1. Review the data flow diagrams you developed for questions in the BEC case at the end of Chapter 5 (or diagrams given to you by your instructor.) Study the data flows and data stores on these diagrams and decide if you agree with the team’s conclusion that there are only the six entity types listed in this case and in BEC Figure 6-1. If you disagree, define additional entity types, explain why they are necessary, and modify BEC Figure 6-1. The six entity types in BEC Figure 1 are the only ones needed to represent the MyBroadway system. However, depending on what data about Customers and Employees are required, entities for these objects may also be required. 2. Again, review the DFDs you developed for the MyBroadway system (or those given to you by your instructor).
Use these DFDs to identify the attributes of each of the six entities listed in this case plus any additional entities identified in your answer to Question 1. Write an unambiguous definition for each attribute. Then, redraw BEC, Figure 6-1 by placing the six (and additional) entities in this case on the diagram along with their associated attributes. The updated ERD appears in the BEC ERD at the end of this section. Microsoft Visio was used to prepare the ERD. The Comment entity has the attributes:
* Comment ID – a number generated by the system to uniquely identify a comment. * Membership ID – the membership number of the customer who makes the comment. * Member Comment – the text that a customer states about a certain product. * Member Name – the name of the customer who makes the comment. * Comment Time Stamp – the date and time that the comment was entered into the system by a customer. * Parent/Child – a designation whether the customer entering the comment is a parent or a child. * Product ID – serves as a foreign key.
The Essay on Steps Involved in the Data Preparation Process
Editing involves reviewing questionnaires to increase accuracy and precision. It consists of screening questionnaires to identify illegible, incomplete, inconsistent, or ambiguous responses. Responses may be illegible if they have been poorly recorded, such as answers to unstructured or open-ended questions. Likewise, questionnaires may be incomplete to varying degrees. A few or many questions may ...
The Pick entity has the attributes:
* Pick ID – a number generated by the system to uniquely identify an employee pick. * Employee Comment – the text that an employee states about a certain product. * Rating – a structured rating given to a certain product by an employee. * Employee ID – the ID number of the employee who submitted the pick. * Employee Name – the name of the employee who entered the pick into the system. * Pick Time Stamp – the date and time that the employee entered the pick into the system. * Product ID – serves as a foreign key.
The Product entity has the attributes:
* Product ID – a number generated by the system to uniquely identify a product offered for sale or rent by BEC. * Title – the title of the product. * Artist – the name of the artist of the product (if applicable).
* Type – an indication if the product is music, a game, or a movie. * Publisher – the name of the publisher of the product. * Category – the category that the product falls under (comedy, drama, etc.).
* Media – the type of media that the product is on (CD, DVD, etc.).
* Description – a description of the product.
* Release Date – the date that the product was released.
* Sale Price – the sales price of the product.
* Rental Price – the rental price of the product.
The Request entity has the attributes:
* Request ID – a number generated by the system to uniquely identify requests made by customers. * Request Time Stamp – the date and time that the request was made by a customer. * Membership ID – the membership ID number of the customer who made the request. * Member Name – the name of the customer who made the request. * Artist – the name of the artist (if applicable) of the product being requested. * Title – the title of the product being requested.
* Type – an indication if the requested product is music, a game, or a movie. * Media – the type of media the customer would like the product on. * Product ID – serves as a foreign key.
The Business plan on New Product Development Process 2
For every successful new product, many new product ideas are conceived and discarded. Therefore, companies usually generate a large number of ideas from which successful new products emerge. I work as a strategic manager in Solarland Co., Ltd. This company does business of electronic appliances. As a Strategic Manager, I have been directed by my BOD to introduce a new product in Bangladesh. I want ...
The Rental entity has the attributes:
* Rental ID – a number generated by the system to uniquely identify a rental of a specific product by a customer. * Membership ID – the membership ID number of the customer who rented the product.
* Member
Name – the name of the person who rented the product, which may be different than the cardholder’s name (child, spouse, etc.).
* Rental Time Stamp – the date that a customer rented the product involved in this rental. * Due Date – the date that the rented product is due back. This may be changed with a rental extension request. * Returned? – an indication if the rented item was returned or not. * Product ID – serves as a foreign key.
The Sale entity has the attributes:
* Sale ID – a number generated by the system to uniquely identify a sale of a specific product to a customer. * Membership ID – the membership ID number of the customer who purchased the product. * Member Name – the name of the person who purchased the product, which may be different than the cardholder’s name (child, spouse, etc.) * Sale Time Stamp – the date and time that the product was purchased by the customer. * Product ID – serves as a foreign key.
