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Capacities, Capacity Demands and Outcomes


Capacities, Capacity Demands and Outcomes John Gilligan Dublin Institute of Technology Professor Peter Smith University of Sunderland – PowerPoint PPT presentation

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Title: Capacities, Capacity Demands and Outcomes

Capacities, Capacity Demands and Outcomes
  • John Gilligan Dublin Institute of Technology
  • Professor Peter Smith University of Sunderland

Assistive Technology
  • Assistive Technology which is defined as Any
    product, instrument, equipment or technical
    system used by a disabled person, especially
    produced or generally available, preventing,
    compensating, relieving or neutralizing the
    impairment, disability or handicap.' ISO 99991998

AT and State Change
  • The central implication of this description of
    assistive technologies is that the technical aids
    bring about a state change. For example glasses
    bring about an improvement in what a user can
    see. Any description of the device must surely
    concern itself with this state change since this
    defines the enablement potential of the device.

  • Coloured Petri Nets Represent State Change -hence
    their suitability for this task

Example Petri Net
Places P1, P2 Transition T1 Guard on T1
G Outcome of T1 O
Elements of Petri Net
How Petri Nets Work
  • Tokens move across Transitions effecting State
  • This state change happens only if the guard is
    satisfied by the tokens at the input place
  • The change is determined by the output expression

CPNS and AT systems.
  • At one level Assistive technology is used by
    somebody in some context to do
  • That is it is characterised by a person
    performing an occupation in some environment
    using technology to assist them. (PEO).
  • It is about a human performing an activity with
    Assistive technology.(HAAT)

How can CPNS model people performing
  • It is necessary to
  • Represent features of the person and the factors
    that impact on their capacity and performance of
    the activity.
  • Characterise the activity in terms of its
    requirements on the person or barriers to its
  • Represent the outcomes or changes that take place
    as a result of the activity being performed.

Transition Representing Action
Input Expression Which defines the Subset of
the Input State Currently in Focus
Tokens Representing State Before
Action Including Person Capacities And
Environment Factors
Tokens Representing State After Action
Guard Representing Barriers to Performance of
Outcome Expression Which defines the Change
which will take place as a result of Action
Petri Net to Represent Action
Input Place
State Before Action
Environmental Capacities in Context of Action and
Agent Capacities in Context of Action and Objects
Output Place
Environmental Capacities in Context of Next
Action and Objects
State After Action
Agent Capacities in Context of Next Action and
Capacity Demands of Action and Objects
Guard which must be satisfied
Expression of Outcome
Activity Make Tea
Input Expression Which defines the Subset of
the Input State Currently in Focus
Tokens Representing State Before
Action Including Person Capacities And
Environment Factors such as location of milk
sugar tea, kettle
Tokens Representing State After Action Including
Person has A Cup of Tea,-and they are happier.
Guard Person must be able to lift Kettle Work
buttons Open Milk carton etc
Outcome Expression Which defines the Change
which will take place as a result of Action
Activity Making A Cup Of Tea
Advantages of Scheme
  • Intuitively seems to have all the elements
  • Barriers to Activity Performance can be
    articulated through Transition Guard
  • Outcomes and Inputs are expressed as apart of
    same mechanism
  • Rich scheme founded in strong formal computer

Tasks and Subtasks
  • CPNs can represent the sub tasks of a task , the
    steps of an algorithm, the subroutines of a
    routine. For example consider.

Multi Step Petri Net
  • Different instances of the same subtask occur
    across the net
  • For example We will lift the kettle and lift the
    sugar bowl at different times in the task
  • This is important later when discussing a link to
    the ICF

Role of AT in Activity Performance
  • So what does AT do.
  • In terms of Activity, what contribution can AT
    make to the overall performance of the activity.

AT as Intervention
  • The roles different technologies play reflect to
    some degree, different intervention strategies
    which someone like an OT can make to increase
    occupational performance.

(No Transcript)
1 Adapting the Task
  • When the Task method is altered the same task
    objects are used in the same environment but the
    method of performing the task is altered to make
    the task feasible given the persons
    circumstances. Examples of this kind of
    intervention, include one handed techniques (ref)
    for tasks normally requiring two hands e.g. one
    handed dressing or typing.
  • Mastering one handed methods require the capacity
    to learn and practice is a necessary component
    of this process.

