Data modeling is used to represent the system visually. It describes how data should be used to meet certain requirements given by the user. (Ref) This helps to ensure that all the requirements of the system have been met. There are numerous types of models used for different reasons, including logical and physical models. Each type of modeling has a specific purpose and is essential to the overall project. Some modeling describes the logic of the system, while others show the flow of information through the system. The purpose of models is to help the team gather enough information about what is required of the system and design the system in a logical manner.
Logical models are used to represent the flow of information through a system. This means that it depicts visually the way data is input into the system, the process the data undergoes by the system, and what is output by the system. This is important because it helps to develop the logic of a system. The main purpose of a logical model is to show what a system must do and does not concern itself with how this will be accomplished. (Rosenblatt, 2014)
Physical data models show how the system requirements will be implemented. (Rosenblatt, 2014) Physical models show the table structures of a database including column names, data types, constraints, and relationships between data. (Mallikaarachchi) The difference between a logical and physical model is that physical models are more detailed and give more information about how the system should look in the end. Further, logical data models do not show technological choices made by the design team. It merely focuses on what is needed of the system. Physical models show the technology choices and the limitations of these choices. Physical models are used to show technological designs, while logical models are used to show business requirements. (“Data modeling”)
Both physical and logical modeling use similar diagrams and documentation. It is the way that these diagrams are used that differentiates them from being either logical or physical. Structured analysis tools, such as Data flow diagrams (DFDs), data dictionaries, and process descriptions are used during the analysis phase of the system development life cycle, while these tools can be used during the system design phase to create a physical model. (Rosenblatt, 2014)
Data flow diagrams display the path that data will take from one part of the system to another. (Rosenblatt, 2014) The result of this diagram in a logical model is a visual for what is input into the system, the process that will occur, and where the data will be stored in the system. The purpose of the DFD is to show how data will be flowing in and out of the system. Data flow diagrams are important because they help to create a logical system.
Data dictionaries are where the details of the data flow diagrams are held. These are important because they hold the information regarding the contents of data flow, data stores,...