The synthesis project is a significant research project that combines different areas each represented by a reader. The project must be proposed, completed, and accepted by your readers before you can submit your portfolio for admission to PhD candidacy.
What does "different areas" mean?
The notion of areas and readers are closely tied together. The project must have at least two readers, each of whom represents a different area. Issues of what constitutes distinct areas are judged by the readers and by the graduate program director. The main criterion is that the sets of techniques are typically quite separate and that the project involves an intellectual stretch to bring them together. The areas (and hence the readers) may be from at least slightly different areas in the school of computer science, or one of them may be from a different department, or conceivably even at a different university. However, at least one of your readers must be a member of the tenure- or research-track faculty.
Typically, the main topic of the project is related to you and your advisor's research interests. You learn about a body of ideas and methods in a different area and attempt to apply these ideas to the problem in question. The key requirement is that different techniques from at least two distinct areas are brought together to attack a problem.
How do you know when you're done?
The readers must agree that you have successfully mastered the distinct techniques of the different areas and done some non-trivial work to apply them to the problem. You must write a paper or report that describes the techniques and progress. (In the best case the paper will be published.) The minimal requirement is that you have mastered the techniques and brought them together in a paper that would be worth at least an A- in a term project.
For some students, the main "evidence of research" in the portfolio is this synthesis project. In this case, the project must unquestionably demonstrate this crucial aspect of the portfolio. Doing so may go well beyond the level needed just to pass the synthesis requirement. In particular, passing the synthesis project does not necessarily provide sufficient evidence of research ability for the student to pass the portfolio.
You are required to complete a research project to the satisfaction of at least two faculty readers, with a grade of B or better. Most students fulfill this requirement in combination with their synthesis project. If you choose to keep the two projects separate, you must prepare and submit a one-page MS Project Proposal (the form is available here) and have it endorsed by the faculty readers and the GPD. After approval, you must enroll in CMPSCI 701 (6 credits). When the project is completed, you will tell the Graduate Program Manager who will get approval from your readers. (The School of Computer Science does not have a Masters Thesis option.)
Combining the Synthesis and Master's project
If you are in the MS/PhD track, you may want to combine the MS project requirement with the synthesis project--i.e., ensure that a non-trivial synthesis of areas was brought together during the work on the master's project. The requirements of the synthesis aren't changed, but the advantage is that for some students the same work can count twice--for both the master's and synthesis projects, or at least that the two projects are closely enough related that the work for the two was coordinated. If the two projects are combined then the Master's project must include a reader outside of the advisor's main area. This reader and the advisor are considered the readers of the synthesis project. There may be other readers or advisors for the Master's project who are unconcerned with the synthesis component of the project.
The Synthesis Project must be approved in advance by the faculty readers and the GPD in the form of the "Synthesis Proposal" online form. This form must be filed no later than the Mid-Semester Date in the semester before the portfolio is due.
If you are in the MS/PhD track and are combining the Synthesis and Masters projects, the on-line form gives you an option to do that. You do not need to file a separate MS Project Proposal. You will, however, need to register for CMPSCI 701 after your proposal is accepted.
At the completion of the project, you must hand in the final report to the graduate program manager. In addition, a "Results of Synthesis Project" report will be requested from the synthesis readers. That report characterizes the results of the project and certifies that it satisfies the synthesis requirement.
Your synthesis project must be completed and approved in order for you to submit your portfolio.