 Within-category patterns of substitution

For a thorough discussion and references, see[START_REF] Delvaux | Contrôle et connaissance phonétique: les voyelles nasales du français[END_REF].

The two authors of this article work within different frameworks, and so have tried to converge on minimal assumptions. One of us (JD) espouses Dependency Phonology(Anderson 2010;[START_REF] Anderson | Principles of Dependency Phonology[END_REF][START_REF] Anderson | Three theses concerning phonological representations[END_REF], the other (TP) Government Phonology[START_REF] Backley | An Introduction to Element Theory[END_REF] Kaye and others 1985; Scheer, 2004).

To distinguish elements from classic binary features, we place them between vertical bars whenever we refer to them individually. Elements characterizing a segment are given a set-theoretic interpretation and are listed within curly brackets.

See Nespoulous et al. (2013) for a recent reexamination of voicing from a phonological and phonetic point of view with participants suffering from left anterior brain damage presenting clinical profiles of Broca's aphasia and/or

Day 1 = one day after the stroke, Day 2 = two days after the stroke, and so on.

The capital letters P, T and K that we use here and below refer not to archiphonemes but to the classes of labial plosives (/p, b/), velar plosives (/k, ɡ/) and coronal plosives (/t, d/).

In this table, 'obs' refers to our observations (i.e., our data) and 'exp' refers to the statistically expected substitutions.


Georg Macher
email: georg.macher@tugraz.at

Harald Sporer
email: sporer@tugraz.at

Eric Armengaud
email: eric.armengaud@avl.com

Eugen Brenner
email: brenner@tugraz.at

Christian Kreiner
email: christian.kreiner@tugraz.at

A Seamless Model-Transformation between System and Software Development Tools

Keywords: Automotive, model-based development, reuse, traceability, model-based software engineering, ISO 26262

The development of dependable embedded automotive systems faces many challenges arising from increasing complexity, coexistence of critical and non-critical applications, and the emergence of new architectural paradigms on the one hand, to short time-to-market intervals on the other hand. This situation requires tools to improve efficiency and consistence of development models along the entire development lifecycle. The existing solutions to date are still all too frequently insufficient when transforming system models with higher levels of abstraction to more concrete engineering models (such as software engineering models). Future automotive systems require appropriate structuring and abstraction in terms of modularization, separation of concerns, and supporting interactions between system, and component development.

However, refinement of system designs into hardware and software implementations is still a tedious task. The aim of this work is to enhance an automotive model-driven system engineering framework with software-architecture design capabilities and a model-transformation framework to enable a seamless description of safety-critical systems, from requirements at the system level down to software component implementation in a bidirectional manner.

I. INTRODUCTION

Embedded systems are already integrated in our everyday lives and play a central role in all domains including automotive, aerospace, healthcare, manufacturing industry, the energy sector, or consumer electronics. In 2010, the embedded systems market accounted for almost 852 billion dollars worldwide, and is expected to reach 1.5 trillion by 2015 (assuming an annual growth rate of 12%) [START_REF] Petrissans | Design of Future Embedded Systems Toward System of Systems -Trends and Challenges[END_REF]. Current premium cars implement more than 90 electronic control units (ECU) per car with close to 1 Gigabyte software code [START_REF] Ebert | Embedded Software: Facts, Figures, and Future[END_REF], these are responsible for 25% of vehicle costs and bring an added value of between 40% and 75% [START_REF] Scuro | Automotive industry: Innovation driven by electronics[END_REF].

The trend of replacing traditional mechanical systems with modern embedded systems enables the deployment of more advanced control strategies providing additional benefits for the customer and for the environment, but at the same time, the higher degree of integration and criticality of the control application is posing new challenges. These factors are resulting in multiple cross-domain collaborations and interactions in the face of the challenge of mastering the increased complexity involved and also to ensure consistency of the development along the entire product life cycle.

