text:
David Clarke
email: d.clarke@unimelb.edu.au

Carmel Mesiti
email: cmesiti@unimelb.edu.au

Yiming Cao

Jarmila Novotna
email: jarmila.novotna@pedf.cuni.cz

The lexicon project: Examining the consequences for international comparative research of pedagogical naming systems from different cultures

Keywords: Professional language, mathematics education, international comparison

. The Lexicon Project investigates the pedagogical naming systems used by educators in nine countries (eight languages).

Drawing on examples from the Australian, Chinese and Czech lexicons, this paper outlines the project's research design and addresses the implications of distinctive lexical features for comparative classroom research between communities employing different lexicons to describe the phenomena of middle school mathematics classrooms.

Introduction

The Lexicon Project involves research teams from Australia, Chile, China, Czech Republic, Finland, France, Germany, Japan and the USA. The project aims to document the naming systems (lexicons) employed by different communities speaking different languages to describe the phenomena of the mathematics classroom. Such lexicons consist of words of locally agreed meaning in a single language that collectively accord to lexical norms and conventions characteristic of the language community (mathematics educators) of the particular country.

The theoretical position adopted by this project is that our experience of the world, our engagement in socio-cultural practices, and our reflection on those experiences and practices are mediated and shaped by available language. The Sapir-Whorf hypothesis suggests that our lived experience is mediated significantly by our capacity to name and categorize our world.

We see and hear . . . very largely as we do because the language habits of our community predispose certain choices of interpretation (Sapir, 1949, p. 162). [START_REF] Marton | Classroom discourse and the space of learning[END_REF] suggest that categories "not only express the social structure but also create the need for people to conform to the behavior associated with these categories" (p. 28). In this project we examine this normative role of language in relation to classroom practice and research.

While a professional language of teaching practice seems lacking in the USA [START_REF] Lampert | Knowing teaching: The intersection of research on teaching and qualitative research[END_REF], such a language seems to be well-established among educators in China and Japan (Fan et al., 2004;[START_REF] Fernandez | Lesson study: A Japanese approach to improving mathematics teaching and learning[END_REF]. Our interactions with classroom settings, whether as learners, teachers, or researchers, are significantly mediated by our capacity to name what we see and experience [START_REF] Clarke | Language mediating learning: The function of language in mediating and shaping the classroom experiences of students, teachers and researchers[END_REF]. Speakers of one language have access to terms, and therefore to perceptive possibilities, that may not be available to speakers of another language. This has implications for international comparative research. Any claim that researchers speaking different languages are analyzing "the same classroom," even when working from the same video records, can be usefully contested. In two published translations of Vygotsky, we find the Russian term, "obuchenie," represented as "instruction" in one translation and "learning" in another. This is not merely a problem of mistranslation. The term refers to an activity in which teachers and students are jointly participant for which there is no equivalent term in English. The term offers a conceptualisation of classroom practice with profound implications for the theorization of classroom teaching/learning. Recognition of these implications is not afforded in English. Educational research increasingly employs English as the primary language through which theory is developed and disseminated. It is essential to recognise the constructs that other cultures have employed in conceptualising their practice and examine the consequences for research and for theory of those distinctive terms (and the designated constructs) that might otherwise be ignored by an international community restricted to communication in English.

Research design

In the Lexicon Project, local teams of researchers and experienced teachers in all nine countries viewed a common set of video records of one eighth-grade mathematics lesson from each participating country. Specific lessons were selected by each country team for the diversity of activities displayed rather than for their representativeness. The purpose of this activity was to stimulate identification of those terms in the local language of each team that constituted the national pedagogical lexicon with respect to the teaching of middle school mathematics (ages 11 to 14). It is via the medium of these terms that teachers plan, engage with, discuss, and reflect upon the mathematics classroom. It was assumed that the vocabulary available to researchers in each country included most terms employed by teachers, but that the researchers' vocabulary would include other terms not necessarily locally derived, being translations or literal appropriations of terms generated by other educational communities. For that reason, because of the focus on the local language, it was the teachers' lexicon that was the principal focus of investigation in each country.

The key prompt used by all teams was: "What do you see that you can name?" Once a term was identified and endorsed by the local team, a consensus description was constructed of the specific classroom phenomenon to which the term referred and examples and non-examples identified to maximize effective communication of the term's meaning and classroom referent. These descriptions, examples and non-examples were crucial to the communication between teams of the meanings of terms that originated in the local (predominantly non-English) language.

But teams were not restricted to only those phenomena visible in the video material. For example, where observation of one type of classroom activity reminded the observer/s of another activity type not evident in any of the video material, that term was included in the lexicon, together with a description, examples and non-examples. It was anticipated that these terms would describe classroom practices, both structures (such as organizational patterns or activity sequences) as well as specific activities observable in the middle school mathematics classroom. The function of the video material was fundamentally catalytic, stimulating recall of the names of classroom phenomena present and absent in the classrooms filmed. However, the video material also assisted communication within and between the different teams, clarifying the meaning of terms.

Local team consensus was required for the inclusion of a term in the lexicon and in problematic cases authority was accorded to classroom experience and the team members' capacity to argue that the term was in current use by teachers. The essential point was to record single words or short phrases that were consistently and widely used by teachers within that country with a consistent and agreed meaning. Subsequently, a process of local and then national validation was pursued to refine and ratify each lexicon. The means by which this validation process was undertaken varied from country to country, but basically involved inviting a national cross section of mathematics educators to comment on the adequacy, accuracy, and clarity of the constructed lexicon for that country.

Of course, such lexicons are continually evolving and a process of regular updating is anticipated. The international project team takes particular interest in the studying the connections between terms within a given lexicon and the consequent clusters of related terms that provide the structure for each country's lexicon. Both teachers and researchers were involved in the identification of these connections. The Chinese example below illustrates one approach to the identification of such structures. Comparison of the emphases evident within each country's lexicon reveals distinctive features of the different countries' mathematics pedagogy and priorities of classroom practice.

Lexicon selection for the purposes of comparison and contrast

In this paper, one English speaking and two non-English speaking communities have been chosen to provide contrasting examples of the language that educators in Australia, China and the Czech Republic employ to describe the objects and events of the middle school mathematics classrooms in their countries. Structural aspects of the lexicons suggest underlying pedagogical principles or associations that shape the ways in which middle school mathematics teachers function and interact within the mathematics classrooms of that country. The lexicons also offer insight into the language available to researchers in each country, by which they study, classify, analyze, conjecture and theorize about the practices and the affordances of the mathematics classrooms of their country.

