Plans and Situated Actions. Planning View Plans are prerequisite to and prescribe action at every level of detail – Plans must exist, even if changed.

Plans and Situated Actions

Planning View

• Plans are prerequisite to and prescribe action at every level of detail– Plans must exist, even if changed during execution, for

action to occur

• Mutual intelligibility results from recognition of plans and shared knowledge

Plan Generation• Early robot planner– STRIPS – backward chaining

planner– PLANEX

• modeled execution of STRIPS planby computing cumulative error

• When error exceeded threshold, camera would be used to more accurately determine position

• NOAH– Planning where human apprentice is executing plan– Needed to communicate about state of world and

relation of goals and actions

Interaction and Plan Recognition

• Interaction (e.g. communication) requires planning where other actors are environmental conditions

• Recognition of plans requires– Generating hypotheses– Modifying or replacing as new evidence is observed

• Plans and Intentions– Intention – “the uncompleted part of a plan whose

execution has already begun”

Speech Acts

• Language is a form of action– Communication subsumed by planning

• Actors have – A model of the world– Model of one

another’s modelof the world

– Goals in changingother’s model

Speech Acts

• Searle’s speech acts as precondition->outcomes rules– Searle argued against

possibility of rule-based inference of meaning

• How much knowledge is needed to understand conversation– Example of implied request for break

Background Knowledge

• Where does observation end and interpretation begin?

• Represent knowledge in domains and general “common sense”

• Scripts as representation of common sense situations– But how do scripts

recover from errors/interruptions

– Error recovery scripts

What knowledge is relevant?

• Is the information relevant to a situation enumerable?– Deciding what to include is ad hoc– What about tacit

knowledge?

How Much is Said

• Communication must reflect principle of communicative economy– Things said or not said based on assumptions of

other’s understanding• Design communication vs. design documentation

• Garfinkel’s students unable to write “everything” communicated in short conversation because act of creating list enlarged the content– Assumptions only exist when premise is questioned

Situated Action• Plans are part of context for practical activity• One definition:– Every course of action

depends in essential ways on its material and social circumstances

• Implications– Need to study how people use circumstances to achieve

intelligent action rather than abstract action away from circumstances

– How people produce and find evidence for plans in the course of action rather than build a theory of action out of a theory of plans

Plans as Representation of Action• Plans abstract away and

generalize potential/previous actions– Example of canoe– Post hoc analysis may turn

actions into plan– Representation and breakdown

• Heidegger's notion ofunreflective action, breakdown, and reflection– Only during reflection are plans made conscious– When situated action becomes problematic then plans are

used for deliberation

Practical Objectivity of Situations• Changing views in social science– Move from traditional view of external, antecedent, and

coercive social facts influencing action to one of actions occurring in a world “under interpretation”

• Ethnomethodology– Studies methods of society in making sense of the world– Asks how objective grounding is accomplished– Looks to describe the practices that produce the

typifications which make schemas and rules– Makes common sense the product rather than the

precondition of action

Indexicality of Language

• Language takes on meaning by being embedded in the world

• Indexical expressions rely on situation for significance– Pronouns, tenses,

time/place adverbs, deictic references, metaphor?

– “That is a nice one” => nice is also indexical

– Indefinite range of features can influence interpretation

• Instructions can never be fully articulated and must be interpreted by the instruction follower

Mutual Intelligibility of Action

• Language and action are part of the situation– Study of work practices (things typically taken for granted)

• Documentary method– Ascribe intent based on evidence– Interpretation of evidence in ascribed intent– Not reducible to rules about action and context– Example of sense making by students receiving random

yes/no answers from “counselor”• Social structure

– Not a prescribed set of rules/alternatives– Emerges from idiosyncratic interactions– This emergence should be focus of social science