Quick Response codes and Bar codes are machine-readable, two-dimensional black and white images that contain some information that can be collected via scanning using the built-in cameras on smartphones. They can encode more than 4000 alphanumeric characters and more than 7000 numeric characters in one image .QR codes were invented in 1994 by a Japanese company called Denso Wave . They are are more powerful than barcodes as they utilise an error correction mechanism that allows the code to be readable by a machine even if part of it is corrupted or missing . Moreover, QR codes are being improved day by day (e.g. Tai-Wei  developed a system to present a 3D visualization of the scanned product rather than just presenting photos and text as shown in Figure 6). This bodes well for the future direction of our project. Our social network takes advantage of the fact that these codes can be decoded using the simple applications in smartphones without the difficulty of requiring special hardware or software. Figure 1 shows an example of a QR code and Figure 2 shows an example of a bar-code.
How were they used in the literature?
Chih-Kai et al. used QR codes to annotate videos and share them in social media websites such as Flicker and Facebook to encourage collaborative learning between students . Their suggested augmented reality system utilises the simplicity of using social media by learners with digital literacy and barcode scanners to learn biological material. Figure 3 shows the architecture of this system. The use of QR codes in this system was mainly deployed in order to solve the usability problem associated with text-based entries on smartphones. It uses QR codes to retrieve the text and annotate the clips before sharing them. QRouteMe  is another system which uses QR codes to guide museum visitors by utilizing the large interactive screens within the environment. Using these screens, the users can browse and identify a specific place that they want to visit inside the museum and they are then provided with a QR code from which they can scan and receive directional information as to how to get there. This system is therefore an example of using QR codes to provide context-related information in indoor environments. Although this system allows users to socialize by linking them to other social networks (e.g. Facebook), and allowing them to communicate with each other during a visit, our social network is different because it uses QR codes to link the real world with the virtual world, it is not designed particularly for indoor environments (e.g. museums) and therefore it is a general social networking platform for sharing rich media content. Figure 4 shows the three types of interaction that can be found in QRouteMe . Similarly, MUZZEUM  platform used Quick Response codes and augmented reality to provide more information about the artifacts of Serbian National Museum. Moreover, PresiShare  allows users to share media content and interact indoors by uploading and downloading their files to public screens using QR codes as shown in Figure 5. As a result, and as far as we know, using QR codes to bridge the gap between the virtual worlds and real worlds and allowing people to share their experiences using different types of rich media content has not been previously developed. Therefore, due to the simplicity and ease of use of these codes, we expect that our system will give its users opportunities to socialize and take advantage of the experiences of other users.
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Edited by FH