The project identified both similarities and differences in the national lexicons, revealing significant differences in the way teachers and researchers from each country perceive the classrooms that are the focus of their professional activity. These differences raise the question of the extent to which the international community of mathematics teachers and researchers can meaningfully and productively share the wisdom of long-established pedagogical traditions of practice, where these are encrypted in the naming systems by which each community identifies those classroom activities that it considers to be significant. Discussion is provided of: (i) the implications for comparison of the lexicons, and (ii) the implications of the lexicons for other comparative classroom research. These two purposes are conceptually distinct but connected.

In this paper, English is used to describe the content and structure of both the Chinese and Czech lexicons. This reflects the underlying purpose and challenge of the Lexicon Project: to identify and make accessible to the international community the pedagogical principles and distinctions encrypted in different lexicons. Examples from the original language are cited for purposes of clarification. For example, some terms can be approximated in English (e.g., "Teacher Feedback" adequately names 教 师反馈 which is "jiào shī fǎn kuì" in Chinese pinyin 1 ) but there are those that have no simple equivalent English term or phrase but can only be represented in pinyin and an extended English description (e.g., 课堂生成 which in pinyin is "kè táng shēng chéng" and which refers to "when the teacher makes full instructional use of an unexpected event beyond the intended plan for the lesson"). Similarly, the Czech term "S cílem objevit" (literally, "with the aim to discover") refers to the occasion when "by solving the problem students discover something new." Examples are used, if needed, in the discussion that follows. The three lexicons: Australian, Chinese and Czech are used to illustrate respectively the methodological processes of Lexicon Identification, Structure and Interpretation.

The Australian lexicon: Generic rather than discipline-specific terms

The Australian National Lexicon consists of 63 terms that are familiar and in widespread use (e.g., Assigning Homework, Rephrasing, Worked Example). A description was constructed for each term, together with both examples and non-examples of the use of the term. Because of the role of video in stimulating the recognition of terms, many terms can also be illustrated with video examples.

In consultation with practicing teachers, the lexical items were organized in five categories: Administration (8 terms); Assessment (11 terms); Classroom Management (6 terms), Learning Strategies (27 terms) and Teaching Strategies (50 terms). A lexical item appeared in more than one category if the Australian team decided on the basis of teacher advice that there was a strong association with each category.

One feature of the Australian National Lexicon is that none of the 63 terms identifies a practice unique to the mathematics classroom. The terms all refer to general pedagogical practices. Also worthy of note is the prevalence of 'gerunds' (a verb form that also functions as a noun; "teaching" and "learning" are relevant examples) in the Australian National Lexicon. This duality provides both advantage and disadvantage: "learning" as a noun is explicitly the product of the activity of "learning" in a way that objectified "knowledge" is not, but this duality can also result in less precise communication due to the inherent ambiguity over what is being referred to: process or product. The duality of simultaneously invoking both object and activity is not available in some languages, highlighting the affordances of particular languages and the difficulties of translation.

The generic character of the Australian Lexicon content suggests that the lexicon might also be applicable to other school settings besides the mathematics classroom.

Integrating forms of connection to structure the Chinese lexicon

In the Chinese Lexicon, 126 terms were identified as being used by Chinese middle school mathematics teachers in describing their classrooms. Within the lexicon, every term is related to some other terms, which makes the teacher's language an organic entirety. The challenge for the Chinese 1 Pinyin is a phonetic rendering of Chinese characters using the Latin alphabet employed in English and four basic tonal annotations.

Thematic Working Group 11 team was to clarify the structure of teacher's pedagogical language as encompassed in these 126 terms. A two-step process was employed by the Chinese team to do this.

Step One: Three types of connections were identified between lexical items: Hierarchical, Coincident and Sequential.

Hierarchical

Level One: In the first level, the terms can be divided according to whether the term referred to Teachers, Students or to Teacher-student Interactions. Level Two: Terms within the category "Teachers" could be divided into: Classroom Management, Demonstration, Questioning, Feedback, Summarizing, Explanation, and Tutoring. The category "Students" included: Classroom Management, Demonstration, Questioning, Feedback, Summarizing, Doing Exercise, Collaborative Studying, Self-learning and Listening. The category "Teacher-student Interaction" had no sub-structure at this level. Level Three (only one example can be shown for reasons of space): "Classroom Management" included: Teaching Affairs Management and Order Management. Apart from the hierarchical links, it was clear that some activities can happen at the same time while others occur in a sequence. This provided two additional mechanisms for the clustering of terms.

Coincident

This category refers to terms used in a teacher's pedagogical language that refer to activities that can happen at the same time. For example, Group Report and Student Listeningwhen a group is reporting their findings or answers, the other students must be listening carefully in the class.

Sequential

Teacher Questioning and Student Answering are an example of a pair of tasks that are intrinsically sequentialwhen the teacher asks a question of the class, this action is typically followed by an individual answering or the class answering together.

Step Two: Using the three types of connections, it was possible to organize the terms in the Chinese Lexicon into a structured array. Experienced teachers were recruited from high achieving schools in different parts of China to identify the connections. In this way, regional variations in interpretation and association could be identified. This illustrates the value of the lexicon in helping to identify regional pedagogical variations in a country as large as China, while also highlighting common pedagogical elements.

Differences between professional language communities: Teachers and researchers in the Czech Republic

As for all the country lexicons, the Czech lexicon does more than simply describe the current pedagogical vocabulary of practising Czech mathematics teachers. It should also be considered as a way to understand the Czech "culture of education" by providing examples that illustrate how it is possible to think about education. The use of pedagogical terms varies according to the groups of users (authors in different fields of pedagogy, teachers, etc.). One purpose of the Czech lexicon at the national level is to provide teacher education with a tool for triggering and framing discussion among pre-service students and practising teachers to facilitate better understanding of lesson structure and classroom practice.

The terms of the Czech Lexicon were classified using the following categories: Classroom Management; Introductory Communication; Explanation of New Topic; Revision of Previously Taught Topic; Solving of a Problem; Checking Individual Work; Institutionalisation; Summary; Non-mathematical Social Interaction; Assessment; Concluding the Lesson; Individual Consultation with a Pupil. The Czech lexicon is highly stratified. There are several sub-categories in each of these themes. One distinctive feature is the prevalence of student-oriented terms that reflect the importance attached within Czech education to the teacher-student relationship. For example, "shrnují na pokyn učitele" (student invited to recapitulate teacher's instruction) and "vysvětlují na pokyn učitele" (student invited to explain teacher's instruction) are distinctively student actions.

