Discovery of a User Interests on the Internet
†
Fang Li, Yihong Li, Yanchen Wu, Kai Zhou, Feng Li, Xinguang Wang Dept. of Computer Science & Engineering
Shanghai Jiao Tong University,
No.800 Dong Chuan Rd. Shanghai 200240, P.R. China
†
fli@sjtu.edu.cn
Abstract
This paper proposes a system for finding a user’s inter- ests on the Internet. It is based on his browsing behaviors and the contents of his visited pages. The system has two features. One is building user’s browsing interests implic- itly, multiple keyword vectors, one per interest. The other is that it can generate interests by selecting different time periods. Dynamical generation can adapt to the change of user interests. Experiments show that most of generated in- terests are matched to user’s real interests. The system finds their interests automatically and dynamically.
1 Introduction
User interests (or user profiles) can be collected by two ways: explicit and implicit collection [5]. Explicit collec- tion is predefined or feedback by user’s ratings through an interface. The users tell the system what their interests are and what they think about the information that they have re- ceived. Many users are not willing to tell the system what their true intentions are, they do not want to spend time on filling forms or rating items. A less intrusive method (Im- plicit collection) is to use an automatic way to find the in- terests of a user, instead of obtaining it directly from the user. There are roughly two kinds of automatic way to cap- ture a user’s interest implicitly: behavior-based and history- based. The behavior-based research [1] proves that the time spent on a page, the amount of scrolling on a page and the combination of them has a strong positive relationship with user interests. Browsing histories capture the relationship between user’s interests and his click history in which suf- ficient contextual information is already hidden in the web log.
We proposed a method to find a user’s interests with the combination of browsing behaviors and contents. User in- terests can be automatically generated by applying cluster-
ing methods on visited web pages, while the degree of his interest can be analyzed based on his browsing behaviors.
The rest of this paper is organized as follows. Section 2 describes our methods. Section 3 gives a running example.
Section 4 presents the experiments and analysis.
2 Finding User Interests
Page contents are important for finding user interests.
Given a set of visited pages, clustering algorithm is applied to divide the pages into several clusters. Based on the clus- tering results, some keywords are extracted to represent user interests in each cluster.
Given the corresponding feature vectors X = {x1, ..., xn} of n visited pages P = {P1, P2, ..., Pn}, where xi = (xi1, ..., xid)T ∈ Rd is the feature vector of the ith page, xijis the value of the jthfeature in the ithpage. The features can be words or phrases after the POS tag1 is ap- plied on the contents. Our clustering algorithm (shown in Algorithm 1) first selects seeds based on Kaufman approach (step 1 to 10) [4], then it uses the selected m seeds as the initial centroids and use the Spherical K-Means algorithm (SK-means) [2] to cluster pages into m clusters (step 11 to 20). The Spherical K-Means has the main advantage of requiring a linear number of comparisons while still guar- anteeing good quality cluster.
Based on the clustering results, a user’s interest is repre- sented as a set of keywords which are the top 3 features of the centroids vector of each cluster. The degree of a user’s (IG) interest is defined as the sum of the corresponding in- terested degrees of pages in a cluster.
IGi= X
Pj∈Gi
IPj (1)
where Gi is a cluster, which represents a user’s inter- est, Pj is a web page belonging to the cluster. IP j is the
1From http://www.hyland.com
interested degree of the page calculated based on the user- interest model we proposed in [3]. We use Gaussian Process Regression model to capture the relationship between user interests and browsing behaviors.
3 A Running Example
We have realized the system based on the proposed methods. The system is called ”family safe”2 because it can help parents to find the browsing interests of their child automatically and implicitly. By choosing different time pe- riods, the interests of the period can be generated dynami- cally. A user was asked to surf the web by using the IE 7.0 that had embedded with our plug-in. We obtained his 2- month browsing log including browsing behaviors and con- tents. Then we used the system to find his interests auto- matically. Some of the results are given in the following:
• Figure 1 shows the result of page clustering. Three keywords of each cluster represent each interest on the left. All generated keywords with translations are com- pared with his real interests (Table 1). The detailed in- formation about the first interest is shown on the right side, which consists of the keywords, the number of the related pages, its summary and the time spent on this interest. The largest interest is shopping. The number of pages in the cluster is 139 pages. The system also extracts some sentences from the viewed pages to pro- vide an overview of the interest. These sentences are shown on the right side of the window.
Figure 1. User Interests Generated
• The user was asked to list his interests during the pe- riod. Table 1 shows the comparison between the
2The project was funded by the Intel China Lt.Co. and the UDS-SJTU joint research lab for language technologies.
Algorithm 1 Page Clustering Algorithm based on KA Ini- tialization and Spherical K-Means
Input: 1. Feature vectors X = {x1, ..., xn} of n pages visited.
2. The predefined number of page clusters m.
Output: The set of page clusters.
1: Seeds ← {xcenter} /* xcenter is the most centrically located page instance in X, regarded as the seeds ini- tially. */
2: repeat
3: for each pagexi ∈ Seeds do/
4: for each pagexj ∈ Seeds do/
5: Cji = max(Dj − dji, 0), in which dji = kxi− xjk and Dj= min
s∈Seedsdsj.
6: end for
7: Calculate the gain of selecting xi as a seed by P
j
Cji.
8: end for
9: Seeds ← Seeds ∪ {xseed} where seed = arg max
i
P
j
Cji.
