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  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>, Ryuuki Sakamoto , Sadanori Ito , Hideaki Takeda , Kiyoshi Kogure</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="editor">
          <string-name>Advanced Telecommunications Research Institute International,</string-name>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>National Institute of Informatics</institution>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>Shonan Village, Hayama</institution>
          ,
          <addr-line>Kanagawa 240-0193</addr-line>
          <country country="JP">Japan</country>
        </aff>
        <aff id="aff2">
          <label>2</label>
          <institution>The Graduate University for Advanced Studies</institution>
        </aff>
        <aff id="aff3">
          <label>3</label>
          <institution>Tokyo University of Agriculture and Technology</institution>
        </aff>
      </contrib-group>
      <abstract>
        <p>In this paper, we propose a system called “Aikuchi,” which enables users to mark a string on a Web page and share it with other users. If users mark a string on their Web browser using their mouse cursor, Aikuchi recommends links to other Web pages based on recommendation algorithms. When a user clicks a recommended link, Aikuchi highlights a marked string. We offered the system as part of a conference support system. According to the analysis of user logs, users preferred Web page recommendations based on strings marked by other users to those based on page similarity using TFIDF and collaborative filtering. As a result, we think that marked strings can act as usergenerated metadata.</p>
      </abstract>
      <kwd-group>
        <kwd>eol&gt;Social tagging</kwd>
        <kwd>marking</kwd>
        <kwd>user-generated metadata</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>-</title>
      <p>Permission to make digital or hard copies of all or part of this work for
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      <p>SAAW’06, November 6, 2006, Athens, GA, USA.</p>
      <p>Copyright 2006 ACM 1-58113-000-0/00/0004…$5.00.
words that differ from what users intended. One possible
solution to this is to employ user-generated tags from Social
Bookmark Services (SBS), enabling users to easily find
appropriate pages. However, as users freely add tags, numerous
other types of tags also accumulate on Web pages.</p>
      <p>Because users view each page subjectively, they add tags to
express the contents, their feelings about the page, the purpose of
the page, and so on. When users find Web pages using such tags,
though, such diversity becomes an obstacle to finding pages that
are actually appropriate. In this research, we employ strings
marked by users as tags to exclusively express a given page’s
contents. The system we have implemented, called Aikuchi,
enables users to mark strings in Web pages and share them with
other others. If a user marks a string in the Web browser using
his or her mouse cursor, Aikuchi recommends links to other Web
pages by applying it recommendation algorithms, and when a
user clicks a recommended link, the system highlights the
marked string, which is called a footprint. The recommendation
algorithms are based on page similarity using TFIDF,
collaborative filtering, and word matching using words in the
footprint or another Web page. We offered the system as a part of
a conference support system and analyzed whether users prefer
the recommendation algorithm based on marked strings to search
Web pages.</p>
    </sec>
    <sec id="sec-2">
      <title>2. RELATED RESEARCH</title>
      <p>
        Semantic annotation systems have previously been proposed
that highlight strings in Web browsers. One example is CHOSE
[
        <xref ref-type="bibr" rid="ref1">1</xref>
        ], which stores metadata as hyperlinks in a Distributed Links
Service [
        <xref ref-type="bibr" rid="ref2">2</xref>
        ] and uses it to highlight ontology terms in the text
strings on the Web browser. Magpie [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ] highlights strings related
to the ontology of the user’s choice on the browser. Both systems
highlight strings to make the connection between a string and an
ontology. Our system links from a string to offered pages and
differs from them by the lack of connection between the link and
a meaning; it is instead related to the user’s interest. In this
paper, we reuse a selected string as metadata to search Web
pages.
