#citation
The number of citations of all publications by an expert.
#publication
The number of all publications by an expert.
H-index
An expert has index h if h of his or her N papers have at least h citations each, and the other (N − h) papers have at most h citations each.
Longevity
Longevity reflects the length of one author’s academic life. We consider the year when one author published his/her first paper as the beginning year of his/her academic life and the last paper as the end year. Then longevity can be defined as:
Impact Factor
Basically, the score reflects the importance of a publication venue and is calculated by http://en.wikipedia.org/wiki/Impact_factor. In Arnetminer, for evaluating a paper published at a venue, we further consider the paper length. Specifically, if the paper length < 3 pages, then we take 1/5 of impact factor of the publication venue; if the 3<= length <5 pages, we take 1/3 of the factor of the publication venue. Formally, the new score can be defined as follow:
In the definition, G is a group of papers. IC (P) means the impact of conference in which the paper published. Weight(P) equals to 1/5 if the paper length<3, while weight(P) equals to 1/3 if the 3<= length <5.
Activity
People's activity is simply defined based on one's papers published in the last years. We consider the importance of each paper and thus define the activity score as:
In the definition, in the year n (n belong to recent N years), G is a group of papers published by author A in the year n. Weight(n) = αthis year – n. We tentatively set the values for N and α. Specifically, we set N = 4 and α = 0.75, if the current month is in the first half year (month < July); and set N = 3 and α = 0.85 if the current month is in the second half year.
Diversity
Generally, an expert's research may include several different research fields. Diversity is defined to quantitatively reflect the degree. In particular, we first use the author-conference-topic model (Tang, et al. 2008) to obtain the research fields for each expert. For example, we can obtain four topics (Database Systems / XML Data, Data Mining / Association Rules, Rough Sets / Information retrieval system, Database Logic / Infinite Databases) for Prof. Jiawei Han. Then we automatically assign his papers to each topic. We calculate the topic distribution based on the assignment results. Given expert A, the research topic distribution 
is defined as
The author diversity is then defined as the entropy of this distribution:
Sociability
The score of sociability is basically defined based on how many coauthors an expert has. We define the score as :
where #copaperc denotes the number of papers coauthored between the expert and the coauthor c. In the next step, we will further consider the location, organization, nationality information, and research fields.
Uptrend
Nothing can catch people's eyes more than a rising star. We use uptrend to define the rising degree of a researcher. The information of each author’s paper including the published date and conference's impact factor. We use Least Squares Method to fit a curve from published papers in recent N years. Then we use the curve to predict one's score in the next year, which is defined as the score of Uptrend, formally
In this definition, 
. N = 3. This year is not included if we calculate the value in the first half year, while this year is included and 
if we calculate the value in the second half year.
For all the 200 topics, we will calculate an author’s uptrend in each topic.