Support for collaborative design reasoning in shared virtual spaces

Ž .Automation in Construction 11 2002 249–259www.elsevier.comrlocaterautcon

Support for collaborative design reasoningin shared virtual spaces

David Latch Craig), Craig ZimringGeorgia Institute of Technology, Atlanta, GA, USA

Abstract

This paper discusses collaborative design, emphasizing the elaboration and transformations of a problem space, and therole that unstructured verbal communication and graphic communication can play in these processes. An asynchronous

Ž .collaborative system, called the Immersive Discussion Tool IDT , is introduced as a means for supporting productive designexchanges. IDT allows collaborators to reason about 3-D models over the Internet using view-dependent and view-indepen-dent diagrammatic marks, dynamic simulations, geometric design surrogates and text annotations. IDT relies on VRML toview the models, with an extensive Java-based interface driving the interactive behavior, including the construction andplayback of graphical annotations, the management of threaded discussions, and the management of file inputroutput. Thedevelopment and initial implementation of IDT has revealed the difficulty of constructing complex marks in a virtual 3-Dspace. Possible strategies for dealing with these problems are suggested. q 2002 Elsevier Science B.V. All rights reserved.

Ž .Keywords: Collaborative design; Immersive discussion tool IDT ; Problem space

1. Introduction

Consider the following scenario. During the plan-ning of a new courthouse, a judge is asked todescribe what goes on in her courtroom and what herparticular needs are. Similar discussions are heldwith the court administrator, clerks and security per-sonnel, while other stakeholders voice their needs astheir time, interest and skills allow. The informationthat is collected is used as input for the design of thenew courthouse. Sometime later, during design de-velopment, the judge is shown plans of the court-

) Corresponding author. Tel.: q1-404-984-6279; fax: q1-404-894-1629.

Ž .E-mail addresses: [email protected] D.L. Craig ,Ž [email protected] C. Zimring .

room, but she has some trouble understanding theexact sizes of spaces and thus is limited in thefeedback she is able to provide. Eventually, she isshown a 3-D computer model of her courtroom.Based on the model, she requests an additional 18 in.behind her chair so she can pull away from thebench, and she tells the architect that the litigationarea of the courtroom looks too cramped. At thetime, she does not realize that space is limited be-cause an administrator has added an area for broad-casting equipment at the rear of the courtroomgallery, and an accessibility expert has widened cir-culation routes to accommodate people in wheel-chairs. The rationales for these requests are notdocumented in the plans.

This scenario is not uncommon in design. Designoften involves significant collaboration with userswhose expertise lies in what they do when they

0926-5805r02r$ - see front matter q 2002 Elsevier Science B.V. All rights reserved.Ž .PII: S0926-5805 00 00102-3

( )D.L. Craig, C. ZimringrAutomation in Construction 11 2002 249–259250

occupy actual physical spaces, rather than in thedesign or construction of such spaces. In addition,each user brings requirements and perspectives thatmay interact with those of others in ways that arehard to predict. In the scenario described above, thejudge can do little more than point out problems andmake requests. It is up to the architects to collect andsynthesize her comments with those received fromother collaborators, a task that is further complicatedby the fact that feedback tends to come in sporadi-cally and at different levels of abstraction.

Ideally, the judge in our scenario would be able toreason directly with other stakeholders and expertsabout conflicts as they arise, not simply to negotiatewho gets priority but rather to find new perspectivesfrom which conflict can be mitigated. Towards thisend, we are building computer tools to help supportasynchronous collaboration among individuals withdifferent backgrounds and expertise, particularlybetween designers, consultants and users. Asyn-chronous interaction solves the problem of how toget such a diverse group of individuals together in anongoing manner. It also, however, constrains interac-tion, forcing us to focus clearly on the kind ofinteractive behavior we want to support. What kindsof behavior might help move a design along and howsuch behavior can be supported are the main issuesaddressed in this paper.

In the sections that follow, we begin by looking atcognitive models of design and by extension, designcollaboration, to see where and how collaborative

Žinteraction can benefit the design process Section.2 . Next, we discuss particular forms of interaction,

highlighting how they might enhance collaborativeŽ .exchanges Section 3 . Finally, we present a shared

computer environment designed to support produc-Ž .tive collaborative behavior Section 4 .