When constructing the Czech lexicon, the research team identified particular characteristics. One characteristic concerned the difference between how the language was used and understood by different target groups. Practising teachers used few technical pedagogical terms and communicated mostly using words from the language of everyday life. Pre-and in-service teachers were more likely to make use of terms drawn from their lessons on mathematical didactics. For example, "Heuristický rozhovor" is an academic term meaning "heuristic dialogue," but a practising teacher would be more likely to say, "řízená diskuse" meaning "guided discussion" to refer to the same classroom phenomenon. The Czech team's concern was how to combine the two ways of using the Czech lexiconas a tool describing the structure of Czech lessons and highlighting important parts of lessons and as a tool to facilitate discussion between different groups. This dilemma is accentuated by the relative paucity of Czech technical terms not only in the domain of didactics of mathematics but also in pedagogy. The Czech example illustrates the different uses of the lexicon for teachers, student-teachers and educational researchers and identifies the potential for the Czech lexicon to serve as a catalytic focus for discussion between these different communities.

Discussion: Implications for comparison

The key steps in lexicon construction of Identification, Structure and Interpretation have been illustrated with examples from the Australian, Chinese and Czech lexicons respectively. Each step offers insights into the pedagogical history encrypted in each lexicon and the potential value of the lexicon to the teaching and research communities in each country. In this section, we explore the question of comparison. Two forms of comparison warrant discussion: within-project comparison of the separate lexicons for the purpose of gaining insight into the pedagogical principles of each language community encrypted in the professional lexicon of middle school mathematics teachers; and, second, the broader implications for international comparative classroom research of the documented differences in how the phenomena of the middle school mathematics classroom are conceptualized within each language community. Each of these is discussed separately below.

Comparing lexicons: Constructs as boundary objects

The primary consideration in making comparison between any two lexicons is the mediating construct that forms the basis of comparison [START_REF] Clarke | Comparative research in mathematics education: Boundary crossing and boundary creation[END_REF]. For example, comparison might be made between the agency accorded in one lexicon to the teacher or to the students. That is, what proportion of lexical terms refer to teacher actions and what to student actions (cf "Level One" in the Chinese lexicon), and what is the nature of the actions in each case: initiating or reactive (for example). The Australian lexicon makes a comparable distinction between Teaching Strategies and Learning Strategies. In this case, "agency" provides the boundary object by which the two lexicons might be compared. Clearly, "agency" need not be a term situated in either lexicon. Instead, it represents an organizing construct with comparable conceptual legitimacy within each lexicon. As such, it constitutes an acceptable boundary object for the purposes of comparison of the lexicons. Other boundary objects might name categories of lexical items, such as: assessment or management. The requirement for legitimate comparison would be that the organizing construct (say, assessment) has local validity within each lexicon as designating a cluster of lexical terms and cross-lexicon validity in characterizing conceptually the same shared attribute for each lexical cluster being compared. Comparison of the Australian and Czech lexicons is possible on this basis, with respect to either of the mediating constructs: agency or assessment.

Comparative research: Validity-comparability compromise

The documentation of the separate lexicons has the potential to heighten the legitimacy of comparative classroom research being undertaken across two communities. For example, application of a measure of participation to the comparative analysis of classroom data from two countries is problematic, unless it can be demonstrated that "participation" has the same cultural relevance within the pedagogical practices of each community. However, if participation is treated not as the basis for an imposed metric, but as a boundary object, then the question can be asked, "What forms of participation are legitimized within the lexicons of the two countries whose classrooms are being compared?" Analysis of the separate lexicons to identify those terms that characterize forms of participation in classroom practices would reveal both similar and different types of participatory activity. For example, choral response has been documented as a frequent form of participatory activity in mathematics classrooms in China and Korea, but not in classrooms in Australia and Japan. Reciprocally, student-student talk is a common form of participatory activity in mathematics classrooms in Australia and Japan but not in China and Korea [START_REF] Clarke | Students speaking mathematics: Practices and consequences for mathematics classrooms in different countries[END_REF]. Any comparison of student participation in classroom activity in these four countries can be undertaken with much greater validity, where attention is given to important distinctions between forms of participation as these are facilitated and named by teachers in each of the countries whose classroom practices are being compared. Utilization of the lexicons from each country to identify legitimate points of comparison would heighten both validity and comparability [START_REF] Clarke | The validity-comparability compromise in cross-cultural studies in mathematics education[END_REF].

Conclusion

The construction of national lexicons representing the naming systems employed by educators using different languages to "name what they see" in the middle school mathematics classroom represents the starting point for the deconstruction of pedagogical histories and norms of practice enshrined in the languages by which classroom phenomena are described, studied and theorized in different countries. The documentation of these lexicons has significant practical value to each participating community and to the international community of mathematics education practitioners and teacher educators. The focus of this paper, however, has been on the implications of such lexicons for the legitimacy of international comparative research and on the use of any named construct as a boundary object for the purposes of comparative research analyses. It is intended that the lexicons serve as tools to interrogate, enhance and advance comparative classroom research internationally.

Proceedings of CERME10

Acknowledgment

This research benefited from a grant from the Australian Research Council (ARC-DP140101361).


Influence of the multipolar order of the source on the viscous decay of inertial waves 19th International Couette-Taylor Workshop (ICTW19)

Nathanaël Machicoane 1 , Pierre-Philippe Cortet 1 , Bruno Voisin 2 and Frédéric Moisy 1 1 Laboratoire FAST, CNRS, Université Paris-Sud, Orsay, France 2 Laboratoire LEGI, CNRS, Université Grenoble Alpes, Grenoble, France

In rotating fluids, the restoring action of the Coriolis force allows for the propagation of a specific class of waves called inertial waves. These waves are of first interest for geo-and astrophysical flows [START_REF] Aldridge | Axisymmetric inertial oscillations of a fluid in a rotating spherical container[END_REF][START_REF] Aldridge | Inertial waves identified in the earth's fluid outer core[END_REF][START_REF] Suess | Viscous flow in a deformable rotating container[END_REF]]. They can for example be excited in the liquid core of planets by tidal, precession or libration motions. The most remarkable feature of inertial waves is their anisotropic propagation in a direction tilted by an angle θ = sin -1 (σ/2Ω) from the rotation axis, selected by the ratio between the wave frequency σ and the background rotation rate Ω [START_REF] Lighthill | Waves in fluids[END_REF]. While the direction of the wavevector is imposed by the dispersion relation, the selection of the spatial scales is governed by boundary conditions and by viscous effects.

