Assertions to better specify the amazon bug

ABSTRACT

Modern Web applications are mainly distributed systems that exploit the Internet as communication means and the Web as neutral interface to access services and data. The addition of services to Web applications poses problems that are usually tackled at the technology level, but that should be addressed during design to deliver quality Web applications. A typical example of these problems is the Amazon bug, an annoying problem that the user could encounter if after adding products to his shopping cart, he rolls back to a page with a previous version of the cart and tries to buy it. This would make the user buy the last version of the cart's contents, which in some subtle cases could be different from what expected.In this paper, we do not want to discuss all design aspects, but only how provided services/operations should jointly be designed with the rest of the system. We propose a new reference model for Web applications: Operations require a more complex model where they are not simply appended to information and navigation elements, but they can cooperate with them. Besides the reference model, the paper proposes the use of assertions to constraint the behavior of designed operations. Assertions do not only predicate on how data should be modified, but must also take into account how presentation and navigation could be affected by the execution of the operation.

REFERENCES

• 1: Luciano Baresi , Franca Garzotto , Paolo Paolini, From Web Sites to Web Applications: New Issues for Conceptual Modeling, Proceedings of the Workshops on Conceptual Modeling Approaches for E-Business and The World Wide Web and Conceptual Modeling: Conceptual Modeling for E-Business and the Web, p.89-100, October 09-12, 2000
• 2: Aldo Bongio , Stefano Ceri , Piero Fraternali , Andrea Maurino, Modeling Data Entry and Operations in WebML, Selected papers from the Third International Workshop WebDB 2000 on The World Wide Web and Databases, p.201-214, May 18-19, 2000
• 3: G. Booch. The architecture of web applications, 2001. http://www.developer.ibm.com/library/articles/booch_web.html.
• 4: Jim Conallen, Building Web applications with UML, Addison-Wesley Longman Publishing Co., Inc., Boston, MA, 1999
• 5: G. Denaro. Extending OCL to meet web application requirements. Technical report, Politecnico di Milano, 2001.
• 6: Piero Fraternali , Paolo Paolini, Model-driven development of Web applications: the AutoWeb system, ACM Transactions on Information Systems (TOIS), v.18 n.4, p.323-382, Oct. 2000 [doi>10.1145/358108.358110]
• 7: Franca Garzotto , Paolo Paolini , Daniel Schwabe, HDM—a model for the design of hypertext applications, Proceedings of the third annual ACM conference on Hypertext, p.313-328, December 15-18, 1991, San Antonio, Texas, United States [doi>10.1145/122974.123004]
• 8: O. M. Group. Object constraints language specification, Feb. 2001.
• 9: R. Hennicker and N. Koch. A UML-based methodology for hypermedia design. In UML 2000 - The Unified Modeling Language. Advancing the Standard. Third International Conference, York, UK, October 2000, Proceedings, volume 1939 of LNCS, pages 410-424. Springer, 2000.
• 10: Tomás Isakowitz , Edward A. Stohr , P. Balasubramanian, RMM: a methodology for structured hypermedia design, Communications of the ACM, v.38 n.8, p.34-44, Aug. 1995 [doi>10.1145/208344.208346]
• 11: G. Kappel, B. Proll, W. Retschitzegger, W. Schwinger, and T. Hofer. Modeling ubiquitous web applications - a comparison of approaches. In Proceedings of the Third International Conference on Information Integration and Web-based Applications and Services (iiWAS2001), Linz, Austria, pages 163-174, sep 2001.
• 12: Nick Kassem , Nicholas Kassem , Enterprise Team, Designing Enterprise Applications: Java 2 Platform, Addison-Wesley Longman Publishing Co., Inc., Boston, MA, 2000
• 13: R. Kramer, iContract - The Java(tm) Design by Contract(tm) Tool, Proceedings of the Technology of Object-Oriented Languages and Systems, p.295, August 03-07, 1998
• 14: Frank Manola, Technologies for a Web Object Model, IEEE Internet Computing, v.3 n.1, p.38-47, January 1999 [doi>10.1109/4236.747320]
• 15: Atif M. Memon , Martha E. Pollack , Mary Lou Soffa, Automated test oracles for GUIs, Proceedings of the 8th ACM SIGSOFT international symposium on Foundations of software engineering: twenty-first century applications, p.30-39, November 06-10, 2000, San Diego, California, United States
• 16: Bertrand Meyer, Eiffel: the language, Prentice-Hall, Inc., Upper Saddle River, NJ, 1992
• 17: San Murugesan , Yogesh Deshpande, ICSE'99 workshop on web engineering, Proceedings of the 21st international conference on Software engineering, p.693-694, May 16-22, 1999, Los Angeles, California, United States [doi>10.1145/302405.302961]
• 18: Oscar Pastor , Vicente Pelechano , Emilio Insfrán , Jaime Gómez, From Object Oriented Conceptual Modeling to Automated Programming in Java, Proceedings of the 17th International Conference on Conceptual Modeling, p.183-196, November 16-19, 1998
• 19: Thomas A. Powell , David L. Jones , Dominique C. Cutts, Web site engineering: beyond Web page design, Prentice-Hall, Inc., Upper Saddle River, NJ, 1998
• 20: Daniel Schwabe , Gustavo Rossi, An object oriented approach to Web-based applications design, Theory and Practice of Object Systems, v.4 n.4, p.207-225, Oct. 12, 1998 [doi>10.1002/(SICI)1096-9942(1998)4:4<207::AID-TAPO2>3.0.CO;2-2]

INDEX TERMS

Keywords:
assertions, web application design, web operation