2. Cognitive models of design

Although individual design has been well re-searched, surprisingly little is known about the cog-nitive reasoning processes designers employ duringcollaboration. More research is needed on this issue.However, existing studies of design suggest that,from a cognitive perspective, designers deal with thesame type of problems whether they are working

alone or in teams, albeit with different degrees andspans of commitment. In this sense, the presence ofcollaborators can be seen as modifying the context inwhich each participant operates, but not the taskitself, at least not in a qualitative way. Exactly howthe presence of collaborators might modify the con-text of design will be discussed later. First, however,we provide a simple cognitive description of theactivity of design and hypothesize where the benefitsof collaboration might lie.

Early attempts to provide a cognitive model ofdesign followed descriptions of general problemsolving processes, particularly Newell and Simon’sw x19 problem space description. According to theproblem space description, a typical problem in-cludes a start state, a goal state, and a set of opera-tions that can be used to transform the start state andall subsequent states. In this case, the problem spaceŽ .or search space is the set of all possible states for a

Žgiven problem, including the start state and pre-.sumably the goal state. Of primary interest for those

studying problem solving behavior is how peopleconstruct a problem space and how they navigate itto reach the goal state.

While the problem-space model has led to a richerunderstanding of how people solve well-definedproblems like chess and the Tower of Hanoi, it hasproven somewhat more difficult to apply to design.The principal difficulty is that most design problemsare not well defined, which is to say the start state,goal state and operations that can be applied are notmade explicit in the problem statement. While Simonw x23 has argued that this only necessitates the defin-ing of the problem prior to the search for solutions,reality is usually messier. Many design problems are

Žcomplex enough by virtue of the complexity of the.world in which they are situated that they cannot be

w xmapped out in full detail at the start 20 . Moreover,moves within a problem space tend to have unantici-pated consequences, which open up new issues andultimately lead to the transformation of the problemspace itself.

As a problem changes during search, the designermust flexibly respond by changing his or her internalproblem space representation. Change can occur indifferent ways. Hierarchical change may occur, onthe one hand, to accommodate the expansion of theissues that frame a search. Hierarchical change is

( )D.L. Craig, C. ZimringrAutomation in Construction 11 2002 249–259 251

usually fruitful, however, only when emerging issuesare linearly separable. Lateral change, on the otherhand, becomes critical when hierarchical changeleads to a problem space that prevents a designerfrom reaching a goal — one in which, in otherwords, all moves are suddenly blocked. This is notuncommon in design. Even though an initial problemspace may fair well in light of initial concerns, it willoften be found to be flawed as new issues are raisedand existing issues are fleshed out. A third type ofchange involves the transformation of the conceptsunderlying an issue. In this case, conceptual explo-ration aims at finding ways of expressing issues sothat they are more compatible prior to the determina-tion of a problem space. It contrasts with seeking

Ž .tradeoffs e.g. prioritizing issues as a way aroundconflict.

Given the view of design described above, collab-orative interaction can potentially be both a hin-drance and an aid to search for suitable designsolutions. On the one hand, collaborators, given theleeway to start with different issues in mind, mayentertain non-overlapping views of the problem andhence be led to battle over competing problem spacerepresentations. That is, individual designers mayface external rather than internal conflicts, withoutthe adequate shared resources to resolve them. Inaddition, the symbolic ambiguity and density of ex-ternal problem space representations like sketches,which arguably facilitate lateral movement in an

w xindividual’s search for solutions 7 , may contributeto confusion in group situations. A classic demon-stration of representational drift between individuals

w xcan be found in Bartlett’s 2 study on memory. Inone of Bartlett’s experiments, subjects memorized apicture, redrew it from memory and then passed theirsketch to another subject who repeated the sequence.Sometimes, only a few sequences of sketching andsharing were needed before a drawing of a catbecame a drawing of something altogether different,in one case an owl.

From a more positive perspective, on the otherhand, collaborators may aid the design process byproviding comments that help others discover newways of looking at existing issues. Collaboratorsmight also contribute new analogs and exemplarsthat point the way to new problem space representa-tions. In these scenarios, it might actually help if

expertise is distributed among participants, as Dun-w xbar 5 has observed in the case of scientists collabo-

rating across domains. If participants have similarbackgrounds they may be led to the same point offixation and hence mutually reinforce blocks. With-out overlap, collaborators may present reasoning orpose questions that others would not have thought of,given a view of the problem that is potentially overly

Žconstrained by prior knowledge for more on theeffects of prior knowledge, see Jansson and Smithw x w x.13 and Ward 26 .

