Question

Database systems and Information systems

An information system performs three sets of services:

• It provides for data collection, storage, and retrieval.
• It facilitates the transformation of data into information.
• It provides the tools and conditions to manage both data and information.

Basically, a database is a fact (data) repository that serves an information system. If the database is designed poorly, one can hardly expect that the data/information transformation will be successful, nor is it reasonable to expect efficient and capable management of data and information.

The transformation of data into information is accomplished through application programs. It is impossible to produce good information from poor data; and, no matter how sophisticated the application programs are, it is impossible to use good application programs to overcome the effects of bad database design. In short: Good database design is the foundation of a successful information system.

Database design must yield a database that:

• Does not fall prey to uncontrolled data duplication, thus preventing data anomalies and the attendant lack of data integrity.
• Is efficient in its provision of data access.
• Serves the needs of the information system.

The last point deserves emphasis: even the best-designed database lacks value if it fails to meet information system objectives. In short, good database designers must pay close attention to the information system requirements.

Systems design and database design are usually tightly intertwined and are often performed in parallel. Therefore, database and systems designers must cooperate and coordinate to yield the best possible information system.  

The SDLC traces the history (life cycle) of an information system. The DBLC traces the history (life cycle) of a database system. Since we know that the database serves the information system, it is not surprising that the two life cycles conform to the same basic phases.

There are two basic approaches to database design: top‑down and bottom‑up.

Top‑down design begins by identifying the different entity types and the definition of each entity's attributes. In other words, top‑down design:

• starts by defining the required data sets and then
• defines the data elements for each of those data sets.

Bottom‑up design:

• first defines the required attributes and then
• groups the attributes to form entities.

Although the two methodologies tend to be complementary, database designers who deal with small databases with relatively few entities, attributes, and transactions tend to emphasize the bottom‑up approach. Database designers who deal with large, complex databases usually find that a primarily top‑down design approach is more appropriate.

Even if a generally top‑down approach is selected, the normalization process that revises existing table structures is (inevitably) a bottom‑up technique. E-R models constitute a top-down process even if the selection of attributes and entities may be described as bottom-up. Since both the E-R model and normalization techniques form the basis for most designs, the top‑down vs. bottom-up debate may be based on a distinction without a difference.  

Assignment

Write two to three paragraphs answering each of the following questions:

• What are business rules? Why are they important to a database designer?
• What is the data dictionary's function in database design?
• What factors are important in a DBMS software selection?

Answer 1

What are business rules? Why are they important to a database designer?

Business Rules are used every day to define entities, attributes, relationships and constraints. Usually though they are used for the organization that stores or uses data to be an explanation of a policy, procedure, or principle.

  The data can be considered significant only after business rules are defined, without them it’s just records, but to a business they are the characteristics that are defined and seen by the company.

  Business Rules help employees focus on and implement the actions within the organizations environment. Some things to think about when creating business rules are to keep them simple, easy to understand, keep them broad so that everyone can have a similar interpretation.

What is the data dictionary's function in database design?

A good data dictionary provides a precise description of the characteristics of all the entities and attributes found with in the database.

The data dictionary makes it easier to check for the existence of synonyms to verify appropriate relationships.

The data dictionary contents are developed and used during six DBLC phases like DataBase Initial Study,DataBase design,Testing and evaluation etc.

What factors are important in a DBMS software selection?

The DBMS manages the interaction between your applications and underlying database.When choosing a DBMS software you should consider some points before making a decision they are

1.Data Model:

To decide on which model works best for you, you should ask yourself: Do you have a data structure which you can easily reflect in a relational model or do you need to work with unstructured data? How do you retrieve and work with the data?

2.Data Consistency:

  Nowadays, collecting data is not a big effort any more. But, keeping the data consistent becomes even more important as more sources feed into the database. Therefore, consistency rules are very important and the ability to define these should be considered when choosing a new DBMS.

3.Data Security:

  Data availability is a key business success factor and should be guaranteed at all times. The ability to backup and restore the databases is essential and needs to be possible with your chosen DBMS.

There are also some other important factors to choose a Database software are DataProtection,Efficiency,Usability etc