      </p>
    </sec>
    <sec id="sec-3">
      <title>3. A SOCIAL TAGGING SYSTEM</title>
    </sec>
    <sec id="sec-4">
      <title>3.1 Overview</title>
      <p>We propose a system called Aikuchi that enables users to mark
strings in Web pages and jump to other pages from the marked
string. The system lets users search pages using marked strings
from other users.</p>
      <p>Details of the system are as follows: Users can mark a string in
their Web browser using their mouse cursor when they find
something of interest on a page. (Fig. 1). Then the
recommendation window pops out to display recommendations
from other pages called recommendation links (Fig. 2). If the
user selects a recommendation link, the system shows the
specified page, and once a recommendation link is selected, the
system highlights the used string. We call this highlighted string
a footprint (Fig. 3). It is shared; i.e., users can see the footprints
added by all other users. If the user places her or his mouse
cursor over the footprint, the recommendation window pops out
again, with Fig. 4 Showing examples of recommendation links
and footprint links. The latter includes Web pages to which some
users have jumped from the marked string.
The left figure indicates title, authors and abstract for a paper.
The right figure is translation of the left it.
The right figure shows translation of the recommendation links</p>
      <sec id="sec-4-1">
        <title>The right figure is translation of the left it.</title>
        <p>The right figure shows translation of the footprint link and the
recommendation links</p>
      </sec>
    </sec>
    <sec id="sec-5">
      <title>3.2 Implementation</title>
      <p>Figure 5 shows the system’s structure. The system runs as a
script on the user client and on the Web server, and is
implemented with JavaScript and PHP.</p>
      <p>When a user accesses a Web page, the JavaScript engine asks
the Web server if a footprint exists, and shows it if that is the
case. When a user marks a string in the Web browser, the
JavaScript engine obtains the marked string and sends it to the
Web server, which then takes the marked string and calculates
the recommendation links according to certain algorithms.
Following calculation, the Web server sends recommendation
links and the JavaScript engine shows the recommendation
window to the user. If the user selects a recommended link, the
JavaScript engine sends it and the Web server saves the
following information related to the selected link as a text file in
the metadata storage.</p>
      <sec id="sec-5-1">
        <title>Date</title>
      </sec>
      <sec id="sec-5-2">
        <title>User ID</title>
      </sec>
      <sec id="sec-5-3">
        <title>Marked string</title>
      </sec>
      <sec id="sec-5-4">
        <title>Position of the marked string on the Web page</title>
      </sec>
      <sec id="sec-5-5">
        <title>URL of the selected recommended link Selected recommendation algorithm</title>
        <p>When a user places his or her mouse cursor over a footprint, the
JavaScript engine takes the string of the footprint and sends it to
the Web server. The Web server gets the footprint’s string,
calculates recommendation links, and obtains footprint links
from the metadata storage. The Web server then sends both
footprint links and recommendation links. Next, the JavaScript
engine again displays the recommendation window to the user
and if the user selects a footprint link or a recommended link, the
JavaScript engine sends it and the Web server saves information
about it.</p>
      </sec>
    </sec>
    <sec id="sec-6">
      <title>3.3 Recommendation algorithms</title>
      <p>When a user marks a string or places the mouse cursor over a
footprint on a Web page, the system shows recommendation
links using four types of algorithms that explore Web pages to
find useful pages based on the string or footprints. To make
recommendations, we use the system in a closed environment
where the available Web pages are fixed1.</p>
      <sec id="sec-6-1">
        <title>The algorithms are as follows: A) B) C)</title>
        <p>D)</p>
      </sec>
      <sec id="sec-6-2">
        <title>Page similarity using TFIDF</title>
        <p>Collaborative filtering using the number of footprints on a
Web page
Word matching between a marked string and footprint’s
strings
Word matching between a marked string and the Web
page’s strings.</p>
        <p>
          In algorithm A, the system employs calculated page similarity
based on TFIDF [
          <xref ref-type="bibr" rid="ref4">4</xref>
          ]. We calculate the TFIDF value of words on
Web pages and cosine similarity using them. If a user marks a
certain string on a Web page, the system recommends
highsimilarity pages to it regardless of the marked string and
footprints.
        </p>
        <p>
          In algorithm B, the system recommends pages with collaborative
filtering [
          <xref ref-type="bibr" rid="ref5">5</xref>
          ], using the number of footprints on a Web page as the
users’ evaluation of that page. We adopt not incoming links but
outgoing links, because selected recommendation links are not
valuable for users. Therefore, the system recommends Web pages
with a high predictive value using the number of footprints.
In algorithm C, if a word in the marked string matches one in
the footprint’s string on other pages, the system recommends the
matched page.
