Engineering the life-cycle of semantic services-enhanced learning systems

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August 13, 2010 19:0 WSPC/117-IJSEKE - SPI-J111 0218-1940 00485

International Journal of Software Engineering1

and Knowledge Engineering2

Vol. 20, No. 4 (2010) 1–213

c© World Scientific Publishing Company4

DOI: 10.1142/S02181940100048525

ENGINEERING THE LIFE-CYCLE OF SEMANTIC6

SERVICES — ENHANCED LEARNING SYSTEMS7

ERNIE GHIGLIONE8

Macquarie E-Learning Centre of Excellence, Macquarie University9

Sydney, NSW 2109, Australia10

[email protected]

JUAN MANUEL DODERO12

Computer Languages and Systems Department, University of Cadiz13

Cadiz, 11001, Spain14

[email protected]

JORGE TORRES16

Distributed and Adaptive Systems Lab for Learning17

Technologies Development, Tecnologico de Monterrey18

Santiago de Queretaro, QRO 76130, Mexico19

[email protected]

Received21

Revised22

Accepted23

Service-oriented learning environments are the new paradigm for interoperability of24

learning management systems. They support a wider range of needs by integrating25

existing and emergent services, leading to an entirely new architectural design for such26

systems. The engineering life-cycle of resources and services can be enhanced and inte-27

grated in current and future virtual learning environments. This work defines a services-28

enhanced learning architecture and describes two levels of integration carried out to29

author, deploy and enact learning services from open web-based interaction protocols30

and semantic web service descriptions.31

Keywords: Semantic web services; virtual learning environments.32

1. Introduction33

Collaborative learning environments are the arena in which active, shared learning34

experiences are developed to involve students in reflecting on their own cognitive35

processes, facilitated and supported by other participants and learning resources36

[1]. The main components required to describe a learning experience should involve37

people and groups of people, engaged in a specific role, that systematically develop38

a number of learning activities. The flow of development of the learning activities39

1

http://dx.doi.org/10.1142/S0218194010004852

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2 E. Ghiglione, J. M. Dodero & J. Torres

can be structured in a pedagogically organized fashion, and supported by a set of1

resources and services.2

Learning experiences should be especially designed, made explicit using an Edu-3

cational Modeling Language (EML), and hosted in a Learning Management System4

(LMS) [2]. Major LMS are prepared to understand EML specifications by installing5

run-time engine extensions — such as CopperCore [3] or GRAIL [4] — that enable6

deploying and running collaborative learning experiences, based on the IMS Learn-7

ing Design (LD) specification. Other systems such as LAMS [5] define their own8

model for users, activities and resources to represent and host such relevant ele-9

ments of a learning experience. These systems are commonly used to deploy and10

execute web resources, applications and tools that keep an asymmetric relationship11

between users, i.e. the instructor produces a resource and the learner consumes12

it. The interoperability issue in such systems has been founded on the use of open13

e-learning standards [6], either based on individual learning contents (e.g. SCORM)14

or collaborative activities (e.g. IMS LD).15

In the search for interoperability, there is an emerging shift from such monolithic16

e-learning platforms towards supporting a wider range of needs by integrating exist-17

ing and emergent services [7,8]. This trend has lead to an entirely new architectural18

design for learning environments that is known as Personal Learning Environment19

(PLE). These are concerned with the practice of learners with external technolo-20

gies, focused on coordinating symmetric relationships between users and services,21

and based on open W3C standards [9].22

This work deals with how Internet-based services can be engineered for cur-23

rent LMS and future PLE. Henceforth we refer to both LMS and PLE as Virtual24

Learning Environment (VLE). The growth of freely available Internet-based services25

during recent years has impelled the demands to harness tailored versions of these26

services within current and future technology-enhanced learning systems. These ser-27

vices include web-based applications such as shared calendars, wikis, blogs, social28

software, and so forth. Service availability leads to implementing service-oriented29

VLE designs [7]. However, their complexity and variability still cause some issues30

for engineering authentic learning experiences, for which every activity must be31

provided with an assessment [10].32

Service-oriented systems architecture can be considered from an anatomical33

viewpoint, focused on how the learning system is cut down in parts so that its34

structure can be analyzed. On the other hand, a physiological viewpoint considers35

the functioning of the system. It is recognized that for an effective resource sharing36

and virtual community support, the physiological view is especially relevant [11].37