3. Using your answer to Question 2, designate which attribute or attributes form the identifier for each entity type. Explain why you chose each identifier. Comment ID and Pick ID are the identifiers of the entities Comment and Pick, respectively, because it would be much simpler to use a number than a long string of text, even though the comments themselves will most likely be unique. Product ID is the identifier of the entity Product because it is possible that more than one product could have the same title. Request ID is the identifier of the entity Request because a customer could make more than one request for a product on a certain day. Sale ID and Rental ID are the identifiers of the entities Sale and Rental, respectively, because a customer could buy or rent more than one product on a certain day.
4. Using your answer to Question 3, draw the relationships between entity types needed by the system. Remember, a relationship is needed only if the system wants data about associated entity instances. Give a meaningful name to each relationship. Specify cardinalities for each relationship and explain how you decided on each minimum and maximum cardinality on each end of each relationship. State any assumptions you made if the BEC cases you have read so far and the answers to questions in these cases do not provide the evidence to justify the cardinalities you choose. Redraw your final E-R diagram in Microsoft Visio.
The Research paper on Entity Relationship Modelling
Definitions Entity an aggregation of a number of data elements each data element is an attribute of the entity Background Introduced by Peter Chen in ‘75 now widely used You’ll find them in: Structured Systems Analysis and Design Methodology (SSADM) Information Engineering (IE) Multiview Yourdon/DeMarco. Entity type a class of entities with the same attributes Relationship an association between ...
The relationships between Product and Comment, Pick, Request, Rental, and Sale are all one-to-many relationships. A Product may have zero or many Comments, Picks, Rentals, and Sales associated with it. Comments, Picks, Requests, Rentals, and Sales must have one and only one Product associated with them. Requests may not have a Product associated with them (until the product goes into inventory).
A suggested ERD is provided at the end of this section.
5. Now that you have developed in your answer to Question 4 a complete E-R diagram for the MyBroadway database, what are the consequences of not having customer or employee entity types on this diagram? Assuming only the attributes you show on the E-R diagram, would any attribute be moved from the entity it is currently associated with to a customer or employee entity type if such entity types were on the diagram? Why or why not? The consequence of not including the customer and employee entity types on this diagram is that names (and possibly other attributes) appear as an attribute on several of the other entities. I would move the Member Name attribute from the Sale, Rental, Comment, and Request entities to the Customer entity and the Employee Name attribute from the Pick entity to the Employee entity if the Customer and Employee entities existed on this diagram.
This would eliminate the duplication of data. 6. Write project dictionary entries (using standards given to you by your instructor) for all the entities, attributes, and relationships shown in the E-R diagram in your answer to Question 4. How detailed are these entries at this point? What other details still must be filled in? Are any of the entities on the E-R diagram in your answer to Question 4 weak entities? Why? In particular, is the REQUEST entity type a weak entity. If so, why? If not, why not? Answers to this question will vary due to specific instructor instructions. Typical dictionary contents for entity, attribute, and relationship objects are listed below.
The Essay on The Entity Relationship Diagram
The Entity Relationship Diagram (ERD) depicts a conceptual data model that incorporates some of the important scientific information about the real world. It adopts a natural view that the real world consists of entities and relations (Chen, 1976). One objective of the ERD is to create a simple, easy to understand and conveniently presented data model consisting of entities, attributes, ...
Entity: Short name, name, plural, volume (initial, maximum, average, growth rate), data warehouse type, list of attributes, description Attributes: Primary UID, optional?, percentage used (initial, average), domain, type, maximum length, average length, decimal places, units, derivation, on condition, null value, default, sequence in sort, sort order Relationships: From entity name, from relationship name, from optionality and degree, to entity name, to relationship name, to optionality and degree, description
7. What date-related attributes did you identify in each of the entity types in your answer to Question 4? Why are each of these needed? Can you make some general observations about why date attributes must be kept in a database based on your analysis of this database? The Sale, Rental, Comment, Pick, and Request entities all have date/time-related entities. The date/time attributes are needed because the same customer could comment on, rent, buy, or request, the same product (on the same day), and an employee could enter a pick of the same product more than once (on the same day).
Also, to archive old, obsolete data, or to see temporal trends, dates are needed.