        </p>
        <p>In algorithm D, if a word in the marked string matches one in
another page’s string, the system recommends the matched page.
Table 1 shows a comparison of recommendation algorithms with
respect to whether they use a marked string and footprints.
Algorithm A makes recommendations based on page similarity
between Web pages without using a marked string or footprints.
This is assumed to be ordinary recommendation. Algorithm B,
meanwhile, uses the number of footprints on a Web page to look
for neighborhood users, and algorithms C and D use a marked
string as a query to search Web pages with matching words. The
difference is the search target: a footprint’s strings or a Web
page’s strings.</p>
        <p>We investigated which algorithms are preferred by users. The
system recommends up to two Web pages for each algorithm and
shows them in random order. Algorithm priority was applied so
that the same link was calculated in order of C, D, B, and A. The
system did not inform users about these algorithms. When users
clicked a recommended page link, we determined that users
preferred its recommendation algorithm.
1 Aikuchi is not limited to closed environments, but we restricted
the system to test recommendations in the following test cases.</p>
      </sec>
    </sec>
    <sec id="sec-7">
      <title>4. ANALYSIS</title>
      <p>We offered Aikuchi as a part of a support system at the
Japanese Society for Artificial Intelligence 2006, which was held
from June 7th to 9th, 2006. The support system was operated as a
Web system, and every conference participant could access it
using a user ID and password. The target Web pages comprised
276 pages that included authors and abstracts for papers. We
prepared recommendation pages using algorithm A. When users
marked a string, the system took a few seconds to display
recommendation links. After the completing the experiment, we
obtained 324 footprints and 172 links from them. Analysis of the
results revealed that there were 45 users who marked strings one
or more times, 28 users who jumped from marked strings to
other pages, 88 users who placed their mouse cursors over
footprints one or several times, and 33 users who jumped from
footprints to other pages. In this section, we describe which
algorithms were preferred by users.</p>
    </sec>
    <sec id="sec-8">
      <title>4.1 Preference of the algorithms</title>
      <p>Figure 6 shows a comparison of the number of selected
recommendation algorithms before and during the conference.
Before the conference, algorithm A was most commonly selected
and the number of selections of B and C were few since the
footprints were few at the beginning the conference. The number
of selections for D was fewer than that of A before the
conference. This means users selected a recommended link based
on similarity without relation to marked strings or footprints.
During the conference, the number of selections of C and D were
more than before it and the number of selections of B was fewer
than before it, since if Aikuchi recommended the same page links
over time, then users would be tired of selecting the links
recommended by B. The number of selections for algorithm A
was also lower during the conference. This means users selected
the recommendation algorithms based on the word in the marked
string. Therefore, we found that users prefer recommendations
based on words rather than similarity over time. As the number
of selections for algorithm C increased, we also found that
footprints are effective for recommending links.</p>
    </sec>
    <sec id="sec-9">
      <title>4.2 Footprints</title>
      <p>When users place their mouse cursor over a footprint, they can
obtain not only recommendations by the algorithms described
previously but also jumped pages. We investigated which
algorithms are preferred by users in such cases (Fig. 7). The
algorithm Z denotes the selection of jumped pages by users, and
the figure shows that Z was selected in an overwhelming number
of cases. Therefore, we found that users prefer to select links by
using footprints.</p>
    </sec>
    <sec id="sec-10">
      <title>5. CONCLUSION</title>
      <p>We proposed to use strings marked by users on Web pages as
tags, and developed a system called Aikuchi with which users
can mark strings and share them as footprints. Aikuchi
recommends links based on a variety of algorithms when a user
marks a string on a Web page.</p>
      <p>Based on the analysis of user logs, we found that users
preferred recommendations based on words in marked strings
rather than page similarity. We consider that footprints are useful
for users to select links because links based on footprints are
frequently selected by users. Consequently, we believe that
strings marked by users on Web pages can be used as
usergenerated metadata for searching pages.</p>
    </sec>
    <sec id="sec-11">
      <title>6. ACKNOWLEDGMENTS</title>
      <p>This research was supported by the National Institute of
Information and Communications Technology.</p>
    </sec>
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