Challenges in web crawling
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Web crawlers are automated programs that scan the internet to index data for search engines, enabling users to find relevant information efficiently. They face several challenges, including non-uniform web structures, AJAX elements that generate dynamic content, real-time data acquisition difficulties, and complexities surrounding user-generated content ownership. Understanding these challenges is crucial for optimizing websites to ensure they are visible and effectively indexed by crawlers.
Challenges in web crawling
- 2. CHALLENGES IN WEB CRAWLING
- 3. WEB CRAWLER Web crawler (also known in other terms like ants, automatic indexers, bots, web spiders, web robots) is an automated program, or script, that methodically scans or “crawls” through web pages to create an index of the data it is set to look for. This process is called Web crawling or spidering.
- 4. CRAWLER A crawler is a program that visits Web sites and reads their pages and other information in order to create entries for a search engine index. The major search engines on the Web all have such a program, which is also known as a "spider" or a "bot." Crawlers are typically programmed to visit sites that have been submitted by their owners as new or updated.
- 5. HOW A WEB CRAWLER WORKS The world wide web is full of information. If you want to know something, you can probably find the information online. But how can you find the answer you want, when the web contains trillions of pages? How do you know where to look? Fortunately, we have search engines to do the looking for us. But how do search engines know where to look? How can search engines recommend a few pages out of the trillions that exist? The answer lies with web crawlers.
- 6. HOW A WEB CRAWLER WORKS Crawlers scan web pages to see what words they contain, and where those words are used. The crawler turns its findings into a giant index. The index is basically a big list of words and the web pages that feature them. So when you ask a search engine for pages about hippos, the search engine checks its index and gives you a list of pages that mention hippos. Web crawlers scan the web regularly so they always have an up-to-date index of the web.
- 7. THE SEO IMPLICATIONS OF WEB CRAWLERS Now that you know how a web crawler works, you can see that the behavior of the web crawler has implications for how you optimize your website. For example, you can see that, if you sell parachutes, it’s important that you write about parachutes on your website. If you don’t write about parachutes, search engines will never suggest your website to people searching for parachutes.
- 8. THE SEO IMPLICATIONS OF WEB CRAWLERS It’s also important to note that web crawlers don’t just pay attention to what words they find – they also record where the words are found. So the web crawler knows that a word contained in headings, meta data and the first few sentences are likely to be more important in the context of the page, and that keywords in prime locations suggest that the page is really ‘about’ those keywords. So if you want search engines to know that parachutes are a big deal on your website, mention them in your headings, meta data and opening sentences. The fact that web crawlers regularly trawl the web to make sure their index is up to date also suggests that having fresh content on your website is a good thing too.
- 9. SEARCH ENGINE INDEXES Once the crawler has found information by crawling over the web, the program builds the index. The index is essentially a big list of all the words the crawler has found, as well as their location.
- 10. CHALLENGES IN WEB CRAWLING • Challenge I: Non-Uniform Structures • Challenge II: Omnipresence of AJAX elements • Challenge III: The “Real” Real-Time Latency • Challenge IV: Who owns UGC?
- 11. CHALLENGE I: NON-UNIFORM STRUCTURES Data formats and structures are inconsistent in the ever-evolving Web space. Also, norms on how to build an Internet presence are non-existent. The result? Lack of uniformity and the vast ever-changing terrains of the Internet. The problem? Collecting data in a machine-readable format becomes difficult. Also, problems increase with increase in scale. Especially, when: a) structured data is needed, and, b) large number of details are to be extracted w.r.t. specific schema from multiple sources.
- 12. CHALLENGE II: OMNIPRESENCE OF AJAX ELEMENTS AJAX and interactive web components make websites more user-friendly. But not for crawlers! The result? Content is produced dynamically (and on-the-go) by the browser and therefore not visible to crawlers. The problem? To keep the content up-to-date, the crawler needs to be maintained manually on a regular basis. So much so, that even Google’s crawlers find it difficult to extract information! The solution? Crawlers need to be refined in their approach to be more efficient and scalable.
- 13. CHALLENGE III: THE “REAL” REAL-TIME LATENCY Acquiring data-sets in real-time is a huge problem! Real-time data is critical in security and intelligence to predict, report, and enable preemptive actions against untoward incidents. The problem? The real problem comes in deciding what is and isn't important in real time.
- 14. CHALLENGE IV: WHO OWNS UGC? User-Generated Content (UGC) proprietorship is claimed by giants like Craigslist and Yelp and is usually out-of-bounds for commercial crawlers. The result? Only 2-3 % sites disallow bots. Others believe in data democratization, but it is possible these may follow suit and shut access to the data gold mine! The problem? Site policing for web scraping and rejecting bots.
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