Model-based development supports the description of the system under development in a more structured manner, in the context of handling upcoming issues with modern realtime systems and also in relation to ISO 26262. Model-based development approaches enable different views for different stakeholders, different levels of abstraction and central storage of information. This improves the consistency, correctness, and completeness of the system specification. Nevertheless, such seamless integrations of model-based development still tend to be the exception rather than the rule and often fall short of target due to the lack of integration of conceptual and tooling levels [START_REF] Broy | Seamless Model-based Development: from Isolated Tool to Integrated Model Engineering Environments[END_REF]. Consequently, this work focuses on improving the continuity of information interchange from system development level to software development level models.

With this objective in mind the work focuses on improving the continuity of information interchange for architectural designs from system development level (Automotive SPICE [START_REF]Automotive SPICE Process Assessment Model[END_REF] ENG.3 respectively ISO 26262 [START_REF]ISO 26262 Road vehicles Functional Safety Part 1-10[END_REF] 4-7 System design) to software development level (Automotive SPICE ENG.5 respectively ISO 26262 6-7 SW architectural design). More specifically, the approach is based on the enhancement of a model-driven system engineering framework with softwarearchitecture design capabilities. The model-transformation framework automatically generates software architectures in Matlab/Simulink described via high level control system models in SysML format. The goal is, on the one hand, to support a consistent and traceable refinement from the early concept phase to software implementation. On the other hand, the bidirectional update function of the transformation framework enables facilitation in gaining mutual benefits for the basic software and the application software development from the coexistence of information for them both within the central database.

The document is organized as follows: Section II presents an overview of related approaches as well as model-based development and integrated tool chains. In Section III a description of the proposed bridging approach for the refinement of the model-based system engineering model to software development is provided. An application and evaluation of the approach is presented in Section IV. Finally, this work is concluded in Section V with an overview of the approach.

II. RELATED WORK

Model-based systems and software development as well as tool integration aim at moving the development steps involved closer together and thus improving the consistency of information over the expertise and domain boundaries. Pretschner's roadmap [START_REF] Pretschner | Software Engineering for Automotive Systems: A Roadmap[END_REF] highlights the benefits of such a seamless modelbased development tool-chain for automotive software engineering. Model-based development is also claimed to be the best approach to managing the large amount of information and the complexity of the modern embedded systems involved by Broy et al. [START_REF] Broy | Seamless Model-based Development: from Isolated Tool to Integrated Model Engineering Environments[END_REF]. Their paper illustrates why seamless solutions have not been achieved so far and mentions concepts and theories for model-based development of embedded software systems. Additionally they make reference to commonly used solutions and problems arising with inadequate tool-chain support (e.g. redundancy, inconsistency and lack of automation). Nevertheless, the challenge of enabling a seamless integration of models into model-chains is still an open issue [START_REF] Quadri | MADES: A SysML/MARTE high level methodology for real-time and embedded systems[END_REF], [START_REF] Rodriguez-Priego | Modeling Issues: A Survival Guide for a Non-expert Modeler[END_REF], [START_REF] Thyssen | A system for seamless abstraction layers for model-based development of embedded software[END_REF] Often, different specialized models for specific aspects are used at different development stages with varying abstraction levels. Traceability between these different models is commonly established via manual linking due to process and tooling gaps.

The work of Holtmann et al. [START_REF] Holtmann | A Seamless Model-Based Development Process for Automotive Systems[END_REF] highlights process and tooling gaps between different modeling aspects of a modelbased development process. Giese et al. [START_REF] Giese | Model Synchronization at Work: Keeping SysML and AUTOSAR Models Consistent[END_REF] address issues of correct bi-directional transfer between system design models and software engineering models. The authors propose a model synchronization approach consisting of tool adapters between SysML models and software engineering models in AUTOSAR representation.