The contribution of this work is how a new anatomy for service-based learning sys-38

tems can enable the flexible engineering of new functionalities in a VLE. In our39

approach, users and activities are decoupled from learning services with the help40

of a mediating layer that contemplates a model of relevant features of services [12]41

and how to interact with them in a decoupled way. In particular, the provision of a42

configurable assessment service allows implementing authentic learning experiences43

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Engineering the Life-Cycle of Semantic Services — Enhanced Learning Systems 3

for any learning activity hosted in a VLE. The proposed service-oriented learn-1

ing architecture has been applied to the combination of the LAMS VLE and an2

implementation of learning assessment services called EvalComix.3

The rest of this paper is structured as follows: First we explain the life-cycle4

engineering issues of a learning service and the motivation of our work. Second,5

a semantic services-enhanced learning architecture is proposed, that focuses on6

how ontology-based learning services annotations support the integration of ser-7

vices throughout their life-cycle. After that, our contribution is evaluated by a case8

study showing how it is applied to existing VLE and learning assessment services.9

Finally, some related work is related on the integration of web services in virtual10

learning environments, along with some conclusions of this work.11

2. Learning Services Life-Cycle: Issues and Motivation12

The engineering life-cycle that must occur before running a collaborative learn-13

ing experience consists of three main phases, namely authoring, deployment and14

enactment [4]. Authoring tasks involve creating courses such as packaged struc-15

tures that hold descriptions for all required activities, resources and services. After16

that, the objective of deployment is that all course elements are properly allocated17

on the VLE, i.e. to prepare learning resources, activities and services, based upon18

the desired flow of activities, and populate the roles defined in the course with the19

actual participants in the learning experience. Finally, enactment begins when users20

have to start interacting with the available resources and services provided in the21

activities.22

The main issue of engineering internet-based services in a collaborative learning23

experience is how these can be seamlessly integrated with the basic components24

of the environment, i.e. activities and user roles. Services may include web-based25

applications that were not designed in principle for an educational purpose. Ques-26

tions about the flexibility of the integration of such learning services can emerge in27

all phases of the engineering life-cycle:28

• On the authoring phase, learning services cannot be packaged and distributed as29

easily as traditional learning resources. The use of existing frameworks and lan-30

guages, such as Web Service Description Language (WSDL) or Web Application31

Description Language (WADL), explicitly document the interface of the opera-32

tions provided by the service. However, if the interface changes or evolves and33

the implementation of activities is not flexible enough, the learning experience34

should be re-engineered from the beginning.35

• In an actual learning environment, a change in services introduced during author-36

ing may have a severe impact on the deployment phase. For instance, when deploy-37

ing an activity, if a required service is not available, some adjustments are needed38

on the VLE to replace the service by another one equivalent (e.g. to replace an39

unavailable videoconferencing service with a chat).40

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• During the enactment stage, users can access all learning resources and services1

via the set of deployed learning activities. However, when dealing with an external2

service, the VLE has to configure information that is not included as part of the3

course. For example, let us consider a learning experience that divides the students4

in groups and requires each group to have a form to exploit a service for group-5

based assessment and reporting. The overall number of users and user groups6

that will take part in the learning experience is not known until deployment,7

when the number of instances of the assessment service must be actually created8

and assigned to the learning activities.9

From a pedagogical perspective, collaborative learning environments provide10

authentic learning experiences as long as every activity is provided with an assess-11

ment [10]. Learning-oriented assessment is focused on assessment tasks as a means of12

self-diagnosing a student’s learning activities, in order to empower him for learning13

in a more effective and autonomous learning [13], as required by modern learning14

environments. Assessment sets up a difference between business processes that are15

based upon regular work flow systems and technology-enhanced learning flows and16

learning processes [14]. It also makes a difference between a general purpose web17

service and another that is specially intended to support a learning experience.18

