11 June 2006

Databases for Laypeople: Part 6 in a series

The Frontend
(Table of Contents--Part 5)

The component of the DBMS devoted to user interface is known as the frontend. In a CMS, the frontend is known as the content delivery application (CDA). Both have closely related functions. The more formal, proper term is "client," which is derived from when databases resided on a remote computer. The distinction is that, today, in a web-delivered DBMS, the client resides with the server on the host.

The client/frontend/CDA, then, is responsible for an immense proportion of the database's usefulness. It is responsible for managing queries, which the user enters in a form of some kind (e.g., entering a search for "database" in Wikipedia; entering an Amazon search for used DVD's with a title of Solaris with an author of Tarkovsky), and replying to the query with data exported from the backend in a form.

While the backend includes features to protect the security of data transferred between it and the frontend, the frontend is responsible for making sure data is both accessible and protected. An obvious and familiar example is the rather large CMS known as Blogger. As the author of a website on Blogger, I have to log in before I can add, edit, or delete entries; change the template; or give permission to friends to edit this particular blog. The reader can access the website, but may not edit entries. Blogger, my gracious host, may suspend my account if I use it to post pornography or participate in racketeering. The Blogger site requires a very complex, high-capacity CDA to allow millions of visitors access to hundreds of thousands of blogs; that CDA must also discriminate among bloggers editing their own sites, Blogger account-holders leaving comments at sites not their own, and readers with no Blogger account, who may not leave comments.*

I use CMS applications as examples, although readers should understand they're used mainly to introduce some ideas. Past a certain point, however, the analogy has to break down. There's really not much relevence between SQL, for example, and most CMS applications. I'm hoping you keep in mind the more literal concept of a local area network (LAN) in a workplace, with the database not available to the Internet.

*Some sites allow anonymous commenting; Blogger allows bloggers to turn that feature on and off.
SOURCES & ADDITIONAL READING: "Your First Database," Webmonkey;

C.J. Date, An Introduction to Database Systems, 7th Edition, 2000; in Date's book, "backend" refers to the server, while "frontend" refers to the client. The book tends to deal with the formal, abstract side of the DBMS topic.



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