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Curriculum Overlay Model for Embedding DigitalResourcesHuda Khan, Keith Maull, Tamara SumnerInstitute of Cognitive ScienceDepartment of Computer ScienceUniversity of Colorado at Boulder, Boulder, CO 80309huda.khan, keith.maull, tamara.sumner@colorado.eduABSTRACTThis paper describes the design and implementation of a curriculumoverlay model for the representation of adaptable curriculum usingeducational digital library resources. We focus on representingcurriculum to enable the incorporation of digital resources intocurriculum and curriculum sharing and customization by educators.We defined this model as a result of longitudinal studies oneducators’ development and customization of curriculum and userinterface design studies of prototypes representing curriculum. Likeoverlay journals or the information network overlay model, ourcurriculum overlay model defines curriculum as a compound objectwith internal semantic relationships and relationships to digitallibrary metadata describing resources. We validated this model byinstantiating the model using science curriculum which uses digitallibrary resources and using this instantiation within an applicationthat, built on FEDORA, supports curriculum customization.Findings from this work can support the design of digital libraryservices for customizing curriculum which embeds digital resources.Categories and Subject DescriptorsH.1.2 [Models and Principles]: User/Machine Systems; H3.7[Information Storage and Retrieval]: Digital Libraries – Userissues; K.3.1. [Computers and Education]: Computer Users inEducation – Computer-assisted instruction.General Terms: Design, Human Factors.KeywordsPersonalization, digital libraries, curriculum, FEDORA, contentmodels, lessons, Teaching Boxes.1. INTRODUCTIONEducational digital libraries and the World Wide Web have madeinteractive educational resources available to educators at anunprecedented scale. The Effective Access project [10], whichsurveyed high school educators’ attitudes towards and use of webbasededucational resources, reports significant enthusiasm for usingweb-based resources in science and mathematics instruction.Respondents to this national survey repeatedly stressed the potentialof interactive resources for creating engaging learning experiences,for incorporating real-world scientific data into classroominstruction, and for generally increasing the relevance of science to“play station nation” [ibid]. However, despite the reportedenthusiasm, interactive educational resources are largely not beingintegrated into mainstream teaching practices. Barriers to useinclude a lack of technical infrastructure in schools, lack ofprofessional development to help educators teach with technology,and lack of alignment with core curricula that have been adopted bytheir school or school district [ibid]. This issue of curricularalignment, which is the focus of our work, transcends nationalborders, as many countries have mandated national curricula, whileothers have recommended educational standards.These findings align with other research on middle and high schooleducators’ interactions with curriculum [4, 9, 20]. Educators do notteach individual resources isolated from curriculum, rather they (a)integrate resources into curriculum aligned with specific standardsand intended learning goals and (b) use resources to customize corecurriculum to fit their specific classroom teaching contexts. Thecontext affecting classroom teaching includes grade level, classroompace, student background in the topic, student misconceptions, andstudent interest. Whereas previous efforts such as the InstructionalArchitect [19] focus on individual educators’ construction of webbasedcontent employing digital resources, we focus on modelingcurriculum which employs educational digital resources. Our workis motivated by the need for a representation of curriculum whichallows the systematic and scalable embedding of web-basededucational resources, which may be created by many differentinstitutions, into middle and high school science curriculum.In this article, we discuss the design and instantiation of acurriculum overlay model that incorporates individual educationalresources into a coherent curriculum context, and supports digitallibrary services for the customization, sharing, and maintenance ofcurricula incorporating interactive resources. This model definescurricular components (such as learning goals, lessons, activities,and resources), related components (such as notes describing thepotential use of resource to teach a particular science concept), therelationships between components, and associated behaviors. Thiscurriculum overlay model offers a general framework for digitallibrary services supporting incorporation of educational resourcesinto curriculum. This framework has been informed by multiplestudies with science educators. These studies, which span threeyears of research, include longitudinal observations of mastereducators engaged in curriculum design and adaptation, analyses ofexisting exemplary science curriculum, and interviews and usabilitystudies on evolving prototypes.In the remainder of this article, we first review related work inlearning objects, digital libraries, and curriculum design. We thendescribe the studies that informed the design of the curriculumoverlay model. An abstract representation of the resultingcurriculum overlay model is then presented, followed by a detailedPermission to make digital or hard copies of all or part of this work forpersonal or classroom use is granted without fee provided that copies arenot made or distributed for profit or commercial advantage and that copiesbear this notice and the full citation on the first page. To copy otherwise, orrepublish, to post on servers or to redistribute to lists, requires prior specificpermission and/or a fee.JCDL ’08, June 16–20, 2008, Pittsburgh, Pennsylvania, USA.Copyright 2008 ACM 978-1-59593-998-2/08/06…$5.00.74discussion of its implementation in the Federated Digital ObjectRepository Architecture (FEDORA) [8]. Finally, we describe howwe validated this model by using it to instantiate existing