From: AAAI Technical Report WS-93-07. Compilation copyright © 1993, AAAI (www.aaai.org). All rights reserved.
Collaborative design system explaining its artifact
T. TAmura
FujitsuLimited
1015Kamikodmvak~4
N~ahara-ku
Kawasaki
211
Japan
1. Introduction
In design environments,collaboration meansmorethan the division of labor. It contains the
notion of cooperationamongagents with his or her independentintention.
In a current design system, for example,VEXED
(Steinberg, 1987), interactions with its user
form a principal part of the design process. The design methodwhich VEXED
employedis
top-downrefinementplus constraint propagation. In this modelof design process, the system
decides what is possible and the user decides what is wise, that is, the user chooseswhich
piece to refine next, out of all those still needingfurther refinement,and also chooseswhich
wayto refine it, out of all the alternatives that the systemknowsaboutthat are consistent with
the current constraints.
Underlyingthis type of interactive systemis the division of labor taking chargeof one part of
the homogeneous
overall design process.
Onthe other hand, interactions foundbetween,for example,an architect and its client, are
moreknowledge-intensive,that is, through interaction, each gets to knowor discovers new
things and makesa newdecision based on themprogressively. Essentially this differs from
merelyproposingand selecting fromamongoptions as in the current interactive design system.
Rather, options at a decision point are collected or inferred fromnewthings a client obtained
hearingfroman architect. For example,considerthe simplified process wherean client asks an
architect to designhis cottage.
The process
a) The client describes his requirements using rather vague terms, such as "modem
style",
"soft touch", or "wide roomsand wide windows".Hemayrefer to several examplesin books.
Andhe mayalso add definite requirementssuch as "two rooms"and the budget.
b) Thearchitect then recalls someconceptssatisfying client’s requirements,enriches themwith
his ownidea, and integrates these conceptsto produceone groundplan.
c) Thearchitect explains on the groundplan to his client especially about what he thought
important,whatare additional factors he involved, whathe neglected. At first, the client has
little idea to decidewhetherhe shouldacceptit, or not. But as hearingarchitect’s explanation,
he increases his knowledgeenoughto form options for his next action and he mayask the
architect to changesomeportion of the plan.
The collaborative design process such as one described above involves manyproblemsto be
313
solved to mechanizeit into the machine.Mainproblemsto tackle for mechanizationare as
follows.
Thedesign systemshould producean artifact from
- incompletedesign specifications
The design system should adopt
- designer’s ownphilosophyand intention on designinghis or her artifact
The design system should have
- explanation
facility onits artifact
Thedesign system should have
- modificationfacility accordingto client’s instructive requirements
Theworkreported here is an attempt to embodythe design process described above. The
attempt, in other words, is to makea knowledge-baseddesign system go beyonda tool for
human
designer,but to a designeritself for a client.
This paperbriefly describesseveral insights into the modelof the design system,its explanation
facility, andthe characteristicsof collaborativeinteractionbasedon the explanationfacility.
2.
Model of the design process
The problemdomainwe are addressing is Floor Planning. Weview the design process as a
opportunistic t concept activation process. The concept is a strategic prescription and
associatedto rhetorical goals. Planningproceedsreferring to rhetorical goals.
Rhetorics is the term used in Natural LanguageField. Andrhetorical goals are invented and
used in the natural language generator PAULINE(Hovy, 1990). PAULINEproduces
stylistically appropriate texts froma single story representation under various settings that
modelpragmaticcircumstances. Pragmaticfeatures considered in PAULINE
are conversational
atmosphere,intedocutor’s personal characteristics and speaker’s goals with respect to the
hearer. But, Hovyargues that mostpragmaticaspects do not influence the generator’s decision
directly, since they are simply too general to be attuned to the requirements of language
production.So, he claims that intermediategoals and associated strategies are neendedthat act
as intermediaries betweenpragmatic aspects and the syntactic decisions the realization
componentshas to makeas being sensitive to those goals. Thesegoals are called rhetorical
goals.
Natural languagegenerationand floor planningare not the samedomain.But still this idea of
rhetorical goal is very attractive to formulatethe modelof the design process, becauseit is
promisingas an anchorto capture the various aspects of designer’s ownintention or strategies
to designan artifact undervarioussituations.