Adapt the Task
2 Adapting the Environment
  • This intervention emphasizes selecting and
    implementing an environment that enables the
    person to perform with current skills and
    abilities (Dunn et al)
  • Examples of environmental adaptation include
    making changes to a home , to facilitate a
    wheelchair user perform every day activities. For
    example a bathroom could be adapted by the
    provision of a higher toilet to facilitate easier
    transfers, grab bars introduced for standing
    pivot transfers and recessed plumbing and drawers
    for easier access to the sink. (ref)

Environmental Change Change Objects
3 Prevent Barriers to Task performance
  • Therapeutic interventions can prevent the
    occurrence or evolution of barriers to
    performance in context.
  • Family members could be trained in a hierarchy
    of assists, for example verbal cues, that can
    help maintain the remaining skills that a person
    with a progressive dementing illness still
    has.(Rogers et al 2000)
  • Technology can help prevent barriers resultant
    from discrepancies in task requirements and
    personal capacity. Consider a standard keyboard.
  • If someone with poor targeting abilities is
    repeatedly hitting two keys at once , then a key
    guard can prevent this difficulty by placing
    raised borders around each key button, which make
    it impossible to hit more than one key at a time.

Restore or Establish Capacities
  • Improve the capacities of the agent through some

Enhance Capacities
4 Create an Environment to Enhance Performance.
  • This therapeutic choice focuses on providing
    enriched contextual and task experiences that
    will enhance performance.
  • Examples of these environments, include
    playgrounds which have soft surfaces and safe
    equipment which allow children to climb and swing
    and slide and push to the limits of physical
    activity without an enhanced risk of injuring
  • Another example is a garden with raised flower
    beds (ref Holms et al)which allow ,say wheel
    chair users, tend to the plants and enjoy the
    experience and rewards of gardening.(Ref?)

Capacity Demands(Capability Demands Clarkson)
  • Looking at the above milk bottle designs
  • Each bottle design demands that the user has a
    capacity to perform a vertical lift by gripping
    the handle with a closed fist grasp.
  • We see that the bottles on the left will allow a
    greater range of hand sizes get a proper grip on
    the handle for lifting since it gives greater
    clearance dimension between handle and jug

  • In other words the structure of each bottle
    implies the user must have particular hand
    dimensions in order to manipulate the bottle
  • Thus each bottle places different demands on the
    user attributes.
  • If these demands are not met then the bottle
    cannot be used.
  • This conflict is the essence of how capacity
    demands define the guards of our petri nets

  • The above is an example of an object capacity
  • There are other kinds of capacity demands based
    around action
  • These must be measured against the personal
    capacities of the agent and the attributes of the
  • This is summarised in the following

Capacity Demands Action and Objects
Agent Capacities,Environmental Factors, State
More formally
Transition Guard representing Barriers ( in terms
of Capacity Demands)
Incoming Tokens representing Person and State
Action Capacity Demands
Person Capacity Tokens
Object Capacity Demands
Environment Attribute Tokens
Environmental Demands
Capacity Demands And Assistive Technology
  • Action and objects place capacity demands on
    people and environment.
  • For example using a standard kettle involves a
    capacity demand of being able to perform a
    vertical lift of up to 1 kg(which is the weight
    of the kettle when full with water), one handed
    using a closed fist grip.
  • Assistive Technology changes the relation between
    personal and environmental capacities and the
    capacity demands of the action being executed.
  • This relationship is represented by the guard of
    the CPN
  • This is shown in the following example

Using a kettle tipper Changes Capacity Demands
In the above example
  • The pouring capacity demand involved in using a
    standard kettle is substantial.
  • Using a tipper, reduces this capacity demand.
  • A person may not have capacity to meet the
    pouring capacity demand of a standard kettle, but
    will have enough using a tipper.
  • The guard which represents capacity demand versus
    personal capacity will fail on the standard
    kettle transition but will be satisfied using the
    tipper transition

Linking to the ICF
  • One of the aims of this work is to link this
    representation scheme to the WHO ICF

Focus of work
  • This work concerns itself with the possible use
    of the World Health Organization International
    Classification of Functioning (ICF) as a basis
    for representing a conceptual model of Assistive
    Technology Systems.
  • Typical AT systems consist of Person-Activity-AT-
    EnvironmentNeed to Link this to ICF

