Asymmetrical Effects of Using Positive and Negative Examples on Object Modeling

Abstract

Analysis and design is a critical distinction (and consummate challenge) of information systems as a discipline. Object orientation as a mantra and central focus has characterized much recent analysis and design attention. The role of object models in information systems development and challenges associated with developing quality object models especially by novice analysts is a salient point of interest. Illustrative examples of good-quality and poor-quality object models or parts of object models offer guidance available for learning and developing object models. Our research attempts to assess the usefulness of using positive versus negative examples in teaching object modeling skills, so as to enable better learning outcomes for novice analysts. Results of a controlled experiment comparing the effects of positive and negative examples on the quality of object models produced show that positive examples enhanced syntactic quality, negative examples improved semantic quality, and neither had much impact on pragmatic quality.

Appendices

Appendix 1: Some Common Quality Problems and Corresponding Positive and Negative Examples

Category	Description	Positive example	Negative example
Syntactic	Class name is a noun, mostly singular, and it begins with an uppercase letter	Class “Sale” is appropriately named using a noun	Class “Sell” is improperly named because it is not a noun
	Association name should be a verb phrase that represents the relationship when it is read along the reading direction from one class to the other	The association name “works at” between “Employee” and “Store” is a verb phrase	The association name “at” between “Store” and “Employee” is not a verb phrase
Semantic	The multiplicity end should have a correct range according to the problem domain description	The multiplicity range for association “places” is correctly specified (a “Customer” places one or more “Orders”)	Multiplicity for association “picked up at” is wrongly specified on the side of class “Order” (i.e., a “Store” can only have zero or 1 “Order” for pickup)
	All attributes relevant to the problem domain entity should be included in the class (i.e., important attributes should not be missing)	The class “Employee” includes many important attributes such as name, phone, and baseSalary	The class “Employee” does not have some important attributes such as name, phone, and baseSalary
Pragmatic	There must be sufficient distinction between (or among) the subclasses (i.e., each subclass has a unique set of attributes and/or relationships)	Sufficient distinction between subclasses “Manager” and “SalesPerson” exists for specialization	Insufficient distinction between subclasses “Manager” and “AssistantManager” for specialization
	Attributes (e.g., age, total amount) which can be computed or replicated from parent side of relationships should not be shown in the conceptual model	No attributes of class “SalesPerson” are redundant	The attribute “storeAddress” in class “SalesPerson” is redundant

Appendix 2: Smallbytes Subscription System Case Study and Expected Solution

Smallbytes is published on a monthly basis; a typical monthly issue consists of 5–10 articles, each written by one or more authors in the software engineering field. The authors receive a year’s free subscription as a token of appreciation for their efforts. Most authors have written only one article during the journal’s 5-year history, but a few have written several. For such authors, another 1-year complimentary subscription is given following the expiry date of the current subscription.

Smallbytes also has an editorial board of advisors, some of whom may also be authors from time to time. The editorial board normally serves for a 1- or 2-year term and they too receive a complimentary subscription to the magazine. The editorial board reviews submitted articles and recommends publication if the article is of good quality.

Smallbytes is sold on a subscription basis. Payments for new subscriptions are normally received by check. Some subscribers pay by credit card. Most subscriptions are for a 1-year period, but the publisher accepts subscriptions for periods longer than or shorter than a year by simply pro-rating the annual subscription price. Most of the subscribers are “single-copy” subscribers; however, some large companies order multiple copies, all of which are sent to the same address. Multiple-copy subscriptions typically involve a small discount from the single-price copy.

Appendix 3: Screenshot of Training Environment Showing a Positive Example (group P)