Seen in a positive light, the effect of collaborationin design would thus be to allow collective reflec-

w xtion-in-action, to build on Schon’s 21 description of¨individual design activity. Collaborators, in otherwords, could help one another discover unintendedconsequences of design moves, collectively reasonabout new issues, and finally, collectively reasonabout the current state of the problem space. On theother hand, collaborators might not share a commonsearch-space representation at all; they might contestthe space of design or at best simply confuse one

Ž w x .another see, e.g. Schon’s 22 Asilent gameB .¨While some amount of conflict between partici-

pants seems inevitable, our view is that it is gener-ally helpful to share emerging issues and collectivelyreason about them in an unstructured setting as thedesign proceeds. A related strategy for dealing withconflict has been to support the sharing of issuesand criteria within a well-structured argumentation

Ž w x.schema e.g. Refs. 6,18 . While such approachesmay help bring multiple viewpoints to the attentionof participants, they do not appear to help partici-pants re-conceptualize those viewpoints when con-flicts arise down the road. People, moreover, may beled to share and discuss issues early on, but withoutany clear idea of how they will interact in an actualdesign proposal.

3. Modes of interaction supporting collaborativereasoning

To facilitate design collaboration, we envision asystem that supports collaborative reasoning aboutissues as they emerge in a situated context. Beforegoing into the details of such a system, we first lookat a few common modes of interaction that may


support collaborative reasoning. In addition, we lookat how the medium of interaction might promotesharing in general.

3.1. Unstructured Õerbal communication

The most ubiquitous component of any collabora-tive process is verbal communication. Not surpris-ingly, verbal communication has received muchattention in studies of collaborative reasoning, partic-

w xularly scientific reasoning 4,5 . In such studies, un-structured verbal communication is seen as morethan simply a means for sharing answers to prob-lems. It is also seen as a means for assemblingpartial solutions to form more complete solutionsŽ w xsee, e.g. Hutchins 10 , for an analysis of evidence-sharing networks and, more generally, distributed

.cognition and for simply getting individuals to at-tend to parts of a problem that were initially ex-cluded out of bias for the current problem space.

w xDunbar 5 , for example, observes scientists askingone another about assumptions made earlier in theproblem-solving process that had since been forgot-ten. Such apparently naive questions appear to helpindividuals back up and move around a point offixation.

Unstructured verbal interaction also promoteswhat has been termed transactive speech — speechthat explicitly makes reference to earlier exchanges.Transactive speech, which include things like para-phrasing, elaboration and clarification, results fromnaturally occurring breakdowns in communication.By forcing participants to seek new ways of express-ing an idea or belief, such expressions foster concep-tual exploration. Looking for a new way to expressan idea might, in another words, naturally lead aparticipant in a collaborative exchange to exploreaspects of a concept that are at first hidden. Findingunexpected gaps or contradictions may then lead toresolutions and new conceptual structures. Althoughresearch has not been done in the field of architec-ture, empirical studies have in fact shown a correla-tion between high levels of transactive speech and

w xsuccess in developing coherent concepts 25 .Although we assume it is important to support

and promote verbal interaction, we make no attemptto structure or formalize it. The purpose of thissection is simply to suggest that verbal communica-tion naturally supports change and improvement in

conceptual reasoning. How to support shared verbalreasoning is, for us, more a question of how tostimulate verbal interaction, rather than how to spe-cialize it.

3.2. Graphical communication

Unlike linguistic representations, graphical repre-sentations make spatial relations explicit, which maybe important for reasoning about both concrete and

Žabstract concepts to the extent that abstract conceptsw xare often metaphorically tied 17 or concretely tied

w x .1 to primitive understandings of space . In thissection, we discuss three types of collaborativegraphical reasoning. In each case, demonstrativebodily gestures serve to illustrate the different waysgraphical representations function. This, however, isnot to suggest that collaborative graphical reasoningis limited to bodily gestures; the literature on ges-tures simply provides a useful way to understand theroles of graphical communication in collaborativesituations. We argue, moreover, that the cognitivevalue of gestures can be captured in other media,including those more commonly associated withcomputer environments.

