Monday, 9 September 2013

Chapter Seven: Storing Organizational Information

Information is stored in databases

Database – maintains information about various types of objects (inventory), events (transactions), people (employees), and places (warehouses)

Database models include: 

Hierarchical database model – information is organized into a tree-like structure (using parent/child relationships) in such a way that it cannot have too many relationships

Network database model – a flexible way of representing objects and their relationships Relational database model – stores information in the form of logically related two-dimensional tables

Entity – a person, place, thing, transaction, or event about which information is stored
The rows in each table contain the entities
In Figure 7.1 CUSTOMER includes Dave’s Sub Shop and Pizza Palace entities

Attributes (fields, columns) – characteristics or properties of an entity class
The columns in each table contain the attributes
In Figure 7.1 attributes for CUSTOMER include Customer ID, Customer Name, Contact Name
Primary keys and foreign keys identify the various entity classes (tables) in the database.

Primary key – a field (or group of fields) that uniquely identifies a given entity in a table
Foreign key – a primary key of one table that appears an attribute in another table and acts to provide a logical relationship among the two tables

Database advantages from a business perspective include 

  • Increased flexibility
  • Increased scalability and performance
  • Reduced information redundancy
  • Increased information integrity (quality)
  • Increased information security

Increased flexibility

  • A well-designed database should:
  • Handle changes quickly and easily
  • Provide users with different views
  • Have only one physical view
  • Physical view – deals with the physical storage of information on a storage device
  • Have multiple logical views
  • Logical view – focuses on how users logically access information

Increased scalability and performance

A database must scale to meet increased demand, while maintaining acceptable performance levels
Scalability – refers to how well a system can adapt to increased demands
Performance – measures how quickly a system performs a certain process or transaction

Reduced information redundancy
Databases reduce information redundancy
Redundancy – the duplication of information or storing the same information in multiple places

Inconsistency is one of the primary problems with redundant information

Increase Information Integrity (Quality)

Information integrity – measures the quality of information

Integrity constraint – rules that help ensure the quality of information
Relational integrity constraint
Business-critical integrity constraint

Increased information security
Information is an organizational asset and must be protected

Databases offer several security features including:
Password – provides authentication of the user
Access level – determines who has access to the different types of information
Access control – determines types of user access, such as read-only access

Database Management Systems

Direct interaction –
The user interacts directly with the DBMS
The DBMS obtains the information from the database
Indirect interaction
User interacts with an application (i.e., payroll application, manufacturing application, sales application)
The application interacts with the DBMS
The DBMS obtains the information from the database

data-driven Web site is an interactive Web site kept constantly updated and relevant to the needs of its customers through the use of a database. Data-driven Web sites are especially useful when the site offers a great deal of information, products, or services. Web site visitors are frequently angered if they are buried under an avalanche of information when searching a Web site. A data-driven Web site invites visitors to select and view what they are interested in by inserting a query, which the Web site then analyzes and custom builds a Web page in real-time that satisfies the query. The figure displays a Wikipedia user querying business intelligence and the database sending back the appropriate Web page that satisfies the user’s request.

Data Driven Web Site Advantages

Development: Allows the Web site owner to make changes any time—all without having to rely on a developer or knowing HTML programming. A well-structured, data-driven Web site enables updating with little or no training.

Content management: A static Web site requires a programmer to make updates. This adds an unnecessary layer between the business and its Web content, which can lead to misunderstandings and slow turnarounds for desired changes.

Future expandability: Having a data-driven Web site enables the site to grow faster than would be possible with a static site.  Changing the layout, displays, and functionality of the site (adding more features and sections) is easier with a data-driven solution.

Minimizing human error: Even the most competent programmer charged with the task of maintaining many pages will overlook things and make mistakes. This will lead to bugs and inconsistencies that can be time consuming and expensive to track down and fix. Unfortunately, users who come across these bugs will likely become irritated and may leave the site. A well-designed, data-driven Web site will have ”error trapping” mechanisms to ensure that required information is filled out correctly and that content is entered and displayed in its correct format.

Cutting production and update costs: A data-driven Web site can be updated and ”published” by any competent data entry or administrative person. In addition to being convenient and more affordable, changes and updates will take a fraction of the time that they would with a static site. While training a competent programmer can take months or even years, training a data entry person can be done in 30 to 60 minutes.

More efficient: By their very nature, computers are excellent at keeping volumes of information intact. With a data-driven solution, the system keeps track of the templates, so users do not have to. Global changes to layout, navigation, or site structure would need to be programmed only once, in one place, and the site itself will take care of propagating those changes to the appropriate pages and areas. A data-driven infrastructure will improve the reliability and stability of a Web site, while greatly reducing the chance of ”breaking” some part of the site when adding new areas.

Improved Stability: Any programmer who has to update a Web site from ”static” templates must be very organized to keep track of all the source files. If a programmer leaves unexpectedly, it could involve re-creating existing work if those source files cannot be found. Plus, if there were any changes to the templates, the new programmer must be careful to use only the latest version. With a data-driven Web site, there is peace of mind, knowing the content is never lost—even if your programmer is.

Integrating Information
among Multiple Databases

Integration – allows separate systems to communicate directly with each other

Forward integration – takes information entered into a given system and sends it automatically to all downstream systems and processes

Backward integration – takes information entered into a given system and sends it automatically to all upstream systems and processes

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