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# 7.2.2 Database servers

To be able to search a website like Amazon’s requires not only a web server, but a database server. Like a web server, a database server is a computer that responds to requests from other computers. Its task is to find and extract data from a database.

The internet and database servers form part of a distributed system. This means that separate computers exchange data and information across a network (in this case the internet) to produce results for a user. For example, suppose you use the keyword search to ask for ‘kitchen cleaners’. This request is transferred to the web server, which has an index of products which can be categorised as kitchen cleaners. It then sends these product numbers to the database server, which locates the correct items in the product database and returns information about them (pictures, description and price), via the web server, to the browser.

Compared with the simple data from which the complex DNA database is built, the data processed by the database servers at a company like Amazon is complex (text, graphics, pictures).

## Activity 22 Information requirements

Allow about 5 minutes

For a company like Amazon:

1. what are its customers’ information requirements?
2. what are the company’s information requirements?

### Discussion

Your answer will probably differ from this list, but you should have a number of similar points.

1. Customers are likely to want to know:
   - the items for sale
   - what items look like
   - details about performance
   - cost
   - other information, such as availability, guarantees, delivery costs, and time of delivery.
2. Amazon’s requirements will be much broader and include information relating to:
   - product suppliers
   - wholesale cost
   - availability and delivery arrangements
   - its own storage and distribution system
   - who buys products from Amazon and why
   - what other products such buyers might be interested in
   - where there might be sufficient customers to warrant opening a new shop
   - hiring, training, promoting and retaining staff
   - competitors and what they offer that Amazon does not
   - accounts and finance
   - legal matters such as product and supplier liability, employment law, contract law.

Let’s see how Amazon’s system addresses some of these requirements in terms of the data they store in their databases. This will include:

- information about customers:
  - names and contact details
  - credit card information
  - the passwords (if any) they use to gain access to the Amazon website
- information about their products for sale:
  - pictures
  - specifications
  - price
  - special offers
- the current stock (inventory) of a particular item
- the position of a product in terms of its popularity
- orders that have been made:
  - when they were made
  - when they were or will be dispatched
  - whether the full order can be satisfied from stock.

What is interesting is that although the data listed above is quite ‘rich’ (i.e. complex), the processing required to extract the data is not very complicated. For example, it takes very little computational effort to extract a customer’s current order. All that is necessary is for the area of the database containing order details to be searched for a match with the customer’s name information or an order number.

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