# On Ontology-Based Tourist Knowledge Representation and Recommendation
## 2 OTR and Ontology Characteristics Analysis
### Analysis of OTR Content Characteristics  
In order to effective analyze OTR, this study first examined the characteristics of OTR content. The results were then used as the basis for developing the system. Related studies were reviewed to help organize the procedure for analyzing OTR content characteristics [5; 6; 24], as shown in Figure 2.  
* Appraisal function: there are many positive and negative appraisals in OTR for a travel attraction. Thus, OTR appraisal can be used as a reference for filtering popular attractions. * Popular attraction filtering: many studies show that online appraisals determine the user's willingness to purchase [6; 24], which also means that the production with higher positive appraisals is the consumers' favorite. That is, the attraction gaining the higher positive appraisals will be tourists' preferences. Therefore, we can judge popular attractions through the total quantity of positive and negative appraisals. * Popular attraction changing: consumer demand for products would change over time. [25] In the same way, travelers' evaluation of attractions will also alter with the time. When the requirement of consumers or travelers changes, the quantity of positive and negative appraisal also becomes different. Therefore, it is necessary to continuously collect the positive and negative appraisal of the attractions, which help travelers understand the latest tourist attractions. This study applied set theory to explain the relationships between different tourist attraction sets. Each piece of OTR content contains a tourist attraction set. There are different types of sets among different tourist attraction sets, and they are classified into two types: disjoint sets and intersections, as explained below:  
* Disjoint sets: If a specific tourist attraction cannot be found in two tourist attraction sets, it is likely that the two OTR do not overlap, and thus there is no direct relationship between the two tourist attraction sets. * Intersection: If two tourist attraction sets share the same tourist attraction information, it means that the two OTR overlap. As shown in Figure 3, OTR 1 contains tourist attraction set 1, and the content includes K, L, M, N, O, P, Q, R, S, and T. As for OTR 2, it contains tourist attraction set 2, and the content has A, B, C, D, K, L, M, N, O, and P. OTR 1 and OTR 2 thus share some of the same tourist attraction information, namely K, L, M, N, O, and P. This indicates that author OTR1 and author OTR 2 may share similar appraisals regarding tourist attractions K, L, M, N, O, and P. In addition, OTR 1 content recommends not only \"K, L, M, N, O, and P\", but also \"Q, R, S, and T\". This means that there is a direct relationship among tourist attractions \"K, L, M, N, and O\" and \"Q, R, S, and T\". On the other hand, OTR 2 content recommends \"K, L, M, N, O, and P\" and \"A, B, C, and D\", which shows that there is a direct relationship among tourist attractions \"K, L, M, N, O, and P\" and \"A, B, C, and D\". Drawing on these relationships, when travelers want to  
Figure 2: Analysis of OTR content characteristics. visit tourist attractions K, L, M, N, O, and P they can also be recommended to visit Q, R, S, and T, and A, B, C, and D.  
Based on the notion that tourist attractions \"K, L, M, N, O, and P\" have direct relationships with \"Q, R, S, and T\" and \"A, B, C, and D\", there may be an indirect relationship between tourist attraction \"Q, R, S, and T\" (OTR1) and \"A, B, C, and D\" (OTR2). As seen in Figure 3, besides tourist attractions \"K, L, M, N, O, and P\", the authors of OTR1 and OTR2 content may also consider \"Q, R, S, and T\" and \"A, B, C, and D\" when they are recommending tourist attractions, When travelers want to visit tourist attractions \"Q, R, S, and T\", they may be recommended to visit tourist attractions \"K, L, M, N, O, and P\", due to the direct relationship. They may also be recommended to visit tourist attractions \"A, B, C, and D\" due to the indirect relationship.