1. Develop a context diagram and a top-level DFD to model the data flows involved in registering for classes at your college or university. Then model the student registration system in a use case diagram and write a textual description for one of the use cases. 2. Discuss the differences between data stores on a DFD and an entity-relationship diagram for the same information system application. What purpose does each serve? What does each explain or show that the other does not?
1. The process of registering for classes at a college or university involves various data flows. To model these data flows, we can begin by creating a context diagram and a top-level DFD.
A context diagram provides a high-level overview of the system, showing the interactions between the system and external entities. In the case of registering for classes, the external entities could include students, instructors, and the registration system itself. The context diagram will show the data flows between these entities, highlighting the inputs and outputs of the registration system.
On the other hand, a top-level DFD is a more detailed representation of the system, showing the major processes and data flows within the system. In the context of student registration, the top-level DFD may include processes such as student information validation, course selection, and enrollment confirmation. The data flows in this diagram will illustrate how data is transformed and circulated within the system.
In addition to the context diagram and top-level DFD, we can also model the student registration system using a use case diagram. A use case diagram illustrates the interactions between actors (users or external systems) and the system, showcasing the different use cases that the system supports. In the case of student registration, potential use cases could include “Search for courses,” “Add course to schedule,” and “Confirm enrollment.” Each use case represents a specific functionality that the system provides to the user.
To provide a textual description for one of the use cases, let’s consider the “Search for courses” use case. This use case allows students to search for courses based on criteria such as course code, course name, or instructor.
Textual description for “Search for courses” use case:
Title: Search for courses
Primary Actor: Student
Description: This use case allows the student to search for courses based on various criteria such as course code, course name, or instructor. The student can enter one or more search criteria and submit the search request to the system. The system will then retrieve the matching courses from the course database and display them to the student.
1. The student enters the desired search criteria (e.g., course code, course name, or instructor) into the search form.
2. The student submits the search request.
3. The system validates the search criteria and retrieves the matching courses from the course database.
4. The system displays the list of matching courses to the student.
5. The student can further refine the search or select a course from the list.
A1. If the search criteria are invalid or incomplete, the system displays an error message and prompts the student to re-enter the search criteria.
A2. If no courses match the search criteria, the system displays a message indicating that no courses were found.
2. Data stores on a DFD and an entity-relationship diagram serve different purposes in modeling an information system application.
A data store on a DFD represents a temporary or permanent storage location for data within a system. It is used to store and retrieve data during the execution of processes. In the context of student registration, a data store could represent the student information database, course database, or class schedule database. The data store on a DFD provides a means to show where data is stored within the system and how it is used by processes.
On the other hand, an entity-relationship diagram (ERD) is a conceptual modeling technique used to represent the relationships between entities in a database. It depicts the entities (such as students, courses, and instructors) and the relationships between these entities. An ERD focuses on the structure of the database and the relationships between entities, rather than the data flows within the system.
The purpose of a data store on a DFD is to show the storage and retrieval of data within a system, providing a representation of where the data is stored and how it is used. It helps to understand the flow of data within the system, including how data is transformed and modified by processes. On the other hand, an ERD focuses on the relationships between entities, illustrating the structure of the database and the dependencies between entities.
In this way, a data store on a DFD explains or shows the storage and utilization of data within the system, while an entity-relationship diagram explains or shows the relationships and structure of the database itself. Each modeling technique serves a different purpose in understanding and representing an information system application.