sciencecurriculum and discuss future work to further demonstrate themodel’s robustness and generalizability.2. RELATED WORKOne prominent area in the design of computational representationsof educational content is the learning objects paradigm. Wileydefines a learning object as “any digital resource that can be reusedto support learning” [22] and describes learning objects as analogsto computational objects in the object-oriented paradigm. A learningobject can thus include educational content in the form of lessons,modules, tutorials, or activities. A “learning content managementsystem” is a course management system which supports theadministration and use of learning objects in online courses.Designing learning objects entails using one of multiplespecification and packaging standards in order to deploy thoselearning objects in different learning content management systems(LCMSs). Examples of learning object specifications and standardsinclude the Sharable Content Object Reference Model (SCORM),developed by the Advanced Distributed Learning Initiative (ADL)to support self-study modules, and the Learning ObjectManagement (LOM) standard, which includes 76 different metadatamarkup fields for the specification of information about learningobjects [2, 7].Learning object research has explored the packaging andspecification of learning objects with an emphasis on how theseobjects can be included in learning content management systems tosupport self-directed learning. Here, in contrast, we focus supportingK-12 educators’ review and customization of curriculumincorporating educational resources for use in formal classroomteaching. We focus not on the packaging of individual resources buton the representation of a coherent yet extensible curriculum ‘layer’which embeds educational resources.Table 1 provides an overview of the terms we use in this paper andtheir associated meaning. In the context of this work, the term‘resource’ refers to a more general term than learning object,encapsulating websites and data-sets with associated metadatadescriptions without requiring a particular specification format.Table 1. Overview of terms.Resource A web-site (e.g. lesson plans, activities, etc.) orweb-based data (e.g. images, data sets, etc.) whichhas associated metadata describing itscharacteristics (e.g. author, title, URL, etc.) Aresource refers to an entity which is more generalthan a ‘learning object’.Curriculum The definitions of this term vary from lessonsactually taught in class to a year-long or multigradelevel description of learning goals andsubject matter to be taught to students [1]. Here,we use the term to refer to educators’ plans forclassroom teaching, including lessons andactivities.FlexiblyAdaptiveCurriculumCurriculum that is designed to provide multiplemodules of instruction or multiple exemplars,promoting adaptation of the curriculum in differentlocal contexts [9, 20].Our research focuses on the representation of ‘sustainable’curriculum [9] overlaid on educational resources. One approachtowards the design of sustainable curriculum is the incorporation ofthe capacity for extension and adaptation in the curriculum,allowing the curriculum to be used and customized long after itsinitial design and in different classroom contexts [4, 9, 20].Educators’ teaching of curriculum is affected by multiple classroomcontextual factors such as student learning styles, studentcomprehension of pre-requisite concepts, and student interest.Furthermore, factors such as location may affect what kinds ofexamples or activities connect with students’ experiences with theirsurroundings and environment. Localized examples, instead ofbeing a hindrance to use of educational resources, provide thecontextual information which supports educators’ understanding ofhow to use resources to achieve particular learning objectives withtheir students [4, 9, 20]. Thus, our research work explores the designof ‘flexibly adaptive’ curriculum to support use of educationalresources by teachers in their individual classroom settings.The conception of curriculum as a layer of contextualizationoverlaid on educational resources relates to research on overlayjournals [21], information network overlay [14, 15], and OpenArchives Initiative – Object Reuse and Exchange (OAI-ORE) [16].Research on overlay journals explores the repurposing of scholarlyjournal articles originally published in different journals andresiding in heterogeneous repositories. Services which allow editorsto integrate these different articles into a new context of citation,while maintaining references to the ‘lineage’ of these articles or theoriginal publication and repository location, support disseminationand scholarly communication. Similarly, our research explores therepurposing of individual resources in new curricular contexts whilemaintaining the links to the digital library origins of these resources(including access to metadata). The information network overlaymodel explores a similar overlay of relationships to externalontologies, such as those for educational standards, onto a networkof digital objects describing National Science Digital Library(NSDL) [18] resources and their associated metadata.Research on OAI-ORE seeks to define an interoperability layerwhich enables the machine-readable sharing and transfer of theinternal structure and relationships within ‘compound objects’.Compound objects refer to objects that have constituentcomponents, such as an object representing an overlay journal(which consists of objects representing articles). As this researchshows, curriculum can be modeled in the form of a complexcompound object consisting of multiple lessons and othercomponents. The curriculum overlay model thus provides aninteresting use case for OAI-ORE. In turn, OAI-ORE could beuseful for sharing curriculum across digital libraries.3. TEACHING BOX AND DESIGN STUDIESThe motivation driving our exploration of curriculum overlay modeldesign is the representation of flexibly adaptive and sustainablescience curriculum which aligns with learning objectives andeducational standards and which incorporates educational resources.Specifically, we explore the design of a curriculum overlay modelwhich can achieve these goals:(a) Supporting middle and high school science educators inaccessing and contributing to contextual information (such asrelated educational standards, learning objectives, lessons andactivities incorporating educational resources, and notes by75educators describing the pedagogical relevance of a resource)that facilitates classroom teaching using educational resources.