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IADIS International Conference WWW/Internet 2010Notice the results of the output list should be considered in inverted order, i.e., it is necessary to departfrom limit and finish on energy. This output list could suggest a sequence of concepts so that a user couldselect matching learning objects from LOM description (keyword) to each concept. From a semioticapproach, this implies that the composition and sequencing is done, so that the path extracted from ontologygraph is the form of content.We took the longest path ['energy', 'work', 'force', 'mass', 'acceleration', 'velocity', 'deriv', 'limit'] and askedthem to put the concepts in the order they think is the best way to be presented to the students. The results areshown in the Table 2.Table 2. Suggestions for sequencing learning objects as tested by physics teacherProfessor Energy Work Acceleration Velocity Limit Force DerivativeA7 6 4 3 1 5 2B 7 6 4 3 1 5 2C 6 7 4 3 1 5 2D 7 6 4 3 1 5 2It is also important to notice that the longest path ['energy', 'work', 'force', 'mass', 'acceleration', 'velocity','deriv', 'limit'] is really similar to the professors’ answer ['energy', 'work', 'force', 'acceleration', 'velocity','deriv', 'limit'], which demonstrates the proposed approach has a good result. A remarkable fact is that all theprofessors defined the same sequence and none included the concept ‘mass’. However, this fact does notseems to be of capital importance, since at graduate level, “mass” is a fundamental concept related to theinertial properties of the particle. Its deep meaning is worth discussing if gravitational or inertial propertieswould be discussed. The other paths were also considered valid by the professors although which is the bestalternative depends on the learning situation. In addition, as the discussion on which were the most adequateLOs for presenting each concept was divergent, we decided not to address such questions, but to investigatepossible reasons as future works6. CONCLUDING REMARKS AND FUTURE WORKSIn this paper we discussed some features of Learning Objects composition and sequencing assuming thatthese objects have some properties or characteristics similar to signs as studied in Semiotics. As anarrangement of signs, this composition shares some features with narrative structures, so that its form ofcontent is given by the ontology of the addressed KD.The ontology was modeled from the dependence relationships between concepts. Since ontologies can berepresented as directed graphs, paths can be defined in these graphs so that they can be interpreted as possiblesolutions for sequencing learning content to be explored in a class. For each concept in the path, somesuitable set of LOs can be assigned according to a specific learning strategy. This association between LOsand the concepts can be achieved by means of LOs descriptors that can be used to tentatively map to the mostadequate set of LO to explore some concepts according to the learning situation (learner’s characteristics,didactical and pedagogical aspects, technological restrictions etc.). Educational descriptors such asInteractivity Type, LearningResourceType, InteractivityLevel, and SemanticDensity as well as the physicalaspects (Format, Size, Location, Operating System or Browser requirements, InstallationRemarks andDuration) are media centric, and generally are closed packed, which demands additional work to decomposeand reuse them.An example was developed and the evaluation of the approach showed promising results. The ontologydeveloped for testing the approach aimed to represent the concepts and their relationships for an ElementaryClassical Mechanics sub domain. Four professors were considered to validate the sequence generated by theprototype.However, our proposal has some limitations. The first one comes from the fact that the selection of LOs isexecuted manually, however, from the use Semantic Web tools, such as SPARQL query language, selectioncould be done by means of the agent technology executing on LOM expressed in OWL DL. The secondlimitation is due to the fact that our model is a simplified one, do not encompassing other intrinsicrelationships among the concepts of a complex domain as Physics. The third limitation comes from the33