1.1 Databases: The Unseen Services

In today's modern societies, we depend on many services from organizations and governments that we take for granted. Often, we are not even aware of the underlying and invisible components that make these services available to us. For example, we live in houses, go to school and work in buildings, exercise in gymnasiums, and attend sports activities in stadiums. We observe and interact with the visible components of these edifices, but we seldom think about the unseen components that provide the comfort and stability that we enjoy on a daily basis.

Databases play the same role in our information-rich, connected, and mobile world. Of course, almost everything we do with an electronic device depends on some underlying databases. In most cases, we do not even think about the source and format of the information that we are retrieving.

Let's examine some examples.

• Log in and use Facebook:  Your login and personal information is kept in a database, as is the information for all of your friends, posts, and messages.

• Make a phone call or send a text message:  The lists of phone numbers and locations in your cell phone is maintained by databases. All the information about your phone calls and text messages is maintained at a very detailed level in databases.

• Read your email: Not only is your login information kept in a database, but the history of all incoming and outgoing emails is also kept in very large databases.

• Go shopping (groceries, clothes, gasoline):  First, the product, inventory levels, and price information is kept in a database so that the checkout register can identify it correctly. Then (if you use a credit or debit card), that information must be retrieved from another database.

• Check a book out of the library:  The database is checked to make sure you are a valid patron of the library. Then, information about the book, its availability, and checkout status is all verified and updated for your library loan. The database is used to obtain both patron information and book information.

• Withdraw money from an ATM:  First, your authorization information must be verified, and then the availability of sufficient funds is also verified. Finally, your account balances must be updated. All this information is stored in the bank's databases.

• Have a physical exam with your doctor:  All of your patient information is maintained in your medical database. Your records will be updated from the results of your exam. The accounting, billing, and insurance records will also all be updated.

We seldom think about these databases, unless they become unavailable or there has been a security breach where private data has been accessed by unauthorized individuals or made public. When they don't work correctly, we get frustrated and upset that the level of service that we expect is not being provided. The availability and integrity of databases is an important issue in the daily activities of each of our lives.