<!DOCTYPE article PUBLIC "-//NLM//DTD JATS (Z39.96) Journal Archiving and Interchange DTD v1.0 20120330//EN" "JATS-archivearticle1.dtd">
<article xmlns:xlink="http://www.w3.org/1999/xlink">
  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>Cooperation on Models and Models for Cooperation</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Tom Gross</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Christoph Beckmann</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Human-Computer Interaction Group, University of Bamberg, Germany (&lt;fistname&gt;.&lt;lastname&gt;(at)uni-bamberg.de)</institution>
        </aff>
      </contrib-group>
      <pub-date>
        <year>2013</year>
      </pub-date>
      <fpage>9</fpage>
      <lpage>16</lpage>
      <abstract>
        <p>In this paper we would like to propose a Janus head perspective on cooperation and models: on the one hand cooperation on models is a very important type of activity for groups who want to create shared models that are accepted by the group members; on the other hand models for cooperation are an essential basis to develop user-centred cooperative systems.</p>
      </abstract>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>1 Introduction</title>
      <p>
        The organisers of this workshop on ‘MoRoCo – Models and their Role in
Collaboration’ at the European Conference on Computer-Supported Cooperative
Work - ECSCW 2013, point out in their call for papers that ‘using visual
representations for work or business processes can be considered a common
practice in modern organisations. These models serve a large variety of different
purposes such as documentation of current practices, or informing and planning
change or software development.’
        <xref ref-type="bibr" rid="ref14">(Nolte et al. 2013)</xref>
        . Indeed, models play an
important role in Computer-Supported Cooperative Work (CSCW) as shared
artefacts in teams that are conceived, developed, and maintained by the teams.
      </p>
      <p>
        Besides cooperation on models, models that structure the cooperation process
are an essential part of cooperation technology. Developing software that supports
teams cooperating—this software is often referred to as groupware—is a
challenging task and has been researched for more than two decades
        <xref ref-type="bibr" rid="ref11 ref7">(Gross 2013;
Marca &amp; Bock 1992)</xref>
        . Groupware often has a strong influence on how teams will
work together. And, in fact, the effectiveness and efficiency of the teamwork as
well as the satisfaction of the individual team members strongly depend on the
quality of the concepts underlying the respective cooperative technology.
        <xref ref-type="bibr" rid="ref18">Schmidt
(2011</xref>
        , p. vii) points out: ‘the development of computing technologies have from
the very beginning been tightly interwoven with the development of cooperative
work’.
        <xref ref-type="bibr" rid="ref18">Schmidt (2011</xref>
        , p. vii) continues that: ‘our understanding of the
coordinative practices, for which these coordination technologies are being
developed, is quite deficient, leaving systems designers and software engineers to
base their system designs on rudimentary technologies. The result is that these
vitally important systems, though technically sound, typically are experienced as
cumbersome, inefficient, rigid, crude’.
      </p>
      <p>In the light of this Janus head perspective—that cooperation on models is an
important part of CSCW, and that the models underlying the cooperative
technology do fundamentally influence its success—this paper looks at the role of
models for cooperation that can be used as basic concepts for cooperative
technology that in return is used for cooperation on models. In the next section we
give a brief overview of the history of models and patterns. We then introduce and
suggest as a point of departure and the framework of Erving Goffman (esp.
(1959)) who studied social interaction among humans and their use of their
technical environment for several decades and derived a framework for social
interaction. Finally, we summarise our contribution.</p>
    </sec>
    <sec id="sec-2">
      <title>2 Models and Patterns</title>
      <p>
        Models and patterns have a long tradition. They have early been used in
architecture, most prominently by Christopher
        <xref ref-type="bibr" rid="ref1">Alexander (1977)</xref>
        . Alexander used
introduced a pattern language to describe solutions that were repeatedly applied to
reoccurring design challenges in the design of buildings.