All learning activities that are implemented through external services (i.e. out of19

the VLE control) should be subject to learning assessments. Therefore, all interac-20

tion and events occurring among an activity and its service implementation must be21

acknowledged, controlled and tracked by the VLE. However, if the learning activity22

yields control to an external service, the VLE will be able to find out what hap-23

pened during the interaction with the service as long as it is explicitly coded as part24

of the activity implementation. This raises again the flexibility issue of the service25

engineering process, but this time concerning authoring, deployment and enactment26

of assessments that are linked to the activities.27

When the learning service model is shared, the client activities are more tightly28

coupled [15]. A change on the service side can provoke undesired changes on a29

coupled implementation of activities. For that reason, the raw API-based integration30

of learning services needs to be enhanced. It means that activities must be aware31

of details of the service API so that explicit calls to service operations have to be32

included in the implementation of activities.33

3. Semantic Services-Enhanced Learning34

In distributed and changing environments, such as new LMS or PLEs, the pro-35

vision and integration of service components is a challenge. A semantic service-36

oriented architecture is presented that meets the flexibility of engineering life-cycle,37

as required by new service-oriented VLEs. Our approach stresses both the protocol-38

oriented description of the anatomy of a services-enhanced learning system, and39

the semantically enhanced physiology of those functionalities that learning services40

can provide to the VLE. The proposed solution ensures a seamless combination of41

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services with learning activities through a learning services ontology that ensures1

the independence of the VLE that hosts the learning experience.2

3.1. Service design principles3

With the aim of supporting the complete life-cycle of service-oriented VLEs, we4

applied the following principles to the design of a Services-Enhanced Learning Archi-5

tecture (SELA):6

(i) Define the Application Programming Interface (API) of services as simple as7

possible.8

(ii) Separate user and role management from service implementations.9

(iii) Decouple as much as possible the service descriptions from the client applica-10

tions (i.e. the VLE) that consume them.11

These design principles will support an enhanced flexibility of learning service12

authoring, deployment and enactment. They describe protocol-oriented issues that13

support the anatomy of the service-oriented VLE. The design principles are aimed14

at decoupling the elements managed by the VLE from the management of learning15

services. Over them we have built a semantic model that integrates in the VLE16

physiology the required functionalities provided by external services.17

3.2. Services-enhanced learning architecture18

The anatomy of SELA is depicted in Fig. 1. Its main components enable to seam-19

lessly connect and interoperate learning activities and services through the following20

layers:21

The LMS interoperability layer is used to plug-in a specific LMS — e.g. LAMS22

or an IMS-LD runtime engine — that can manage learning activities. The VLE23

Fig. 1. Layer structure of the services-enhanced learning architecture.

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provides user and activity management and the interoperability component connects1

them to learning resources and services.2

The Web Service Access (WS-Access) API defines the service operations allowed3

to be issued from the VLE or VLE-managed learning activity. Service interfaces can4

be specified using WSDL or WADL. The WS-Access API could be used to directly5

hard-code the requests to available services as part of the implementation of a VLE-6

managed activity — i.e., to skip the SEE and SWS layers. Nevertheless, this is not7

sufficient to promote interoperability among the VLE and services, since it would8

be difficult to overcome the issues described above.9

The Service Enactment and Execution (SEE) server is used to manage the learn-10

ing services life-cycle and issue service calls to the right learning services. It is11

provided with a formal description of learning processes called LPCEL (Learning12

Process Composition and Execution Language) that includes the modeling of user13

roles, learning activities and services.14

Although the VLE can delegate partially the management of activities to the15

SEE server, this work deals only with the management of services lifecycle. On16

the run time, the SEE layer also provides the service information model needed to17

transform all user interactions that happen on the activities’ user interface into real18

service calls. The mapping between the SEE server and actual learning services is19

based on augmenting the service APIs with RDF annotations that facilitate the20

automated generation of the activities’ user interfaces and service composition.21

The User Interface Generator (UIG) component provides activities with a22

generic user interface to exploit the service. The UIG component uses as input the23

WSDL/WADL service specification to generate a ready-to-use generic user interface24

to consume the service.25

The semantic meta-model of RDF annotations are grounded on an ontological26

combination of the LPCEL information model and the service description model.27

The LPCEL information model is used to specify learning processes including activ-28

ity structures, user roles, groups, restrictions, scenarios, contents, services, assess-29

ments and other learning resources, which can interact to achieve a set of learning30

objectives [16]. Since learning activities are not performed in an anarchic way, it is31

necessary to orchestrate and control the flow of activities in a learning process for32

every participant user role.33

The Semantic Web Services (SWS) layer maps the execution of activities to34

actual service calls. It is provided with an extended semantic model of specific35

services to be exploited in the learning activities, such as assessment, project man-36

agement or collaborative work services. When the SWS layer operates, interfaces37

generated by UIG can be enhanced with more usable interfaces, since the latter38

knows the type and semantics of the inputs to and outputs from service operations.39

