Thursday, October 29, 2009
Chapter 4: Database Management Systems
1. What are some of the difficulties in managing data?
- The amount of data increases exponentially with time. Much historical data must be kept for a long time, and new data are added rapidly. For example, sports data.
- Data are scattered throughout organisations and are collected by many individuals using various methods and devices. Data are frequently stored in numerous servers and locations and in different computing systems, databases, formats, and human and computer languages.
- New sources of data, such as blogs, podcasts, videocasts, and RFID tags and other wireless sensors are constantly being developed. Examples of unstructured data are, digital images, digital video, voice packets, and musical notes in an MP3 file.
- data decays overtime. For example, customers move to new addresses or change their names
2. What are the various sources for data?
Data sources can be internal, personal, clickstream (from your company’s Web transactions), and external (particularly the Internet). Internal data are usually located in corporate databases and are usually accessible via organization’s intranet. IS users create personal data by documenting their own expertise. These data can reside on the user’s PC, or they can be placed on corporate databases or on corporate knowledge bases. Sources of external data range from commercial databases to sensors and satellites. Government reports constitute a major source of external data. Many thousands of databases all over the world are accessible through the Internet.
3. What is a primary key and a secondary key?
A primary key is the identifier field or attribute that uniquely identifies a record. For example, a student record in a U.S. college would probably use the Social Security number as its primary key. A secondary key is and identifier field or attribute that has some identifying information, but typically does not identify the file with complete accuracy. For example, the student’s major might be a secondary key if a user wanted to find all students in a particular major field of study. It should not be the primary key, however, because many students can have the same major.
4. What is an entity and a relationship?
An entity is a person, place, thing or event (such as a customer, an employee, or a product) about which information’s maintained.
5. What are the advantages and disadvantages of relational databases?
- Based on the concept of two-dimensional tables.
- Not always a big table (called a flat file), that contains all of the records and attributes.
- Usually designed with a number of related tables. Each of these tables contains records, listed in rows, and attributes, listed in columns.
- Allows users great flexibility in the variety of queries they can make.
- Large-scale databases can be composed of many interrelated tables.
- The overall design can be complex
- Therefore have slow search and access times.
6. What is knowledge management?
Knowledge management (KM) is a process that helps organizations manipulate important knowledge that is part of the organization’s memory, usually in an unstructured format. For an organization to be successful, knowledge, as a form of capital, must exist in a format that can be exchanged among persons. In addition, it must be able to grow.
7. What is the difference between tacit knowledge and explicit knowledge?
Tacit knowledge is the cumulative store of subjective or experiential learning. In an organization, tacit knowledge consists of an organization experiences, insights, expertise, know-how, trade secrets, skill sets, understanding, and learning. It also includes the organizational culture, which reflects the past and present experiences of the organization’s people and processes, as well as the prevailing values. Tacit knowledge is generally slow, imprecise, and costly to transfer. It is also highly personal.
Explicit knowledge deals with more objective, rational, and technical knowledge. In an organization, explicit knowledge consists of the policies, procedural guides, reports, products, strategies, goals, core competencies of the enterprise and the IT infrastructure. In other words, explicit knowledge is the knowledge that has been codified in a form and can be distributed to others or transformed into a process or strategy.