Dealing with this gap between system architecture and software architecture, especially while considering componentbased approaches such as UML and SysML for system architecture description and AUTOSAR for SW architecture description, is one of the most important topics in this entire issue. Two common variants in the automotive domain are the usage of SysML [START_REF] Boldt | Modeling AUTOSAR systems with a UML/SysML profile[END_REF], [START_REF] Giese | Model Synchronization at Work: Keeping SysML and AUTOSAR Models Consistent[END_REF], [START_REF] Kawahara | Verification of embedded system's specification using collaborative simulation of SysML and Simulink models[END_REF], [START_REF] Macher | Automated Generation of AUTOSAR Description File for Safety-Critical Software Architectures[END_REF], [START_REF] Meyer | Eine durchgaengige modellbasierte Entwicklungsmethodik fuer die automobile Steuergeraeteentwicklung unter Einbeziehung des AUTOSAR Standards[END_REF] or X-MAN [START_REF] Lau | A Holistic (Component-based) Approach to AUTOSAR Designs[END_REF] approaches for architectural description and AUTOSAR for software system description. Boldt [START_REF] Boldt | Modeling AUTOSAR systems with a UML/SysML profile[END_REF] proposed the use of a tailored Unified Modeling Language (UML) or System Modeling Language (SysML) profile as the most powerful and extensible way to integrate an AUTOSAR method in company process flows.

The approach of bridging the gap between model-based system engineering and software engineering models based on EAST-ADL2 architecture description language and a complementary AUTOSAR representation is also very common in the automotive software development domain [START_REF] Chen | Modelling Support for Design of Safety-Critical Automotive Embedded Systems[END_REF], [START_REF] Mader | A Bridge from System to Software Development for Safety-Critical Automotive Embedded Systems[END_REF], [START_REF] Sjoestedt | Mapping Simulink to UML in the Design of Embedded Systems: Investigating Scenarios and Structural and Behavioral Mapping[END_REF]. EAST-ADL represents an architecture description language using AUTOSAR elements to represent the software implementation layer of embedded systems [START_REF] Blom | EAST-ADL -An Architecture Description Language for Automotive Software-intensive Systems[END_REF]. More recently the MAENAD Project 1 is also focusing this approach. Kawahara et al. [START_REF] Kawahara | Verification of embedded system's specification using collaborative simulation of SysML and Simulink models[END_REF] propose an extension of SysML which enables description of continuous time behavior. Their tool integration base on Eclipse and couples SysML and Matlab/Simulink via API.

1 http://maenad.eu/ Farkas et al. [START_REF] Farkas | An Integrative Approach for Embedded Software Design with UML and Simulink[END_REF] describe in their paper an integrative approach for Embedded Software Design with UML and Simulink. Their presented approach aims in a stepwise migration towards model-based development and enables the cooperative usage of MATLAB/Simulink & UML for functional specification and code generation. The focus of this work is on the combination of source codes generated by different modelbased tools, rather than the interchange of data between the different model representations.

SysML and model-based development (MBD) as the backbone for development of complex safety critical systems is also seen as a key success factor by Lovric et. al [START_REF] Lovric | SysML as Backbone for Engineering and Safety -Practical Experience with TRW Braking ECU[END_REF]. The paper evaluates key success factors of MBD in comparison to legacy development processes in the field of safety-critical automotive systems.

Tool support for automotive engineering development is still organized as a patchwork of heterogeneous tools and formalisms [START_REF] Blom | EAST-ADL -An Architecture Description Language for Automotive Software-intensive Systems[END_REF]. On the one hand, general-purpose modeling languages (such as UML or SysML) provide modeling power suitable for capturing system wide constraints and behavior, but are lacking in synthesizability. On the other hand, specialpurpose modeling languages (such as C, Assembler, Matlab, Simulink, ASCET ) are optimized for fine granular design, but are less efficient in high-level design.

The issue of improving these interactions, especially those which deal with cross-domains affairs (such as the architectural design refinement from system development level to software development level), thus requires a comprehensive understanding of related processes, methods, and tools. The work of Sechser [START_REF] Sechser | The marriage of two process worlds[END_REF] describes the experiences gained when combining two different process worlds in the automotive domain.

