Table 5: Scientific classification scheme.

Research QuestionFeatureDescription

RQ1AlgorithmThis feature defines if the primary study proposes an algorithm or series of algorithms
SystemThis feature defines if the primary study is a software system based on different components
FrameworkThis feature defines whether the primary study is based on a framework
MethodThis feature defines if the primary study is a set of procedures to obtain a result
AnalysisThis feature defines if the primary study is a theoretical study based on surveys or systematic reviews among others

RQ2ValidatedThis feature defines whether the primary study has been validated with experiments, use cases, or surveys
Not validatedThis feature defines if the primary study has not been validated with experiments, use cases, or surveys
AcademicThis feature defines if the primary study has been validated with some academic case study
IndustrialThis feature defines if the primary study has been validated with some case study in the industry
ExperimentThis feature defines if the primary study has been validated with the elaboration of different experiments
Use caseThis feature defines whether the primary study has been validated with the study of a use case
SurveyThis feature defines if the primary study has been validated with the elaboration of some type of survey

RQ3Content basedThis feature defines whether the solution proposed by the primary study is based or composed of a recommendation system with a content-based filter
CollaborativeThis feature defines whether the solution proposed by the primary study is based or composed of a recommendation system with a collaborative filter
HybridThis feature defines whether the solution proposed by the primary study is based or composed of a collaborative and content-based filter conjunction
Graph kernelThis feature defines whether the primary study is based or composed of a graphic classifier
Naive BayesThis feature defines whether the primary study is based or composed of a naive probabilistic classifier naive Bayes
Logistic regressionThis feature defines whether the primary study is based or composed of a classifier by logistic regression
Decision treeThis feature defines whether the primary study is based or composed of a classifier by decision trees
LexicalThis feature defines whether the primary study is based or composed of a classifier based on textual features
Based on rulesThis feature defines if the primary study is based or composed of a rule-based classifier
Neural networksThis feature defines if the primary study is based or composed of a classifier based on neural networks
ClusteringThis feature defines if the primary study is based or composed of a non-supervised cluster classifier
BoostingThis feature defines if the primary study is based or composed of an ensemble classifier with a boosting scheme
Linear algorithmThis feature defines if the primary study is based on or composed of a classifier based on a linear algorithm
Based on attributesThis feature defines whether the primary study is based or composed of a classifier based on attributes
MulticlassThis feature defines if the primary study is based or composed of a multiclass classifier
WarehouseThis feature defines if the primary study is composed of a classifier based on data warehouse
SVM vectorsThis feature defines if the primary study is composed of a classifier that makes use of support vector machines
Neighbor methodThis feature defines if the primary study is composed of a classifier based on the neighbor method
Opinion-basedThis feature defines if the primary study is composed of an opinion-based classifier
Target-basedThis feature defines if the primary study is composed of a target-based classifier
Random forestThis feature defines if the primary study is composed of a random forest classifier

RQ4NoveltyThis feature defines if the primary study is a new proposal that does not exist in the literature
AnalysisThis feature defines if the primary study is an analysis of several existing proposals in the literature
ResearchThis feature defines if the primary study is an investigation of existing or new proposals
ImprovementThis feature defines if the primary study is an improvement of an existing proposal in the literature