## 4 Implementation and Experiments
### Results and Evaluation
#### 4.2.1 Qualitative Results  
The proposed SFWC was evaluated over two sets of seed URLs from a different source: (i) seed URLs retrieved from the Google search engine and (ii) seed URLs selected from the built corpus (Wikipedia category). Tables 4 and 5 show the results per topic after processing both sets of seed URLs. The first column corresponds to the topic. The second column is associated with the number of seed URLs retrieved from the Google search engine and Wikipedia. In the case of the search engine, it was queried with the topic name, e.g., the query string \"computer science\" was used to retrieve the web pages related with the topic of computer science. For the case of Wikipedia, the set of seed URLs was randomly selected for each category from the built corpus, e.g., 50 Wikipedia pages were randomly selected from the politics corpus. The last three columns show a summary of the processed seed URLs: (i) crawled, (ii) not crawled, and (iii) not processed Wikipedia pages. The _seed URLs crawled_ column defines the number of seed URLs whose content was similar to the corresponding topic after computing the similarity measure, i.e., the similarity measure result was in the threshold. The _seed URLs not crawled_ column defines the seed URLs whose content was not similar to the corresponding topic, i.e., the similarity measure result was not in the threshold. The last column (_seed URLs not processed_) defines the number of seed URLs that was not processed because an error occurred, e.g., the seed URL returns the HTTP 400 error code (Bad Request Error). That means that the request sent to the website server was incorrect or corrupted and the server couldn't understand it. The results from Google's seed URLs (Table 4) got the lowest number of seed URLs crawled in comparison with the Wikipedia's seed URLs results (Table 5) in which all topic seed URLs crawled are above 50%. Additionally, the Google's \begin{table}
\begin{tabular}{p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt}} \hline \hline
**Category** & \begin{tabular}{c} **Number of** \\ **Pages** \\ \end{tabular} & \begin{tabular}{c} **Total Enriched Nouns** \\ **(Average per Document)** \\ \end{tabular} & \begin{tabular}{c} **Total Enriched Nouns** \\ **Associated with a KB** \\ **(Average per Document)** \\ \end{tabular} \\ \hline \hline Computer science & 1151 & \begin{tabular}{c} 289,950 \\ (251.91) \\ \end{tabular} & \begin{tabular}{c} 24,993 \\ (21.71) \\ \end{tabular} \\ \hline Diabetes & 202 & \begin{tabular}{c} 83,723 \\ (414.47) \\ \end{tabular} & \begin{tabular}{c} 14,470 \\ (71.63) \\ \end{tabular} \\ \hline Politics & 1717 & \
\begin{tabular}{c} 793,137 \\ (461.66) \\ \end{tabular} &
\begin{tabular}{c} 80,024 \\ (46.58) \\ \end{tabular} \\ \hline
**TOTAL** & **3070** & \
\begin{tabular}{c} **1,166,810** \\ **(380.07)** \\ \end{tabular} &
\begin{tabular}{c} **119,487** \\ **(38.92)** \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Category information per topic and enriched noun extraction statistics. seed URLs were prone to errors, being the most recurrent the HTTP 400 error code (bad URL request). In contrast, Wikipedia's seed URLs were not prone to these kinds of errors. The URLs crawled from the seed URLs were not restricted or limited to be from the same domain name as the seed URL (e.g., [[http://en.wikipedia.org](http://en.wikipedia.org)]([http://en.wikipedia.org](http://en.wikipedia.org))), that is, the URLs added to the queue could be from any other domain different from the seed URL. Tables 6 and 7 show the crawling results for each topic. The first column defines the topic. The second column defines the number of seed URLs crawled. The number of seed URLs processed is in correspondence with the third column (seed URL crawled) from Tables 4 and 5.