Data Modeling
Why are data models important?
Data models are important because they provide a blueprint or structure for data making it easier to access, manage, and share.
What is a process and what is its symbol in DFDs?
A process is a task that receives input data and produces output data that has a different form or content. It is represented in DFDs using a rectangle with rounded corners.
True or false: A data flow must be connected to a process with a data store.
No, A data flow does not have to be connected to a process, let alone one with a data store.
A use case can be thought of as a what?
A use case can be thought of as a scenario.
What is the difference between a logical model and a physical model?
A logical model describes what the system must do, whereas a physical model illustrates how the system will be constructed.
What is a data flow and what is its symbol in DFDs?
A data flow is a path within a system where data is able to traverse from one part of the system to another. In a DFD the symbol for data flow is a line with either a single or double arrowhead.
What must a data element have?
A data element must have a standard name, that is meaningful to the user.
What is the first step in the process of creating a DFD using a use case?
Determining the actors and use cases.
What is the purpose of a data flow diagram (DFD)?
A data flow diagram is used to illustrate how data input into a system is transformed and transported throughout said system.
What is the purpose of a data store? What is the symbol used to represent a data store in a DFD?
A data store is used to store data that the system may need to access later. A data store is represented by a flat rectangle that is open on the right side and closed on the left side.
What is the difference between a source and a sink?
A source is an entity that is the origin point of the data and supplies it to other entities via a data flow, whereas a sink is an entity that is the final destination of the data.
What can be thought of as a process?
Anything that meaningfully alters data can be considered a process.
What is the four-model approach?
A four-model approach involves an analyst creating a physical model and logical model of the current system and then creates another physical and logical model for the new system.
What is an entity? What is the symbol used for it in a DFD?
An entity is a node that represents the origin point or final destination of data.
What is a black hole? (In terms of DFD fallacies)
A black hole is an input that has no output.
True or False: A single use case can involve multiple actors.
True
What are the benefits of using the four-model approach? What is the disadvantage?
The benefit of using this approach is that it creates a clear picture of the current system and how it functions before any changes are made. The disadvantage to using this approach is the added time and costs associated with creating another physical and logical model.
How do all four of these concepts (entities, data flows, data stores, and processes) work in tandem? (Give an example)
The general idea is that either an entity receives data from another entity or process via a data flow or it sends data to another process or entity via a data flow. A data store is used to hold data for a process to access during this chain of events. Example: A customer (the entity) places an order (sends data via data flow) at an online store (data goes into the process represented by the store and stored in a data store) after the system confirms the order it sends a confirmation (via data flow) back to the customer.
What are the four requirements of a DFD process?
1) A process name or label
2) A description of the process' purpose.
3) A reference number for the process.
4) Input and output dataflows.
True or False: Use cases are only used during the software testing phase.
False