One function of graphical expressions in collabo-rative reasoning processes, as typified in gesturalbehavior, is to allow individuals to publicly ArunBmental models, thereby externalizing logical reason-

w x w xing 14 . For example, Hutchins and Palen 11 de-scribe the behavior of an airline pilot who waves hishands over an instrument panel to reason about aproblem with the aircraft in flight. In this case, theinstrument panel serves as a static external model ofsome functional system in the airplane, while handmovements represent hypothetical behavior withinthe system. By graphically ArunningB a mental modelin this way, individuals can test or explore tentativeconcepts — the airline pilot, for example, can testhis concept of what he believes is wrong with theaircraft — and share their reasoning simultaneously.To the extent that diagrams can also be used toexternally represent the behavior of systems, weassume that the cognitive value of bodily gestures

Žcan also be captured albeit with different degrees of.clarity in non-gestural diagrammatic media as well.

In addition to being used to run mental models,gestures and their diagrammatic counterparts are also


useful in describing systems and system componentsin simple ways. Individuals in collaborative settings,for example, often move their hands to describeimaginary elements ranging from whole buildings tosmall building components. Graphical expressions,in this case, serve as design surrogates, which in turnhelp collaborators carry out collaborative move ex-periments. In protocol studies, designers have alsobeen observed to pick up and position arbitrary

Ž .physical artifacts e.g. a pen or ruler for the samew xpurpose 9 . Sketches, of course, can also support

this kind of interaction, although perhaps without thesame flexibility afforded by gestures and objects-at-

Žhand if nothing else, gestures and objects-at-handallow participants to better collectively explore the

.3-D consequences of a design move .Shared graphical expressions are also important

for simply grounding verbal exchanges. Deictic ges-tures, for example, are commonly used to disam-biguate references and to abbreviate exchanges thatwould otherwise require drawn-out verbal descrip-tions. Although attempts have been made to supportsimple bodily gestures in computer-based communi-

Ž w x.cation environments e.g. Refs. 12,24 , variousnon-embodied media may be able to serve the same

w xpurpose. Kumar et al. 16 , for example, describe acomputer system that records voice and cursormovements simultaneously and plays them back to-gether. Even media that lack synchronization be-tween representational components might be usefulin this regard. Text-based verbal references, for ex-ample, could be coordinated with spatial referencesby non-temporal means, such as color or hyperlinks.In this case, though, more effort would be requiredto connect references, both in terms of the authoringand reading of collaborative exchanges.

3.3. The context of sharing

So far we have discussed the merits of graphicaland verbal communication as vehicles for collabora-tive reasoning. Although not our main area of focus,it should be noted that communication media canpotentially influence collaboration by influencing itssocial dynamics as well. Specifically, media canaffect how participants view the collective space as asocial space, which in turn could affect their willing-

w xness to engage with others 3 . Certain communica-

Žtion constraints for example, where information isposted, how discussions are organized, who can

.modify statements, etc. structure the social space ofinteraction by establishing boundaries and markingoff shared and personal territory. If the resulting

Žstructure fosters a sense of community i.e. a sense.of shared ownership of the system as a whole it can

encourage participation as a means of reinforcingcommunity identities and community membership.While some sense of community, even if it involvesweak social ties, commonly influences behavior in

Žreal environments e.g. in offices, studios, residential.neighborhoods, etc. , it is generally more elusive in

computer environments, where explicit socio-spatialw xmetaphors are often lacking 8 .

4. A prototype system to support shared designreasoning

In this section, we describe a simple prototypesystem aimed at supporting collaboration in the de-sign of courthouses, called the Immersive Discussion

Ž .Tool IDT . IDT is geared specifically to support thediscovery and sharing of emergent design issues, aswell as the sharing of reasoning about those issues.The system consists of a 3-D digital model of adesign proposal or exemplar that can be annotatedasynchronously using a variety of editable and, insome cases, interactive 3-D elements. The annotationelements are specifically aimed at supporting thetypes of graphical expressions discussed above,namely, behavioral diagrams and simulations, designsurrogates, and deictic references. In addition, sup-port for threaded text-based communication is perva-sive: any user can attach a discussion window to amark simply by clicking on it. While we realize thattext may not be as spontaneous as voice and may cutback on the rapid give-and-take of a face-to-facedialog, we like the fact that it can be easily scannedand searched by users, and can be automaticallyindexed for reuse. Moreover, the lack of spontaneitymay actually help by promoting more careful reflec-tion on the part of the users.

