UML Use Case Models and Modular Programming Session 3 LBSC 790 / INFM 718B Building the Human-Computer Interface

Agenda UML Overview Use Case Models Modular Programming Working with Java Team Project Show and Tell

Unified Modeling Language Systems can get more complex than people can comprehend all at once Key idea: Progressive refinement –Carve the problem into pieces –Carve each piece into smaller pieces –When pieces are small enough, code them UML provides a formalism for doing this –But it does not provide the process

Getting to the Object Structure Capturing the big picture –Use case diagram (interactions with the world) –Narrative –Scenarios (examples to provoke thinking) Designing the object structure –Class diagram (“entity-relationship” diagram) –Object diagram (used to show examples)

Specifying Behavior Represent a candidate workflow –Activity diagram (a “flowchart”) Represent object interactions for a scenario –Collaboration diagram (object-based depiction) –Sequence diagram (time-based depiction) Represent event-object interactions –Statechart diagram (a “finite state machine”)

Good Uses for UML Focusing your attention –Design from the outside in Representing partial understanding –Says what you know, silent otherwise Validate that understanding –Structuring communication with stakeholders

Where does UML fit in? Evaluate Refine Design Specification Identify needs/ establish requirements Build Prototype Final specification Start

Avoiding UML Pitfalls Don’t sweat the notation too much –The key is to be clear about what you mean! Don’t try to make massive conceptual leaps –Leverage abstraction encapsulation Don’t get to attached to your first design –Goal is to find weaknesses in your understanding

First Steps in UML Identify the key actors Identify the use cases Draw a use case diagram

Use Case Design Use Case Diagram –Input-output behavior Use Case Narrative –Explains each use case Use Case Scenario –Activity diagram shows how the use cases are used together

Use Case Diagram External “actors” –Roles of people –Types of systems Use cases –Top-level functions (solid arrows to/from actors) Relationships among use cases –Always-depends-on (dashed >) –Sometimes-is-depended-on (dashed >) –Inherits-from (solid triangle-arrow)

Example Use Case Diagram ILL Request Desk clerk Self-service Checkout Check-out Update Book > Patron

Assumptions Pre-conditions Initiation Dialog Termination Post-conditions Other requirements –Open issues, security, audit, … Use Case Narrative

Team Project In groups of 3 develop an application with significant UI functionality Every project should have a true client –Someone with a real need for the product that is not a member of the project team –Team experience, researcher at UMD, work and academic connections We will hold an “idea rally” next week –So in the next week, get thinking about some ideas! –Talk to potential clients – are they interested?

Team Project – Idea Rally Each student gives 90 second idea pitch. Including: –Why you think it is both interesting and feasible –At least one strength that you can bring to a project team Prior to class, prepare one sheet of paper with: –Your name, photo, and contact information –A sketch of the idea (bring 20 copies)

Team Project – Idea Rally Pitches rigidly timed Focus on the points that you believe will most impress your classmates Not graded Presenters may pre-load one slide for use during their idea –Must receive your PPT by COB Wed

Coming up Homework 1 –Will post by Friday evening –Graded; due before class –Study groups are encouraged See policy in course description Next week: –Object-oriented programming –Class and object diagrams