Social Networks and Online Markets

Academic year 2017–2018

We are surrounded by networks. The Internet, one of the most advanced artifacts ever created by mankind, is the paradigmatic example of a "network of networks" with unprecedented technological, economical and social ramifications. Online social networks have become a major driving phenomenon on the web since the Internet has expanded as to include users and their social systems in its description and operation. Technological networks such as the cellular phone network or the energy grid support many aspects of our daily life. Moreover, there is a growing number of highly-popular user-centric applications in Internet that rely on social networks for mining and filtering information, for providing recommendations, as well as for ranking of documents and services. In this course we will present the design principles and the main structural properties and theoretical models of online social networks and technological networks, algorithms for data mining in social networks, and the basic network economic issues, with an eye towards the current research issues in the area.


Topics that we will cover

  • Properties of social networks
  • Models for social networks
  • Community detection
  • Spectral techniques for community detection
  • Centrality measures
  • Cascading behavior in social networks and epidemics
  • Influence maximization and viral marketing
  • Influence and homophily
  • Game theory on networks
  • Network traffic
  • Selfish routing and price of anarchy
  • Auctions
  • Algorithmic market design
  • Market Equilibria: characterization and computation
  • Two-sided markets and sharing economy


    The third homework is out. It is due June 176.

    The second homework is out. It is due May 6.

    The first homework is out. It is due April 22.

    On Monday, March 19, we will have class at 13.00–16.00.

    Notice the class time schedule for Mondays.

    There is no class on March 5, as Sapienza cancelled teaching because of the elections.

    There is no class on February 26, as Sapienza cancelled teaching because of the weather forecast.

    There is no class on March 1, because of the OpenDIAG event.

    We start classes on February 26.



    Aris Anagnostopoulos, Sapienza University of Rome

    Vincenzo Bonifaci, IASI-CNR


    When and where:

    Monday 14.00–17.00, Via Ariosto 25, Room A6

    Thursday 11.00–13.00, Via Ariosto 25, Room A5


    Office hours

    You can use the office hours for any question regarding the class material, general questions on networks, the meaning of life, pretty much anything. Send an email to the instructors for arrangement.


    Textbook and references

    The main textbook is the book Networks, Crowds, and Markets: Reasoning About a Highly Connected World, by David Easley and Jon Kleinberg.

    In addition, we will cover material from various other sources, which we will post online as the course proceeds.


    Exam format

    The evaluation has two parts: a set of three theoretical homeworks, which will be due during the semester, and a final project. During the exam period we will assess the quality of the projects and the extent you have learned the class material. Students are highly encouraged to do the homeworks. Whoever does not do the homeworks will have to do a final written exam on the entire class material and a final project. In this case as well we will have an oral exam during the exam session.



    Date Topic Reading
    March 8 Introduction to social networks and online markets. Chapters 1, 2
    March 12 Strong and weak ties, homophily, affiliation networks, structural balance Chapters 3.0–3.5, 4.0–4.3, 5.0–5.5.A
    March 15 Approximately balanced networks Chapter 5.5.B
    March 19 Random graph model, small world Notes
    March 22 Watts–Strogatz model, navigability in social networks Notes
    March 26 Graph matrices and eigenvalues Notes on matrices
    April 4 Gershgorin circle theorem; Centrality measures: degree and closeness Notes on matrices and centrality
    April 9 Eigenvector centrality
    April 12 Seminar on private data release
    April 16 Analysis of the power method
    April 19 Katz centrality, PageRank
    April 23 Power laws and preferntial attachment, revision of basic game-theoretic concepts Notes, Chapters 6, 18
    April 26 Cascades in networks Chapter 19
    April 30 Selfish routing Chapter 8
    May 3 Non-atomic selfish routing Notes
    May 7 Auctions Chapter 9
    May 10 Matching markets Chapter 10
    May 14 Sponsored-search markets, VCG mechanism Chapter 15
    May 21 Generalized second-price mechanism, Voting Chapter 23
    May 21 Arrow's theorem and beyond




    Collaboration policy (read carefully!): You can discuss with other students of the course about the homeworks and the projects. However, you must understand well your solutions and the final writeup must be yours and written in isolation. In addition, even though you may discuss about how you could implement an algorithm, what type of libraries to use, and so on, the final code must be yours. You may also consult the internet for information, as long as it does not reveal the solution. If a question asks you to design and implement an algorithm for a problem, it's fine if you find information about how to resolve a problem with character encoding, for example, but it is not fine if you search for the code or the algorithm for the problem you are being asked. For the projects, you can talk with other students of the course about questions on the programming language, libraries, some API issue, and so on, but both the solutions and the programming must be yours. If we find out that you have violated the policy and you have copied in any way you will automatically fail. If you have any doubts about whether something is allowed or not, ask the instructor.