The viscous spreading of an inertial wave beam emitted from a 2D point source has been characterized experimentally by Cortet et al. [START_REF] Cortet | Viscous spreading of an inertial wave beam in a rotating fluid[END_REF]. This work however did not address the issue of the influence of the multipolar order of the source on the decay law of the wave amplitude. For the analogous problem of internal waves in stratified fluids, Voisin [START_REF] Voisin | Limit states of internal wave beams[END_REF] showed theoretically from a non-uniform asymptotic expansion that the decay exponent should be a function of the multipolar order of the source.

In this work, we derive theoretically the decay exponents for the inertial wave problem using a quasi-parallel approximation, similar to the work of Thomas and Stevenson [START_REF] Thomas | A similarity solution for viscous internal waves[END_REF] for the case of internal waves. We demonstrate the key role played by the instantaneous flowrate of the source: a zero flowrate (dipolar or higher order source) imposes a vorticity decay steeper than a nonzero flowrate (monopolar source).

We designed an experiment aiming to confirm these predictions for the wave beam emitted by two different sources: a pulsating cylinder (monopolar source) and a vertically oscillating cylinder (dipolar source). The wave beam is measured over a large range of distances x using a two-camera-multi-resolution particle image velocimetry (PIV) system (fig. 1(a)). The whole experimental apparatus is mounted on a platform rotating at a constant rate. The measured decay exponents, different for both sources, are in good agreement with the predictions. These findings are of first interest for localized wave beams propagating in geo-and astrophysical fluid systems. Such wave beams often originate from the eruption of Ekman layers at critical latitudes, caused by precession or libration motions in the fluid core of planets or by interactions between tides and topography in oceans. These wave beams have a non-zero instantaneous flow rate, so they can be described as originating from a localized monopolar source. The combination of beams emitted by such monopolar sources can yield far-field beams corresponding to either a monopolar or dipolar effective wave source depending on the phase shift between each monopolar source.

Figure 1 :

 1 Figure 1: Vorticity fields measured by both cameras: one is a close view around the source while the other extends over large distances from the source. The scales are the same for both fields but the colormap is different for better visibility.

Acknowledgements

We acknowledge A. Aubertin, L. Auffray and R. Pidoux for experimental help. This work is supported by the ANR Grant No. 2011-BS04-006-01 "ONLITUR". FM would like to thank the Institut Universitaire de France for its support.


Aurélie Mahalatchimy
email: aurelie.mahalatchimy@gmail.com

Anne-Marie Duguet

Wen Meng

Heidi Carmen Howard

Anne Cambon-Thomsen

Emmanuelle Rial-Sebbag

A.-M Duguet

In need for a modern Daedalus? The challenging regulatory path for marketing gene

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

Main text:

Advanced therapies raise critical questions, especially concerning their premarket evaluation, which could differ greatly between regions worldwide, and in particular between Europe and China.

After years of hopes and disappointments in the field of gene therapy where failures gave rise to high effervescence widely relayed by the media at the detriment of rare successes, few Gene Therapy Medicinal Products (GTMP), (the use of genes to treat or prevent a disease), have ever reached the market. In 2003 Gendicine was approved by the Chinese State Food and Drug Administration (SFDA). It became the first GTMP to be marketed in the world. Its European counterpart, Advexin, as well as Cerepro did not obtain European marketing authorization. Almost ten years later, in October 2012, Glybera was finally granted marketing authorization by the European Commission after scientific assessment by the European Medicines Agency (EMA) (Table ). After a complex regulatory process it became the first GTMP to be approved in Western countries. Finally, two new GTMP have obtained a marketing authorization in the European Union (EU), Imlygic in December 2015 and Strimvelis in May 2016. Although approvals of these GTMP have mainly been presented as a huge step forward for patients' treatments and for the development of GTMP in general, no publication has addressed the major challenges present in the regulatory processes as revealed by the examples of these products both in China and in the European Union.

Table: GTMP regulatory assessment in the world

Regulatory paths for new drug approval

In the EU, the commercialization of GTMP relies on a marketing authorization which involves both the European Medicine Agency (EMA) and the European Commission. As part of a specific regulation1 , the EMA, in charge of the evaluation process of new drugs, has set up a new specific and multidisciplinary committee to assess advanced therapy medicinal products, including GTMP, called the Committee for Advanced Therapies (CAT). In the EU, a regulation is a powerful legal harmonization instrument; it directly applies "as is" in the various EU Member States and unlike EU directives, it does not require a specific transposition into national legal systems. One of the CAT tasks is to formulate draft opinions on the quality, safety and efficacy of GTMP for final opinion by the Committee for Medicinal Products for Human Use (CHMP). Scientific experts have a main role in the assessment of risks and benefits linked to the use of the products. The final decision of granting marketing authorization is in the remit of the European Commission. This political body takes the final decision integrating other dimensions above and beyond the scientific evaluation.

In China, the SFDA is the only competent organization to evaluate the safety, efficacy and quality of drugs for marketing, and has the power to decide whether or not a product is approved 2 . A registration approval for the manufacture of the new drug is needed for market access. It involves obtaining the following approvals by the SFDA: new drug certificate, new drug registration certificate and drug Good Manufacturing Practice certificate 3 . Within the SFDA, the Center of Drug Evaluation which organizes panels of experts is in charge of the technical assessment of applications but the final decision is taken by the SFDA. Since February 22 nd , 2013, the SFDA has been restructured and renamed the China Food and Drug Administration (CFDA). It became a ministerial-level agency to improve food and drug safety 4 , and included several proposals "to boost confidence in the drug review and approval process as well as help promote regulatory oversight" 5 , as deemed necessary 6 .

Assessment process of GTMP

Among the GTMP that have been assessed at this time, we target our analysis on those that aimed to reach the European or Chinese markets (although it should be noted that Rexin reached the Philippines' market in 2007 to treat all chemotherapy resistant solid tumors).