(b) Supporting curriculum customization services which enableeducators’ (i) integration of educational resources into existingcurriculum and (ii) adaptation of curriculum using educationalresources to fit their classroom teaching constraints.To meet these goals and to ensure that the design of the curriculumoverlay model was based on best practices of designing adaptivescience curriculum, we embarked on human-centered design studiesexploring the development and structure of science curriculum withembedded digital resources. These studies included two longitudinalstudies of educators’ curriculum development in the 2004 and 2005DLESE Teaching Box workshops [6] and our interface designstudies [11, 12, 13].The DLESE Teaching Boxes workshops [6], employing educatorsas primary participant designers of curriculum, sought to alignlearning objectives, educational standards, and lessons witheducational resources. Because of the alignment of these curriculardesign goals with the motivation for our work, we selected the studyof these workshops as part of the empirical basis for our curriculumoverlay model. We refined the pilot curriculum overlay model basedon the results of the Teaching Boxes workshops in our interfacedesign studies.3.1 2004 Pilot Teaching Box Workshops‘Teaching Boxes’ are so named as an analogy to the binders orboxes of lessons and teaching materials which educators accumulatethroughout their teaching careers. Educators reuse and customizethese materials in their teaching. The DLESE Teaching Boxworkshop series thus was exploring the design of collections oflessons and activities which can support educators’ use and reuse ofeducational digital resources. This series consisted of two 2-daylong sessions and one 5-day long session where educators,scientists, and digital library staff collaborated to create TeachingBoxes.7 middle and high school educators participated in the 2004Teaching Box workshop series. These educators were tasked withidentifying the curricular information which should be included inthe Teaching Boxes to enable their use and customization by othereducators. Educators also had to teach the Teaching Boxes theydeveloped in their own classrooms. Through a process ofbrainstorming and providing feedback on mockups of Teaching Boxcontent, these educators identified three main categories ofcurricular content: (a) a concept map or list showing the intendedconceptual progression for the students and the educationalstandards supported by teaching these concepts, (b) a set ofsuggested lessons targeting one or more of these concepts, and (c) aset of the educational resources included in the lessons. Figure 1shows excerpts of screenshots of this content in the Plate TectonicsTeaching Box.This workshop series also resulted in the definition of templateswhich described the structure of Teaching Box content. The contentof the two Teaching Boxes resulting from this workshop series wasorganized using these templates. For example, the lesson templatedefined a lesson as consisting of fields describing title, relatedconcepts, and one or more activities. These templates and ourobservations of educators’ organization of Teaching Box contentinformed the pilot version of the curriculum overlay model.Figure 1. Excerpts of (a) concept map, (b) list of lessons, and (c)resources from Plate Tectonics Teaching Box.This pilot model provided a decomposition of this content intocurricular components (lessons, activities, concepts, and resources).Although the templates described activities as a set of fieldsencapsulated within a lesson, we identified the need to representactivities as separate components which embed digital resources. Inaddition, our analysis of the conceptual dependencies between themain categories of content helped us to define the relationshipsbetween these components. For example, understanding that a givenlesson addresses a set of concepts, we defined the need to model arelationship between lessons and concepts.3.2 2005 Teaching Box WorkshopsIn this workshop series, 8 middle and high school educatorsdeveloped four additional Teaching Boxes using a refined version oftemplates resulting from the 2004 workshops. These educators didnot request any modifications to the categories of content or fieldsincluded in the templates, showing the effectiveness of the templatesfor defining the main categories of content to be included inTeaching Boxes. At the same time, the educators employed theirown documents to organize content before committing this contentto the templates. Furthermore, educators, providing feedback on aprototype we designed to represent Teaching Box content, indicateda need for additional technological support for development andcustomization of Teaching Box content. These findings thusrevealed that (a) the pilot curriculum overlay model’s definition ofcomponents based on content categorization did not need to beupdated and that (b) additional support for curriculum customizationwas required on the levels of the overlay model and services built onthis model. Educators’ feedback on the prototype, and other relatedinterface design studies, are discussed in the next section.3.3 User Interface Design StudiesWe conducted multiple studies evaluating design features forrepresenting and customizing Teaching Box content. As part ofthese studies, we analyzed observations from the Teaching Boxworkshops in addition to obtaining evaluation and feedback fromother educators and participants. For our 2004 design study, werecruited middle and high school science or Earth Science educatorswho were unaffiliated with the Teaching Boxes project. As part ofthis design study, we interviewed 6 educators regarding their lessonplanning practices. Using Think Alouds [17], we obtained feedbackfrom 4 educators on the design of a prototype representing the maincomponents of our pilot curriculum overlay model. We alsoobtained feedback on different versions of the prototype from76participants in a critique lab as well as from the educators in the2005 Teaching Box workshop series (see [11, 12, 13] for moredetails). These studies:(a) Revealed the need to model relationships between curricularcomponents to allow the display and modification of andflexible query across these relationships. For example, insteadof views of concepts isolated from lessons and activities,understanding the relationships between concepts, educationalstandards, and lessons could support educators’ navigation andcustomization of the conceptual progression of Teaching Boxcontent.