A specific goal of the system is to put a diverseset of reasoning tools under one roof, such thatdifferent styles of interaction are supported within anexplicitly shared space. Ultimately this is to help


Fig. 1. A simple deictic mark.

foster a sense of community among participants anddiminish the sense that those with non-overlappingbackgrounds are in adversarial positions. The 3-Dmodel should also provide richer feedback than tradi-tional drawings, particularly when dealing withuser-centered issues. Participants can explore andcommunicate issues without having to rely on ab-stractions or fixed perspectives. The spatial and tem-poral continuity of the context of communicationmay help to clarify and give meaning to argumentsthat are shared in the space, and open up the space ofreferents in which arguments can be transformed.Although the use of immersive models for the shared

w xanalysis of design proposals is not new 15 , IDT

extends the benefits by allowing participants tographically reason about issues as they are discov-ered.

IDT relies on VRML for the display of the 3-Dmodel. On the backend, however, an extensiveJava-based interface powers the interactive construc-tion and playback of graphical annotations, the man-agement of threaded discussions, and the manage-ment of file inputroutput. Most of our effort hasthus far been spent fine-tuning how graphical ele-ments are constructed by users and how they behaveonce in the space, with the goal of supporting thekinds of behavior described earlier. In the sectionsbelow, we discuss how the various marking elementswork. Incidentally, the system includes a simplemodeling environment for interactively modelingcourthouse layouts. All of the figures referred tobelow show models generated in this fashion. Mod-els can, however, also be generated in more tradi-tional CAD environments and ported into the system.

4.1. Simple graphical marks

The simplest type of mark a user can createconsists of a single arrow. Users can attach arrows toobjects by clicking on any surface in the VMRLenvironment. The arrows are automatically orientedperpendicular to the targeted by surface at the pointof contact. Single arrows are meant to support deictic

Ž .Fig. 2. The dimensioning tool. At left is the fully open mark. At right is the more compact closed representation.


Fig. 3. A diagram consisting of connected bi-directional arrows.

behavior — in other words, to clarify statementsŽ .made in verbal discussions Fig. 1 . A second type of

mark also intended for simple references is the di-mension-line marker. To create a dimension line inthe VRML world, a user clicks on two points in thespace. A 3-D representation of a traditional 2-Ddimensioning symbol then appears. It can be interac-tively tilted or spun to get the appropriate orienta-tion. When the user is finished orienting the lines,the final distance is automatically computed and

Ž .displayed as text Fig. 2 . To improve readability,the text is AbillboardedB so that it can be seen fromany orientation. Because this particular mark tends toobstruct further viewing of the space, it collapsesinto a simpler representation when not in use.

4.2. Diagrammatic marks

The system provides two methods for construct-ing simple diagrams in the VRML world. One methodis to click on a sequence of points in the space,

Žleaving behind connected bi-directional arrows Fig..3 . The resulting chain of arrows is intended for use

in pointing out multiple relations within an environ-ment or simply circling a region in space. Like thesimple reference marks discussed above, this type ofmark should be coherent from any point of view,except when occluded by other objects.

The second method for constructing diagrams in-volves attaching marks to a specific view. Userssimply place, scale and orient arrows and circles on

Ž .the screen Fig. 4 . While this method is analogousto the use of overlays in conventional two-dimen-sional media, the diagrammatic marks used in oursystem actually consist of 3-D objects placed on animaginary sphere concentric with the user. This is

Fig. 4. At left is a diagram consisting of circles and arrows from the judge’s point of view. At right is the diagram as seen from outside theŽ .imaginary sphere onto which it is projected normally the marks would not be shown from this perspective . In the back is a view marker

that can be used to transport users to the viewpoint.


done by calculating the vector from the user’s loca-tion to the point in the environment that was clickedon, positioning the mark a fixed distance along thatvector and orienting it perpendicular to the vector.

