Design Tools in Databases

Design tools are used to describe the design process in a standard way. A standard tool is important because it provides the standard notation for designing specific systems. If there is no standard tool, everyone may use different design notation that can be difficult to understand for other. This situation can result in the more critical problem if both people are working on the same system.

Data flow Diagram

The most commonly used tools to design database system are data flow diagram (DFD). A data flow diagram shows the flow of data through an organization. It is used to design system graphically. DFD is very simple and hides complexities of the system.

Advantages of DFD

DFD provides the following advantages:

• It helps in the further understanding of interrelationships of system and subsystems.
• It is helpful in communicating current system knowledge to users.
• It is an analysis of proposed system to determine if all the data and processes have been defined.

Limitation of DFD

DFD has the following limitations:

• DFD does not provide any way of expressing decision points.
• DFD is only focused on the following of information.

Symbols in DFD

Data flow diagram uses the following symbols:

Data Flow

The data flow symbol is used to express the flow of information from one entity to another entity in the system. Data flow is a pipeline through which packets of information flow. An arrow labeled with the name of data is used for data flow.

Data Store

The data store symbol is used as a repository for the storage of data. It indicates that data is permanently stored in the database. It is expressed with a rectangle that is open on the right. The right width of the rectangle is drawn with double line

Process

The process symbol is used to express the transformation of incoming data flow into routing data flow. It is used to indicate the occurrence of an action it is used when data is transformed from to another form. An oval or round rectangle is used for this:

External Entity

An entity that interacts with the system from outside the system is called external entity. The external entities interact with the system in two ways. They may receive the data from the system or may produce data from the system.it is expressed as rectangle:

Collector

The collector symbol is used to express several data flow connection terminating at a single location. It is used to show the convergence of data to a single point. The following symbol is used to represent a collector:

Separator

The separator is used to separate data from a single source to multiple sinks. The following symbol is used to represent a separator: