# Comprehensive Review and Future Research Directions on Dynamic Faceted Search
## 2 Preliminary Study
### Research Questions  
In view of conducting a systematic literature review, the research questions play a prominent role in deciding the search strategy and analysis. We identified the following Research Questions (RQs) for this research:  
* What does the existing research literature reveal about the faceted search approach of web search service providers?
* What are the primary aims, vision, and trends for faceted search, and what research can be highlighted in this area?
* What are the existing gaps for research prospects in the faceted search approach for web search services?
* What are the existing motivations for usage, concerns, challenges, and recommendations to enhance the faceted approach of web search service providers?  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Criteria** & **Faceted Search** & **Search Engine** & **Search Directories** & **Form-Based Search** \\ \hline \multirow{6}{*}{Search Interface} & \multirow{6}{*}{\begin{tabular}{c} It uses dynamic and multidimensional \\ taxonomies to satisfy \\ various search needs [19]. \\ \end{tabular} } & Crawlers visit a website, read & & & \\  & & the information on that site & & \\  & & and the meta tags and & & \\  & & download documents. Then, & & \\  & & the crawler returns all the & & hyperlinks to web pages and \\  & & information to a central & presentations, broken down & \\  & & repository of the SE, which & & \\  & & indexes the data, for example & & \\  & & Google. & & \\ \hline \multirow{3}{*}{Support Previous Knowledge} & \multirow{3}{*}{\begin{tabular}{c} Handles uncertainty in the \\ search and the possible \\ lack of knowledge [7]. \\ \end{tabular} } & \multirow{3}{*}{\begin{tabular}{c} It searches documents for \\ specific keywords and returns \\ a list of documents. \\ \end{tabular} } & Human editors commonly & & \\  & & & review and classify the web & \\  & & search and the possible & & pages and presentations, & \\  & & a list of documents. & & which are added to \\ \hline \multirow{6}{*}{Discovery Function} & \multirow{3}{*}{\begin{tabular}{c} (1) It refines search results \\ using different facets; \\ (2) the number of data \\ items in each category \\ can be used in the \\ next navigation. \\ \end{tabular} } & \begin{tabular}{c} The SE allows the user to ask \\ for content that meets specific \\ criteria and retrieve a list of \\ references that match \\ these criteria. \\ \end{tabular} & Web directories collect & & \\  & & & different resources. & \\ \hline \multirow{6}{*}{Ranking} & \multirow{6}{*}{\begin{tabular}{c} It supplies and parses the \\ searches result in \\ rankings. \\ \end{tabular} } & \multirow{3}{*}{\
\begin{tabular}{c} It applies and parses the \\ search request into a form \\ that the SE can understand. \\ The SE then executes the \\ search operation on index files. \\ The SE interface returns the \\ search results to the user \\ after ranking. \\ \end{tabular} } &
\begin{tabular}{c} Although many web \\ directories offer a search \\ functionality of some kind, \\ search directories are \\ fundamentally different from \\ \end{tabular} & Similar to SE. \\ \cline{1-1}  & & & \\ \cline{1-1 RQ5. What are the points of interest, such as the architecture, applications, issues, research questions, motivations, recommendation criteria, and open challenges, in using faceted search?