Finally, the Learning Services Bus (LSB) layer brings together all available ser-40

vices, independently of their location. Figure 1 depicts some types of services, such41

as: WS-TestMobile (an implementation of IMS QTI for mobile environments); WS-42

Wiki (a web service-based implementation of a wiki); WS-Project (a web service43

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interface to the Trac project tracking system); and WS-Assessment (an extensible1

service implementation of regular competence assessment instruments, such as con-2

trol lists, rubrics, and so forth). WS-Assessment instances are especially relevant,3

since they must be coordinated with the rest of services, independently of their kind,4

to implement real learning experiences that are founded on evaluation practices.5

3.3. Learning service ontology6

External services are integrated within activities of a learning experience by the7

semantic description of services at two levels. The first level is called Learning8

Service Ontology (LSO), which serves to portray general issues concerning service9

access the LSB; the second level is called Specific Service Ontology (SSO), which10

describes each service facility that is useful for any learning activity specific purpose.11

The flow control of learning activities is beyond the scope of this paper and12

is discussed in more detail elsewhere [17]. The LPCEL model defines a number of13

components needed to describe a learning experience, including learning objectives,14

outcomes, composite activities, resources, services and user roles. Since or goal deals15

with the services life-cycle, we stress on the part of LPCEL (see Fig. 2) that deals16

with resources and services integration. The model has been used as the basis to17

define The LPCEL LSO, from which an excerpt is shown next:18

@prefix: <http://example.org/lpcel.owl{\#}> .19

<http://example.org/lpcel.owl>20

rdf:type owl:Ontology .21

:ComponentActivity22

rdf:type rdfs:Class .23

:LearningActivity24

rdf:type rdfs:Class ;25

rdfs:subClassOf :ComponentActivity .26

:AssessmentActivity27


rdfs:subClassOf :ComponentActivity .29

:LearningService30


rdfs:subClassOf :Resource .32

:Service33

rdf:type :LearningService .34

:ServiceType35


:AssessmentServiceType37

rdf:type :ServiceType .38

:WebServiceClient39

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:UserInterfacePage1


:inputPage3

rdf:type owl:ObjectProperty ;4

rdfs:domain :WebServiceClient ;5

rdfs:range :UserInterfacePage .6

:resultsPage7


rdfs:domain :WebServiceClient ;9

rdfs:range :UserInterfacePage .10

:AccessMethod11


:RPCBasedAccess13


rdfs:subClassOf :RemoteAccess .15

:WebServiceDefinition16


In the LPCEL LSO, a ComponentActivity can be of one of three types:18

LearningActivity for describing activities that involve a specific learning objective;19

AssessmentActivity for activities that are extended with an evaluation of the learn-20

ing objective fulfillment; and ContextActivity for activities that do not involve21

learning but are needed to complete successfully a learning experience in which22

other activities are involved. A ComponentActivity can include the specification23

of several Resources to be harnessed during the activity execution. These can rep-24

resent local resources (e.g. SCORM contents) or remote applications (e.g. project25

repositories, virtual labs, simulators, or collaborative work tools). A specific kind of26

remote resources are RPC-based applications, which can be reached by a Service-27

Bus. The LSB puts together a number of services generally described by WSDL or28

WADL specification. Such services are represented in the LPCEL by the Interface29

element. An interface describes a learning service of one Type — e.g. assessment,30

collaborative writing, project management, and so forth. The Type element is used31

to select a specific learning service, whilst the Interface element is used to actually32

connect the LSO with the SSO.33

If a service is of type AssessmentServiceType, the LSO is connected with the SSO34

of an assessment service called EvalComix [18] for which we provide an assessment-35

specific ontology. EvalComix is the implementation of a general-purpose assessment36

service that allows authoring, deploying and enacting competence assessment instru-37

ments, such as control lists, rubrics, and so forth. EvalComix service is designed to38

fulfill the first two principles explained above through a decoupled design of the39

protocols that enable the interoperation of activities and services [19].40

The third design principle is put into practice through SA-REST semantic41

annotations [20] defined on the EvalComix SSO. This ontology is used to describe42

