ARTICLE N PRESS C-S. Wang, H.-L Yang/ Expert Systems with Applications xxx(2011)xXx-XXX 一c=03 C=03 C=05 35 Generations (a)M=0.01 Fig. 13. Convergence of different parameter combinations in Experiment 1 domain knowledge and the certification she obtained. The connec- apparently requires another career plan, so she could decide to tion between domain knowledge and IT certification, furthermore, work toward PMP certification. The applications constraints, how- represents the domain knowledge she needed to pass the certifica- ever, warned her that she was not qualified to take the PmP exam, tion exam. The recommendation mechanism also offered a as the project management institution s regulations stipulate that sequence of two Ir certification exams in case she wanted the sys- all examinees must attend at least 30 h of training classes at an tem to provide her with IT certification planning advice in two approved institution. She therefore must decide whether to work to fulfill this requirement or apply for some other certification. The system therefore recommended that she obtain the Project From a lifelong learning perspective, recommending a series of Management Professional (PMP)certification first because it related IT certifications to learners would enable them to feel con- required no further preparation, followed by the Oracle OCA 10 g. fident that their career planning will match their expectations. Pro- which is an OCA 9i upgrade that requires more feature-domain viding them with a choice of a series of certification paths could knowledge in addition to that of the 10 g, and the oracle OCP 9i, also increase their confidence about their upcoming certification hich is another advanced dBa certification requiring further examinations. domain knowledge. The multi-path mechanism arranged the prior ities for the certification paths based on their domain knowledge 5. conclusions coverage. Fig 14 shows the eight learning paths to which the sys- tem referred her. These are: OCP 91-0CA 10 g OCP 9i→PMP.{OCA10g→ocP10g.{OcA10g→PMP.OCP9 This study has proposed an HCA method for describing compli- OCA 10 g-OCP 10 g]. OCP9i, OCA10 g- PMP), OCA 9i (if failed, cated real-world decision-making problems. Its problem descrip- test again)+OCA 9i], [OCA 10 g (if failed, test again)-oCa decisions systematically. HCA is, furthermore, a generalized prob- She therefore had to consider whether she wished to become a lem-representation methodology that subsumes the traditional fessional DBA, for which an Oracle database certification would method of describing multiple-objective problems. This pape has also proposed the next generation case-based recommender be suitable, or to extend her career's scope, as project management mechanism GCBR for solving HCA problems. GCBR retrieves feasi- ble cases for reference and then applies the KDd mechanism to provide decision makers with refined information upon which to Microsoft win2000 configuration take action Microsoft system security administration Interconnecting Cisco Device This study then found that GCBR can be implemented with a GA algorithm to accelerate the convergence of complex problems that DBA Foundation Il Microsoft win2000 installation its convergence rate is satisfactory, and that in the experimenta Microsoft soL server Oracle 10g case it reduced effort by approximately 80% from that of traditional CBR. It can also provide solutions for problems with multiple BA Foundation H DB Performance Tu working infrastructure PMP 3rd stages. This study's hypothetical scenario illustrated that using it as an IT certification recommender can provide learners with a s ies of IT a certification path that enables them to feel confident that their career planning will match their expectations. These charac CCNA OCP 9i teristics enable decision makers to apply the GCBr algorithm as a general case-based recommendation mechanism. The quality of each case obviously limits what case-based ommender mechanisms can do, so future studies need to address the problem of case cleaning. Other studies need to consider more real-world applications for the algorithm and user satisfaction Please cite this article in press as: Wang, C-S, Yang. H.-L A recommender mechanism based on case-based reasoning Expert Systems with Applicatior (201).do1010160eswa201109.161domain knowledge and the certification she obtained. The connec￾tion between domain knowledge and IT certification, furthermore, represents the domain knowledge she needed to pass the certifica￾tion exam. The recommendation mechanism also offered a sequence of two IT certification exams in case she wanted the sys￾tem to provide her with IT certification planning advice in two stages. The system therefore recommended that she obtain the Project Management Professional (PMP) certification first because it required no further preparation, followed by the Oracle OCA 10 g, which is an OCA 9i upgrade that requires more feature-domain knowledge in addition to that of the 10 g, and the Oracle OCP 9i, which is another advanced DBA certification requiring further domain knowledge. The multi-path mechanism arranged the prior￾ities for the certification paths based on their domain knowledge coverage. Fig. 14 shows the eight learning paths to which the sys￾tem referred her. These are: {{OCP 9i ? OCA 10 g}, {OCP 9i ? PMP}, {OCA 10 g ? OCP 10 g}, {OCA 10 g ? PMP}, {OCP 9i, OCA 10 g ? OCP 10 g}, {OCP9i, OCA10 g ? PMP}, {OCA 9i (if failed, test again) ? OCA 9i}, {OCA 10 g (if failed, test again) ? OCA 10 g}}. She therefore had to consider whether she wished to become a professional DBA, for which an Oracle database certification would be suitable, or to extend her career’s scope, as project management apparently requires another career plan, so she could decide to work toward PMP certification. The application’s constraints, how￾ever, warned her that she was not qualified to take the PMP exam, as the project management institution’s regulations stipulate that all examinees must attend at least 30 h of training classes at an approved institution. She therefore must decide whether to work to fulfill this requirement or apply for some other certification. From a lifelong learning perspective, recommending a series of related IT certifications to learners would enable them to feel con- fident that their career planning will match their expectations. Pro￾viding them with a choice of a series of certification paths could also increase their confidence about their upcoming certification examinations. 5. Conclusions This study has proposed an HCA method for describing compli￾cated real-world decision-making problems. Its problem descrip￾tions enable decision makers to clarify problems requiring decisions systematically. HCA is, furthermore, a generalized prob￾lem-representation methodology that subsumes the traditional method of describing multiple-objective problems. This paper has also proposed the next generation case-based recommender mechanism GCBR for solving HCA problems. GCBR retrieves feasi￾ble cases for reference and then applies the KDD mechanism to provide decision makers with refined information upon which to take action. This study then found that GCBR can be implemented with a GA algorithm to accelerate the convergence of complex problems that its convergence rate is satisfactory, and that in the experimental case it reduced effort by approximately 80% from that of traditional CBR. It can also provide solutions for problems with multiple stages. This study’s hypothetical scenario illustrated that using it as an IT certification recommender can provide learners with a ser￾ies of IT a certification path that enables them to feel confident that their career planning will match their expectations. These charac￾teristics enable decision makers to apply the GCBR algorithm as a general case-based recommendation mechanism. The quality of each case obviously limits what case-based rec￾ommender mechanisms can do, so future studies need to address the problem of case cleaning. Other studies need to consider more real-world applications for the algorithm and user satisfaction with GCBR. Fig. 13. Convergence of different parameter combinations in Experiment 1. Domain Knowledge PL/SQL DBA Foundation I DB Performance Tunings DBA Foundation II PMP 3rd Microsoft win2000 installation Microsoft win2000 configuration Oracle 10g new features Microsoft system security administration Networking Infrastructure Interconnecting Cisco Device Microsoft SQL server OCA 9i OCP 9i OCP 10g PMP MCSA 2003 CCNA IT Certification Fig. 14. Multiple recommendation stages. 8 C.-S. Wang, H.-L. Yang / Expert Systems with Applications xxx (2011) xxx–xxx Please cite this article in press as: Wang, C.-S., & Yang, H.-L. A recommender mechanism based on case-based reasoning. Expert Systems with Applications (2011), doi:10.1016/j.eswa.2011.09.161