Oscar Rodríguez Rocha

Catherine Faron Zucker

A Formalization Of Standard Knowledge And Skills For The French Elementary School Curricula

Keywords: e-Education, Ontologies, Semantic Web, Knowledge Extraction, Knowledge Representation

In the education field, in order to achieve learning goals, it is necessary to define learning paths that foresee a gradual and incremental acquisition of certain knowledge and skills that students should acquire. In this paper we analyze the educational progressions of the French educational system, we show how to formalize them through a web ontology and how to perform knowledge extraction from the official texts describing them to automate the population of such an ontology.

Introduction

In the education field, in order to achieve learning goals, it is necessary to define learning paths that foresee a gradual and incremental acquisition of certain knowledge and skills that students should acquire. Such educational programs are usually defined by a body (a ministry or department of education) and then implemented by the schools or institutes that are part of the educational system. Nowadays it is not possible to find them in a standardized format that can be accessible and queried automatically.

In this context, this paper proposes an answer to the following research questions:

1. How to model educational programs into a formal machine understandable ontology that can be processed and queried? 2. How to extract the knowledge and skills that an educational program requires from the official texts describing them? 3. How to automate the population of the ontology based on the extracted knowledge? 4. How can we exploit these formal representations? Our scientific contribution is first, a web ontology that describes and represents an official standard of knowledge and skills, in this case the French educational system. It is formalized in the OWL Web Ontology Language, which enables to process and query it with SPARQL, the standard query language for the Web of data. Second, we propose a process to extract knowledge and skills from the official texts describing the French educational program. Finally, we propose a process to automatically populate our ontology with the knowledge extracted from the official texts which we further enrich with the web of data.

The remainder of this paper is structured as follows: Section 2 presents state of the art approaches of ontology-based modeling in e-Education. Section 3 introduces to the French common base of knowledge and skills for students as well as the official educational progressions. In Section 4 we propose EduProgression: an ontology to model the educational progressions of the French educational system. We show, in Section 5, how to exploit the data of the progressions modeled through EduProgression and its thesaurus. Section 6 presents our method to automate the population of this ontology by extracting elements of knowledge and skills from the official texts and Section 7 describes how to link them to relevant resources available on the Web of Data. Finally, the conclusions and future work are presented in Section 8.

Related work

The term of "educational ontology" covers very different types of ontologies, modeling different kinds of knowledge related to e-Education. In [START_REF] Yahya | Ontologies in e-learning: Review of the literature[END_REF], the authors provide a literature survey of the development and use of ontologies in the domain of e-learning systems. According to the classification proposed in this survey, our work falls within the "curriculum modeling and management" category. Among such works we have CURONTO [START_REF] Al-Yahya | Curonto: An ontological model for curriculum representation[END_REF][START_REF] Alfaries | Curonto: A semantic model of the curriculum for program assessment and improvement[END_REF], an ontological model designed for the management of a curriculum and to facilite program review and assessment". Compared to it, our ontology is not focused on giving the means to conduct a review of the program nor an assessment; it focuses on the description and representation of the knowledge and skills required by an educational system and it provides the means to link knowledge and skills with resources from the web of data.

In the same category, Gescur [START_REF] Dexter | An ontology-based curriculum knowledgebase for managing complexity and change[END_REF] is a tool dedicated to the management and evaluation of the implementation of the curriculum, which facilitates the curriculum management process". It relies on an ontology of concepts relevant to curriculum management in Secondary Schools, such as teachers, departments, objectives, subjects, modules, tasks, documents, policies, activities, learning objects, quality criteria, etc. While this ontology focuses on the administration of the curriculum ours focuses on the management of the knowledge and skills required in each school year in the French educational system. In this sense, both ontologies could be complementary.

Besides the above cited literature review, the educational semantic web ontology proposed in [START_REF] Bucos | Designing a semantic web ontology for elearning in higher education[END_REF] focuses on representing higher education concepts and assisting specialized e-learning systems. In contrast to this work, we propose an ontology that focuses on representing the elements of knowledge and skills of an educational system.

Finally, the OntoEdu educational platform architecture for e-Learning proposed in [START_REF] Guangzuo | Ontoedu: a case study of ontologybased education grid system for e-learning[END_REF], relies on an activity ontology that describes all the education activities and the relations among them, and a material ontology which describes the educational content organization. The ontology is not available online, therefore it is not possible neither to analyze its classes and properties nor to determine the feasibility of use it in other scenarios outside the OntoEdu platform. Additionally their ontology does not contemplate the use of resources of the web of data to enrich the educational material.

