Schematic illustration of the probable coevolving process of common interests and trust relations in this paper.

<p>Suppose there are a pair of users, say user <i>u</i> and user <i>v</i>, and four reviews as the items. We assume that the items both user <i>u</i> and user <i>v</i> commented are the common interests for them. At Initial state, both user <i>u</i> and user <i>v</i> comment item 2 as well as user <i>u</i> also comments item 1. The overlap between the two users equals the ratio for the numbers of the items commented by user <i>v</i> and user <i>u</i>, i.e., <math><mrow><mn>1</mn><mn>2</mn><mo>=</mo><mn>0</mn><mo>.</mo><mn>5</mn></mrow></math>. At Final state, the value of overlap between the two users has increased to <math><mrow><mn>2</mn><mn>3</mn><mo>=</mo><mn>0</mn><mo>.</mo><mn>67</mn></mrow></math> since both of them commented item 4. Meanwhile, user <i>u</i> has trusted user <i>v</i>. However, there are two probable ways for the two users to reach the Final state from the Initial state, say Path <i>a</i> and Path <i>b</i>. Path <i>a</i> indicates that the increment of the common interests between users can bring new trust relation; Path <i>b</i> implies that the creation of trust relation is the reason for users to have more common interests.