(b) Confirmed the need to include a personal collection ofresources and notes in the curriculum overlay model.Supporting a collection and notes can enable educators torevise their selection of resources and record suggested uses ofresources in activities. For example, educators in the TeachingBox workshops changed which resources they included inactivities as they refined Teaching Box content.These requirements for the curriculum overlay model intersect withrequirements for the curriculum customization services whichoperate on this model. These service requirements, also based on theresults of these studies, include (a) support for modification ofcomponents in the curriculum overlay model, including integrationof search results or resources from the personal collection intocurricular content, and (b) the display and modification ofrelationships between components in the curriculum overlay model.The sections below discuss the curriculum overlay model whichresulted from this research and the validation of this model throughits instantiation within an application which incorporates curriculumcustomization services.4. CURRICULUM OVERLAY MODELThe design requirements for the curriculum overlay model, asdescribed in the previous section, include support for modeling (a)the main curricular components, such as lessons, activities, learningobjectives or target concepts, and resources, and (b) therelationships between these components. Furthermore, therequirements include the need to support educators’ collection ofresources of potential relevance and association of notes withresources describing the relevance of those resources for use in aparticular activity4.1 OverviewFigure 2 provides a high level overview of the curriculum overlaymodel, displaying the main components and their relationships inthe model. Based on the main categories of curricular content whichwe defined as a result of the studies described in Section 3, weidentified five types of components representing curricular content:module, lesson, activity, resource, and concept. Componentscorresponding to these types encapsulate associated curricularcontent. For example, a component modeling a lesson may containcontent describing the lesson title, suggested grade level, suggestednumber of classroom periods to teach the lesson, vocabulary termsfor students, and an overview of the lesson. Similarly, an activitymay contain content describing procedures for students andrationale for how this activity helps to address particular concepts.In addition to the five component types representing curricularcontent, the model also includes the collection and note componenttypes. A personal collection component serves as an aggregationobject that allows for the storing of resources which educators findof potential relevance. This component can include resources whichinitially may not be incorporated into the curriculum but which canlater be embedded into activities. Educators can use notes to recordwhy they consider an educational resource potentially useful in thecontext of a particular activity, suggestions for use of the resource,or insight from their own use of the resource in their teaching.Analyzing the hierarchical and conceptual dependencies betweencurricular content in the studies described in Section 3, we definedthe different types of relationships between components in thecurriculum overlay model. Module, lesson, activity, and resourceare all related to each other as part of a hierarchy of components. Amodule represents an aggregation of lessons targeting a particularoverarching set of concepts or learning objectives. We use the term‘module’ to refer to any such collection of lessons and aninstantiation of this curriculum overlay model may use a differentterm (such as unit or Teaching Box)depending on the curriculum being modeled.Modules themselves can be combined into alarger set which could span multiple topicsrelated to high level concepts. Each modulecan have one or more lessons. Each lessoncan have one or more activities and eachactivity can further incorporate multipleeducational resources. The model alsodescribes the association between lessonsand concepts they address and therelationship between different concepts. Alesson addresses a set of concepts and is thusrelated to one or more concepts describinglearning objectives. The set of lessons in amodule address the intended studentprogression through the target concepts forthat module. Understanding a given conceptmay be a prerequisite for understandinganother concept. We thus modeledrelationships between concepts which definehow certain concepts can be consideredb prerequisites for other concepts.Figure 2. Overview of Curriculum Overlay Model77One of the goals of the design of the curriculum overlay model wasto support the integration of national and state science educationalstandards with curriculum which embeds digital resources. Inaddition, our aim was to maintain the connection between resourcesembedded in curriculum and the digital library metadata describingthose resources. Concept components encapsulate content whichdescribes related national and state science standards, thus providinga link between the target concepts which teachers address in formalclassroom teaching and standards related to these concepts. Themodel can support the association of a resource component withrelated metadata records from one or more digital libraries. In