1. Web crawler is a program that automatically extracts web pages. It downloads web pages for search engines from the World Wide Web and is an important part of search engines.
2. According to the system structure and implementation technology, web crawler can be roughly divided into the following types: general web crawler, incremental web crawler and deep web crawler. The actual network crawler system is usually realized by combining several crawler technologies.
3. The goal of the crawler is to improve the freshness of the page as much as possible, while reducing the obsolescence of the page. This goal is not exactly the same. In the first case, the crawler is concerned about how many pages are outdated; In the second case, the page that the crawler cares about is out of date. If you are interested, click here to study for free.
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