# Enhancing Recommender System with Collaborative Filtering and User Experiences Filtering
## 4 Previous Works  
In our previous work [22], a method to retrieve relevant sentences from opinions was defined. A set of categories to group relevant sentences was established, as well as a set of rules to classify sentences into these categories. The defined categories were:  
**Definition 1**.: _Evaluation: Information to evaluate the item or parts of it._  
**Definition 2**.: _Sensation: Information that represents the effect, sensation or emotion caused by the item to the user._  
**Definition 3**.: _Recommendation: Information where the user suggests or recommends the item and considers it advantageous, beneficial, adequate or timely for useonsome occasion or situation._  
**Definition 4**.: _Target users: Information about people, animals, entities, etc. that are related to the user or item and those subparticipated in the experience._  
This kind of information answers the questions posedby users before buying an item, as can be concluded from the survey we carried out. The set of rule defined in [22] is the following:  
* R1. w\({}_{i}\) = \"for\" or \" for\" + nou. person or \"to\" + verb. motion -> Recommendation
* R2. Syntactic_cat (wi) = Ad. all -> Evaluation
* R3. Syntactic_cat (wi) = verb. emotion -> Sensation
* R4. Syntactic_cat (wi) = verb. perception -> Sensation
* R5. Syntactic_cat (wi) = verb. change. -> Sensation
* R6. Syntactic_cat (wi) = nou. artifact -> Recommendation
* R7. Syntactic_cat (wi) = noun. location -> Recommendation
* R8. Syntactic_cat (wi) = verb. weather -> RecommendationR9. Syntactic_cat (wi) = verb. motion -> Recommendation
* R10. Syntactic_cat (wi) = verb.communication -> Recommendation
* R11. Syntactic_cat (wi) = noun.communication -> Recommendation
* R12. Syntactic_cat (wi) = noun. act -> Recommendation
* R13. Syntactic_cat (wi) = verb. consumption -> Recommendation
* R14. Syntactic_cat (wi) = noun. time -> Recommendation
* R15. Syntactic_cat (wi) = verb. social, -> Recommendation
* R16. Syntactic_cat (wi) = noun. cognition -> Recommendation
* R17. Syntactic_cat (wi) = noun. person -> Target_User
* R18. Syntactic_cat (wi) = noun. group -> Target_User
* R19. Syntactic_cat (wi) = noun. animal -> Target_User  
In the present work, the rules are only used to retrieve relevant sentences concerning recommended products.  
**5. Proposal: A Recommender System That Recommends Products and a List of Relevant Sentences from User Reviews**  
A process that, upon receiving a query from a user, recommends an item and retrieves the most relevant user experiences from user reviews is proposed. Reviews can contain many sentences that are not relevant. Figure 1 presents the process proposed to achieve this purpose.  
The user enters a query into the system. Then, recommended items are obtained through a CF method. The ratings of users with similar preferences are used to predict the ratings of other items to recommend. The items to be recommended are ordered according to the values of their predicted ratings. Then, the first 10 item are recommended to the user. For each 10 items, the opinions of other users are retrieved. A process to obtain the experiences that other users had with that item is applied to the retrieved opinions. Only the most relevant experiences are presented to the user. Details of each step in this process are presented in the following subsections.