Location

Binary attribute, whether u and v belong to the same city

14

Gender

Binary attribute, whether u and v belong to the same gender

15

Age

Absolute difference of ages

12

Library

Cosine similarity between library vectors

5

Groups

Cosine similarity between group membership vectors

7

Group size

Size of the smallest group the two users have in common

6

Vocabulary

Cosine similarity between sets of tags used

16

Contact list

Cosine similarity of the vectors of social contacts

2

Outdegree

Sum of the out degrees (${k}_{\mathrm{out}}(u)+{k}_{\mathrm{out}}(v)$)

11

Preferential attachment

Product of the out degrees (${k}_{\mathrm{out}}(u)\cdot {k}_{\mathrm{out}}(v)$)

13

Common neighbors

Number of common neighbors, directed case ($CN(u,v)={\mathrm{\Gamma}}_{\mathrm{out}}(u)\cap {\mathrm{\Gamma}}_{\mathrm{in}}(v)$)

4

Triangle overlap

$\frac{CN(u,v)}{{\mathrm{\Gamma}}_{\mathrm{out}}(u)}$

1

Reciprocation

Binary attribute, whether the inverse link (v,u) is already present

9

Resource allocation

${\sum}_{z\in ({\mathrm{\Gamma}}_{\mathrm{out}}(u)\cap {\mathrm{\Gamma}}_{\mathrm{in}}(u))}(\frac{1}{{k}_{\mathrm{out}}(z)})$ [37]

3

Local path

Linear combination of common neighbors and common distance2 neighbors ($CN+\u03f5\cdot C{N}_{2}$) [37]

10

Weighted flow

$wf(u,v)=CN(u,v)+\frac{{\sum}_{x\in CN(u,v)}min(w(u,x),w(x,v))}{CN(u,v)}$

8