ŽSince the resulting diagram is view dependent re-quiring users to be at the center of the imaginary

.sphere , a simple viewpoint symbol is left behindwhen the diagram is completed. When other usersclick on the viewpoint symbol they are transported tothat point in space and oriented automatically. Tokeep the environment from getting cluttered, both

Žstyles of diagrammatic marks view dependent and.view independent collapse into smaller discrete rep-

resentations when not in use.

4.3. Dynamic simulation

A special annotation tool allows users to markroutes on the floor of the VRML world. In this case,a series of connected unidirectional arrows are leftbehind as the user clicks on a series of points. Oncethe route is drawn, the user is asked whether he orshe wants the path to be animated and, if so, at what

Ž .pace Fig. 5 . If the user selects this option, a simplekeyframe animation is computed that moves andorients a viewpoint along the path at a constant rateof speed. Other users who subsequently click on the

route marker are presented with a dialog window inwhich they can choose whether to run the animation.If they do, they will be transported to the start of thepath, guided along the path and returned to theirinitial location when finished.

4.4. Design surrogates

Design surrogates are highly abstract geometricrepresentations of proposed design elements. Whereface-to-face collaborators might use hand gestures orrandom artifacts as 3-D surrogates for imagined de-sign elements, our system provides users with theability to construct simple surrogates consisting of

Ž . Ž .nodes spheres and edges cylinders . Two construc-tion methods are provided. Using the first method,users simply connect edges one after another, orient-ing them as they go by dragging on their endpoints.This construction method allows users to quickly

Ž .sketch out irregular geometry Fig. 6 . Using thesecond method, users draw a simple outline on thefloor and then extrude it upwards to create an open

Ž .structure Fig. 7 . This method is more convenientfor sketching out volumes and surfaces. Both typesof surrogates can subsequently be annotated withother graphical marks.

Fig. 5. At left is a floor marker tracing a circulation route. At right is a frame in the floor marker animation. The animation runs at a speedŽ .in ftrs chosen by the annotation author.


Fig. 6. A simple design surrogate consisting of bendable stems.

4.5. Miscellaneous features

To help keep clutter down, users can at any timehide all the marks in the space, re-opening them onlywhen necessary. This is particularly useful when auser needs to clear out some space to construct anew mark. In addition, users can open and close

marks individually from a comprehensive index ofall marks currently in the space. Also, to help get aquick overview of the space, we provide users with

Ž .the ability to move into plan view Fig. 8 . This isdone simply by moving the user’s viewpoint to aposition high above the room and orienting it downŽusers will automatically see through the ceiling of

Fig. 7. A simple design surrogate consisting of an extruded horizontal section.


Fig. 8. Plan view.

the room because of backface culling in the render-.ing pipeline . From plan view, users can zoom in or

out as necessary and continue to annotate the space.

5. Conclusions

An important task in supporting collaborationwhen interests and expertise are divided among par-ticipants is helping people modify their problemspace representations in a collaborative fashion, asconflicts between issues arise. Our approach is toprovide participants with a diverse array of graphicalannotation tools that support text-based and graphi-cal interaction. We also argue that it is worthwhile tosupport interaction in the context of a 3-D model.Being situated helps participants highlight issues,provides a shared space of experiential referents inwhich arguments can be expanded and provides anexplicitly shared social setting in which collaboratorscan participate as equals.

Much of our time in designing IDT has beenspent figuring out how exactly to support graphicalreasoning in a shared 3-D space. The tools we havecome up with support deictic references, view-de-pendent and view-independent diagrams, dynamicsimulations, and the use of design surrogates. In eachcase, the main difficulty has been creating a simpleinterface for generating marks in three dimensions.Ideally, we see a 3-D sketch system as serving all the

needs discussed in this paper. At this stage, however,we have relied on simple constrained objects asalternatives to freeform sketch marks. While lessflexible, constrained objects provide a simple solu-tion to the problem of building a usable interface.

Ultimately, we hope that a system such as ourswill bring more people into the design process andwill allow contributions beyond simply voting for aparticular alternative or registering a particular de-sire. The system is stable and reasonably easy to use.Our next step is to test the system in a variety of usescenarios, with different kinds of users focusing ondifferent kinds of issues. We also hope to expand thefunctionality of the system, such as using the 3-Drepresentation as an interface for accessing a widerange of building-related information including in-formation culled from prior discussions.

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Support for collaborative design reasoning in shared virtual spaces