The French educational model

In France, there is an official common base of knowledge and skills created by the Ministry of Education and published in the Official Journal; it is called the "Socle commun de connaissances et de compétences" 3 . It states that, compulsory education should at least guarantee to each student the necessary means to acquire a common base consisting of a set of knowledge and skills that are essential to master in order to successfully complete her education, build her personal and professional future and succeed in her life in society. The French common base is organized according to seven skills:

-Mastery of the French language -Practice of a foreign language -Basic math skills and scientific and technological culture -Mastery of the common information and communication techniques -Humanistic culture -Social and civic competences -Autonomy and initiative of the students In order to organize a gradual acquisition of the knowledge and skills of the French common base, some official learning progressions "Progressions pour l'ecole elmentaire" 4 for the educational areas of the French elementary school have been defined and published (official bulletin of January 5, 2012) 5 . For each elementary school cycle, the progressions are organized by area of education and strictly follow the program labels to offer a comprehensive approach to knowledge, skills and attitudes to be mastered by the students. Our study is based on the analysis of these progressions (which are based on the French common base of knowledge and skills). By generalizing them, we built a standard model of the knowledge and skills necessary for the students through their educational path and a method to automate the population of this model by extracting knowledge from the texts describing these progressions. Being a standard model, it is also possible to model progressions from other educational systems in the world, such as the U.S. academic standards6 defined by the Common Core State Standards (CCSS) 7 .

4 The EduProgression ontology and associated thesaurus The EduProgression ontology is freely accessible online.8 It is composed of 7 OWL classes and 8 OWL object properties. The relationships between them can be seen in Figure 1.

The two following excerpt is the description of the History progression and a related EKS representing the "european construction" based on EduProgression. We highlight with three different colors the three different types of resources related to specific thesaurus described in the following (see Section 4.2): @prefix edp : < http :// ns . inria . fr / semed / eduprogression > . edp : Histoire a edp : Progression ; rdfs : label " History " @en , " Histoire " @fr ;

Three thesaurus associated to each educational progression

Each formalized progression is associated to three thesaurus: one for its knowledge pieces, one for its vocabulary items and another one containing its learning domains. As a result, knowledge pieces, vocabulary items and learning domains are represented by instance classes of the EduProgression ontology which also are SKOS concepts belonging to one of these thesaurus. Grouping these elements in thesaurus allows, among other benefits, to manage in a simple and structured way the knowledge of each progression [START_REF] Pastor-Sánchez | Advantages of thesaurus representation using the simple knowledge organization system (skos) compared with proposed alternatives[END_REF].

The following excerpt shows the structure of the three thesaurus of the progression of History (in blue the thesaurus of knowledge pieces, in green the thesaurus of learning domains and in red the thesaurus of vocabulary items).

edp:ElementsConnaissanceHistoire a skos:ConceptScheme ; skos:prefLabel "Knowledge pieces of History"@en . skos:prefLabel "Elements de connaissance de l'Histoire"@fr . edp:Le_role_de_Robert_Schuman a edp:Knowledge, skos:Concept ; skos:inScheme edp:ElementsConnaissanceHistoire ; skos:prefLabel "Know the role of Robert Schuman in European construction"@en . skos:prefLabel "Connaître le rôle de Robert Schuman dans la construction européenne"@fr . edp:DomainesApprentissageHistoire a skos:ConceptScheme ; skos:prefLabel "Learning domains of History"@en . skos:prefLabel "Domaines d'apprentissage de l'Histoire"@fr . edp:Le_XXe_siecle_et_notre_epoque a edp:LearningDomain, skos:Concept ; skos:inScheme edp:DomainesApprentissageHistoire ; skos:prefLabel "Elements of knowledge and skills on the twentieth century and our time"@en ; skos:prefLabel "Éléments de connaissances et de compétences sur le XXe siècle et notre époque"@fr . edp:VocabulaireHistoire a skos:ConceptScheme ; skos:prefLabel "Vocabulary of History"@en ; skos:prefLabel "Vocabulaire de l'Histoire"@fr . edp:Euro a skos:Concept ; skos:inScheme edp:VocabulaireHistoire ; skos:prefLabel "Euro"@en, "Euro"@fr .

To give a clearer view of the elements of the History progression described in the previous excerpts, Figure 2 presents it as a graph.