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August 13, 2010 19:0 WSPC/117-IJSEKE - SPI-J111 0218-194000485


different types of assessment instruments (e.g. rubrics and control lists) and their1

assessment values, as described next:2

@prefix: <http://example.org/evalcomix.owl #> .3

<http://example.org/evalcomix.owl>4

rdf:type owl:Ontology .5

:Instrument6


:AssessmentValues8


:InstrumentType10


:Rubric12


rdfs:subClassOf rdfs:InstrumentType .14

:ControlList15


rdfs:subClassOf rdfs:InstrumentType .17

:RubricAssessmentValues18


rdfs:subClassOf rdfs:AssessmentValues .20

:ControlListAssessmentValues21


rdfs:subClassOf rdfs:AssessmentValues .23

:publicId24

rdf:type rdfs:Property ;25

rdfs:domain :Instrument ;26

rdfs:range rdfs:Literal .27

:title28




:type32



rdfs:range :InstrumentType .35

:description36




:assessmenValues40



rdfs:range rdfs:Collection .43

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3.4. Authoring interface for learning services1

The web services of the LSB are actually exploitable as long as an authoring inter-2

face is provided to the VLE. This section explains how the SELA ensures the3

exploitation of LSB services by providing the user interface needed to consume4

service operations. From the WSDL or WADL service specification, the SELA UIG5

component can generate a general-purpose interface based on web forms. However,6

such general-purpose forms can be replaced by enhanced interfaces that exploit the7

service in a more usable fashion.8

In particular, the user interface component for exploiting a learning assessment9

service is especially improved by the EvalComix authoring facilities. Such instru-10

ments enable creating adaptable instruments to assess all types of learning activities.11

The authoring service allows for extensions or additions of new types of instruments12

to the assessment service. The structure of every instrument is completely editable.13

It allows for the creation of dimensions to gather new assessment attributes or fields14

having features in common. Each field can be graded in a canonic scale that can15

be mapped to other grading schemes as required by the VLE. Besides, such fields16

can be weighted to adjust the relevance of each attribute for the overall evaluation.17

Nonetheless, some pre-defined assessment types of assessment instrument have been18

provided, including the following:19

• Control lists allow checking if qualitative evaluation criteria are properly fulfilled.20

• Value lists are used to provide quantitative values to a list of evaluation criteria.21

• Control +value lists are a combination of a control list and a value list. This type22

of instrument allows to check if the evaluation criteria are fulfilled and to provide23

each one with an assessment value.24

• Rubrics are structured instruments used to transform qualitative perceptions for25

a set of evaluation criteria into qualitative or quantitative assessment value sets.26

• Decision matrices are used to evaluate by selecting among a number of assessment27

choices, all of them equally relevant.28

• Mixed instruments are the combination of a number of instruments that can be29

structured on nested, weighted levels.30

Figure 3 depicts how a control list assessment instrument is edited with the31

authoring interface service provided by EvalComix. Such facilities are provided as32

part of the web-based implementation of the service, as described below.33

4. LAMS and EvalComix Service Integration34

Learning experiences require a loose coupling between the learning activities hosted35

in the VLE and their supporting services. This section describes how to achieve36

a flexible, decoupled integration of a VLE and learning services via a case study37

designed in two levels. The first level is known as raw integration, in which the archi-38

tectural style of Representational State Transfer or ReST [21] is followed to design,39

deploy and enact learning assessment services from a LAMS learning activity. In the40

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Fig. 3. EvalComix user interface delivered for editing an assessment instrument of type control list.

second level, known as semantic integration, the SELA approach is applied to inte-1

grate a set of assessment services in learning activities. That shows how an external2

service can be further decoupled from the VLE, which then does not need to be so3

aware of the service API as to hard-code it in the implementation of activities.4

