Peer Review

Conceptual Design: Entity Relationship Models

Material Detail page

Reviewed:: Mar 22, 2008 by Business

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Ratings

Overall Rating:

Content Quality:

Effectiveness:

Ease of Use:

Overview:

Authors Van Slyke and Day provide a 24 page book chapter (2004 copyright). Sections within the chapter include: the entity relationship diagram, how to create the E-R diagram using a sales order entry example, and special topics in E-R diagramming. Subtopics in the first section include: entities, attributes, primary keys, relationships, and cardinalities. Section two details a 5 step process for creating an E-R diagram. Special topics include: resolving many-to-many relationships, supertypes and subtypes, and unary relationships.

Type of Material:

Reference

Recommended Uses:

Individual homework to read, or as a lecture on the topic

Technical Requirements:

Internet browser and PDF Reader

Identify Major Learning Goals:

Define terms related to entity relationship modeling, including entity, entity instance, attribute, relationship, cardinality and foreign key.
Describe the entity modeling process.
Discuss how to draw an entity relationship diagram.
Describe how to recognize entities, attributes, relationships and cardinalities.
Describe how to model supertype/subtype structures and unary relationships.

Target Student Population:

College undergraduate or graduate MIS, AIS or computer science classes that includes coverage of semantic modeling and the construction of Entity Relationship Diagrams.
Professionals and persons interested in creating relational databases.

Prerequisite Knowledge or Skills:

Understanding of basic database structure and design concepts.

Content Quality

Rating:

Strengths:

Database modeling is a difficult area and this chapter is informative with examples provided to highlight the troubling areas. This chapter discusses concepts utlizing the Barker E-R diagramming technique (although the specific method is not identified). Concepts are nicely integrated and informed by scholarship
Overall Figure 6 is a good straightforward diagram.
A great discussion of primary keys appears on page 10.
Using an interview with illustrated transcripts to demonstrates the dynamics involved in developing an E-R model is nicely done, linking theory to practice. In addition, how a form can be used to identify entities is something generally not seen in AIS textbooks.

Concerns:

The chapter contains several well-known references, but does not show the bibliography.
The point that no standardized process exists for creating E-R diagrams is not made nor the are the variety of acceptable diagraming notations mentioned.
A few ambiguities and inaccuracies exist as follows:
1. Page 2 is unclear right before Figure 1. It indicates rectangles represent entities. However, rectangles appear within rectangles making the discussion confusing until the reader progresses further. This ambiguity could be easily clarified by stating Four entities are shown in Figure 1.
2. An inaccuracy exists at the top of page 3 regarding attributes being represented by ellipses. Relationships are represented by elipses. A similar inaccurate reference is made on page 11.
3. The material before and after Figure 3 on page 3 is also confusing. Does the composite primary key consist of three or two attributes? The paragraph before the figure says two, the paragraph after Figure 3 says three.
4. The last paragraph on page 12 is vague regarding attributes appearing on the same form. Including a sentence referring to the same entities as described in Table 5.1 would help the reader to better follow the discussion because the example used 5 pages prior may not be remembered.
The concept of foreign keys is not defined in the chapter as indicated in objective #1.
Examples are rather limited to a single sales order activity illustrated by a form, when in reality the entire revenue cycle would need to be modeled. Current AIS textbooks due a better job discussing and illustrating concepts found in sections one and two.
The discussion of minimum and maximum relationships/cardinalities is incomplete. In particular how to decipher minimum cardinalities is omitted. Only three examples are provided when two other possibilities exist (O,N) and (0,1). Furthermore the difference in meaning associated with using a comma versus a colon in representing the relationship is not mentioned.
No mention is made of the imporance of normalization.
The summary is rather scant given the content covered.
Whether the module is self-contained is questionable, as no exercises or discussion questions and solutions have been included to reinforce teaching and learning.

Potential Effectiveness as a Teaching Tool

Rating:

Strengths:

Four objectives have been identified and a chapter overview is included. Concepts are reinforced in a progressive fashion building on prior discussions and demonstrating relationships between and among them. Other comments:

Nice tip provided on page 7 about the difficulties in identifying cardinalities.
Great advice on page 8, about being aware of the nouns that a user mentions in interviews.
Another helpful tip appears at the top of page 9 about the more difficult of two challenges, identifying missed entities than removing unneeded entities.
Good example about the assumption being explained on page 15.
Great explanation on page 17 about determining whether price is a function of the single entity product or both the product and order entities.
Nice job with Figure 16 and the corresponding explanation.
Great inclusion of disjoint and overlap subtypes on page 21.

Concerns:

No prerequisite skills have been identified and certainly would be required for this chapter to realize its full potential.
No formative or summative activities have been included either within the chapter or at the end of the chapter.
Current AIS textbooks do a better job explaining and illustrating E-R Diagramming.
The model has not been tied to an actual implementation. Showing how the E-R diagram would be converted to tables and attributes in Access would have been a nice addition.
In terms of efficiency, the reader has to really concentrate to grasp what is being explained. The authors have done the public a service in providing the readers examples with explanation and diagrams that should be able to be followed. However, close attention is required to read the text and unerstand the diagrams. In addition, it will take some time to get through and understand all 24 pages. This concern may actually be a veiled compliment to the authors for their thoroughness.

Ease of Use for Both Students and Faculty

Rating:

Strengths:

Because this module is a book chapter, many of the MERLOT criteria applied to digital learning objects does not directly apply. The chapter is well written and relatively easy to understand by someone who is familiar with E-R modeling. Key terms are highlighted with bold font. Illustrations are nicely done but average from a design standpoint when compared to similar illustrations provided in published textbooks.

Concerns:

One major concern is the lack of practice exercises or discussion questions to add an element of interactivity.
No use of color has been incorporated to add interest.
Using a copy of an actual sales order form would have been a better graphic.

Other Issues and Comments:: This module is a generous offering on the part of the authors to individuals learning about ERD. The chapter, however, would likely be more valuable for a MIS class as AIS discussions of the topic focus on REA modeling entire business processes.
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