At the time of writing, we have created the thesaurus of the vocabulary, knowledge pieces and learning domains relative to three progressions from the French curricula: History, Geography and Experimental sciences and technology, and we have populated the EduProgression ontology with the concepts in these thesaurus. For the progression on History, we identified 29 elements of knowledge and skills (instances of edp:EKS), the thesaurus of vocabulary items comprises 131 concepts, the thesaurus of knowledge pieces 45 concepts and the thesaurus of learning domains 7 concepts. For the progression of Geography, 32 elements of knowledge and skills were identified; its thesaurus of vocabulary items is composed of 131 concepts; its thesaurus of knowledge pieces and learning domains Fig. 2. Graph of the History progression excerpt contaisn 34 and 6 concepts respectively. Finally, the pogression of Experimental sciences and technology was populated with a total of 50 elements of knowledge and skills; It has the largest vocabulary since it comprises 265 elements. Its thesaurus of knowledge pieces was populated with 40 concepts while its thesaurus of learning domains with 10 concepts. These thesaurus can be freely accessed online: http://ns.inria.fr/semed/eduprogression/thesaurus.

Exploitation of EduProgression and the associated thesaurus

As Similarly, we can retrieve the required vocabulary for the first-year intermediate course (CM1) of Geography, within the learning domain of "Elements of knowledge and skills on the territories at different scales". ? progression a edp : Progression . {? progression rdfs : label " Geography " @en } UNION {? progression rdfs : label " Experimental sciences and technology " @en } ? progression edp : hasEKS ? eks . ? eks edp : hasCourse edp : CE2 . ? eks edp : hasKnowledge ? knowledge . }

It is important to note that thanks to the EduProgression ontology it is possible to make queries to the existing progressions filtered by specific courses. This is the basis for the implementation of educational applications adapted to each student profile.

Knowledge extraction from texts and formalization

For the extraction of the information contained in the progressions for elementary school we had to consider first, that the progressions are only available in PDF format, that is, a PDF document for each learning domain. The data contained in each PDF, was inside tables without a standard format, therefore, when we tried to use common techniques for PDF data extraction 9 such as OCR or data extraction from tables 10 , the resulting extracted text was mixed among various tables and/or incomplete.

This first led us to perform a preliminary manual extraction of knowledge from text. The first process that we experimented aimed at directly extracting RDF data from PDF texts. This involved to copy textual data directly from each PDF file, and then to paste it into an RDF description as literal values of some RDF triples (also manually written). Not only this process was time-consuming but also it was prone to human errors in the format of the data and the resulting RDF triples.

To solve these problems, we split the data extraction process in two steps, the first one consisting in manually filling a JSON intermediate data structure, the second one consisting in automatically transforming JSON data into RDF data. We designed an intermediate data structure in JSON format in which we represented each progression as a JSON object containing the following information:

-The name of the progression -An array of the different learning sub domains involved in the progression -A dictionary with the French scholar courses covered -An array of the elements of knowledge and skills (EKS) involved in the progression. Each EKS itself contains:

• a title and a description in French • the scholar cycle covered by this EKS • the learning domain covered by this EKS • a dictionary of the knowledge pieces (titles and descriptions in French) required by this EKS • a dictionary containing the required skills (titles and descriptions in French) required by this EKS • an array of the vocabulary items required by this EKS • an array of points of reference required by this EKS 9 https://en.wikipedia.org/wiki/Optical_character_recognition 10 http://tabula.technology/ This allowed us to manually fill the data structure in a much faster and much more reliable way. In addition, in order to validate the format of the data, we defined a JSON schema11 representing these aforementioned structural constraints. This enabled us to automatically validated the JSON objects representing a progression manually entered.

As a second step, we defined and performed an automatic conversion process of JSON objects into RDF graphs. It uses the EduProgression ontology to automatically generate an RDF graph.

The following excerpt is the intermediate JSON representation of the EKS on the Age of Discovery, which conversion in RDF is presented in the excerpt of section 4.2, which illustrates the use of the EduProgression ontology.

" EKSs ": [{ " short_label ": [{" fr ": " Les Grandes Découvertes " , " en ": " Age of Discovery "}] , " label ": [{" fr ": " Les Grandes Découvertes " , " en ": " Age of Discovery "}] , " course ": " CE2 " , " le arning Domai n ": " ECC sur les Temps Modernes " , " knowledge ": [{ " short_label ": [{" fr ": " Les Européens se lancent à la découverte du monde "}] , " label ": [{" fr ": " Savoir que les Européens se lancent à la d ecouverte du monde grâce notamment aux progrès de la cartographie et de la navigation "}] }] , " skills ": [{ " short_label ": [{" fr ": " Raconter le voyage de Christophe Colomb "}] , " label ": [{" fr ": "Être capable de raconter le voyage de Christophe Colomb et la découverte d ' un nouveau monde "}] }] , " p o i n t s _ o f _ r e f e r e n c e ": [] } ,... ]

Entity Linking

We enriched the EduProgression ontology and its related thesaurus by conducting an entity linking process. It allows us to link the EKS instances of our already populated progressions, with DBpedia resources related to the textual values of the properties describing EKS instances. The information provided by these linked resources may be further exploited directly as learning material or to discover related learning resources.