4.1. Raw integration of learning services5

The first integration level deals with protocol-oriented issues involved in the inter-6

action with the learning service. In this level, the allowed interactions between7

activities and services are available by providing activities with special-purpose8

user interfaces that enable accessing learning service functionalities. Although facil-9

ities of the semantic layer are not harnessed yet, the approach can still be useful10

to decouple users and services, since the VLE that manages users can also manage11

the user-activity mapping with a disregard for activity-service mapping.12

A ReST-based architectural style has been used to achieve the raw integration13

of services into LAMS activities. For that aim, ReST provides an explicit, resource-14

based representation of the service operational model that is exchanged with the15

activities. LAMS activities are free to use this model for their implementation, but16

also to map it to an appropriate internal model that can be exploited from the user17

interface of the activity.18

In the LAMS VLE, activity evaluations are implemented as a LAMS core ser-19

vice. LAMS core services are available for use by all activity tools requiring minimal20

coding efforts for a tool developer. The Eval Svc core service is the LAMS imple-21

mentation of SELA interoperability component, ready to interact with the API22

WS-Access of the assessment service. It acts as an abstraction layer between LAMS23

activity tools and EvalComix service API.24

(1) Authoring: As the teacher created the content for an activity tool, she can25

choose to create an evaluation instrument. The LAMS core service then creates26

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a new instance of evaluation and passes the request to EvalComix to return its1

interactive flash authoring interface for the teacher to create the instrument.2

Once the teacher has created the evaluation, upon save, the instrument is stored3

in EvalComix and the instance identifier is returned to the LAMS core service4

as reference (see Fig. 4).5

(2) Deployment: After a student or a group of students complete an activity, then6

the teacher or tutor evaluates the work using the authored instrument. The7

evaluation instruments can be deployed individually or for the whole group,8

depending on the assessment procedure defined by the activity, as shown in9

Fig. 5. We remind that users and user groups are known and managed by LAMS,10

Fig. 4. UML sequence diagram showing how a teacher requests the ReST-based EvalComix serviceto create a new assessment instrument through LAMS core services.

Fig. 5. UML sequence diagram showing how a teacher completes the assessment of a student’swork by requesting the EvalComix service for an instance of the evaluation instrument that waspreviously created.

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and not by the learning service, as stated in the second design principle.1

This procedure facilitates deploying self-assessments or peer assessments among2

students as readily as traditional teacher-based evaluations, since the LAMS3

Eval Svc (i.e. the VLE) manages the activities and knows which users have to4

execute them.5

(3) Enactment: Both teachers and students can complete the assessment forms that6

are delivered to them by LAMS. In Fig. 5, when the instrument is delivered for7

self-assessment, the student is also able to submit her own assessment values,8

according to the assessment interface of EvalComix.9

The integration described so far is simple, scalable, and allows for open integra-10

tion, fine-grained access control and user interface decoupling. Besides, LAMS core11

services mediate all user interactions with the assessment service. That enables the12

VLE to track and log all completed evaluations. However, since the learning assess-13

ment service model is shared, this model makes client activities tightly coupled. A14

change on a service interface, or its replacement by another functionally equivalent,15

can provoke undesired changes on a coupled implementation of activities. For that16

reason, the solution presented so far is enhanced, as described in the next section.17

4.2. Semantic integration of learning services18

This level of integration aims at decoupling further the VLE and the learning ser-19

vices, as required by the third design principle. Semantic integration is enabled by20

the SELA SWS layer. It has been tested on the EvalComix assessment service. The21

VLE and learning service models are integrated on the basis of LPCEL LSO and22

EvalComix SSO.23

The integration process is done in several steps. First, each LAMS activity is24

described based on the LPCEL LSO. For instance, the following is an RDF Turtle25

specification of a learning activity that has to be prepared to include an evaluation.26

@prefix: http://example.org/lpcel .27

<http://example.com/activity/11242>28

:identifier ‘‘11242’’ ;29

:title ‘‘Self-assessment activity’’@en ;30

:type :AssessmentActivity31

:description ‘‘This activity is used to...’’@en32

:parent <http://example.com/activity/11241> ;33

Second, the service is described by the assessment SSO. For instance, the fol-34

lowing specification describes a control list instrument, based on the EvalComix35

SSO:36

@prefix: http://example.org/evalcomix .37

<http://example.com/instrument/123456789>38

:identifier ‘‘123456789’’ ;39

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:type ‘‘ControlList’’^^:InstrumentType ;1