10: until |Seeds| = m
11: Centroids(t) ← Seeds /* Centroids = {c(t)1 , ..., c(t)m}, c(t)j denotes the centroid vector of the jthpage cluster, t is the iterative times and t = 0 initially. */
12: repeat
13: for j ← 1 to K do
14: Cj(t+1) ← ∅ /* Cj(t+1) denotes a cluster with the centroid c(t)j . */
15: end for
16: for each page ∈ X do
17: Cj(t+1)← Cj(t+1)∪ {xi}, where j = arg max
l xTi · c(t)j
18: end for
19: Recalculate c(t+1)j = kuku , where u = P
xi∈G(t+1)j
xi
20: until
c(t+1)j − c(t)j < ε
21: Output the set of page clusters C = {C1, ..., Cm}
22: return C;
user-predefined and the system-found interests. All the keywords can be matched to his interests.
• Figure 2 illustrates the distribution of the user’s inter- ests. Each of the interests is represented by 3 key- words, the percentage of the interest, the degree of the interests and the view time. For example, the great interest is shopping guidance. Three keywords are:
shopping guidance, discount and Baishen (name of the
shopping mall). The interested degree is 79.41, the percentage is 23.57%. The time spend on viewing pages of shopping is 4744 seconds.
Figure 2. User interests Distribution
• During the period, the change of interests of per day, per week, or per month can be analyzed using a time series chart. Figure 3 shows the evolution of the user’s interests per day from Nov.11, 2007 to Dec.15, 2007.
It is easy to observe that his shopping interests of 15, Nov. is the greatest, and then he gradually lost interest in shopping. Some interests such as education (univer- sity, Jiaotong, course), Blog (life, blog, original) are constantly keeping.
Figure 3. User interests evolution from Nov.11 to Dec,15. 2007
4 Experiments
4.1 Clustering Evaluation
We choose two test sets: sohu (news.sohu.com) and sina (sina.com.cn) as references (the ground truth). Each set has
Table 1. Comparison of interests found User
predefined interests
System-found interests
shopping
(Shopping guidance), ò(discount), z(BaiSheng: the name of a shopping mall)
blog Life, F(Blog), ©(original)
Entertainment W(Entertainment), ±#Ô(Jielun Zhou:
a famous popular singer),ü(director) TV movies u <(Overseas Chinese), > À ì(TV
movies),n²(all kinds of art)
Education Æ(University), Ï(Jiao Tong),
§(Course)
weather í (Meteorologic)§ Ï 1 y(pass)§ U íý(Weather forecast)
book VeryCD, iPac2.0, ý(Reservation) Cartoons Ä x(motive)§ i 4 |(caption)§ Ä
û(cartoons)
Mobile phone ÃÅ(Mobile phone), Oá&(Ericsson), ¢ Z(Sony)
shopping |G(pay)§´(transaction)§G±(pay money)
BBS ØYg (BBS of SJTU), ;(major), © Ù(article)
Entertainment (Singer)§ , |(Welcome for singer)§ü ¬(Music show)
10 categories and 100 pages of each category. We use K- means from Weka and SK-means as baseline. K is set to 10, it is a reasonable assumption based on our experiments. Pre- cision and recall are widely used in information retrieval.
We use cluster precision and recall to evaluate the correct- ness of clustering results. They are defined in the following:
precision = 1
|P | X
pi∈P
| C(result, pi) ∩ C(ref erence, pi) |
| C(result, pi) |
recall = 1
|P | X
pi∈P
| C(result, pi) ∩ C(ref erence, pi) |
| C(ref erence, pi) |
Where C represents “Cluster”, P is the set of pages,
|P | is the number of pages. Cluster(result, pi) is the system generated cluster where page pi belongs;
cluster(ref erence, pi) is the cluster where pi is accord- ing to the reference result. We also use Entropy and Purity to evaluate the clustering results. The entropy is a more comprehensive measure than purity. It considers the en- tire distribution. Both purity and entropy are biased to fa-
vor large number of clusters. The results of clustering web pages from Sohu and Sina are shown in the Table 2.
Table 2. Result of Clustering
Entropy Purity Precision Recall
SohuNet
K-means 2.8337 0.2460 0.1675 0.2802 SK-means 0.8587 0.7698 0.6686 0.6988 Our method 0.7464 0.8121 0.7109 0.7342
SinaNet
K-means 2.9084 0.2410 0.1674 0.2364 SK-means 0.9583 0.7260 0.6320 0.6796 Our method 0.6902 0.8105 0.7460 0.7965
Both results show that our method outperforms the base- lines. The algorithm has a high purity of 81%, with the average precision of 72.5%, recall of 76%. Results show that there are lots of different noises on the web pages, such as advertisements. Some advertisements are regarded as the contents of the pages, which has reduced the precision.
4.2 Human reviews
There are 10 voluntary students jointed in our experi- ments. Each participant was installed our system for half a year. We use their two months data as the test set. There are 8621 pages which cover different topics including politics, culture and so on. We ask each student to rate the interests generated with the rating scale of 1 to 5. Figure 4 is the average score of keywords rated by each user.
Figure 4. The average score of user rating
The percentage of different rating scale for keywords is show in Table 3. Rating 5 means three generated keywords are correct user interests, rating 4 means two of three key- words are correct. Based on the results, about 59.14% in- terests (keywords vectors) generated are rated as 5 and 4.
Only 13.98% interests generated by the system are proved irrelevant with user’s interests.
Table 3. Human Evaluation score percentage
Score 5 4 3 2 1
Keyword
vectors 25.81% 33.33% 19.35% 7.53% 13.98%
5 Conclusion
In this paper, we propose a system to investigate the problem of finding user interests. Our system utilizes the implemented plug-in to collect the data of the pages visited by a user and track his browsing behaviors. The system combines the page content and browsing behavior analysis to find and generate the user’s interests automatically. By selecting different time periods, user interests can be gener- ated dynamically. The change of interests can be analyzed.
One of the applications of our system is to be installed in a home PC. Parents can know their child’s browsing interests implicitly and relieve their worries for unhealthy informa- tion on the Internet.
References
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