Q2. What is the expected value of Fi(k)?
In their case, when α is not necessarily zero, by using (2) instead of the more natural (6), there is no problem in computing the expectation of Fi(k), since the parameter p is a constant, allowing us to find the expected value of Fi(k) by using the linearity of expectations.
Q3. What is the probability of a new word appearing in a urn?
Fi(k)k(1 + αp) + α(1− p) , (1)a new ball is added to urn1 (provided that 0 ≤ pk+1 ≤ 1) or,(ii) with probability 1− pk+1, an urn is selected − urni being chosen with probability(1− p)(i + α)
Q4. What is the probability that p3 be ill-defined?
It can be verified that the probability that p3 be ill-defined is 0.15, that p4 be ill-defined is about 0.1905, that p5 be ill-defined is about 0.1769 and that p6 be ill-defined is 0.
Q5. What is the probability of adding a ball to a urn?
In the discussion at the end of Section 3 the authors suggest that, in practice, starting from a typical initial configuration of balls in the urns, it is likely that pk+1 will be well defined for all k, even if (5) does not hold.
Q6. What is the probability of adding a ball to urni?
The probability (2) is a combination of a preferential component (proportional to the number of pins in urni) and a non-preferential component (proportional to the number of balls in urni).
Q7. What is the first formal proof of Simon’s model?
As far as the authors are aware, their convergence proof given in the Appendix is the first formal proof validating Simon’s model − it does not rely on the mean-field theory approach, as for example in [BAJ99].
Q8. What is the probability of a link being placed in a Web graph?
A situation when α > 0 might occur if there is a choice of Web pages to link to and the actual decision of which links are put in place has a random component.