HI-600: Analysis and Design of Health Information Systems

Analysis: Part IIUse Case Analysis

USE CASES (UC)• A use case depicts a set of activities that produce

some output result.• Each use case describes how an external user

triggers an event to which the system must respond.

• Perceives the system strictly from users’ perspective.

• With this type of event-driven modeling, everything in the system can be thought of as a response to some triggering event.

• Creation of use cases is often done as a part of interview session with users or a part of JAD sessions.

Use Cases: Outline• Elements of a use case• Alternative use case formats• Use cases and testing• Building use cases• Identify the major use cases• Identify the major steps within each use case• Identify elements within steps• Confirm the use case

• Basic Information• A descriptive name and brief description• ID Number (usually sequential)• Priority: how important is it for the new system• Actor (user role): something that interacts with

system to achieve a goal• Triggers (external or temporal): what starts the

UC• Preconditions• Most UCs are sequential • What must happen before this UC occurs

Elements of a Use Case

Elements of a Use Case• Big picture of user interactions with the system• List of steps needed to execute• Inputs needed for and outputs produced by the steps

• Normal Course• Everything goes as planned (happy path)• Default options are chosen

• Alternative Course• If normal course includes conditional steps• Branch logic (user chooses non-default option)• Still want to reach the desired end result

Elements of a Use Case• Post-Conditions• What happens after the end result is reached? • Also defines preconditions of the next UC

• Exceptions• What possible errors/exceptions could be

encountered and at which step?• What should happen is such error is

encountered?

Elements of a Use Case• Summary Inputs and Outputs• List of all inputs and outputs (including all

courses)• Including input sources and output destinations

• Additional Use Case Issues• Frequency of use• Business rules• Special requirements• Assumptions• Notes and issues

Alternative Use Case Formats• A full-dressed use case is very thorough,

detailed, and highly structured.• The project team may decide that a more

casual use case format is acceptable.

Use Cases & Testing• Now that we know what the system must

do…• Can create test plans for developers to test

against• Test plans upfront to designate success / failure

of a particular sequence of events

Building Use Cases• Through interviews, interactions, and

observations of the as-is system or work-flow• Identify the major use cases• Identify the major steps within each use case• Identify elements within steps• Confirm the use case

Use Case Building Example• Want to build a new EHR• What are some of the possible major use

cases?• Physician Order Entry• Medication Reconciliation• Pharmacy Verification• Pharmacy Order Placement• Medication Delivery• Inventory Management

Use Case Building Example: POE• Identify the major use cases (con’t)• Basic Information for Physician Order Entry• Name: Physician Order Entry• Actor: Physician (MD)• ID: EHR-UC1• Description: Physician places a medication order for a

patient by identifying the patient, the drug, and the dosage. The system creates the order and places it in the pharmacy verification list.

• Trigger: Physician wants to place a medication order (External)

Use Case Building Example: POE• Identify major steps and their elements for Physician Order

Entry1. MD navigates to the intended patient

1. MD navigates to the floor / unit of the patient2. System displays a list of patients for the floor / unit3. MD navigates to the patient’s profile

2. MD navigates to the intended drug1. MD navigates to the ordering section2. System displays the formulary3. MD selects a specific medication and enters dosage

3. MD places order1. System displays the order, current medications, and their interactions2. MD verifies and submits the order or cancels it (alt. course 3.2.1)3. System creates an order pending pharmacy verification4. System notifies the pharmacy

Patient LocationExisting Patients List

Patient ID

Orders Section IDExisting FormularyMed ID and dosage

Current Meds and IntSubmission

Pending OrderPending Order Notice

Use Case Building Example• Confirmation• Was the medication order produced with all of

the steps listed?• Would a developer be able to take those steps

and understand what he/she is developing for?• Revise functional requirements based on

use cases

SUMMARY• A use case contains all the information

needed to build one part of a process model, expressed in an informal, simple way.

• When writing a use case, • identify the triggering event,• develop a list of the major steps,• identify the input(s) and output(s) for every

step,• have the users role-play the use case to verify.