Gendicine and Oncorine

Since 1999, the development of Gendicine and Oncorine was has been financially supported through several Chinese government plans. For Gendicine, the

Glybera

Amsterdam Molecular Therapeutics B.V. applied for marketing authorization at the EMA in October 2009. Before the process was completed the applicant changed from Amsterdam Molecular Therapeutics to UniQure Biopharma. In June 2011, the CAT and CHMP adopted negative opinions because of a lack of evidence of longlasting benefit in the patients studied and a lack of reduction in the rate of pancreatitis (the clinically relevant endpoint). Additionally they had concerns over the risks linked to the associated immunosuppressive treatment. The company requested a reexamination. After several procedural steps, the CAT adopted in October 2011 a positive opinion conditioned by the restriction of the indication. But, the CHMP maintained its previous negative opinion concluding that benefits did not outweigh the risks. In January 2012, the European Commission requested a re-evaluation in a restricted group of patients with severe or multiple pancreatitis episodes. In April pharmatechnologist.com/Regulatory-Safety/SFDA-Aims-to-Stimulate-R-D-Accelerate-Approvals-and-Improve-Distribution-Practices (Access date 6th October 2014).

2012, the CHMP gave a third negative opinion. However, for procedural reasons it was invalidated and a new examination was performed; it was conducted in June 2012 and resulted in a final positive opinion. However, 15 CHMP members (out of 32) had a divergent opinion and considered that efficacy and safety had not been sufficiently demonstrated. Finally, the European Commission granted a marketing authorization under exceptional circumstances to Glybera; these include specific obligations for post-authorization measures (such as the setting up of a long term surveillance of patients) to be conducted in a specified timeframe 7 .

Advexin and Cerepro

Both Gendux Molecular Ltd for Advexin and Ark Therapeutics for Cerepro withdrew their applications for marketing authorization at the EMA. The former specified that the company's marketing strategy had changed 8 while the latter admitted it was not able to provide meaningful evidence of benefits compared to the risks 9 . At that time, the CHMP was about to give a negative provisional opinion for Advexin as it had concerns about the lack of evidence regarding the benefits and safety of the product for patients, for people in close contact with them and for the environment 10 . Regarding Cerepro, the CHMP had already delivered a negative opinion. Following a request of re-examination by the company, the CHMP was about to give a new negative opinion due to the lack of effectiveness which caused an emphasis on the concerns regarding side effects 11 . All the other decisions relied on scientific evaluations which resulted in concerns that were greater regarding the drugs' efficacy than their safety. These decisions, both in Europe and in China, were also largely influenced by other types of variables, such as economic, political and ethical considerations.

Imlygic and Strimvelis

The scientific evaluation of GTMP: what prevails efficacy or safety?

Both in China and in the EU, the scientific evaluation of GTMP based on the assessment of the quality, safety and efficacy of the product is difficult even though experts are involved in the process. Based on the media focus on negative outcomes of the use of GTMPs, one could think that the most important challenge of GTMP meeting evaluation criteria would be their safety, but in fact, showing the efficacy of these products has also been shown to be problematic. The approval of Gendicine has been criticized by Western countries as efficacy was based on tumor shrinkage rather than extension of patient lifetime 13 . A Greater emphasis may have been placed on safety than on efficacy. Meanwhile safety and lack of transparency on studies' results have also been challenged. Moreover in the EU, Glybera, Advexin and Cerepro suffered from several negative (provisional) opinions at the EMA's relevant committees also regarding the lack of proven efficacy. For all these GTMP, the concerns raised have been linked to the lack of data due to the low number of patients involved in clinical trials. Given that Advexin, Cerepro and Glybera, have been designated as orphan drugs in the EU, it is not surprising that they have this problem.

The questioning on efficacy of GTMP challenged the benefits/risks balance: should GTMP considered safe be authorized if their efficacy is limited? Interestingly in the USA, the Advexin application file was refused as not complete while Glybera, in December 2015, abandoned its plans to win the US market after the US Food and Drug Administration indicated it would require additional clinical studies for the product 14 . It seems the acceptability threshold may differ according to the national agencies.

Other influences beyond the scientific evaluation of GTMP

When scientific assessments do not give a clear answer, other dimensions are taken into account and this is particularly true for GTMP. First, the marketing authorization is a political decision deemed to represent what is acceptable for society. Both in China and in the EU, the political decisions played a major role in the marketing authorization of Gendicine, Oncorine and Glybera. Second, economics is a main dimension. As "the global gene therapy industry has the potential to become a multi-million dollar industry by the end of 2017 as new products […] may enter the market to boost the growth."15 , the race is launched for the leadership in this field.

Whereas China authorized the first gene therapy in the world, the EU adopted a specific regulation aiming to enhance competitiveness of European enterprises developing advanced therapies. The authorization of Glybera demonstrates that a marketing authorization can be obtained for GTMP in the EU 16 . But going through the whole regulatory process is complex, costly and time consuming. When withdrawing its application for Advexin, Gendux Molecular Ltd gave the argument of limited resources to face the regulatory demand. After several negative opinions of the CHMP, Amsterdam Molecular Therapeutics stopped investment in Glybera and transferred gene therapy assets to Uniqure [START_REF] Moran | First gene therapy nears landmark European market authorization[END_REF] . Moreover, the price of GTMP will be a high burden. Glybera "could cost as much as $1.6 million for the single injection necessary to confer lifetime therapy", a pricing that would be inappropriate for more common diseases [START_REF] Whalen ; Ghivizzanib | Arthritis gene therapy and its tortuous path into the clinic[END_REF] . Finally, ethical considerations may also influence marketing authorization of GTMP. Medical tourism is an issue for patients 'safety and for the environment. Despite the lack of clear data on its real extent, it seems that 300 to 600 patients travelled to China for Gendicine [START_REF] Kaptein | Gene Therapy in China from a Dutch perspectives[END_REF] . This very complex issue gives rise to large bioethical discussions that will not be developed in this paper notably as many countries, including the emerging ones, target the global health care market.

A new era for the regulatory support to GTMP development?

While no new GTMP seems to have been approved in China from the approval of Gendicine and Oncorine, it appears the two new GTMP authorised in 2015 and in 2016 in the EU did not raise so much concern during their assessment. Moreover, the main issue seems to have been redirected towards the effective access to innovative drugs, on the basis of cost-effectiveness in the context of Healh Technology Assessment [START_REF] Mahalatchimy | Reimbursement of cell-based regenerative therapy in the UK and France[END_REF] . Indeed, although Glybera was authorized in 2012, it has been administered to one patient only in September 2015 in Germany and it is not reimbursed by national insurances in the EU. Known as the 'one million drug' [START_REF] Morrison | 1-million price tag set for Glybera gene therapy[END_REF] , the Glybera's cost-effectiveness ratio has not been considered acceptable by the French, German and Dutch authorities.