To make this possible, we have created an automated process that first extracts literal values of the properties of each EKS and builds a textual representation of the latter by concatenating these literal values, and then retrieves the related DBpedia resources by using the DBpedia spotlight web service. The process is as follows:

1. All the instances of EKS are retrieved from the populated progressions. This is the result of a SELECT SPARQL query processed by a SPARQL engine on our local triple store.

2. For each retrieved EKS instance, the textual values of its properties are extracted and concatenated into a string which will be considered as a whole as the EKS text representation. 3. The process takes each EKS text representation and analyzes it by using the DBPedia Spotlight web service. 4. Each related resource obtained from the previous step is linked to the EKS by using the edp:hasRelatedResource property of EduProgression. This is done with an INSERT SPARQL query applied to our triple store.

The whole process is shown in Figure 3. Currently, our process creates links between EKS instances and related resources in DBpedia. We chose to link EKS since they are conceived in our model as the main concept that represents skills and knowledge. Eventually, for other case studies, the EduProgression ontology could be adapted in such a way that the property hasRelatedResource can be applied to other types of instances, among which skills, knowledge pieces and vocabulary items, making it possible to link their instances with related resources from the web of data.

As a result of our process, we have obtained 187 resources related to the EKSs of the Geography progression with a precision of 94%, 205 for the History progression with a precision of 95% and 220 for the progression of Experimental Sciences and technology with 94% of precision. For these experiments DBpedia was configured with a confidence of 0.15 and a support of 20.

Conclusions and future work

In this paper, we have shown how to model an educational program by formalizing it as a Web ontology in OWL that is understandable by machines and that can be queried and processed. In particular, we have taken as a case study the French education system, from which we have extracted and formalized educational progressions in an ontology called EduProgression. We sketched how this ontology can be used through some example SPARQL queries. We have described a process for populating the EduProgression ontology, by extracting the knowledge elements and skills involved in the educational progressions from the official texts describing these progressions. Additionally, we showed how we managed to automatically link the ontology instances to Web resources.

At the time of writing, the current "Socle commun de connaissances et de compétences" in France (which constitutes the basis of this work) is that of 2006. As of September 2016, an update to such document will be made12 , although it will involve minor changes, this scientific work will be adapted accordingly.

Future work includes the use of the EduProgression ontology and its related thesaurus for the indexation of educational resources to the French curricula through our ontology, with the aim of recommending them to students in their learning path. This activity will be performed in collaboration with our two industrial partners. In addition, we look forward to apply this work to other educational systems in the world as suggested in Section 3.

4. 1 -

 1 The EduProgression ontology We created EduProgression, an ontological model for educational progressions, formalized in the standard Ontology Web Language (OWL). Its main classes are: Element of Knowledge and Skills (EKS). It is the key concept of our model. It is represented by the EKS class, which is the central class of the EduProgression ontology. An element of knowledge and skills is associated to a set of knowledge pieces (class Knowledge) and skills (class Skill) for a specific French school cycle (class Course) containing reference points (class PointOfReference) and also a vocabulary of associated terms (class Vocabulary). More precisely: • Knowledge. Instances of class Knowledge are also instances of skos:Concept and each one belongs to a skos:ConceptScheme that contains all the knowledge pieces of a given progression. An instance of EKS is related to an instance of Knowledge through the property hasKnowledge. • Skill. An instance of EKS is related to an instance of Skill through property hasSkill. • Course. In the French educational system, skills that students are expected to develop, are defined by cycle and each cycle is organized into courses. For example, "the consolidation cycle" includes "the second year elementary course" (CE2), "the first-year intermediate course" (CM1) and "the second year intermediate course" (CM2). In this context, an instance of class Course represents a course in a cycle. An instance of EKS is related to an instance of Course through property hasCourse. • PointOfReference. An instance of class PointOfReference represents an educational reference element on a specific element of knowledge and skills (an instance of EKS). An instance of EKS is related to an instance of class PointOfReference through property hasPointOfReference. • VocabularyItem. Each element of knowledge and skills has vocabulary items. An instance of EKS is related to an instance of class Vocabu-laryItem through property hasVocabularyItem. A vocabulary item is also an instance of skos:Concept and it is related to an instance of skos:ConceptScheme which gathers the concepts of the thesaurus of the progression. -Progression. A progression is represented by an instance of class Progression. It can be associated to an existing learning domain (through property hasLearningDomain) and to one or several EKSs (through property hasEKS). -Learning domain. A learning domain is represented by an instance of the LearningDomain class, and it is also an instance of skos:Concept that is part of (only) one skos:ConceptScheme containing the only learning domains of a progression. Also, as they are SKOS concepts, learning domains are hierarchically organized by using the skos:broader and/or skos:narrower properties. A learning domain can be associated to a Progression or an EKS.