thisway, the model facilitates linking components with external contentand information which provides additional pedagogical anddescriptive context for these components.This curriculum overlay model, breaking curricular content intoseparate yet related components, supports educators in reviewingand customizing a particular component while understanding theinterdependencies between a component and the remaining content.Integrating educational objects into this framework allows us tobenefit from opportunities to make these educator-developed,‘reused’, and adapted educational curricular objects available tocollections spanning multiple digital libraries. Services operating onthis curriculum overlay model can allow educators to get a quickglimpse of the structure of the content and how the differentcomponents are related. FEDORA’s approach of focusing ondigital components or objects thus fits well with the focus of thisresearch on balancing content and context. The next sectiondescribes the implementation of this curriculum overlay model inFEDORA.4.2 FEDORA implementationEducational digital resources span multiple types (e.g. lesson plans,tutorials, etc.) and media formats (text, images, animations, realtimedata, etc.). FEDORA [8], an architecture being adopted bymultiple digital libraries and repositories such as NSDL [18],provides a solution for representing such educational resources andthe curriculum overlaid onto these resources. FEDORA’s supportfor sharing of resources between different repositories and the use ofmultiple metadata formats makes this technology a prime candidatefor representing and sharing curricula to engage educators as bothusers of educational resource and creators of annotations andcurricular context around educational resources.FEDORA provides a basic generic framework for representingcontent in the form of digital objects called ‘data objects’ which actas containers for content. We represented each of the componentsin Figure 2 as a FEDORA data object which contains the curricularcontent associated with that component. We used FEDORA’scapabilities for representing relationships between data objects toimplement the relationships between the components in thecurriculum overlay model. We specified the different types ofcomponents (e.g. lesson, activity, etc.) using FEDORA ‘contentmodels’, which are conceptual descriptions of ‘types’ of dataobjects. Before describing the content models, we first brieflyreview the generic structure of FEDORA data objects.FEDORA data objects store content in ‘datastreams’ which cancontain any XML content or a reference to externally hosted XML.In addition, FEDORA allows repository developers to associateparticular behaviors with a data object. This form of behaviorlinking is accomplished through the use of ‘disseminators’ whichassociate web-services with a data object.Akin to the definition of an interface for abstract data types,FEDORA ‘content models’ allow the specification of ‘types’ of dataobjects. A content model describes the structure of a data object of aparticular type in terms of the object’s constituent datastreams andassociated disseminators. We utilized FEDORA content models todescribe the different component types in the curriculum overlaymodel, the content included within those components, and thequeries and behaviors associated with those component types. Table2 provides an overview of the content models we have definedcorresponding to the five component types representing curricularcontent: Module, Lesson, Concept, Activity and Resource. We alsoused a similar content model for the Note object which containsannotation content.Table 2. Overview of main elements of content models forModule, Lesson, Activity, Resource, Concept, Note.Reserved FEDORA Data StreamsDublinCore (DC)Title (title of object as accessed for display),Description (short summary or overview text to bedisplayed with object, e.g. lesson overview, mainconcept text, activity summary, etc.)ExternalRelationships(RELSEXT)Defines relationships with other objects.Relationships include “isMemberOf” which definedirect hierarchical relationships between objects,e.g. Resource is a member of an Activity. Nonhierarchicalrelationships include links to relatedconcepts (e.g. the “Has Description” relationshiplinks a Lesson to a Concept object) and annotationrelationships (e.g. the ‘IsAnnotationOf’relationship links Note to a Resource object) .Custom Data StreamsContent(Content-Desc)This datastream contains the main XML contentthat correlates with the Module XML model thatdefines the component represented by the Fedoraobject.QueryResults(e.g.Activities-XML)Different objects may have different sets ofdatastreams that refer to the results of querydisseminators. For example, a lesson object maycontain results of a query that specifies thedifferent included activities and of another querythat specifies related concepts.Stylesheet These XSL datastreams provide the stylesheetinformation for a default display transformingXML results for the web. An application utilizingthis content model does not necessarily need toemploy the default display.Resource:MetadataFor the resource object, a datastream is reservedwhich references the metadata for that resource inthe digital library.DisseminatorsDisplay Utilizing the default stylesheet, displaydisseminators allow FEDORA’s SAXON or XSLtransformation service to provide a default displayof the component.Query An object can have multiple relationship querydisseminators (depending on the object-type).These disseminators execute queries that explorerelationships between the object and other objects.78To represent the curricular content associated with a componenttype, we created a custom datastream called ‘ContentDesc’. Thisdatastream is used to store an XML description of curricularcontent. We included this custom datastream in the content modelsfor all the object types except for that of Collection (which serves asan aggregation object without internal curricular content). Forexample, the ‘ContentDesc’ datastream in the Lesson objectincludes XML defining the title, grade level, overview, and otherrelated information. We also used this custom