Agile Software Development, UML Use Cases, Class Diagrams, and Sequence Diagrams

Agile Principles in Extreme Programming (XP)

The Agile manifesto (Appendix 1) states the 12 principles of Agile software development. Using examples from Extreme Programming (XP), suggest whether and how XP meets the following principles:

1.Welcome changing requirements, even late in development. Agile processes harness change for the customer's competitive advantage.

2.Business people and developers must work together daily throughout the project.

3. Continuous attention to technical excellence and good design enhances agility.

4.At regular intervals, the team reflects on how to become more effective, then tunes and adjusts its behaviour accordingly

Draw a UML use case diagram for the following scenario. 

A customer can browse the catalogue and select one or more items to buy by adding them to their basket. The customer then goes to check out their basket. They must provide a delivery address and select the method of delivery (next day, standard delivery). The system updates the delivery costs. The customer then adds their credit card information. The system checks the payment information via an external payment gateway. If the payment is authorised then the system authorises the purchase and the payment is processed by the payment gateway. The system sends a confirmation email to the customer.

There is more than one valid solution to this question.

Explain what a UML class diagram is and illustrate (with appropriate UML examples) the following concepts. 

a)class, association and multiplicity 

b)composition and aggregation 

In a review of UML in practice, Petre (2013) reported that some people using UML found sequence diagrams useful for requirements elicitation with technical stakeholders. 

A sequence diagram is one of the UML interaction diagrams. It models a single scenario executing in a system. It shows what messages are sent and when. A sequence diagram includes the following elements:

1.Participant: an object or an entity

2.Message: communication between participants

The horizontal axis in a sequence diagram shows which participant is acting, whereas the vertical access shows the flow over time (moving top to bottom over time).

Draw a UML 2.0 sequence diagram for the following use case. Use any appropriate reference, e.g. online access via UCL library to Learning UML 2.0 by Miles and Hamilton (page 108, sequence diagram).

According to the Object Management Group (OMG) who maintain it, the Unified Modelling Language (UML) is a “graphical language for visualizing, specifying, constructing, and documenting the artefacts of distributed object systems”. While this course (and others) teach the use of UML, Petre (2013) finds that many companies do not use it, or only use selected models, and even these are often used informally.

To what extent do you think UML should be used in a software development project for a web application? Which UML models (diagrams) do you think may be of most use in this context? Use examples and appropriate references to support your answer. 

References do not need to be from academic journals or books; references to blogs/wikis may be used. However, consider the authority of the author e.g. a comment from an unknown contributor on stack overflow is probably not useful, a comment from a blog or wiki from someone respected in the software engineering community such as Ivar Jacobson, Robert Martin, Ron Jefferies, Martin Fowler, or an organisation such as Google or Microsoft, is likely to be more relevant.