Fig. 1 .

 1 Fig. 1. Classes and Properties of the EduProgression Ontology

  edp : hasEKS edp : L a _ c o n s t r u c t i o n _ e u r o p e e n n e . edp : L a _ c o n s t r u c t i o n _ e u r o p e e n n e a edp : EKS ; rdfs : label " The european construction " @en ; rdfs : label " La construction européenne " @fr ; edp:hasKnowledge edp:Le_role_de_Robert_Schuman ; edp:hasLearningDomain edp:Le_XXe_siecle_et_notre_epoque ; edp:hasVocabularyItem edp:Euro . edp : hasCourse edp : CM2 ; edp : h a s P o i n t O f R e f e r e n c e edp : E u r o _ m o n n a i e _ e u r o p e e n n e ; edp : h a s R e l a t e d R e s o u r c e dbpedia -fr : Union_européenne ; edp : hasSkill edp : P r i n c i p a l e s _ e t a p e s _ d e _ l a _ c o n s t r u c t i o n _ e u r o p e e n n e ;

  PREFIX edp : < http :// ns . inria . fr / semed / edup rogres sion # > PREFIX rdfs : < http :// www . w3 . org /2000/01/ rdf -schema # > SELECT ? vo ca b ul a ry _i t em WHERE {? g e o g r a p h y _ p r o g r e s s i o n a edp : Progression .? g e o g r a p h y _ p r o g r e s s i o n rdfs : label " Geography " @en .? g e o g r a p h y _ p r o g r e s s i o n edp : hasEKS ? eks . ? eks edp : hasCourse edp : CM1 . ? eks edp : h a s L e a r n i n g D o m a i n edp : E C C _ s u r _ l e s _ t e r r i t o i r e s _ a _ d i f f e r e n t e s _ e c h e l l e s . ? eks edp : h a s V o c a b u l a r y I t e m ? vo c ab ul a ry _i t em . } Finally, the following query allows to retrieve the necessary knowledge pieces of History and Experimental sciences and technology for the second year elementary course (CE2).

  PREFIX edp : < http :// ns . inria . fr / semed / edup rogres sion # > PREFIX rdfs : < http :// www . w3 . org /2000/01/ rdf -schema # > SELECT ? knowledge WHERE {

Fig. 3 .

 3 Fig. 3. Process to link EKS instances of a given progression to DBpedia resources

  the EduProgression ontology has been populated, we can exploit it with SPARQL queries. For example, to retrieve the EKS required for the students attending the second year intermediate course (CM2) of History, we can use the following query:

PREFIX edp : < http :// ns . inria . fr / semed / edup rogres sion # > PREFIX rdfs : < http :// www . w3 . org /2000/01/ rdf -schema # > SELECT ? eks WHERE { ? h i s t o r y _ p r o g r e s s i o n a edp : Progression . ? h i s t o r y _ p r o g r e s s i o n rdfs : label " History " @en . ? h i s t o r y _ p r o g r e s s i o n edp : hasEKS ? eks . ? eks edp : hasCourse edp : CM2 . }

http://www.legifrance.gouv.fr/WAspad/UnTexteDeJorf?numjo=MENE0601554D

http://eduscol.education.fr/cid58402/progressions-pour-l-ecoleelementaire.html

[START_REF] Guangzuo | Ontoedu: a case study of ontologybased education grid system for e-learning[END_REF] http://media.education.gouv.fr/file/1/58/7/programmes_ecole-primaire_ 203587.pdf

http://www.corestandards.org/read-the-standards/

http://www.corestandards.org/

http://ns.inria.fr/semed/eduprogression

http://json-schema.org/

http://cache.media.education.gouv.fr/file/17/45/6/Socle_commun_de_ connaissances,_de_competences_et_de_culture_415456.pdf