Petries Electronics Case Structuring Systems Requirements
Petries Electronics Case Structuring Systems Requirements Petries
Petrie’s Electronics Case, Chapter 7, Questions 2, 3, and 4 (page 231) involves developing an Entity-Relationship (E-R) diagram based on prior Data Flow Diagrams (DFDs) for Petrie’s customer loyalty system. The task requires identifying attributes for each entity, defining unambiguous attribute descriptions, determining primary identifiers (keys) for each entity, and establishing relationships with appropriate cardinalities. The process includes reviewing existing DFDs, creating detailed entity attribute definitions, selecting keys, and illustrating the relationships between entities with proper cardinalities, culminating in an updated E-R diagram. The context involves entities such as Customer, Coupon, Product, Promotion, Service, and Transaction, along with possible additional entities, to accurately model the system's data structure for the loyalty program, guiding database design and system implementation.
Paper For Above instruction
The Petries Electronics case presents a comprehensive scenario for developing a detailed Entity-Relationship (E-R) model based on initial Data Flow Diagrams (DFDs). This task involves a systematic process of translating system requirements into data entities, accurately defining their attributes, establishing clear identifiers, and illustrating the relationships among these entities with appropriate cardinalities. This process is crucial for designing an efficient database that supports the customer loyalty system and its associated operations.
To begin with, reviewing the existing DFDs is essential to understand the data flow and identify all relevant entities involved in the system. The key entities identified from the case include Customer, Coupon, Product, Promotion, Service, and Transaction. Each entity has specific attributes that describe its characteristics and distinguish one instance from another. For example, the Customer entity might include attributes such as Customer ID, Name, Contact Information, and Membership Status. The Coupon entity could have attributes like Coupon ID, Value, Issue Date, and Expiration Date. Defining these attributes unambiguously ensures clarity in data representation and facilitates accurate database implementation.
Following the identification of attributes, the next step is to designate the primary key or keys for each entity. The primary key must be unique for each instance of an entity to serve as an unambiguous identifier. For the Customer entity, Customer ID would serve as the primary key, since each customer has a unique identifier. Similarly, Coupon ID, Product ID, Promotion ID, Service ID, and Transaction ID would be appropriate keys for their respective entities. The selection of these keys is based on their uniqueness and stability over time, ensuring reliable identification of entity instances within the database.
Once entities and their keys are defined, the focus shifts to establishing relationships between entities, reflecting how data related to different entities interacts within the system. For example, a Customer can have multiple Coupons, making this relationship a one-to-many link. A Transaction involves one or more Products and may be associated with a Customer, suggesting a many-to-one or many-to-many relationship, depending on specific system rules. Promotions can be linked to Products or Coupons, representing a one-to-many or many-to-many relationship based on the scenario. Defining cardinalities—such as one-to-one, one-to-many, and many-to-many—and justifying them based on system requirements are critical. For instance, each Coupon might be associated with exactly one Coupon Code, but a Coupon Code might be linked to multiple Coupons, indicating a one-to-many relationship. Assumptions are made where the case information is insufficient to specify exact cardinalities, and such assumptions should be clearly documented.
The final step involves synthesizing all this information into an updated E-R diagram, ideally using diagramming tools such as Microsoft Visio. This diagram visually represents entities, their attributes, primary keys, relationships, and cardinalities, providing a comprehensive blueprint of the data structure for Petrie’s customer loyalty system. The resulting model will facilitate system development, ensuring that data management is consistent, efficient, and aligned with the system’s functional requirements.
References
- Database Systems: Design, Implementation, & Management. McGraw-Hill Education.