datastream for theNote object to include annotation content directly in the object. Inaddition, we employed this datastream in the Concept object to bothprovide the main text of that concept (e.g. ‘Volcanoes provideevidence for plate tectonics’) and to list the state science educationstandards related to that concept.Datastreams supported our implementation of relationships betweendata objects as well as an object’s reference to external data. Usingthe RELS-EXT datastream reserved by FEDORA to describerelationships between objects, we defined aggregation andconceptual relationships between data objects using ResourceDescription Framework (RDF) triples [15]. For example, theinclusion of a Lesson object within a particular Module is describedusing the ‘isMemberOf’ relationship between the Lesson and itsparent Module object. In order to relate a Resource object tometadata describing that resource in a digital library, we defined acustom datastream in the Resource object to include an externalreference to digital library metadata. In this manner, we utilize bothFEDORA’s built-in datastreams and our own custom datastreams tocapture curricular content as well as relationships between objects ofdifferent content models.Supporting the integration of different repository services (such assearch) with the underlying content in a data object, FEDORAallows repository developers to associate particular behaviors with agiven object. This form of behavior linking is accomplishedthrough the use of ‘disseminators’ which associate web-serviceswith each of the objects. We designed two main classes ofdisseminators to support the design requirements for the curriculumoverlay model that resulted from the studies described in Section 3.These requirements included supporting educators’ navigation ofrelationships between curriculum components and educators’querying across these relationships. Table 2 provides an overview ofthe disseminator classes: display and query. Supporting a defaultmechanism of displaying the content of an object, the ‘display’disseminators provide an overview of the content in the displayedobject and the relationships between this object and other objects.This default display facilitates an at-a-glance review of theassociated curricular content as well as hierarchical or conceptualrelationships between the displayed object and other objects. Forexample, the default display for a Lesson object shows the title,overview, and related information for that lesson as well as theActivities included within the lesson. We included a customdatastream to store a stylesheet used in generating this defaultdisplay.The query disseminators enable querying across relationshipsbetween objects representing components in the curriculum overlaymodel. The content models reviewed in Table 2 include customdatastreams which refer to the results of these disseminators. Thequeries for these disseminators can be characterized as including:queries about direct membership relationships (e.g. find all activitieswhich are a member of this lesson or find all activities of which thisresource is a member, find all resources which are part of thispersonal collection), queries traversing the aggregation hierarchy(e.g. provide the hierarchy for all the activities which utilize thisresource, returning activity, lesson, and module information), andqueries returning associated objects (e.g. find all concepts related tothis lesson, find all lessons which relate to this concept, find allnotes for this resource).For example, the disseminator GetModules for a Resource objectruns a query to select all modules that include lessons which haveactivities that employ this resource. The result of this disseminator isa list of Resource object identifiers and this list is accessible throughthe RelatedModules datastream.Figure 3 displays the relationships between data objects representingcomponents in the curriculum overlay model. For example, thefigure shows the Resource object is a member of two aggregationobjects: the Activity which embeds the resource and the personalCollection object. In addition, the Resource object is annotated by aNote object. This figure also shows the content models for theModule and the Resource objects which respectively constitute thehighest and lowest level in the aggregation hierarchy of objectswithin the Module. The fields marked ‘R’ represent the Dublin Coreand relationship datastreams that are automatically reserved in everyFEDORA object.Figure 3. Module and Resource Content Models.79The fields marked ‘C’ represent the custom datastreams which arespecific to the curriculum overlay model while the fields marked‘D’ represent the query and display disseminators. The customdatastream fields include the content or ‘ContentDesc’ datastreamand the datastreams which reference the results of the querydisseminators. For example, the three datastreams in the Moduleobject, ConceptsXML, LessonsXML, and ResourcesXML, includeresults of the GetConcepts, GetLessons, and GetResourcesdisseminators. These three disseminators execute queries identifyingrelated concepts, included lessons, and embedded resourcesrespectively. The DisplayOverview disseminator provides a defaultdisplay of the Module object using the Stylesheet datastream.Content models thus can capture the relationships between lessons,activities, educational resources, and science concepts, integratingdigital library metadata descriptions of educational resources andeducators’ own annotations of those resources. These contentmodels can provide a framework for the description of curriculum inorder to allow educators interacting with digital libraries to addexamples of curriculum using digital resources, include their ownextensions, and be able to search not just for resources but alsoexplore different pedagogical contexts of use of those resources.Furthermore, basic services and behaviors associated with thesecurricular components can provide default displays of thesecomponents. In the next section, we discuss the instantiation of thiscurriculum overlay model in the Teaching Box Builder application.5. TEACHING BOX BUILDERIn order to assess the validity of this curriculum overlay