That is why, the current trend is to develop new regulary tool to support medicines development as well as early access. Chinese reforms aim notably to emphasize the clinical value of innovative drugs, to encourage the development of drugs that answer clinical needs and have a better therapeutic effect, through a speedup review 22 . Similarly, the EMA adopted the PRIority Medicine scheme, an enhanced early dialogue to facilitate accelerated assessment for PRIority Medicines 23 . It is also developing the Adaptive Pathways concept: "a prospectively planned, iterative approach to bringing medicines to market. The iterative development plan will initially target the development to a well-defined group of patients that is likely to benefit most from the treatment. This is followed by iterative phases of evidence gathering and progressive licensing adaptations, concerning both the authorised indication and the potential further therapeutic uses of the medicine, to expand its use to a wider patient population as more data become available" 24 . The latter aims notably to reduce the gap between market approval and reimbursement decision for patients to have real and earlier access to these new medicines. However, here again, safety seems to appear as a secondary criterion as long as "safe access" could be claimed instead of "early access".

The development of gene therapy medicinal products is clearly a race as it is shown with Chinese scientists being, again in the field of gene therapy, the first to use the CRISPR-CAS9 gene-editing technique in humans 25 . Thus, it is clear that approvals do not rely only on scientific assessment and include other factors. If a country approves a GTMP, patients will benefit from new treatments which could lead toward less medical tourism out of that country.

However, the question remains: will these patients really have access to effective drugs? Regarding the efficacy criterion, collaboration between EMA and CFDA is necessary for the benefits of patients. For drugs focused on rare diseases, it would permit to have a higher number of patients to assess the therapeutic effect. Moreover, a lot of data are generated from Gendicine in China that would be useful worldwide for the future of gene therapy if transparency is improved. Even though the EMA supports the European Commission's collaboration with China, regulators agreements

are not yet developed at a scale and place that would match the level of scientific 22 CFDA, [Ideas on deepening the reform of pharmaceutical review and approval and further encourage innovation], 26 February 2013 (In Chinese; http://www.sfda.gov.cn/WS01/CL0051/78609.html). 23 collaboration. To achieve translational medicine, all dimensions at stake including the regulatory ones needs to be collaboratively developed26 .

  SFDA delivered the Biological type I New Drug Certificate in October 2001, the Production Permit in January 2004, and the Drug GMP Certificate in March 2004. Gendicine also obtained the National Key New Product Certificate in 2005 issued jointly by the Ministry of Science & Technology, the Ministry of Commerce, the General Administration of Quality Supervision, Inspection & Quarantine and the Bureau of Environmental Protection. Oncorine obtained the Biological type I New Drug Certificate in November 2005, the Drug GMP Certificate and the Production Permit in 2006. Since 2004 and 2006, the Production Permits of Gendicine and Oncorine have been regularly renewed.

  melanoma that is regionally or distantly metastatic. It obtained a marketing authorisation on 16 December 2015 after positive opinions of the CAT and the CHMP issued both in October 2015. The same month, on 27 October 2015, the US Food and Drug Administration have approved Imlygic for the US market. Strimvelis was designated as an orphan medicinal product for the treatment of severe combined immunodeficiency (SCID) due to adenosine deaminase (ADA) deficiency in the EU on 26 August 2016. GlaxoSmithKline Trading Services submitted an application for Marketing Authorisation to the EMA for Strimvelis on 1 May 2015. One year later (on 26 May 2016), it obtained a marketing authorization after positive opinions of both the CAT and the CHMP, respectively issued in March and April 2016. Contrary to the other GTMP, Imlygic and Strimvelis did not raise particular concerns during their scientific evaluation although one divergent position was expressed for efficacy and safety reasons regarding the marketing authoirsation of Imlygic 12 .

  On 28 August 2014, Amgen Europe B.V. submitted a marketing authorization application to the EMA for Imlygic. Its indication is the treatment of adults with

	7 Glybera European Public Assessment Report, European Medicines Agency (EMA/882900/2011,
	2012;			http://www.ema.europa.eu/docs/en_GB/document_library/EPAR_-
	_Public_assessment_report/human/002145/WC500135476.pdf).
	8	Letter	of	withdrawal	for	Advexin	(Gendux	Molecular	Limited,	2008;
	http://www.emea.europa.eu/docs/en_GB/document_library/Other/2010/01/WC500063082.pdf).
	9	Letter	of	withdrawal	for	Cerepro	(Ark	Therapeutics,	2009;
	http://www.ema.europa.eu/docs/en_GB/document_library/Other/human/001103/WC500076159.pdf).
	10 Withdrawal Assessment Report For Advexin, European Medicines Agency (EMEA/692328/2008;
	http://www.emea.europa.eu/docs/en_GB/document_library/Application_withdrawal_assessment_repor
	t/2010/01/WC500063080.pdf).
	11	Withdrawal	Assessment	Report	For	Cerepro,	European		Medicines	Agency
	(EMA/CHMP/798830/2009;
	http://www.ema.europa.eu/docs/en_GB/document_library/Application_withdrawal_assessment_report/
	2011/02/WC500101545.pdf).

  EMA, Enhanced early dialogue to facilitate accelerated assessment for PRIority MEdicines, 25 February 2016, EMA/CHMP/57760/2015. 24 EMA, Final report on the adaptive pathways pilot, 28 July 2016, EMA/276376/2016. 25 David Cyranoski, Chinese scientists to pioneer first human CRISPR trial, Nature 535, 476-477 (28 July 2016) doi:10.1038/nature.2016.20302.

Regulation (EC) N°1394/2007 of the European Parliament and of the Council on advanced therapy medicinal products and amending Directive

2001/83/EC and Regulation (EC) N°726/2004 OJ L324, 10/12/2007, p.121. 2 Article 3, SFDA Order N° 28, Provisions for drug registration, 01/10/2007. 3 H. Yin, Regulations and procedures for new drug evaluation and approval in China, Hum. Gene Ther. 17, 970-974 (2006). 4 China State sponsored news-site 'xinhuanet': Bi Mingxin, China gets stronger food, drug regulator, March 22nd, 2013: http://news.xinhuanet.com/english/china/2013-03/22/c_132253914.htm (Access date 6th October 2014). 5 H. Jia, China overhauls drug regulation agency, Nature Biotechnol. 31, 5: 375 (2013). 6 Gareth Macdonald, SFDA aims to stimulate R&D, accelerate approvals and improve distribution practices, 5 March 2013, in-Pharma Technologist. Com website: http://www.in-

Annex 1, Imlygic European Public Assessment Report, European Medicines Agency, EMA/734400/2015, p. 150 ; http://www.ema.europa.eu/docs/en_GB/document_library/EPAR_-_Public_assessment_report/human/002771/WC500201082.pdf).