So, we assume here that someintermediate description and associated strategies can be
identified in a class of design domainincludingfloor planning.Wecall it also rhetorical goals
which exist between, on one hand, initial designer’s considerations such as client’s
requirements,client’s life style, the environmentof a site and a cost etc., and, on the other
hand, a domaintheory.
t Opportunistic planning is argued ia (tlayesRoth, 1985)
314
2.1 l’lanninl~ and realization
In PAULINE,
planner performs two types of planning, prescriptive planning and restricive
planning. Prescriptive planningacts over and gives shape to long ranges of text. Restrictive
planningacts over short ranges of text, usually as a selection fromsomenumberof alternatives.
Both planningsare performedonly whennecessiated by the realization process and inquire to
rhetorical goals and associatedstrategies, but not to syntacticinformation.
Realizationin PAULINE
is performedby a syntactic specialist to satisfy the syntax goal of the
foremostunit in a stream, the central generator data structure, posted by the planner or a
precedingspecialist.
In floor planning, planningand realization processeswill be different fromin text generation,
becausea text is a sequenceof wordsand has no strict limitation to overall size and shape, but a
floor is at least twodimensional,and so, elementson a floor are two-dimensionally
related to
eachother and has limited size and shape.
PAULINE’s
control structure is a stream, a list of units. Eachunit is one of three things: a
word, a topic goal, or a syntax goal. A syntax goal expands into several syntax goals
maintaininga syntax environment.
Onthe other hand, in floor planning, DesignConcept,a networkof concepts, is a basic control
data structure, and plays a role of blackboardin a blackboardcontrol architecture.
In this scheme,levels of blackboardin a floor planningare whatkind of roomsor sections there
are, whatfunction eachsection has, whatfunctionalrelation eachsection has to other sections,
whattopological relation each section has to other sections, whereeach section is located, and
what area and shape each section has. Prescriptive planner exists as a knowledgesource
correspondingto all levels. Realizer and restrictive planner exist as a knowledgesource
correspondingto lower levels.
Prescriptiveplannerin floor planningalso refers to rhetorical goals andassociatedstrategies and
derives prescriptive concepts from strategies. These derived concepts are placed in an
appropriatelocation in the networkof DesignConcept.
Symbolanalyzer expandsconcepts in DesignConceptinto moreconcrete ones.
Realizer determinesprimitive elements,i.e., points, edges and parts guidedby DesignConcept
refefing to a domaintheory.
2.2 Construction of design story as a policy of designing
Adesignerconstructs his owndesign story as a policy before he begins to determinedetails, as
consideringvarious design conditions with his ownphilosophy,or intention.
Thedesign story reducesa search space for designing.
In floor planning,the constructionof designstory is composed
of twostages, in the first stage,
the systemposts rhetorical goals, consideringclient’s requirements,client’s life style, the
environment
of a site, anda cost.
For example,if a client is youngand brisk, uses the site only for cooking,eating and relaxing,
and the site is narrow,rhetorical goals suchas Simplicity,Youthfulnessand Noveltywill be all
postedas High.Strategies associatedto the rhetorical goals are as follows.
- whenSimplicityis high, if site is narrow,limit the numberof sections as fewas possible.
- whenYouthfulness
is high, if kitchenis involved,locate kitchenat light place.
315
- whenYouthfulnessis high, if living roomis involved, makeliving roomas wide as
possible.
- whenNoveltyis high, if living roomis involved,give variation to living room.
In the secondstage, prescriptive plannercorrespondingto eachlevel of blackboardis activated
opportunistically, and places concepts derived from strategies into DesignConcept. When
prescriptive planningin the secondstage is over, initial DesignConceptas a design story will
be as follows.
- Living-Room;shape:Variation;
from
RG:Novelty
width: Wide;
from RG:Youthfulness
position: South;
fromgeneral strategy
- Kitchen;
position: LightPlace;
from RG:Youthfulness
2.3
Explanationfacility
Thedesign system can explain on its artifact refering to DesignConcept. The purpose of
explanationis to let its client knowoverall designrationale, helphimor her to decidewhetherto
changeor not the artifact, and in the ease of changing,capturethe right wayto changeit.
