## 2 Related Work: Ontology and IoT-Based Emotion Aware Recommender Systems
### Selected Ontology-Based Emotion Aware Projects Due to Ontology Availability  
We collected the ontology-based emotion projects that share online the ontology code and emphasize them in this section. **Emotion Ontology (EMO) ([PERSON] et al. [22])** describes types of emotion for the affective science domain. EMO is aligned with Basic Formal Ontology (BFO) and the Ontology of Mental Disease (OMD). **Mental health and disease ontologies (MFOEM) ([PERSON] et al. [48])** provides a taxonomy of emotions. Affective science, psychology, and the psychiatric domains are interconnected with the Mental Functioning Ontology (MF) ([PERSON], [PERSON] et al. [23]), which describes concepts such as consciousness, perception, thinking, and believing. Within their state of the art [23]), only few ontologies are men \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Authors** & **Year** & **Project** & **OA** & **Reasoning** & **Text Analysis** \\ \hline [PERSON] et al. [40] & 2011 & OLA: Ontology for Predicting Learners’ & No & \(\surd\) inference, & No \\  & & Affect to infer Emotions & & Decision Tree (Weka) & \\ \hline [PERSON] et al. [41] & 2010 & Recognizing emotions from voice and text & No & \(\surd\) OWL DL, Pellet, Racer & \(\surd\) \\  & 2006 & & & owl:Restriction, inference & \\ \hline [PERSON] et al. [42] & 2011 & Human Emotion Ontology (HEO) for voice, text, gesture, and face & No & No & \(\surd\) \\ \hline [PERSON] et al. [43] & 2009 & \begin{tabular}{c} Smiley Ontology (SO): emoticons \\ (smileys as texts or pictures) \\ with annotation of emotion classes \\ \end{tabular} & No & No & \(\surd\) \\ \hline [PERSON] et al. [44] & 2008 & \begin{tabular}{c} Chinese emotion ontology based on \\ HowNet for text analysis \\ \end{tabular} & No & \(\begin{tabular}{c} \(\surd\) Rules for \\ annotation \\ \end{tabular} & \(\surd\) \\ \hline [PERSON] et al. [45] & 2007 & User’s affective states & No & \(\begin{tabular}{c} \(\surd\) Fuzzy Logic in \\ OWL \\ (logical inference) \\ \end{tabular} & No \\  & 2005 & \begin{tabular}{c} Emotional face and body expression \\ profiles \\ \end{tabular} & No & \(\
\begin{tabular}{c} \(\surd\) RacerPro and \\ nRQL \\ (natural Racer \\ Query Language) \\ \end{tabular} & No \\ \hline [PERSON] et al. [47] & 2005 &
\begin{tabular}{c} Ontology for description of emotional \\ cues \\ \end{tabular} & No & No & \(\surd\) \\  & 2003 & from different modalities (text, speech) & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Cont. tioned, such as Gene Ontology (GO) and [PERSON]'s ontology [48]. For this reason, we deeply investigated ontology-based emotion projects (see Table 1). **Patient-facing software tool, based on Visualized Emotion Ontology (VEO) and Emotion and Mood Ontology ([PERSON] et al. [24; 25])** describes and references 25 emotions and their visualizations to enhance patient interaction in clinical environments. The Visualized Emotion Ontology is based on the revised [PERSON], [PERSON], and [PERSON] models of emotions (OCC model). OntoKeeper is used to evaluate ontology quality. **EEG neuroheadset-based online learning used the Emotion and Cognition ontology to understand emotions ([PERSON] et al. [26]). **  
**Bodily expression-based emotion detection uses the Emotion Ontology (EmOCA) for Context Awareness ([PERSON] et al. [28; 29]). The ontology references six emotions and focuses on describing philia/phobia and their impact on emotion. Reasoning is achived with the CORESE inference engine, a SPARQL request, and the regression algorithm. This ontology-based motion detection is experimented with six men and four women between 20 and 36 years old. **  
**Emotion annotation of corpora using Web of Data (Linked data) is achieved within the Eurosentiment EU FP7 project, which develops the Onyx ontology ([PERSON] et al. [30]). The Onyx ontology is aligned with the Provenance Ontology, Lexicon Model for Ontologies (LEMON), EmotionML, NLP Interchange Format (NIF), OpenAnnotation, and WordNet-Affect. Differences between Onyx and Human Emotion Ontology (HEO) from [PERSON] et al.