Analysis Modeling CpSc 372: Introduction to Software Engineering Jason O. Hallstrom jasonoh@cs.clemson.edu Authorship Disclaimer. These slides are intended to serve as teaching instruments for an undergraduate course in Software Engineering. While the slides were formatted by Dr. Hallstrom, the content is compiled from other sources, including the readings listed on the course website, Dr. Pressman’s Software Engineering textbook, and various internet materials. In almost every case, the ideas belong to someone other than Dr. Hallstrom. Indeed, text is often quoted verbatim without an explicit citation (to improve the readability of the slides). The original authors retain all copyrights. If you are interested in citing any of the material in these slides, please contact Dr. Hallstrom for the original source(s). DO NOT CITE THIS PRESENTATION. THE CONTENT SHOULD NOT BE ATTRIBUTED TO DR. HALLSTROM. SEE DR. HALLSTROM IF YOU HAVE ANY QUESTIONS.

The Analysis Model The analysis model consists of a wide variety of diagrammatic forms used to bridge an important gap. System Description Design Model Analysis System information System function System behaviors Purpose: Describe what the customer wants built Establish the foundation for the software design Provide a set of validation requirements

Some Rules of Thumb Make sure all points of view are covered Every element should add value Keep it simple Maintain a high level of abstraction Focus on the problem domain Minimize system coupling

Analysis Modeling Approaches Structured Analysis: Object-Oriented Analysis Models data elements Attributes Relationships Models processes that transform data Models analysis classes Data Processes Models class collaborations Techniques from both approaches are typically used in practice.

A Roadmap We are going to examine some of the key tools used for creating an analysis model. General Use-cases Use-case diagrams Activity diagrams Swimlane diagrams These tools are not specific to either structured analysis or OO analysis. Structured Analysis OO Analysis Data object diagrams ERD diagrams Data flow diagrams Process specifications Class diagrams Packages CRC cards Sequence Diagrams

Use-Cases Key Points: Example: “[Use-cases] are simply an aid to defining what exists outside the system (actors) and what should be performed by the system (use-cases).” –Ivar Jacobson Key Points: A scenario that describes a thread of usage for achieving a functional requirement Actors represent roles people, devices, or external systems play System internals are ignored Example: See Pressman Chapter 8, Section 8.5.1, pg. 190

The Key Elements of a Use-Case A descriptive name for the scenario e.g., “Customer Checkout”, “Browse Products” The primary actor in the scenario Who is interacting with the system? The primary actor’s goal What is the actor trying to accomplish? Scenario pre-conditions What assumptions are being made? Scenario trigger How was the scenario initiated? The “sunny day” scenario In the best case, how does the user interact with the system? Exceptions What might go wrong? Remember why we’re interested in use-cases!

Developing a Use-Case What are the main tasks or functions that are performed by the actor? What system information will the actor acquire, produce or change? Will the actor have to inform the system about changes in the external environment? Does the actor wish to be informed about unexpected changes? …

Example: The Online Bookstore Consider the following excerpt from the initial scope document of a system that will be used by a local bookseller. The Online Bookstore System (OBS) will be a web-based application that allows customers to browse and purchase online product offerings. The application will support the notion of an online shopping cart, similar to other online retailers such as Amazon.com. The checkout features of the system will be integrated with our credit card transaction processor, as well as our internal billing system. The system will also provide an administrator-view that will allow authorized employees to view and administer products, customers, and orders. Based on this description, what are the key use-cases?

Activity Diagrams For complex use-cases, the process flow may be difficult to understand. Activity diagrams provide a graphical view of the interactions in a use-case. Example: See Pressman Chapter 8, Section 8.5.2, pg. 192

Swimlane Diagrams In some cases, it help to indicate which actors (or analysis classes) are responsible for which activities. A swimlane diagram serves this purpose. Example: See Pressman Chapter 8, Section 8.5.3, pg. 193

Use-Case Diagrams You’ll probably have a lot of use-cases! Use case diagrams (UCD) provide a diagrammatic table of contents, and a high-level overview of the system. Diagrams Show: Actors Use-cases Relationships among them Example UCD