III. MODEL-TRANSFORMATION BRIDGE APPROACH

This paragraph gives a brief overview of the underlying framework and related preliminary work which supports the proposed approach. The presented framework focuses on improving the continuity of information interchange from system development level to software development level. The basic concept behind this framework is to have a consistent information repository as central source of information, to store all information of all the engineering disciplines involved for embedded automotive system development in a structured way [START_REF] Macher | Bridging Automotive Systems, Safety and Software Engineering by a Seamless Tool Chain[END_REF].

The methodical support of system architectural design and refinement of this design to software design often fell short of the mark. To handle this situation the AUTOSAR methodology [START_REF] Kreiner | AUTOSAR AUTomotive Open System ARchitecture[END_REF] provides standardized and clearly defined interfaces between different software components and development tools and also provides such tools for easing this process of architectural design refinement. Nevertheless, the enormously complex AUTOSAR model requires a high amount of preliminary work and projects with limited resources often struggle to achieve adequate quality within budget (such as time or manpower) using this approach. This approach thus arises out of common AUTOSAR based approaches and forces a direct model transformation from SysML representation to Matlab/Simulink. The reason for making the decision of not fostering an AUTOSAR approach is based on the one hand on Figure 1 shows an overview of this approach and the imbedded bridging of abstract system development and concrete software development models. More specifically, our contribution consists of the following parts:

• SW modeling framework: Enhancement of a SysML profile for the definition of SW component interfaces and SW architecture composition. Required for consistent SW system description, see Figure 1 -model addon.

• SW architecture exporter: Exporter to generate the designed SW architecture in Matlab/Simulink for further development of SW functions, see Figure 1 -tool bridge.

• SW architecture importer: Importer to integrate refined SW architecture and interfaces from the software development tool (to support round-trip engineering), see Figure 1 -tool bridge.

This proposed approach closes the gap, also mentioned by Giese et al. [START_REF] Giese | Model Synchronization at Work: Keeping SysML and AUTOSAR Models Consistent[END_REF], Holtmann et al. [START_REF] Holtmann | A Seamless Model-Based Development Process for Automotive Systems[END_REF], and Sandmann and Seibt [START_REF] Sandmann | AUTOSAR-Compliant Development Workflows: From Architecture to Implementation -Tool Interoperability for Round-Trip Engineering and Verification & Validation[END_REF], between system-level development at abstract UML-like representations and software-level development modeling tools (e.g. Matlab/Simulink or Targetlink). The bridging supports consistency of information transfer between system engineering tools and software engineering tools and minimizes redundant manual information exchange between these tools. This contributes to simplifing seamless safety argumentation according to ISO 26262 [START_REF]ISO 26262 Road vehicles Functional Safety Part 1-10[END_REF] for the system developed. The benefits of this development approach are highly noticeable in terms of re-engineering cycles, tool changes, and reworking of development artifacts with alternating dependencies. As can be seen in Figure 1, the lack of supporting tools for information transfer between system development tools and software development tools can be dispelled by our approach. The implementation of the bridge based on versatile C# class libraries (dll) and Matlab COM Automation Server ensures tool in-dependence of the general-purpose UML modeling tool (such as Enterprise Architect or Artisan Studio) and version in-dependence of Matlab/Simulink through API command implementation. This makes the method especially attractive for projects and companies with limited resources (either in manpower or finances). Small projects or start-up companies in particular often struggle with the problem of setting up their development processes so as to achieve adequate quality.