model, weinstantiated this model using a specific curriculum within aparticular application, called Teaching Box Builder, designed tosupport customization of curriculum using educational digitalresources. We explored whether the curriculum overlay model wassufficiently expressive to represent a section of the 2004 PlateTectonics Teaching Box curriculum and to support curriculumdevelopment and customization tasks identified as part of the studiesdescribed in the Teaching Box studies section. We implemented thecurriculum overlay model using content from the Plate TectonicsTeaching Box.As discussed in Section 3, our interface design studies and studieson the Teaching Box workshops yielded requirements for thecurriculum customization service operating on the curriculumoverlay model. These requirements, and our review of the literatureon educators’ curriculum planning and adaptation processes,informed the design of the Teaching Box Builder [11, 12, 13]. Therequirements for the Teaching Box Builder include support for: (a)the iterative elaboration and modification of Teaching Box contentincluding integration of search results into content, (b) the displayand modification of relationships between components of theTeaching Box curriculum, and (c) a personal collection of resourcesof potential interest.We designed the Teaching Box Builder architecture to be a threetieredarchitecture (see Figure 4) to provide separation between thecurriculum overlay model and other layers, providing the ability touse different interface layers interacting with the same underlyingcurriculum overlay model. The three layers are: Curriculum OverlayModel, Web Services, and Interface. This architecture employs aclient server model where the presentation layer (Interface) isseparated from the application logic (Web Services and API) andthe application model (the instantiation of the curriculum overlaymodel using Teaching Box content in FEDORA). This separationenables flexible configuration of the multiple layers.Figure 4. Teaching Box Builder Architecture OverviewThe Teaching Box content is modeled as separate yet relatedcomponents in the curriculum overlay model layer. Each of theTeaching Box components contains within it information thatdescribes the content and the pedagogical context for thatcomponent. For example, the Teaching Box component, which is aninstantiation of the Module component in the general curriculumoverlay model, includes information about teacher backgroundneeded to use this Teaching Box and the suggested grade level. Anactivity includes information about rationale for use of that activityas well as suggested procedures. Components can be associated witheach other and queries can then extract which components arerelated through specific relationships. For example, a Teaching Boxcan ‘know’ what lessons are included within it, what activities areincluded within those lessons, and which resources are employed inthe activities in those lessons. Components can also provideinformation about their relationships with other components throughthe use of disseminators. Finding annotations for a particularresource requires running a query which will return all annotationsfor a particular resource.Figures 5 shows an example of a Lesson object representing Lesson2 of the Volcanoes section of the Plate Tectonics Teaching Box.The figure shows the content model for this object and excerpts ofthe ConceptsXML and ContentDesc datastreams. ConceptsXML isan example of a datastream which refers to results of a querydisseminator which returns a SPARQL list of the concepts whichare related to this lesson. The excerpt shows the URIs of the conceptobjects within the repository. The excerpt of the ContentDescdatastream shows the XML description of the lesson content,including title, classroom time, and vocabulary.80Figure 5. Overview of Lesson Object.The Web Services layer provides access to the underlyingcurriculum overlay model and its implementation in FEDORA. Thislayer allows the execution of commands to store, retrieve, andmodify Teaching Box components and their relationships. WebServices enable the use of digital library services (such as DLESEsearch) and support the execution of remote procedures over theinternet. The Interface layer employs Web 2.0 technologies tosupport the streamlined delivery of the results of multiple queriesand tasks. For example, these technologies enable educators tosimultaneously view within the same page the results of a real-timesearch of a digital library and of a query returning the resourcesembedded within an activity. Traditional web pages would haveforced educators to reload the page for each these tasks, whereasWeb 2.0’s support for asynchronous transactions enables thesemultiple tasks to be carried out within the same page withoutreloading. In addition, Web 2.0 does not require the installation ofadditional plug-ins and thus allows easier deployment of TeachingBox Builder over the web for use by educators in schools.Figure 6 illustrates some of the design features which support therequirements for modifying component content, viewing andmodifying relationships between Teaching Box components, andmaintaining a personal collection. As an example illustrating howactivity customization can involve modifications to relationshipsand objects in the curriculum overlay model, imagine Susan is a 7thGrade Earth Science teacher who is in the process of reviewing andcustomizing an activity. The ‘Click to Edit’ link toggles betweenedit and ‘Click to Save’, allowing Susan to make in-line edits toactivity content and then commit these modifications. While she isediting the content, she can select the 'Search/Browse' action whichexpands the search/browse pane in the right side of the window.This pane consists of a search section in the top right which allowsFigure 6. Screenshot of Activity Customization page from Teaching Box Builder.81Susan to make real-time search queries to DLESE and a browsesection in the bottom right which displays Susan’s personalcollection of resources. Displaying resources from the personalcollection entails querying the repository for which Resources arepart of the Collection and