Pervasive and Mobile Computing 9 (2013) 437–453 Contents lists available at SciVerse ScienceDirect Pervasive and Mobile Computing journal homepage: www.elsevier.com/locate/pmc Review Mobile social networking middleware: A survey Paolo Bellavista a,* , Rebecca Montanari a , Sajal K. Das b,1 a University of Bologna, Viale Risorgimento, 2 – 40136 Bologna, Italy b The University of Texas at Arlington, P.O. Box 19015, Arlington, TX 76019, USA article info Article history: Received 26 July 2011 Received in revised form 4 March 2013 Accepted 9 March 2013 Available online 21 March 2013 Keywords: Mobile social networking Middleware Social communities Mobile applications Opportunistic computing abstract The convergence of social networking and mobile computing is expected to generate a new class of applications, called Mobile Social Networking (MSN) applications, that will be of significant importance for the coming years. Indeed, MSN enhances the capabilities of more traditional Online Social Networking (OSN) to a great extent by enabling mobile users to benefit from opportunistically created social communities; these communities should be determined not only by common interests or contacts but also by mobility-related context, such as physical location and co-presence. In this paper we precisely define what we intend for MSN applications and overview the primary MSN support solutions available in the current literature and that specifically address the underlying technical challenges, design issues, and emerging middleware guidelines. Our primary goal is to identify engineering design criteria for future MSN middleware solutions, capable to flexibly adapt to different application domains and deployment requirements. To this purpose, we present a novel taxonomy of MSN structures and describe how various existing middleware approaches fit the proposed classification; moreover, the survey takes the opportunity of these descriptions to discuss related middleware design/implementation choices determining specific tradeoffs between expressive power, flexibility, and scalability. © 2013 Elsevier B.V. All rights reserved. Contents 1. Introduction............................................................................................................................................................................................. 438 2. The MSN paradigm shift and a classification of MSN structures ......................................................................................................... 438 2.1. A classification of MSN structures ............................................................................................................................................. 439 2.2. Spatial and temporal scopes ...................................................................................................................................................... 442 3. State-of-the-art research efforts in MSN ............................................................................................................................................... 444 3.1. MSN middleware proposals ....................................................................................................................................................... 444 3.1.1. MobiSoC ....................................................................................................................................................................... 445 3.1.2. SAMOA.......................................................................................................................................................................... 446 3.1.3. MobiClique ................................................................................................................................................................... 446 3.1.4. Yarta ............................................................................................................................................................................. 447 3.1.5. Comparison of existing MSN middleware ................................................................................................................. 447 4. MSN middleware: architecture and primary design guidelines .......................................................................................................... 448 4.1. Primary guidelines for architectural and design choices ......................................................................................................... 449 5. Conclusive remarks and open challenges .............................................................................................................................................. 451 References................................................................................................................................................................................................ 452 * Corresponding author. Tel.: +39 051 2093001; fax: +39 051 2093073. E-mail addresses: paolo.bellavista@unibo.it (P. Bellavista), rebecca.montanari@unibo.it (R. Montanari), das@cse.uta.edu (S.K. Das). 1 Tel.: +1 817 272 7405; fax: +1 817 272 3784. 1574-1192/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.pmcj.2013.03.001