:title ‘‘Evaluation instrument No. 1’’@en ;2

:title ‘‘Instrumento de evaluacion no 1’’@es ;3

:description ‘‘This control list is used to evaluate...’’@en4

:description ‘‘Esta lista de control sirve para evaluar...’’@es5

Third, the SWS layer maps the required assessment service to an actual service6

that is available through the LSB. The mapping must resolve the three phases of7

the service life-cycle, i.e. authoring, deployment and enactment.8

(1) Authoring: The following XHTML specification for a Create service operation9

is annotated with SA-REST to describe how an activity can apply for the author-10

ing facilities of the service and request an interface to design a new assessment11

instrument of a given type:12

13

<meta property=’’sarest:operation’’ content=14

‘‘http://example.com/evalcomix.owl # InstrumentAuthoring’’/>15

<meta property=’’sarest:lifting’’16

content=‘‘http://evalcomix.uca.es/api/lifting.xsl’’/>17

<meta property=’’sarest:lowering’’18

content=‘‘http://evalcomix.uca.es/api/lowering.xsl’’ />19

The logical input of this service is an20

21

http://example.com/lpcel.owl # ServiceType22

23

object. The logical output of this service is an24

25

http://example.com/lpcel.owl # UserInterfacePage26

27

object.28

This service should be invoked using an29

30

HTTP GET31

32

33

Lifting schema mappings transform XHTML annotations to a semantic model of34

the service (e.g. RDF instances of the EvalComix SSO), whereas lowering mappings35

transform data from that semantic model into an XML structure that is consumable36

by the applicant activity [22].37

(2) Deployment: After creating the assessment instrument, the VLE that hosts the38

activity can deploy as many service instances as required for the number of users or39

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user groups involved. For that, the VLE can call the New operation of the learning1

service with the required parameters as described next:2

3


‘‘http://example.com/evalcomix.owl # NewInstrument’’/>5




content=‘‘http://evalcomix.uca.es/api/lowering.xsl’’/>9



http://example.com/evalcomix.owl # InstrumentIdentifier12

13

object. The logical output of this service is a14


http://example.com/evalcomix.owl # Instrument16

17

object.18



HTTP GET21

22

23

(3) Enactment: the service enactment phase is not shown in this case since it is inter-24

nally managed by the VLE, which maps users’ and instrument identifiers. Should the25

VLE not manage users or user groups, enactment should be managed by an exter-26

nal server exploiting an additional service (e.g. http://example.com/assessment/27

assign/) that receives as input the assessment and users’ identifiers, and associates28

the instrument to each user or group of users.29

Finally, the service can be exploited by the activity. The following describes the30

functionality of the Grade operation of the service, to be called whenever the VLE31

decides it.32

33


‘‘http://example.com/evalcomix.owl # Grade’’/>35




content=‘‘http://evalcomix.uca.es/api/lowering.xsl’’/>39

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http://example.com/evalcomix.owl # AssessmentValues1

2

object. The logical output of this service is a3


http://example.com/evalcomix.owl # Grade5

6

object.7



HTTP GET10

11

12

One advantage of this approach is that there is no need to hard-code the user13

interaction with the service in the activity. Instead the learning activity VLE man-14

ager can locate, replace or extend the learning service as semantically described by15

the SWS layer of SELA. Furthermore, the user interface generation can be improved16

by semantic annotations after the enactment phase. For instance, an improved user17

interface specially prepared for completing an assessment can be generated from18

SSO annotations of the previous example, since now the Grade operation is known19

to require an evalcomix:AssessmentValues type of input.20

If the service API changes, we only need to provide a new SA-REST specification21

of the service. From this specification, the SEE server can issue calls according to the22

new service interface. Since the user interface to consume the service is generated23

by the UIG, the VLE and their contained activities are not affected by the change24

on the service.25

5. Related Work26

The problem of integrating services in a learning experience has been thoroughly27

studied by the technology-enhanced learning community. First proposals were made28

on the bosom of the IMS Learning Design specification, which defines a set of roles29

to be played by users in groups to engage in learning activities using an environment30

with the required resources and services [23]. IMS LD-based CopperCore Service31

Integration (CCSI) [3] considers learning services as a type of functional concept32

supporting a user in the learning process. CCSI implements a run-time service that33

provides an API for interacting with e-learning applications, as part of the ELF34

e-learning framework (www.elframework.org). Although it provides the required35

service functionality, the life-cycle of a new service is very time consuming and not36

suitable for the integration of many different services. The tight coupling between an37

