Likely the most frequent technique used customarily to extract data from websites this is to cook up some regular expressions that match the pieces you want (e. g., URL’s and hyperlink titles). Our screen-scraper software actually started out as an application written in Perl for this very reason. In addition to regular expressions, you might also use some code written in something like Java or Active Hardware Pages to parse away larger chunks of textual content. Using raw regular movement to out the data can be a little intimidating to the uninformed, and can get somewhat messy when a software contains many of them. At the same time, if you’re already acquainted with regular expressions, and your scraping project is relatively small, they could be a great solution. yelp scraper
Other techniques for getting the data away can get very superior as algorithms that employ artificial intelligence and such are applied to the page. Some programs will actually analyze the semantic content of an CODE page, then intelligently get the pieces that are of interest. Still other approaches deal with growing “ontologies”, or hierarchical phrases meant to represent the content domain.
There are numerous of companies (including our own) offering commercial applications specifically designed to do screen-scraping. The applications vary a lot, but for medium to big projects they’re often a good solution. Each one will have its own learning curve, so you should plan on taking the perfect time to learn the inches and outs of a new application. Especially if you plan on carrying out a fair amount of screen-scraping it’s probably a good idea to at least shop around for a screen-scraping application, as it can likely save you time and money in the long term.
Therefore what’s the best way to data extraction? It will depend on what your preferences are, and what resources you have at your disposal. Here are some of the advantages and cons of the many techniques, as well as ideas on when you could use each one:
Raw regular expressions and code
– If you’re already familiar with regular expression including least one encoding language, this can be a quick solution.
– Regular expressions allow for a reasonable amount of “fuzziness” in the matching such that minor changes to the content won’t scramble them.
– You likely don’t have to learn any new languages or tools (again, assuming you’re already familiar with regular expressions and a programming language).
– Regular expressions are recognized in virtually all modern coding languages. Heck, even VBScript has an everyday expression engine. It’s also nice because the various regular appearance implementations don’t vary too significantly in their format.
– They can be complex for those that don’t have a lot of experience with them. Learning regular movement isn’t like going from Perl to Java. It can more like going from Perl to XSLT, where you have to place your brain around a completely different way of looking at the problem.