Table 2.

Overview of the link predictors used in the experiments. In the table, $A=N(x)\cap N(y)$ and $c=U\cup V$. (For the other definitions, refer to Sects. 2 and 3)

Type	Link predictor	Score function $P_{\mathit{xy}}=$
CN-based	Common Neighbors (CN)[20]	$|N(x)\cap N(y)|$
	CRA[32]	${\sum }_{a\in A}\frac{|N(a)\cap A|}{|N(a)|}$
L3-based	L3[18]	${\sum }_{U,V}\frac{1}{\sqrt{|N(u_i)|·|N(v_j)|}}$
	CH2_L3 (CH2)[23]	${\sum }_{U,V}\frac{\sqrt{(1+|N(u)\cap c|)·(1+|N(v)\cap c|)}}{\sqrt{(1+|N(u)\backslash c)\backslash \{x,y\}|)·(1+|N(v)\backslash c)\backslash \{x,y\}|)}}$
	Sim[33]	${\sum }_V\frac{|N(v)\cap N(x)|}{|N(v)\cup N(x)|}+{\sum }_U\frac{|N(u)\cap N(y)|}{|N(u)\cup N(y)|}$
	NormalizedL3 (L3N) predictors	Plug in either $f_1$ or $f_2$ into Formula (6) or (7)
control	rand	Rank the edges uniformly at random