IMS LD-enabled VLE and the service does not allow an efficient creation and deploy-38

ment of learning experiences. Other generic approaches have defined an interaction39

protocol for information exchange among courses and services, but are especially40

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August 13, 2010 19:0 WSPC/117-IJSEKE - SPI-J111 0218-194000485


committed to the IMS LD specification [4]. Aside from IMS LD, other approaches1

to service-oriented architectures for learning have been proposed [7, 24, 25].2

All analyzed approaches fall out when having to deal with authoring of learning3

services. A review of authoring issues can be found elsewhere [26, 27]. All of them4

complain about the difficulty of editing and adapting activities and resources. When5

such resources are also web services, the procedure has been extended by import-6

ing XML-based service specifications [8]. The latter approach delivers IMS Con-7

tent Packaging (CP) specifications of courses, which are thought for self-contained8

course contents that are seldom liable to changes. However, a learning service can9

change and evolve, either by altering its interface or replacing the whole service by10

another.11

Wilson [28] and the TENCompetence project [29] have explored the provision of12

widgets or small applications as a way to include service-based external functional-13

ity in a VLE. Learning environments that are based on the combination of widgets14

(known as mashups) [30] are recently accepted to build up PLEs for informal learn-15

ing. Widgets unify all functions required by the VLE/services integration in a single16

widget management component that must be installed in the LMS. The approach17

is simple and powerful enough, but precludes a solution to manage the learning ser-18

vices life-cycle that does not involve re-engineering the complete widget. Besides,19

current VLE implementations are not aware of widget-based extensions and do not20

expose a fine-grained control over learning services.21

At a more abstract level, the IMS Tools Interoperability specification (www.22

imsglobal.org/ti/) provides guidelines to integrate third party tools in a traditional23

LMS. But the emerging trend in web-based learning scenarios is toward orches-24

trating the functionalities and services provided by multiple sources, instead of25

unrealistically requiring all these services to be present in the LMS. The variety of26

Internet-based service functionalities make interoperability difficult to approach by27

simply providing a function-oriented API, such as the Open Knowledge Initiative28

(www.okiproject.org) or the IMS Abstract Framework (www.imsglobal.org/af/).29

Function-orientation involves the function-based access to a model of the service30

provider that is often not exposed but assumed to be shared by all learning activi-31

ties that require such services. The resource-oriented ReST API [19] and the loosely32

coupled architecture described in this work enhances the flexibility of service man-33

agement by keeping the connection between the VLE and learning services as simple34

and decoupled as possible.35

Ontologies and semantic web services have been thoroughly used in e-learning,36

among other things, to provide a richer framework for the expression of learning37

object metadata [31], to formally describe teaching processes and learning designs38

[32–34], to rank and match the web services that better adapt to a learning sce-39

nario [35] or enable selecting an educational offer [36]. Future challenges of the40

semantic web in education have to do with the social web [37]. In general, semantic41

web services are suited to build more loosely coupled systems that improve their42

modularity, interoperability and extensibility [38].43

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6. Conclusions1

Engineering a collaborative learning experience involves a development life-cycle2

consisting of (1) authoring the learning activities, resources and services; (2) deploy-3

ment of such elements on a virtual learning environment by assigning them to the4

participants; and (3) enactment of the course to start interacting with available5

resources and services. The main issue of engineering internet-based services in6

such collaborative learning experiences is how these can be seamlessly integrated7

with the rest of the components of the learning environment in order to describe8

authentic, assessment-oriented learning experiences.9

This work relates a services-enhanced learning architecture that allows integrat-10

ing web services in the learning environment in a decoupled manner. Integration is11

accomplished in two levels across all phases of the service life-cycle. First level of12

integration makes the learning environment to have visibility on inbound learning13

resources through the service ReST-based API. Second level of integration is based14

on the provision of generic plus specific learning service ontologies that enable the15

learning environment to manage the service life-cycle in a more decoupled fashion.16

As further work, we aim at extending the SELA approach and its semantic model to17

integrate and engineer other types of web services to support advanced pedagogical18

strategies, such as web-based project management applications for project-based19

learning, and wikis for collaborative learning environments.20

Acknowledgments21

Research of this work is partly funded by the ASCETA Project of the Government22

of Andalucıa, Spain (ref. PR09-TIC-5230).23

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Engineering the life-cycle of semantic services-enhanced learning systems

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