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ASF Architecture: Presentation Layer

Mental Models and Metaphors

An Overview of Presentation Layer Conceptual Modeling

"All our ideas and concepts are only internal pictures".

-- Ludwig Boltzmann (1899)

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Introduction

Mental Models Psychological representations of real, hypothetical, or imaginary

situations First postulated by the Scottish psychologist Kenneth Craik (1943)

“The mind constructs ‘small-scale models’ of reality to

anticipate events, to reason, and to underlie explanation”

Their structure corresponds to the structure of what they represent. They are accordingly similar to

architects’ models of buildings molecular biologists’ models of complex molecules physicists’ diagrams of particle interactions.

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Background

Mental Models Users acquire mental models through…

Interaction Explanation

Two types of mental model: Functional – knowing what to do but not why (e.g. shutting down OC

before switching off) Structural – understanding the components and their relationships (why)

Structural models allow us to solve problems

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Mental Models

Example The heating has just come on but the room is cold. The room

thermostat is set where you normally have it (higher than the current temperature)

Do you… Turn it up hoping that the room will heat faster? Leave it where it is and just wait?

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Mental Models

Example A room thermostat is not like a tap (valve)

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Mental Models

Example A room thermostat is like a switch

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Mental Models - Notation

Primary entities and their relationships

User’s mental model of central heating system in UML Class Diagram Notation

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Mental Models – Whose?

Different roles need different models

Engineer’s mental model of central heating system

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Mental Models – Whose?

Designer’s and user’s models for an interactive system (Don Norman in User-Centered System Design)

Book available from Will’s Desk

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Mental Models – Whose?

Mapping the three models using UML

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Conceptual Models

To… Distinguish between the various models Reflect that mental models are not directly under our control

…We will call the mental model we want users to acquire the users’ conceptual model (or just conceptual model)

Purpose of conceptual model is to leverage the user’s experience from the physical world enable them to form accurate and useful expectations about what

type of functionality or content is available. It helps them answer the question, “is this thing a store, a brochure, a

newspaper, a reporting system, or what?”

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Conceptual Models

Conceptual models invariably represent real world objects and experiences

Examples: blogs are a like a diary, iTunes is like a jukebox, Microsoft Word is like a typewriter ATM is like a bank teller.

Not one of these models tell the user how something is likely to be organized or structured, they do tell them what types of transactions, features, objects, and capabilities are likely to be present.

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Conceptual vs Mental Models

By contrast, mental model describes: How a user expects a particular system or service to be

organized. It helps them say, “Given that this thing is a store, I expect there to

be a place dedicated to product X, a space for product Y, and a place to complete my transaction.”

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Conceptual Models

How can users acquire the ‘right’ mental model? Training Documentation Interaction with the system

In systems for general use (e.g. e-commerce), interaction is usually the only realistic approach

In systems for specialized use (e.g. CLASIC/2), all three are means by which we can help bring the system models into greater alignment with the users’ mental models.

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Conceptual Design

To create a system that will be easy to use, the conceptual model must be…

Deliberately designed Simple enough to be understood through minimal training Able to scale to greater levels of understanding through repeated

interaction Appropriate to users’ tasks Aligned with internalized workflow processes

Use familiar concepts and terms Provide adequate feedback Be consistent (especially with users’ expectations)

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Example – Inappropriate Concept

Expiration Date What are common examples of expiration dates?

Deli meat, milk, ALERT account?

What action(s) do you associate with expiration dates? Throw out?

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Example – Inappropriate Concept

Secure email certificates have expiration dates

But discarding a certificate means loosing access to all email encrypted with it.