First, the design systemexplains aboutoverall design rationale based on the designstory which
it constructedbeforestarting to designdetails.
In Explainable Expert Systemsframework[EESl
and its prototype expert system, the Program
Enhancement
Advisor[PEA](Nechs
et al., 1985), an extensive developmenthistory is created
that records the goal structure and design decisionsbehindthe expert system. This structure is
available for use by the explanationfacility, but reflects only goalrefinementprocess.
The design process discussed abovemainly comprisesopportunistic concept activations, so
moredynamicstructure, i.e. DesignConceptis necessaryto record design rationale.
Varioustypes of explanation needs to follow that, respondingto various types of question
including "whatif" or "why"(Moore
et al., 1989).
Topicsof explanationis collected from conceptsposted in DesignConcept.So, DesignConcept
serves as a topics reservoir. For explanationof designstory, topics collection and organization
are determined heuristically in the order of hieararchical levels of Design Conceptas a
blackboard. The main issue for responding to questions is focus control. Focus control
mechanism
needsto cooperatewith user interface feature.
3. The characteristics
of collaborative
interaction in floor planning
If in the proposedfloor plan, a kitchen is located at the cornerof south-east, and a living room
has the shapeof characterL, the designsystemwill explain aboutthis floor plan as follows.
I limit the kind of roomsto a living roomand a kitchin to makethe configurationsimpleand the
living roomwide.
I give shapeof L to the living roomto producenovelty.
31G
I locate the kitchenat the south-eastcornerto produceyouthfulnessby makingit light.
After hearingthis explanation,the client gets to knowdesigner’sbasic intention. Andoften, this
intention is amazement
and newidea for him.
Explanationof design story also informs client of accompanying
design conditions, if any,
besides designrationale.
For example,at first beforehearingdesignstory, the client feels unsatisfactoryto the locationof
the kitchen. Andafter hearing it, in one case, he mayagree to designer’s intention. But in
another case, he remains still not satisfied and he tries to knowwhether changingit is
appropriate or not. Andif there can be found no additional conditions which justify the
proposedplan, and the explicit condition whichprevents to movethe kitchen to his favorite
location, he will decideto changekitchen’s location to, for example,the south-westcomer.
If the client wantsto changethe proposedartifact, he will ask the design systemto changeit as
he instructs through user interface feature. If so, the design system first modifies the
appropriate portion of DesignConcept, and restarts planning and realization. This redo is
different fromchronologicalbacktracking.
Thecollaboration in this design systemis characterized by two mainfacilities. Oneis the
explanation facility to help a client to capture the most appropriate changeto satisfy and
convincehimselfand to instruct it to the designsystem.Theother is the redo facility to change
the artifact acxxrrding
to client’s instruction.
4.
Conclusion
Wehave partly hypothesizedseveral principles for the modelof collaborative design system.
But muchremainsto be resolved to formulateprinciples on the blackboardcontrol architecture
of planningand realization, explanationfacility, and redo mechanism.
Theworkto be donenext is to implementa prototype systemrealizing the model.
Westarted this workfor the purpose of developing a design system for entertainment for
consumermarket. But someprinciples developedin this workwill be applicable to other fields
of design.
5.
References
Hayes-Roth,B.(1985). A BlackboardArchitecture for Control, Artificial Intelligence 26:251321
Hovy,E.H. (1990). Pragmaticsand Natural LanguageGeneration, Artificial Intelligence 43:
153-197
Moore,J.D. and Swartout, W.R.(1989). A Reactive Approachto Explanation, in Proceedings
of EleventhInternationalJoint Conference
on Artificial Intelligence, Detroit: 1504-l 510
Nechs, R., Swartout, W.R.and Moore,J.D. (1985). Enhancedmaintenanceand explanation
expert systems through explicit modelsof their development,IEEETransactionson Software
Engineering SE-II(1 l)
Steinberg, L.A. (1987). Designas refinement Plus Constraint Propagation: The VEXED
Experience,in Proceedings
of Sixth NationalCon.ferenceon Artificial Intelligence, Seattle: 830835
317