Links to ICF typically made through Crosswalking
from Profiling Instruments such as Scherers MPT
  • Difficult Process
  • Issues with incomplete matches, loose matches
  • And so on
  • Cieza et al suggested rules for this in 2002
  • Upgraded these in 2005

Here the concern is linking ACTIVITY to ICF using
Ciezas et al Rules
  • The rules of Cieza et al
  • dictate that for example,
  • Each meaningful concept is linked to the most
    precise ICF category.
  • Not to use other specified or unspecified
  • They introduce new codes such as nd and pf to
    cover gaps in ICF classification
  • Here we link to the ICF using these rules from a
    Natural Language description of the Activity.
  • From there move to a formal description of the

Of Particular Interest is Rule 3
  • Rule 3. Do not use the so-called other
    specified ICF categories, which are uniquely
    identified by the final code 8.If the content of
    a meaningful concept is not explicitly named in
    the corresponding ICF category, the additional
    information not explicitly named in the ICF is
  • Example
  • Concept Pain in left foot
  • The meaningful concept pain in left foot is
    linked to b28015 Pain in a lower limb and the
    additional information left foot not contained
    in that category is documented.

Example -Consider an every day activity such as
making tea
  • The person making tea will have to lift a number
    of different objects including the kettle,
    teapot, tea caddy sugar bowl and so on.
  • All of these instances of the activity to Lift
    have different characteristics and place
    different capacity demands on the person
    performing them.
  • For example lifting a full kettle requires
    greater strength and a different grip than
    lifting a sugar bowl.
  • The ICF code D4300 ( Lifting and carrying objects
    ) is not explicitly bound to specific objects
    and hence does not distinguish between different
    instances of lifting.
  • This distinction is not possible without
    documenting this additional non- ICF information
    as specified in rule 3 of Cieza et al.
  • In rule 3 no formal way of documenting this is
  • It is presumed that informal natural language is

Proposed Approach to extending Rule 3
Formalise Documentation Using Cases
  • The work described here proposes to document this
    additional information through a process of
    semantic role labelling around the action, which
    is based on case structure grammar 4
  • This will provide information on the action such
    as the agent of the action, the object of the
    action , for example the kettle, the duration of
    the action and instruments used in the
    performance of the action including assistive
  • These components can change as we move through
    different instances of the action to lift.

Lift Sugar Bowl
ACT(LIFT-D4300) OBJECT (Sugar Bowl)
ACT(LIFT-D4300) OBJECT( Kettle)
Lift Kettle
Pour Kettle using Tipper
ACT (Pour D560) OBJECT( Kettle) Instrument
Person Capacity Tokens
Semantic Role Labelling Extension Of ICF link
Will Inform Definition of components of Petri Nets
Environment Attribute Tokens
Benefits and References
  • Documentation will include cases of activity in a
    formal way
  • These include agent, objects, location, duration
    and much more.
  • These can change as objects of action change.
  • Assistive technology can be linked to an act via
    the instrument case
  • Much richer representation of action which
    includes ICF
  • Representation rooted in classic representation
    scheme of Artificial Intelligence
  • References
  • 1 Cieza A, Brockow T, Ewert T, Amman E,
    Kollerits B, Chatterji S, et al. Linking
    health-status measurements to the international
    classification of functioning, disability and
    health. J Rehabil Med 2002 34 205210.
  • 2 Cieza A., Geyh S. Chatterji S,Kostanjsek
    N.,Ustun B., Stucki G., International
    Classification of Functioning Linking rules an
    update based on lessons learned J Rehabil Med
    2005 37 212218.
  • 3 Cook AM, Hussey SM. Assistive technologies
    principles and practice. Baltimore Mosby 1995.
  • 4 Fillmore C.J. The Case for Case, Bach and
    Harms 1968
  • 5 World Health Organization. International
    Classification of Functioning, Disability and
    Health International Classification of
    Functioning. Geneva WHO 2001

  • The informal CPNS presented here seem a good way
    to represent AT knowledge
  • In surveys respondents were favourable to their
  • Thought they were both intuitive and naturally
    expressive of AT knowledge

Possible Applications of This
  • Model AT systems
  • Teach about AT systems
  • Investigate impact of AT on Capacity Demands
    versus Capacities
  • Demonstrating how modelling AT systems is rooted
    in Mainstream Computer Science
  • Can be used as the basis for Serious Games and
    for Intelligent systems around AT