then parsing the returned XML results todisplay title, url, and content from associated Note objects. If aresource from the search results or the personal collection appearsrelevant, this resource can be added to the activity. On the display,the title and url of the resource are automatically inserted into theactivity text. On the component model side, adding this resourceresults in the editing of the relationship between the Resource objectrepresenting the resource and the Activity object. If the resourcedoes not already exist in the repository, a new Resource object iscreated with a metadata datastream referring to the correct DLESEmetadata record. In addition, if the resource is not already in thepersonal collection, the Resource is added to the personal Collectionobject. The content model supports the creation of a Note objectdescribing educators’ reasoning or impressions about the usefulnessor relevance of a resource for a particular activity [11].This instantiation of the curriculum overlay model using DLESETeaching Box content successfully represented Teaching Boxcontent as separate yet related components where each componentcarries with it information about its suggested pedagogical context.The example above shows the model represents content andexpresses relationships in a manner facilitating the curriculumdevelopment and customization tasks supported by the TeachingBox Builder. Modeling the dependencies and relationships betweencomponents supports searching across these relationships as well asnotifying users whether a particular dependency is affected byadaptations of a particular component. For example, if a user adds anew concept to the list of concepts, this change may affect howlessons cover these concepts and subsequently which activities andresources they should employ to teach those concepts.6. CONCLUSIONSTackling questions of the design of sustainable inquiry-orientedcurriculum using educational digital resources, our researchexplored the use of curriculum overlay models to support digitallibrary contextualization services for educators. We used a humancentereddesign approach to design the curriculum overlay model,reviewing the results of longitudinal studies of educators’ TeachingBox development and of usability studies on prototypesrepresenting curricular content. We developed a curriculum overlaymodel that represents curriculum in the form of separate yet relatedcomponents and that supports a personal collection of resources andresource annotations describing the relevance of these resourceswith respect to a particular activity. In this paper, we described theimplementation of this curriculum overlay model using FEDORAcontent models.The Teaching Box Builder application, implemented usingFEDORA, modeled Teaching Box content using the curriculumoverlay model. In FEDORA versions prior to version 3.0 betarelease, content models were not supported programmatically butwere abstractions that allowed FEDORA developers to describe thetypes of content represented in the repository. Future work thusincludes utilizing FEDORA’s beta or future release’s content modelarchitecture to implement the curriculum overlay model using thedifferent object types and content models described above.Furthermore, our work with FEDORA utilized pre-existingrelationship types to define the relationships between components.By supporting simplicity, this research’ preliminary exploration intocontent model design for curriculum sought to build a basicrepresentation. Future work thus can focus on using the latestFEDORA release to create and implement a custom ontology thatcan be used to capture additional pedagogical relationships betweencomponents.We have demonstrated the validity of the curriculum overlay modelby instantiating this model using Teaching Box content. We haveyet to assess the utility of this model in the context of educators’customization of curriculum using services based on this model andthe generalizability of this model across different curricula. We planto assess the utility of the content model by conducting anevaluation study of the Teaching Box Builder application witheducators. Having the educators complete curriculum customizationtasks with the application and debriefing them after the completingof these tasks, we will examine the effectiveness of the curriculumoverlay model in capturing the content of curricular components andthe relationships between these components. To assess thegeneralizability of the curriculum overlay model, we will use thismodel to represent other inquiry-oriented science or math curricula.Modeling other curriculum using the content models for ourcurriculum overlay may lead to further extensions or refinement ofthe overlay model. Examining the utility and generalizability of thecurriculum overlay model may thus lead to new insights andopportunities for refining the model.Contextualization services, such as those we envision will employcurriculum overlay models, provide added value to digital librariesand educators in two ways: in enabling educators to find curriculumusing rich multi-media educational resources and to customize thiscurriculum to fit their local contexts, and in enabling educators toadd to the context describing pedagogical use of resources bysharing their annotations and their customizations of thiscurriculum. A possible avenue for future research is support forversioning of curriculum overlaid on educational resources,supporting provenance and information about the lineage ofparticular curriculum. Aligning with current work in OAI-ORE, thisresearch provides a basis for the exploration of the sharing andcustomization of compound objects representing curriculum acrossheterogeneous repositories. We hope that this research will lead tofurther exploration of contextualization services targeting educators’use of educational resources, benefiting not only educators butdigital libraries.7. ACKNOWLEDGMENTSThis work is funded in part by the National Science Foundationthrough NSF Awards 0622010 and 0428469.8. REFERENCES[1] American Association for the Advancement of Science(AAAS), Project 2061 (2000). 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