13 M. L. Edelstein, M. R. Abedi, J. Winxon, Gene therapy clinical trials worldwide to 2007-an update, The Journal of Gene Medicine, 9: 833-842, DOI: 10.1002/jgm.1100 (2007).

FDAnews Drug Daily Bulletin, UniQure Won't Seek U.S. Regulatory Approval for Glybera Gene Therapy Program, 9 December 2015 : http://www.fdanews.com/articles/174384-uniqure-wont-seek-usregulatory-approval-for-glybera-gene-therapy-program

 15 Global Gene Therapy Market Anlaysis, Global Biological Therapy Industry (

2013).16 Geoff Watts, Gene therapy to be authorised for first time in EU, BMJ 2012: 345.

E. Meslin, A. Blasimme, A. Cambon-Thomsen Mapping the Translational Science Policy 'Valley of Death', Clin Transl Med. Jul

27, 2(1):14 (2013).

Acknowledgements: This work has been supported by CAI YUANPEI Program 2012-2014 on Medical Law and Bioethics (N°28007 UF) co-led by E. Rial-Sebbag (France) and Q. Yanping (China) and XU GUANGQI Program 2012 on Patients' rights and access to genetic testing (N°27974 QH) co-led by A. Cambon-Thomsen (France) and H. Man (China). It has also been supported by REGenableMED, UK ESRC Project ES/L002779/1, led by A. Webster.


Michaël Roy

Sebti Foufou

Frédéric Truchetet

GENERIC ATTRIBUTE DEVIATION METRIC FOR ASSESSING MESH SIMPLIFICATION ALGORITHM QUALITY

This paper describes an efficient method to compare two triangular meshes. Meshes considered here contain geometric features as well as other surface attributes such as material colors, texture, temperature, radiation, etc. Two deviation measurements are presented to assess the differences between two meshes. The first measurement, called geometric deviation, returns geometric differences. The second measurement, called attribute deviation, returns attribute differences regardless of the attribute type. In this paper we present an application of this method to the Mesh Simplification Algorithm (MSA) quality assessment according to the appearance attributes. This assessment allows the appreciation of local quality and the computation of global quality statistics of a simplified mesh.

INTRODUCTION

Many applications (geometric modelers, 3D scanning, etc.) generate very complex meshes that contain geometric data as well as appearance data. Geometric data describe the surface and the dimension of the mesh. Appearance data, called attributes, represent information describing the aspect of the mesh such as colors, texture,. . . High quality meshes usually contain a high number of vertices and faces that cause non interactive rendering or high storage space. Some results have been presented in the last few years in order to reduce the mesh surface complexity. The methods proposed simplify meshes either by merging/collapsing elements or by re-sampling vertices. MSAs use different error criteria to measure the fitness of the approximated surfaces. Usually, MSAs do not return measurements of the error introduced while simplifying the mesh. A measurement tool would be useful to precisely compare different simplification algorithms or parameters. In literature some methods are presented to assess the quality of a simplified mesh compared with the original one. We present a new, generic metric to assess mesh attribute quality after a simplification process by comparison between the original and its simplified representation. The method is suitable for numerical models from real scenes and for synthetic models.

It can be used for many applications: mesh simplification, multiresolution analysis (comparison between different levels of detail), reverse engineering (comparison between a CAD model and a numerical model of a real object), mesh segmentation, etc.

SIMPLIFICATION ALGORITHMS AND ERROR METRICS

MSAs use their own error metrics to guide the simplification process. These metrics are either local or global. Cignoni et al. [START_REF] Cignoni | Comparison of mesh simplification algorithms[END_REF] has presented the various techniques used to evaluate and bound the error introduced by the mesh simplification process.

Most of these metrics use geometric measurements of distance or curvature. Schroeder et al. [START_REF] Schroeder | Decimation of triangle meshes[END_REF] use a vertex-toplane distance as decimation criterion. Reddy [START_REF] Reddy | Scrooge: Perceptually-driven polygon reduction[END_REF] uses a function based on curvature to guide its simplification process. Klein et al. [START_REF] Klein | Mesh reduction with error control[END_REF] use an error metric based on the Hausdorff distance. Ronfard et al. [START_REF] Ronfard | Full-range approximation of triangulated polyhedra[END_REF] use two energy functions: local tessellation error and local geometric error. Guéziec [START_REF] Guéziec | Surface simplification inside a tolerance volume[END_REF] uses a tolerance volume as an error bound measure. Rossignac [START_REF] Rossignac | Geometric simplification and compression[END_REF] uses an error bound metric based on distances to supporting planes. Lindstrom et al. [START_REF] Lindstrom | Fast and memory efficient polygonal simplification[END_REF] use an area and a volume metric.

These algorithms simplify the geometry and ignore the distortion caused due to surface attributes (colors, texture, normals,. . . ). Thus, more complete algorithms are needed to manage mesh attributes during the simplification process. Hoppe [START_REF] Hoppe | Progessive meshes[END_REF] uses energy functions, which preserve surface geometry, scalar attributes and discontinuity curves. Cohen et al. [START_REF] Cohen | Simplification envelopes[END_REF] use no error measure but only a geometric construction, called simplification envelopes, to minimize the surface deviation. Garland et al. [START_REF] Garland | Surface simplification using quadric error metrics[END_REF][START_REF] Garland | Simplifying surfaces with color and texture using quadric error metrics[END_REF] use a quadric error metric giving vertex-to-plane distances; this metric works for meshes with attributes. Hoppe [START_REF] Hoppe | New quadric metric for simplifying meshes with appearance attributes[END_REF] has improved this technique for meshes with attributes.

Toubin et al. [START_REF] Toubin | Multiresolution wavelet analysis for simplification and visualization of multitextured meshes[END_REF] have presented a new method for simplifying numerical models from real scenes. This method works with multi-modal models containing several types of appearance information (such as several textures, one for each wavelength band). Mesh simplification is performed by the quicunx wavelet transform. This method allows the conservation of important data in terms of geometric or appearance data. Thus, the original mesh is simplified according to the pre-defined important data. If the important data are appearance attributes, we need a tool to verify that these data are conserved.

