The Google license key allows you to use the Google Web Application Programming Interfaces (APIs) to build Web searching into your Web-enabled applications using the Google engine and database. Google requires the license key to be included with every query that your application sends so they can validate that you are a registered user and track the number (and possibly the contents, though they don't say) of the queries that you send. Once Google has validated the query, the search results are returned to your application as structured data for processing and presentation using your interface.
The Google license key is free and is very easy to get. You simply supply Google with a valid e-mail address and a password that you specify. Google then sends you an e-mail message that you use to verify your address. When you have done that, Google sends the license key. It's just that easy. The Google Web APIs are free to download and use, subject the Terms and Conditions of Service.
The Google Web APIs use the Simple Object Access Protocol (SOAP) to communicate with your application. SOAP is an XML-based protocol for exchanging information that is widely supported by programming languages. Some of the languages supported out-right are: Java, Microsoft Visual Studio .NET family, and Perl. The Google Web APIs distribution also includes a Web Services Definition Language (WSDL) file that programmers in other languages can use to develop their own interfaces.
Using your Google license key, your queries to the Google Search Engine can make use of most Google search features. The features that you can use include automatic results filtering (restricts the display of similar results and results from the same Web host), SafeSearch (filters out adult content from the search results, the + (include) and - (exclude) operators, phrase searching using double quotes (" "), and using the Google spell checker to suggest an alternate spelling for a word.
More advanced features are also available through the Google Web APIs. These include restricting the search to a particular country, topic, language, date range, or site; searching for words only within URLs, titles, body text, or links; restricting the search to only particular file types (or excluding particular file types from the search); listing Web pages that link to the specified page; listing Web pages that are similar to the specified page; and retrieving a particular Web page from Google's cache. You can also use the Boolean AND (.), OR (|), and NOT (-) operators within your query and use parentheses to force terms to be evaluated in a particular order.
The availability of these query features to an application allows you to develop very powerful and flexible querying and data analysis tools. By doing much of the preliminary filtering through the structure of the query, you can eliminate most false hits ahead of time, saving time (and money) for the end user.
Search results are returned in a form similar to what you see on Google's Search Results pages with the various data elements separated into fields. These fields contain The Open Directory Project summary (if the site is listed in the ODP), the page's URL, a snippet showing the query term(s) in context on the Web page, the title of the Web page, the cached size of the page, and a Boolean value indicating whether or not related links are available for this page. If filtering is active, the second result returned from a particular site contains the host name for the site.
The separation of the returned data into fields allows your application to perform analysis on the data automatically. It may filter, sort, or weight the data based on the contents of certain fields and return a numerical analysis or sorted or separated lists. Your application can also automatically store the data in a dataase for later retrievalor analysis.
For you as a Web or Web-enabled software developer, the only limit on the usefulness of this capability is your imagination. Some potential uses might include automatically running certain queries on a regular basis to retrieve updated information, doing market research by monitoring the number of hits returned by specific queries, automatically searching certain sites for certain queries on a regular basis, retrieving and analyzing the results of a query in a single step, or using Google's spell-checking capabilities to enhance your application.
For software developers, the Google license key opens the door to the Web and puts billions of Web pages at your fingertips.
