Automated Web Scraping And Data Extraction Tools

Web scraping is a technique used to automatically gather and manipulate website information on the user's behalf and then export it into a database or an Excel spreadsheet. It is an alternative to manual or customized data extraction procedures, which are tedious and error-prone. An automated web scraping tool is an important part of any web data extraction process.

Let us take a look at some web scraping basics and one of the easiest web scraping tools available, Data Toolbar.

What Makes Web Scraping Possible?

A wide range of Web resources show information that is typically a description of objects retrieved from underlying relational databases and displayed on Web pages following some fixed templates. In other words, most Web pages show already-structured data. 

These data are formatted for use by people, and the relevant content is embedded into HTML tags. It is natural for HTML tags to inherit and reflect the structure of the underlying data. Most of the time, that structure does not depend on the actual value of the data fields. 

Because HTML is an open, non-proprietary standard, the page structure can be accessed and parsed by external programs back to its relational form. This applies to almost any HTML content generated by a web server or by a browser engine using JavaScript.

There are alternative web technologies like Flash and Silverlight that do not expose the document's model and can protect displayed information from an automated web scraping tool.

Lists And Details

Let's start with web scraping basics with this example. 

The image above and the image on the left show two examples of structured data objects.

The first image is a Web page segment containing a list of several products. The description of each product is called a data record. Such a page is called a list page. When the number of records is too large to be displayed on one page, list pages are often linked together by a pagination control. 

The second image shows a page segment containing a detailed description of one product. Such a page is called a detail page. The objective of a web scraping tool is the automated detection of the record structure on the list page and the extraction of relevant text and images. The screen scraping tool then discards irrelevant material, such as HTML tags or advertisements.

Setting Up A Project

In most cases, it is not possible for a program to automatically detect which content is relevant and which is not, even with the easiest web scraping tool. Therefore, to set up an automated web scraping tool, you need to teach the program what information you require. Thus, the program has to go through a supervised learning procedure to retrieve data extraction rules from a manually labeled example.

Manual labeling requires a user to point to the text and images of interest and select a crawling rule (next page element). The web scraping software will then detect the template pattern from the manual sample and web page structure based on a tree-matching algorithm, and the rest can be done automatically.

DOM Tree Parsing And Regular Expressions

There are many obstacles that an automated web scraping tool has to overcome to extract all data records correctly. Inline frames, dynamically generated content, inline ads, asynchronous page updates, and page errors are typical problems that can break data extraction or crawling logic.

To resolve these problems, web scraping programs use a combination of regular expression matching and DOM tree parsing. Although it is possible to build a DOM model directly by parsing HTML text, it is better to retrieve it through an embedded web browser. Besides parsing HTML code and generating a DOM tree, the embedded browser executes all client-side scripts and communicates with a web server. 

The only disadvantage of using the embedded browser compared with direct HTML parsing is its relatively slow performance. Regular expression matching is usually efficient only for final refinement, for example, when the content to be extracted is a fragment of the HTML element that cannot be broken down into any sub-elements.

How To Get Started

If you are tired of manually scraping websites for data, then it is time to get the easiest web scraping tool available. It is added to your browser as a data scraper extension. Using the web scraper for Chrome or Firefox will make your data extraction a lot easier. Once you’ve gone through the web scraping basics with the program, you can effortlessly screen scrape the data to Excel.

Best of all, you get a 14-day free trial version to test how an automated web scraping tool works. When you purchase the Data Toolbar web scraping tool, you will say goodbye to tedious manual copying and hello to efficient web data collection.

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