      </p>
      <p>
        Later, in Software Engineering design patterns serve a similar purpose—design
patterns here have been considered as a successful approach for documenting and
reusing knowledge providing a ‘way of supporting object-oriented design’
        <xref ref-type="bibr" rid="ref20">(Sommerville 2007, p. 422)</xref>
        . Software design patterns basically have the following
structure: a pattern name, a description of the problem, a description of the
solution, and the consequences of the use of the pattern
        <xref ref-type="bibr" rid="ref5">(Gamma et al. 1994)</xref>
        .
      </p>
      <p>
        Design patterns are also used for documenting knowledge and experience with
the development of cooperative technology.
        <xref ref-type="bibr" rid="ref19">Schuemmer and Lukosch (2007</xref>
        ,
p. 22) write that ‘developers building groupware applications are challenged with
technical problems that are outside the focus of average software developers’.
        <xref ref-type="bibr" rid="ref12">Martin and Sommerville (2004)</xref>
        analysed social interaction and translated their
results into the format of design patterns. They (2004, p. 61) point out that
‘patterns of cooperative interaction highlight similar findings across studies
related to particular socio-technical configurations, and the accompanying
activities given those configurations. They start to address the question of how we
generalise from ethnographic studies to provide guidance for system designers
and other users’ and ‘patterns can be of relevance and practical use to researchers
and practitioners from technical or social scientific backgrounds who have an
interest in social aspects of systems design’.
      </p>
      <p>All these patterns provide valuable input for generating models underlying
cooperative technology. And they are interesting artefacts to study when
developing tools that aim at supporting teams working on them.</p>
      <p>Yet, software design patterns primarily help structuring software, and
cooperative design patterns are primarily based on the analysis of existing
cooperative systems or on some ethnographical studies. In the next section we
introduce Goffman’s framework of social interaction, which is based on decades
of observations.</p>
    </sec>
    <sec id="sec-3">
      <title>3 Goffman’s Framework of Social Interaction</title>
      <p>Goffman’s framework of social interaction is based on decades of observations
and study of related work of Goffman and provides a substantial peace of
knowledge and insight into the way social interaction among humans works.</p>
      <p>Goffman uses the metaphor of a theatre stage and points out that humans in
any kind of social interaction do a performance in front of other humans who are
listening and watching and interpreting the performance. Goffman writes: ‘for the
purpose of this report, interaction (that is, face-to-face interaction) may be roughly
defined as the reciprocal influence of individuals upon one another's actions when
in one another's immediate physical presence’ and ‘a “performance” may be
defined as all the activity of a given participant on a given occasion which serves
to influence in any way any of the other participants’ (1959, p. 15).</p>
      <p>His concepts that are most relevant with respect to modelling social interaction
as basis for cooperative technology can be grouped into three categories: primary
participants, performance, and secondary participants. Figure 1 depicts these three
categories and the concepts they contain respectively.</p>
      <p>
        Primary participants are humans who act according to their social status (i.e.,
socio-economic standing in the society). They perform a routine (i.e., a
‘preestablished pattern of action which is unfolded during a performance’
        <xref ref-type="bibr" rid="ref6">(Goffman
1959, p. 16)</xref>
        ). According to Goffman humans have kinds of ideal interactions with
each other: the optimistic ideal of full harmony (i.e., being in harmony with
oneself and with others), which according to Goffman is hard to achieve; and the
pragmatic ideal as a projection that should be in accordance with reality and that
others can accept—at least temporarily—without showing deep and inner feelings
of the self.
      </p>
      <p>An interaction takes place between at least one performer and one person in the
audience. The performer defines a situation through a projection of reality as
expressions of a character bound to a certain social role in front of the audience.
The performer anticipates the audience and continuously adapts the performance
accordingly. Audiences can be of three different types: Present audience refers to
persons who attend the performance, receive expressions, verify these in
accordance to the projected situation and reality, and respond accordingly. Unseen
audience are imaginary persons; the performer can use them in order to anticipate
a performance. Finally, week audience are real persons who are not present at the
performance (e.g., other performers giving similar performances).</p>
      <p>Multiple performers can act as a performance team. The members of a
performance team need to fit together as a whole—to either present similar
individual performances to amplify a projection, or to present dissimilar
performances that complement to a projection.</p>
      <p>For a performance, performers prepare a set of fronts shown to the audience.
