What is Design Tools

Design Tools

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

Data Flow Diagram
The most commonly used tool to design a database system is a data flow diagram (DFD). A data flow diagram shows the flow of data through an organization. It is used to design systems graphically. DFD is very simple and it hides the complexities of the system.

Advantages of DFD
DFD provides the following advantages:

1. It provides the freedom from committing to the technical implementation of the system too early.
2. It helps in further understanding of interrelationships of systems and subsystems.
3. It is helpful in communicating current system knowledge to users.
4. It is an analysis of a proposed system to determine if all the data and processes have been defined.

Limitations of DFD
DFD has the following limitations:

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

Symbols in DFD
The data flow diagram uses the following: 

Data Flow
The data flow 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 datastore 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 lines.

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

External Entity
An entity that interacts with the system from outside the system is called an 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 a rectangle:

collector
The collector symbol is used to express several data flow connections 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:

Context diagrams are also used to represent and depict a system. A DFD is a more detailed representation of the system. A context diagram only deals with the boundary of the system. It gives the overall picture of a system. It represents the software model as a single and large process with input and output data. It is displayed by incoming and outgoing arrows respectively. It focuses on the main data flow in a system. It establishes the relationships between external entities of a system and the system via the data (flows) that they exchange. To enable a DFD to start from a context diagram, a single bubble of the context diagram is partitioned into more bubbles to reveal the details of processing in the system.
The data flow diagrams are basically process-oriented. They are used to model the functions performed by a system.

• Database Environment