Web crawler is a program or script that automatically crawls World Wide Web information according to certain rules. They are widely used in Internet search engines or other similar websites. , can automatically collect the content of all pages it can access to obtain or update the content and retrieval methods of these websites. Functionally speaking, crawlers are generally divided into three parts: data collection, processing, and storage.
Traditional crawlers start from the URL of one or several initial web pages and obtain the URL on the initial web page. During the process of crawling the web page, they continuously extract new URLs from the current page and put them into the queue until the system requirements are met. Certain stopping conditions. The workflow of the focused crawler is more complex, and it requires filtering links unrelated to the topic based on a certain web page analysis algorithm, retaining useful links and putting them into the URL queue waiting to be crawled. Then, it will select the web page URL to be crawled next from the queue according to a certain search strategy, and repeat the above process until it stops when a certain condition of the system is reached. In addition, all web pages crawled by crawlers will be stored by the system, subjected to certain analysis, filtering, and indexing for subsequent query and retrieval; for focused crawlers, the analysis results obtained in this process may also be Give feedback and guidance for future crawling processes.
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