# Toward Addressing Location Privacy Issues: New Affiliations with Social and Location Attributes
## 2 Materials and Methods  
We have screened a total number of 1,626,800 papers in our review. The purpose of this study is to employ a systematic mapping that identifies specific users' socio-spatial characteristics in addressing privacy concerns and potential threats. Existing research work on the field will assist in identifying opportunities and gaps for future research. In order to carry out the systematic review, we utilized guidelines and research recommendations based on the conceptual model of the PRISMA 2009 flow diagram in our methodology [11]. The study was conducted from the second half of 2018 to the first trimester of 2019 and it covers papers from 2001 to 2018 publications about the socio-spatial characteristics of users, as well as the spatial and the social privacy concerns of users in online social networks. More precisely, the review was conducted through database searching in google scholar, Scopus, IEEE, ScienceDirect, and Semantic Scholar. The database searching was initiated by inserting the aforementioned research words and synonyms, which were categorized in four main categories--privacy threats/concerns/risks (approximately 560,000 papers), location and proximity services, location-based services and applications (approximately 401,500 papers), privacy location/geolocation privacy, privacy requirements (approximately 35,300 papers), and identity location, identity, and privacy, social identity/digital identity (approximately 630,000 papers)--in all five search engines. The result was concluded after arriving at a significant number of articles that should be narrowed down not only in terms of duplicate articles but also in terms of combining both social identity and location privacy theories in an interdisciplinary way. In that way, we narrowed down the results of the search to 82 papers in the first phase of the selection of our papers. Table 1 presents the criteria applied during the exclusion process. After proceeding with that necessary step, we have also applied a second phase of exclusion criteria for choosing the reviewed papers. Table 2 summarizes the exclusion criteria for the second phase. After that phase, we ended up with 36 research papers for conducting our review. A Prisma 2009 flow diagram was also utilized as a means to visually represent the reviewing process of our paper. Figure 1 represents an adjustment of the proposed visualization of this process:  
As the primary concern of this paper is to specify proper attributes for identifying users' geospatial and social characteristics before designing socially aware information systems, the reviewed papers were focusing on characteristics of social or digital identity, and thus face and geospatial characteristics. Previous literature [1] suggests that location privacy is not just linked to GPS coordinates (x, y) or representations of names, but most importantly, it includes user's identity, position/place in the world, and time of the action. At this point, the analogy among identity (who), position (where), and time (when) is rather obvious. Going a step further and drawing on that theory [1] while reviewing the aforementioned papers, we concluded that except for these three very important attributes of location information, it is important to add a fourth one: the attribute of the activity, or in other words, what is the action or what is happening (what). Thus, our study identified four attributes of location information, namely the attributes of who, what, when, and where before moving to the research questions of the study. Based on the aforementioned characteristics, the following research questions were also formulated, as shown in Table 3. \begin{table}
\begin{tabular}{c} \hline
**Exclusion Criteria** \\ \hline
1. Studies dealing only with geolocation privacy risks \\
2. Studies dealing only with personal identity in social media \\ \hline \end{tabular}
\end{table} 
Table 1: Exclusion Criteria (first phase).