SI 683 Reputation Systems
Instructor: Rahul Sami
1.5 Credit, 7-week course module
Second half of Winter 2012
Tuesday, Thursday 8:30-10:00am, 2245NQ
Office hours: Mon 4-5pm, Tue 3-4pm (#4340NQ)
Course Learning Objectives:
In this course, you will learn about the design of reputation systems:
design choices, benefits, threats, and limitations. At the end of this
course, a student should be able to critically analyze a reputation
system design to identify strengths and potential weaknesses, and to
design a reputation system for a particular domain with a clear idea
of the tradeoffs involved.
Academic Integrity Policy
The UM and SI Academic Integrity Policy applies to this course:
Collaboration while working on homework
problems, and while discussing and interpreting the reading assignments, is
learning is effective. Collaboration will be especially valuable in summarizing the
reading materials and picking out the key concepts. You must, however, write your
homework submission on your own, in your own words, before turning it in. If you
worked with someone on the homework before writing it, you must list any and all
collaborators on your written submission.
All written submissions must be your own, original work. Original
work for narrative questions is not mere paraphrasing of someone else's completed
answer: you must not share written answers with each other at all. At most, you
should be working from notes you took while participating in a study session. Largelyduplicate copies of the same assignment will receive an equal division of the total
point score from the one piece of work.
You may incorporate selected excerpts from publications by other authors, but
they must be clearly marked as quotations and must be attributed. If you build
on the ideas of prior authors, you must cite their work. You may obtain copy
editing assistance, and you may discuss your ideas with others, but all substantive writing and ideas must be your own, or be explicitly attributed to another.
Rackham Graduate policy on Academic and Professional Integrity
for the definition of plagiarism, and associated consequences.
Accommodations for Students with Disabilities
If you think you need an accommodation for a disability, please let me
know at your earliest convenience. Some aspects of this course, the assignments, the in-class activities, and the way we teach may be modified
to facilitate your participation and progress. As soon as you make me
aware of your needs, we can work with the Office of Services for Students
with Disabilities (SSD) to help us determine appropriate accommodations. SSD (734-763-3000; http://www.umich.edu/~sswd) typically rec-
ommends accommodations through a Verified Individualized Services and
Accommodations (VISA) form. I will treat any information you provide
as private and confidential.
The Internet enables interactions, commercial and non-commercial, between
people across geographical and social boundaries. Ideally, these
interactions are mutually beneficial, but they may also be
exploitative or fraudulent.
For example, buying an item on an online auction may get you a bargain, but
you may also lose money if the other party ships you poor-quality goods, or
does not send anything at all.
Ideally, you would like to engage in interactions with reliable and
trustworthy entities, but this is often difficult for two reasons: (1) You
may not have information about the quality of the other party, or the value of the exchange; (2) The other party may have incentives that conflict with your own, and may thus seek to manipulate the interaction to your detriment.
Reputation systems are widely used to address these problems in online
forums; for example, eBay.com, Amazon.com, and Yahoo.com all use reputation
systems in their auctions.
A user's reputation is an aggregate of feedback from all her past trading partners.
Ideally, it will reveal information about the average quality of those
transactions; further, the desire to maintain a high reputation gives
her an incentive to honestly execute the current transaction.
However, a reputation system needs to be designed carefully, and tailored to
its application setting: poorly designed reputation systems may be
uninformative or prone to manipulation.
In this course, we will study the design and critical analysis of
reputation systems. We will discuss incentive issues involved in
motivating users to behave honestly and to give honest feedback, as well as
other practical aspects of designing a reputation system, such as the format of feedback input and retrieval. We will also study ways in which
strategic parties may try to circumvent the system, and techniques to defend against these attacks.
- A basic introduction to game theory: old SI 625, SI652 or equivalent,
or permission of instructor.
- Week 1:
Introduction to reputation systems
Measuring the value of reputations
- Week 2:
Negative feedback: incidence and response
Incentives for feedback contribution
- Week 3:
Economic models of reputation.
- Week 4:
Identity attacks on reputation systems: Changing names
Graphical models and reputation on networks
- Week 5:
Identity attacks on reputation systems: Sybil attack
Reputations based on textual feedback
- Week 6:
Point, currency, and token reputation systems
Alternatives to reputation systems
- Week 7:
Case study of example recommenders
Course Work and Assessment
- 4 Assignments 30%
Assignments will include exercise problems on the economic models studied, and short-answer questions on the papers and topics discussed in class.
- Class Participation 10%
- Final Project 60%
The final project will involve designing a reputation system for a
particular domain. Students will submit a paper (about 6-8 pages) describing
the design, outlining the strengths and weaknesses of the system (including
potential attacks), and explaining the design choices they made.