Fronts consist of material and immaterial parts. The material part is the sign
equipment and are all properties required to give a convincing performance. The
immaterial part is the personal front and refers to a performer’s types of behaviour
such as speech patterns. During interaction performers appear on stage through a
character. A character as figure is composed of a ‘front’, which is adapted to the
audience and performance. In a performance team, the team as whole has a united
front (e.g., according to a professional status) and each member has a character
with an associated front to invoke during staging.</p>
      <p>A performance as social interaction is a finite cycle of expressions to define a
situation and responses to feedback the validity of the expressions. Characters
plays routines during performances to convey acceptable and to conceal
inacceptable expressions—in a performance team multiple characters will follow
this behaviour. Expressions are information that is communicated by a character,
which use ‘sign-vehicles’ (i.e., information carriers). There are wanted
expressions that are acceptable and foster a situation as a valid projection of
reality, and unwanted expressions that are inacceptable and inappropriate for a
given performance in front of a particular audience. In order to manifest a
performance that is coherent, a performer strives to communicate expressions
consistently through their characters towards an audience. Thus a performer’s
character endeavours to conceal unwanted expressions. Responses are feedback
from the audience, which continuously verifies the performance according to the
defined situation and the overall reality as well as to the front of the character, and
responds the result to the performer.</p>
      <p>Disruptions can result from wrong or undefined projection—a consequence of
a false or doubtful projection of reality based on contradictive expressions or
discrediting actions. To prevent accidental disruptions a performer and an
audience can agree on: the ‘working consensus’ as an agreement on the definition
of the situation to describe a temporal value system among all participants;
‘reciprocity’ that means that performers guise their characters to act according to
the situation (i.e., provoke neither intentionally nor factually misunderstandings)
and that the audience responds to performance according to the situation (i.e.,
allege neither consciously nor unconsciously false behaviour); and ‘interactional
modus vivendi’ that describes that an individual in the audience only responds to
expressions that are important for the individual; the individual in the audience
remains silent in things which are only important to others.</p>
      <p>Stages provide a setting for the interaction and are embroidered with decorative
properties (i.e., decorum). They support performers when fostering a situation.
Both performers and the audience have access to the stage. The backstage is a
region, which only performers can access to prepare and evaluate their
performance. Also team members suspend backstage. The outside region denotes
to neither stage nor backstage. Although it will be excluded in a performance,
performers will prepare and use a dedicated front for the outside (e.g., the façade
of buildings of a company).</p>
      <p>We put other participants of Goffman’s framework who are of minor important
for cooperative technology in the category secondary participants. Participants
who are involved, but are not participating in a performance are: team support
(colleagues who constitute the weak audience, training specialists that build up a
desirable performance and service specialists that maintain a performance,
confidants that listen to a performer’s sins, and renegades that preserve a idealistic
moral stand that a performer or team did not kept), and sidekicks that support a
single performer during performance, but in a subordinate role. Non-persons are
present but neither participate nor are involved in a performance (e.g., servants).
