What does "the thesis of this dissertation" mean?

Solution 1:

Per Merriam-Webster:

thesis, n. 1 a : a claim put forward : STATEMENT, PROPOSITION; specifically : a position or proposition that a person (as a candidate for scholastic honors) advances and maintains or offers to maintain by argument

dissertation, n. : 2 : an extended usually systematic oral or written treatment of a subject : TREATISE, DISQUISITION; specifically : a substantial paper that is submitted to the faculty of a university by a candidate for an advanced degree that is typically based on independent research and that if acceptable usually gives evidence of the candidate's mastery both of his own subject and of scholarly method

The terms are not equivalent in this context (although they are commonly used as though they are).

A dissertation makes the case for its thesis. Dr. Cafarella's dissertion is going to make the case ‒ argue the thesis ‒ that "managing and accessing the Structured Web poses unique difficulties which neither traditional database systems nor search engines address."

Solution 2:

A thesis is the idea put forth to be discussed or proven.

A dissertation is usually a written essay, often written by a student in order to get a higher degree (otherwise, it would probably just be called an essay). In order to get a doctorate you have to research and write so many pages on a subject.

So a dissertation will likely contain a thesis, and that up there in your quote is what's known as the "thesis statement", usually found near the beginning, where one clearly states exactly what the thesis is.

Now, dissertation and thesis can sometimes be used interchangeably, but usually that is only encountered pertaining to the writing assignment itself. So you can say that you "have to finish your thesis for class on Monday" instead of using "dissertation."