Cohen [START_REF] Cohen | Appearancepreserving simplification[END_REF] has proposed a texture deviation metric to assess the texture coordinate distortion introduced during a simplification process. Given two meshes ¢¡ and ¤£

, their respective surface ¥ ¡ and ¥ £ , and a point ¦ ¨ § © ¥ ¡ , the texture deviation ¦ § ¥ £ between ¦ § and ¥ £ is defined as:

!¦ " § ¥ £ # %$ ¦ " § '& )( 10 £ & ¡ !¦ ¨ § ' 2 (1)
where & ¡ ¦ " § 3# 54 '6

is the texture coordinates of the vertex ¦ " § on the surface ¥ ¡ , and & ( 70 £ 98 '@ A# ¦ CB the point on the surface ¥ £ with the texture coordinates D4 26

. The texture deviation is the distance between a given point on ¥ ¡ and the point on ¥ £ with the same texture coordinates. The measurement of texture deviation was made to guide a simplification process. However, it is not suitable for assessing simplification quality. We propose a more general method to assess surface attribute distortion after a simplification process. This method does not depend on the attribute type.

Currently there is no tool to measure error introduced on attribute data by a simplification process. The purpose of this work is to define a method to assess MSA quality according to appearance attributes.

MESH COMPARISON METRICS

Geometric deviation

Simplification usually implies a local geometric difference between the original surface and the simplified surface. We call this difference: geometric deviation.

Given two meshes ¡

and £

, their respective surfaces ¥ ¡ and ¥ £ , and a point ¦ § © E¥ ¡

, the geometric deviation

$ GF ¦ § ' ¥ £ between ¦ § and ¥ £ is defined as: $ HF ¦ § ' ¥ £ # PI RQ TS U WV YX Hba $ ¦ § ' ¦ B (2)
with $ !¦ § ' ¦ B

the Euclidian distance between two points. The geometric deviation is defined as the distance between a point ¦ § on the surface ¥ ¡ and the nearest point on the surface ¥ £ . This metric is based on the geometric error used by Metro tool [START_REF] Cignoni | Metro : Measuring error on simplified surfaces[END_REF].

Attribute deviation

Attributes are data defined at each vertex of a mesh (diffuse color, normal, texture coordinates). They are essential elements to numerical models of real scenes. The number of attributes per vertex changes according to the context. Geometric simplification of a mesh implicitly introduces a modification of the attributes. Thus, we can measure the local difference of the attributes between the original mesh and the simplified mesh. We call this difference: attribute deviation.

Given two meshes ¤¡

and c£

, their respective surfaces ¥ ¡ and ¥ £ , and a point ¦ ¨ § d© e¥ ¡

, the attribute deviation

$ ¡ !¦ ¨ § ¥ £ between ¦ ¨ § and ¥ £ is defined as: $ f¡ ¦ § ' ¥ £ # g$ 5h !¦ § h pi c !¦ § ¥ £ 2 ' (3)
where h !¦ is the attribute at the point ¦ and i c ¦ ¥ q# ¦ "r the nearest point to ¦ on the surface ¥ . The attribute deviation is defined as the distance between the attribute of the point ¦ ¨ § and the attribute of the nearest point to ¦ s § on the surface ¥ £ . There may be many nearest points on the surface ¥ £ with the same distance to the point ¦ s § . In that case, the attribute distance is the minimum distance between the attribute of ¦ ¨ § and the attribute of the nearest points. The attributes are considered as vectors in the Euclidian space.

Discussion

The deviation measurements are not symmetric. Given two meshes c¡ and c£

, deviations are measured from a point ¦ " § on the surface of ¤¡ to the surface of ¤£

. If meshes are inverted, deviation measurement may give different results. For our investigation we measure the deviations both ways: from ¡ to £ and from £ to ¡

. Both measurements give different information but results are relatively close.

Geometric deviation is the main measurement because the mesh simplification process is essentially a geometric simplification. Attribute deviation is useful to assess appearance modification of the simplified mesh. When an important simplification is proceeded (90% or more reduced faces), we usually note important attribute modifications. Attribute deviation can be computed either for one attribute type or for all attribute types. If there are several attribute types (e.g. normal + diffuse color), the global deviation is a vector containing the deviation for each attribute type.

These two mesh simplification quality metrics (geometric and attribute deviations) are measured for a set of points ¦ § given on the surface of the mesh ¡ . This allows great liberty for the choice of ¦ § points. Usually deviations are measured for the entire mesh. Thus, the ¦ § points may be the mesh vertices. The measurement resolution can be increased using a surface sampling technique.

RESULTS

Figure 1 shows geometric and texture deviation measurement. Figures 1(e) and 1(f) show results obtained with the texture deviation measurement proposed by Cohen et al. [START_REF] Cohen | Appearancepreserving simplification[END_REF]. With low texture deviation (Figure 1(e)), Cohen's texture deviation measurement has the same visual results as the geometric deviation measurement. Nevertheless, both measurements cannot be numerically compared. The geometric deviation is based on the nearest neighbor distance, whereas Cohen's texture deviation is based on the corresponding point distance. Figures 1(g) and 1(h) show results obtained with attribute deviation, where considered attributes are the texture coordinates. The attribute deviation gives better results than Cohen's texture deviation. If no real texture deviation does exist, Cohen's measure indicates a deviation coming from strictly geometrical distortion.

Figure 2 shows a comparison between the three simplification software programs for different face simplification percentages. QSlim is Michael Garland's simplification software using quadric error metric. Jade is simplification software developed by the Visual Computing Group using a global error metric. ProgMesh is an implementation of Hoppe's progressive meshes. Figure 2(a) shows mean geometric deviation in terms of simplification percent. Figure 2(b) shows mean deviation of normals in terms of simplification percent. QSlim software has obtained the best results on our test mesh.

CONCLUSION AND FUTURE WORK

We have described two measurements for assessing MSA quality. Each measurement manages a specific data group: the geometry and the appearance attributes. The local measurement allows one to precisely view simplified regions on the mesh. As the simplification process is primarily a geometric simplification, geometric deviation measurement is the most important measure. Attribute deviation measurement is efficient to measure appearance modification. Our experimentation software is available online 1 .

We are testing different simplification software packages including professional software using different kinds of meshes (digital elevation maps, synthetic meshes). This test will allow the comparison of MSA algorithm quality according to appearance attributes.

Fig. 1 .

 1 Fig. 1. Deviation assessment results. Comparison between results from the Cohen et al. algorithm [15] (e,f) and our algorithm (g,h).

Fig. 2 .

 2 Fig. 2. Simplification software comparison.

http://meshdev.sourceforge.net