James Lockerbie introduced social modelling in the context of requirements engineering, covering social technical systems, strategic relationships between actors and non-functional requirements. He described the i* goal modelling approach through examples and demonstrated the REDEPEND tool developed by the Centre for HCI Design. Finally, James presented a case study for an advertising microsite, and described how i* modelling was used to capture relationships and dependencies between qualities associated with the path of the user experience.

1. Social Modelling
James Lockerbie
Centre for HCI Design Open Day
21st April 2010
Centre for HCI Design

2. Social Modelling
• For our purposes in the context of requirements
engineering
• Socio-technical systems: Software-based systems
that also include physical components, humans
and organizations
• Modelling goals, rationales, and strategic
relationships among social actors for the future
system
• Explore and identify system requirements,
including non-functional requirements e.g.
performance, reliability, usability and so on.

3. Centre for HCI Design
The i* (Eye-Star) Goal Modelling Approach
From research at the University of Toronto (Eric Yu PhD 1995)
Two model types: USP1:
• SD model Dependencies
–Identify actors
–Identify their goals
–Identify who they depend on for those goals
• SR model
–Decompose actors
–Translate qualities into functional elements
–Demonstrate quality trade offs USP2:
Desired qualities
“soft goals”

4. Centre for HCI Design
i* Modelling Basics
Key modelling semantics Actor Passenger Airline
– Intentional strategic actor (roles)
• Intentional aspects such as objectives, rationale & commitments
– Goal (functional)
• Condition or state of the world that can be achieved or not
– Task
• One particular way of attaining a goal - a detailed description of
how to accomplish a goal
– Resource
• Physical or informational objects in the world. Used by tasks or
produced by tasks
– Soft goals (non-functional)
• Goals that cannot be so sharply defined, such as goals that
describe properties or constraints of the system being modelled

5. Strategic Dependency Modelling
Network of dependency relationships among actors
Goal Dependency Passenger Ticket purchased Airline
– Depender depends upon the dependee to be able to
bring about certain state in the world
Task Dependency
– Depender depends upon dependee to be able to carry
out task
Resource Dependency
– Depender depends upon dependee for the availability of
entity
Softgoal Dependency
– Depender depends upon dependee to perform some
task that meets the softgoal or to perform the task in a
particular way.

6. Departure Management System

7. Knowledge management tool
Learning soft goals – get domain
experts and end users involved
e.g. relevant learning provided,
learning planned etc. Independent
of “how”
Possible technical solutions – get
technical partners involved. Need
more than just a goal hierarchy,
as we need the tasks to give is
the “how”

8. Centre for HCI Design
Tool Support
REDEPEND (REquirements DEPENDencies)
– Centre prototype for developing i* SD and SR models
– MS-Visio plug-ins to draw and analyse models
MS Visio
REDEPEND REDEPEND
SD stencil drawing page
REDEPEND
SR stencil

9. Centre for HCI Design
Model Checking with REDEPEND
Model checking
– i* models are large, complex and necessitate
computational model checking
– Check for unrecognised connections, invalid
connections and model bottlenecks
REDEPEND
validation
REDEPEND features
error tracking

10. Advertising Microsite example
• e.g. Got milk?

11. Advertising Microsite example
• Keep users as long as possible before sending
users to product site
• Ideal path
– user arrives at the landing page
– intrigued and starts exploring.
– learns how to interact
– It’s lots of fun.
– user looses himself – flow
– through the experience, user is changing attitude
towards the brand
– comes across advertising messages, learns about
several products.
• Create a model using i*