A. Software Modeling Framework

The first part of the approach is a specific SysML modeling framework which enables the possibility of designing software architectures in an AUTOSAR aligned manner within a system development tool. The profile enables an explicit definition of AUTOSAR components, component interfaces, connections between interfaces and makes the SysML representation more manageable for the needs of the design of an automotive software architecture. Furthermore, it opens up the possibility for defining software architecture and ensures establishment of communication between architecture artifacts with interface specifications (e.g. upper limits, initial values, formulas). Special basic software and hardware abstraction modules are assigned to establish links to the underlying basic software and hardware abstraction layers. Moreover, these SW modeling artifacts can be linked to the system model artifacts and requirements in such a manner that traceable links can be established more easily. This has further benefits in terms of constraints checking, reuse, and reporting generation (e.g. for safety case generation). Figure 2 shows an example of software architecture artifacts and interface information represented in Enterprise Architect. Furthermore, this integrated definition of system artifacts and software module in one tool supports the work of safety engineers by adding values and visual labels for safety-relevant software modules.

In addition to standard VFB AUTOSAR profiles the profile features assignment and graphical representation of ASIL to dedicated signals and modules and provides specification of runnables with timing constraints (such as WCET), ASIL, and priority. This additional information enables mapping of tasks to a specific core and establishment of a valid scheduling in a later development phase. Further benefits result in terms of constraints checking and traceability of development decisions.

B. SW Architecture Exporter

The second part of the approach is the SW architecture exporter. The implementation of the exporter is based on Matlab COM Automation Server and generates models through API command implementation, which ensures tool version-independence. The export functionality enables the export of software architecture, component containers, and their interconnections designed in SysML to the software development tool Matlab/Simulink. The SW architecture artifacts to be transferred can be selected by user input and the corresponding Matlab/Simulink model is generated by a background task. As can be seen in Figure 3 the user is able to select the SW artifacts for exporting, the desired model representation in Matlab/Simulink (either TargetLink or Simulink representation), and the exporting mode (m-file based, API based, or as ARXML file). The export mode variants also enable exporting if Matlab/Simulink is not available (m-file based) or an AUTOSAR based SW development toolchain is used (ARXML file based). Listing 1 shows some excerpts of the automatically generated Matlab API commands. As can be seen in this listing, each model artifact, parameter, and connection is transferred to Matlab/Simulink, where the blocks are arranged and sized in a correct manner. Besides this, unique links to the EA representation and assigned safety-criticality marking of the artifact (Listing 1 line 3 and 8) are established.

C. SW Architecture Importer

The last part of the approach is the import functionality add-on for the system development tool, which in combination with the export function, enables bidirectional updates of software architecture representations in the system development tool and the software modules in Matlab/Simulink. The Thereby new and modified model artifacts can be differentiated and changes made in the software development tool can be kept consistent within the system development model representation. This ensures consistency between the models, enables importing of newly available software modules from Matlab/Simulink, and therefore guarantees consistency of information across tool boundaries. Figure 4 shows the user interface within the system development tool. As can be seen in this figure, modifications between the two models are identified and a selective update of the SysML representation can be triggered by the user. Furthermore, a highlighting of the type of change can also be depicted. Table I shows the different change type indicators and types of changes.

IV. APPLICATION OF THE PROPOSED APPROACH

This section demonstrates the introduced approach by an automotive embedded system use-case. To provide a comparison and highlighting of the improvements of our approach we use the 3 layer monitoring concept [START_REF] Zurawka | Method for checking the safety and reliability of a software-based electronic system[END_REF] as an evaluation use-case. This elementary use-case is well-known in the automotive domain, but is nevertheless representative. Moreover, this elementary use-case is illustrative material, which is also used for internal training purposes with students and engineers. The disclosed and commercially non-sensitivity use-case is not intended to be exhaustive, nor to be representative of leadingedge technology.

The definition of the software architecture is usually performed by a software system architect within the software development tool (Matlab/Simulink). With our approach this work package is included in the system development tool (depicted in Figure 5). This does not hamper the work of the software system architect, but it enables constraint checking features and helps to improve system maturity in terms of consistency, completeness, and correctness of the development artifacts. Besides this, the change offers a significant benefit for the development of safety-critical software in terms of traceability, replicability of design decisions and it unambiguously visualizes dependencies while putting visual emphasis on view-dependent constraints (such as graphical safety-criticality highlighting of SW modules in Figure 5).

