Sunday, 1 May 2011

Databases and Data Warehouses


1. List, describe, and provide an example of each of the five characteristics of high quality information.
The five characteristics of high quality information are:
1.    Accuracy
Whether or not the information displayed is correct.
Eg. Customers details being inputted correctly into the database.
2.   Completeness
If the data is complete.
Eg. The customer’s address is fully put into the system, including the street name, the postcode, etc.
3.   Consistency
Whether or not all the data in the system is in agreement with each other.
Eg. All transactions from a customer’s file add up to their total.
4.   Uniqueness
When any business process is represented only once in the system.
Eg. Each customer is given an individual customer number in the system.
5.    Timeliness
Whether or not the information in the system is current.
Eg. Customer’s details are updated monthly.

2. Define the relationship between a database and a database management system.
A database is something that maintains information about various types of objects (such as inventory), events (transactions), people (employees) and places (warehouses).
A database management system (DBMS) is software that is used to manage and query a database.
The relationship between these two is that they both depend on each other. A DBMS couldn’t exist without databases. And the use of databases would be very difficult without them being properly managed.

3. Describe the advantages an organisation can gain by using a database.
An organisation can benefit from databases in these ways:
·      Increase flexibility
A good database can adjust quickly with the business changes. Therefore keeping all their data readily accessible.
·      Increased scalability and performance
Scalability and performance would increase once all their information is easier to access and stored logically.
·      Reduced information redundancy
Information redundancy would decrease because redundancy is the duplication of information. Once the information has been stored in the database it would be less likely to be entered in twice.
·      Increased information integrity (quality)
Information integrity is a measure of the quality of information. The quality of information would increase with the use of a database because of the introduction of integrity constraints – which are rules that ensure information quality.
·      Increased information security
Information security with increase because of protection measures that will be put in place to protect the databases – including passwords, antivirus software, access levels/controls. These things all ensure authentication.


4. Define the fundamental concepts of the relational database model.
The concepts are:
·      Entities
A person, place, thing, transaction or event about which information is stored.
·      Attributes
(AKA fields or columns) Characteristics or properties of an entity class.
·      Keys & Relationships
Developers need to identify keys and create relationships between them. These keys include:
- Primary keys: a field (or group of fields) that uniquely identify a given entity in a table.
- Foreign keys: a primary key of one table that appears as an attribute in another table and acts to provide a logical relationship between the two tables.

5. Describe the benefits of a data-driven website.
The benefits include:
·      Development
Website owner is allowed to make changes any time they want. These websites allow updating to occur with little/no training.
·      Content management
Changes can happen automatically.
·      Future expandability
The site can grow faster than a static website.

6. Describe the roles and purposes of data warehouses and data marts in an organisation.
The roles and purposes of data warehouses are:
·      A data warehouse is a logical collection of information. It’s gathered from different databases.
·      The role of a data warehouse is to store all the data from several databases.
·      The purpose of a data warehouse is  for all the information that it collects, to come together and support business analysis activities and decision-making tasks.
The roles and purposes of data marts are:
·      A data mart is an object that contains a subset of data warehouse information.
·      The role of a data mart is to store subsets of data warehouse information.
·      The purpose of a data mart is to make it easier to find and access information from data warehouses.

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