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Example – Inappropriate Concept

Security certificates are more like insurance policies than foods or drugs

Renewal date would have been a better concept

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Reverse Engineering

Conceptual models can be ‘reverse engineered’ from existing applications or web sites

Expert review or with users Three Step Process:

Visual Inspection Interaction with controls (but no navigation) Unrestricted Use

Alternatively, a user’s conceptual model can be elicited following use of the system

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Reverse Engineering

Major concepts and relationships should be apparent from visual inspection

Primary results are entities and relationships (operations and attributes at a more detailed level)

Users’ conceptual models can be compared with designers’ Careful questioning of users might be necessary to validate

results (e.g. ‘what would happen if…’)

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Reverse Engineering

Entities from visual inspection of Amazon Website

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Reverse Engineering

Reverse-engineered conceptual model of Amazon Site

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Reverse Engineering - CATStation

Entities from visual inspection of CATStation

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Reverse Engineering CATStation

Reverse-engineered conceptual model of CATStation Report Generation

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Reverse Engineering

Entities Usually Nouns Frequently gleaned from navigation (e.g. menus, tabs, links) Can be other User Interface components (e.g. panels, popups,

dialogs)

Relationships Need not be named Gleaned from visual relationships More reliant on interaction with the system

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Metaphors

Metaphor L. metaphora, fr. to carry over, transfer; meta: beyond, over The transference of the relation between one set of objects to another

set for the purpose of brief explanation (Webster’s revised)

Analogy A resemblance of relations; an agreement or likeness between things

in some circumstances or effects, when the things are otherwise entirely different. (Webster’s revised)

Similarity in some respect between things that are otherwise dissimilar: "the operation of a computer presents an interesting analogy to the working of the brain“ (WordNet)

Logical inference that if things agree in some respects they probably agree in others (WordNet)

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Metaphors

Lakoff & Johnson “...the way we think, what we experience, and what we do every day

is very much a matter of metaphor.'' in our language & thinking - “argument is war”

…he attacked every weak point ... criticisms right on target ... if you use that strategy

“business as war” versus “business as game” metaphors launch a ‘hostile takeover’ we should ‘touch base’

We can use metaphor to highlight certain features & suppress others

There is some systematicity to the transference

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Metaphors

Metaphors make use of existing conceptual models

Do not have to be literal or visual, but they can provide a source of images

Desktop metaphor: inbox, folder, phone Wild Harvest metaphor: shopping basket, checkout

Relationships of interest need to be related in some way: ‘systemic’ (e.g. we are not interested in the size of shopping baskets,

just the ‘idea’ of a shopping basket)

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Metaphors

Myths About Metaphors Difficulty usually comes from visual metaphors (e.g. Microsoft’s BOB

UI)

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Metaphors

Myths About Metaphors To limiting

Only when taken literally or visually Confusing

Only when inappropriate metaphor is used Windows desktop proves metaphor is bad

Broken metaphors are bad Windows bears little resemblance to ‘real’ desktop metaphor

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Desktop Metaphor

‘Real’ desktop metaphor is closer to Xerox Star than Windows

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Desktop Metaphor

The Xerox Star Computer with Star Desktop GUI

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Metaphors

Other Aspects of Metaphors Metaphors can be used at different levels

High level: desktop, shopping Low Level: scissors for ‘cut’, green, right facing arrow for “Play”

Iceberg model of metaphor Some terms have hidden relationships

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Design Exercise (optional)

Consider metaphors that might be appropriate for managing money and allowing greater flexibility (what did people use to do before everyone had a bank account?)

Further: Think of coin/paper money as a store of value – now extend those metaphors

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Design Exercise

People used to put money (store value) into different containers: Jars Tins Socks Mattresses Bags Envelopes Goats

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Design Exercise

What are the basic operations that can be performed on these containers?

What extensions could we make for a web implementation?

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Design Exercise

Solution Basic operations

Create/Destroy View Balance Add Funds Remove Funds

Extensions Automatic interest calculation Regular credits or debits Limits (e.g. when enough funds for holiday, boat)

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Design Exercise

Conceptual model for ‘Jars’ account

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Design Exercise

This is where you would now be in the process: Contextual enquiry Abstract use cases Conceptual design Concrete use case Prototype Visual Design Implementation

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Notes

Add Notes here.