The 3 layer monitoring concept use-case presented consists of 7 SW modules with 34 interfaces and 30 signal connections. Hereby the SW module representations contain 3 configurable attributes per element and the SW interfaces 34 attributes per element. The use-case thus sums up to a total count of 41 model artifacts with 361 configuration parameters and 30 relations between the elements. This elementary example already indicates that the number of model elements and relations between the model elements already becomes confusing. A manual transformation of the information represented within the models would already be cumbersome, error-prone, and would involve a great amount of additional work to ensure consistency between the two models.

The presented approach in this work checks the information and model artifacts for point-to-point consistency of interface configurations before automatically transferring the model representation via 212 lines of auto-generated Matlab API code, which provides evidences and ensures the completeness of the model transformation. The presented SW architecture importer functionality enables round-trip engineering and bi-directional updates of both models and therefore supports evidence for the consistency of both models.

In terms of safety-critical development and reuse the features of the approach presents are crucial to transfer information between separated tools and link supporting safetyrelevant information. Moreover, the approach eliminates the need for manual information reworking without adequate tool support, ensuring reproducibility, and traceability argumentation.

V. CONCLUSION

The challenge with modern embedded automotive systems is to master the increased complexity of these systems and ensure consistency of the development along the entire product life cycle. Automotive standards, such as ISO 26262 safety standard provide a process framework which requires efficient and consistent product development and tool support. Nevertheless, various heterogeneous development tools in use are hampering the efficiency and consistency of information flows. This work thus focuses on improving the continuity of information interchange of architectural designs from system development level (Automotive SPICE ENG.3 respectively ISO 26262 4-7 System design) to software development level (Automotive SPICE ENG.5 respectively ISO 26262 6-7 SW architectural design). For this purpose, an approach to seamlessly combine model-based development tools on system level (such as Enterprise Architect) and on SW development level (such as Matlab/Simulink) has been proposed.

The applicability of the approach has been demonstrated utilizing an elementary automotive use-case, the 3 layer monitoring concept, which is an illustrative material and does not represent either an exhaustive or a commercially sensitive project. The main benefits of the presented approach are: improved consistency and traceability from the initial design at the system level down to the software implementation, as well as, a reduction of cumbersome and error-prone manual work along the system development path.

Fig. 1 .

 1 Fig. 1. Portrayal of the Bridging Approach Transferring System Development Artifacts to SW Development Phase

Fig. 2 .

 2 Fig. 2. Screenshot of the SW Architecture Representation within the System Development Tool and Representation of the Interface Information

Fig. 3 .

 3 Fig. 3. Screenshot of the SW Architecture Exporter GUI

Fig. 4 .

 4 Fig. 4. SW Architecture Importer User Interface

TABLE I .

 I SW ARCHITECTURE IMPORTER INDICATORS OF TYPE OF CHANGE

	Indicator	Type of Change
	A	model artifact added
	AC	interface connection added
	D	model artifact deleted
	DC	interface connection deleted
	U	model artifact updated
	UC	interface connection updated

ACKNOWLEDGMENTS

This work is partially supported by the EM C 2 and the M EM CON S projects.

The research leading to these results has received funding from the ARTEMIS Joint Undertaking under grant agreement nr 621429 (project EM C 2 ) and financial support of the "COMET K2 -Competence Centers for Excellent Technologies Programme" of the Austrian Federal Ministry for Transport, Innovation and Technology (BMVIT), the Austrian Federal Ministry of Economy, Family and Youth (BMWFJ), the Austrian Research Promotion Agency (FFG), the Province of Styria, and the Styrian Business Promotion Agency (SFG).

Furthermore, we would like to express our thanks to our supporting project partners, AVL List GmbH, Virtual Vehicle Research Center, and Graz University of Technology.