WebCrawler’s and Comparison of Their Efficiency

Running head: WEBCRAWLER’S AND COMPARISON OF THEIR EFFICIENCY
WebCrawler’s and comparison of their efficiency
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1WEBCRAWLER’S AND COMPARISON OF THEIR EFFICIENCY
Introduction
Web crawlers are the software programs that helps the analysts or developers to
browse the web pages on internet in an automated manner. These web crawlers are also
helpful in automated maintenance of the websites in order to check different link to the
internal and external destinations as well as validation of the HTML code of the website
(Farag, Lee and Fox 2018). In addition to that, the crawlers are mostly used in order to gather
specific types of data from the different Web pages of a site. Mostly this information
includes collecting e-mail addresses.
Functionality of the web crawlers
The web crawlers somehow behave like the librarian in real life. It looks for certain
data on the internet and when it is found it is categorized by the crawler. The type of
information needs to be defined by particular predefined instructions.
Main usage of the open source web crawlers
The web crawlers are mainly used for price comparison on different e-commerce
portals search in order to get information about some specific products. In this way the prices
on different websites can be compared precisely in real time. In addition to that, in case of
data mining, a crawler is also capable of collecting publicly available e-mail or other similar
kind of data about the different organizations. Moreover, it is very helpful in order to collect
information about page views for a web page, incoming or outbound links to the pages.
Techniques to use in web scraping
Crawling and scraping Websites and pages requires ability to use the available
network bandwidth, conforming robot exclusion standards or policies of the web sites,
refreshing the web pages logically to get the required data, selection of the high quality and

2WEBCRAWLER’S AND COMPARISON OF THEIR EFFICIENCY
significant pages in order to explore the available data, use of the available disk space in an
efficient manner (Farag, Lee and Fox 2018). In addition to that, the crawler should also
continue working on the pages or websites even if the crawler counters large sized
documents, slow responsive servers, multiple URLs that are leads to the similar documents,
broken links as well as corrupted files.
Furthermore, the crawlers also let the users to invoke and direct for a text search and
get the results accordingly. In addition to that, the hypertext nature is also helpful for getting
the result in an enhanced manner over the text-search engine, through the use of the link-text
indexing and analysis.
Open sources crawlers
Following are the list of open source crawlers that are used widely by the
organizations and individuals;
Scrapy
Apache Nutch
Heritrix
WebSphinix
JSPider
GNUWGet
WIRE
Pavuk
Teleport

3WEBCRAWLER’S AND COMPARISON OF THEIR EFFICIENCY
WebCopierPro
Web2disk
Features for a good web crawler
There are certain features that must be satisfied by any web crawler to be one of the
best crawlers.
Being robust: The web crawlers must be intended to be flexible as well as resilient
against the traps that are used by the different web servers (Agre and Mahajan 2015). This
traps direct the crawlers in fetching the boundless number of pages from a specific domain of
the website. Some such traps are noxious which results in erogenous development of the site.
Maintaining the web server policies: most of the web servers have some policies or
approaches for the crawlers which visit them so as to abstain the crawlers from over-
burdening the websites that leads degradation in performance.
Distributed execution: An efficient crawler ought to be able to be executed in a
distributed manner over various servers or systems (Farag, Lee and Fox 2018).
Scalability of the operation: The architecture of the crawler must allow scaling up the
rate of crawling by including additional computers/systems as well as bandwidth or
transmission capacity to the targeted website.
Execution and productivity: The crawler framework should utilize different
framework resources including processor, system band-width and storage efficiently.
Quality: Quality characterizes how significant the crawled pages are fetched by the
crawlers. Crawler attempts to download the significant pages in the first attempt.
Features of Scrapy