Outsiders are neither performers nor audience and have little or no knowledge of
the performance. They can access the outside region; however they can invade a
performance and cause a collision of performances: the outsider sees a
performance that eventually is reserved for the future when the outsider is part of
the audience.</p>
      <p>Overall, Goffman’s framework provides an inspiring point of departure when
conceiving of basic concepts for a model of cooperation. These concepts can be
brought together in a shared model that can then—in a cooperative endeavour—
be worked on in a group. The group can work on a model for any domain or
business, but it can also work on a model that represents its own structure and
roles of actors and ways of interaction among actors and with third parties.</p>
    </sec>
    <sec id="sec-4">
      <title>4 Informing the Design of Modelling</title>
      <p>The framework of social interaction of Goffman provides multifarious insights
that have the potential to positively influence cooperation on models as well as
models for cooperation.</p>
      <p>Cooperation on models—based on the concepts above—can be characterised
as follows. During the cooperation process there are typically active group
members and passive group members. A group members’ expressions in terms of
activities can include oral or written communication, new additions to models,
changes of their own parts of a model, changes of parts of the model that have
been created by others, and so forth. Passive group members might watch the
active person and respond (e.g., confirm that changes to their parts of the model
are welcome). On the other hand the active group members might have
sophisticated routines that allow them not only to concentrate on their own
communication and activities, but also on the others’ reactions. Active members
can tightly cooperate with other active members in performance teams. The team
support might include lab administrators who are responsible for maintain the
distributed modelling software and hardware. Researchers have only very recently
started looking at these subtleties of users’ performances and others responses to
them. For instance, Birnholtz et al. presented a study of collaborative writing and
point out that: ‘people are also concerned about how their behaviours—and they
themselves—will be perceived by others’ (2013, p. 961). Despite the fact that this
study was on collaborative writing and not editing models, it showed interesting
evidence that active users in team do care about other users responses to their
performance.</p>
      <p>
        Models for cooperation should use Goffman’s notions as input for entities.
According to Goffman several roles need to be considered by modellers of
cooperative processes: performers who actively communicate and change
artefacts, performance teams which consist of multiple performers, as well as
audiences which can be present and visible to the active performer, unseen and
weak audiences which are absent yet important. Furthermore, models for
cooperation might foresee secondary participants such as team support or
outsiders. In early cooperative systems and early research
        <xref ref-type="bibr" rid="ref16">(cf. e.g., Rodden 1991
for an overview)</xref>
        the notion of a role was clear-cut to and distinct. For instance, a
chair-person has specific rights and duties, and a participant has others. More
recently—and in accordance with Goffman—roles have been seen as emerging
and evolving over time
        <xref ref-type="bibr" rid="ref4">(Finholt et al. 2012)</xref>
        .
        <xref ref-type="bibr" rid="ref18">Schmidt (2011</xref>
        , p. 31) writes: ‘the
apparent stability of organizational roles and patterns of communication is a
superficial hide … Cooperative work arrangements should rather be conceived as
emerging formations that change dynamically in accordance with the
requirements of the situation, and cooperative work involves, inescapably, the
vicissitudes of distributed decision making. These characteristics have important
implications for CSCW systems design’.
      </p>
      <p>
        As these short examples show, it is important for system designers with respect
to cooperation on models and models for cooperation, to find a balance between
having a structured, effective, and efficient process and providing lightweight
adequate adaptability, flexibility, and spontaneity
        <xref ref-type="bibr" rid="ref17 ref8">(Gross &amp; Marquardt 2010;
Schirmer &amp; Gross 2011)</xref>
        . This has been pointed out very early in the CSCW
literature
        <xref ref-type="bibr" rid="ref2">(esp. Bannon &amp; Schmidt 1989)</xref>
        , but neglected by some system
designers.
      </p>
    </sec>
    <sec id="sec-5">
      <title>5 Conclusions</title>
      <p>
        This introduction of key concepts from Goffman’s framework of social
interaction is only a starting point towards a more comprehensive discussion of
key concepts—in the sense of reoccurring design patterns—of models for
cooperation underlying cooperative technology. Conversely, since these key
concepts and their mutual relationships can evolve into complex models it would
be great to have approaches and tools to cooperatively work on them. Goffman’s
framework is just one part of the overall picture; other researchers have been
using other frameworks, most prominently activity theory
        <xref ref-type="bibr" rid="ref10 ref13">(Kaptelinin &amp; Nardi
1997; Nardi 1996)</xref>
        or distributed cognition
        <xref ref-type="bibr" rid="ref9">(Hutchins 1995)</xref>
        <xref ref-type="bibr" rid="ref15">(Perry 2003)</xref>
        .
      </p>
      <p>In this workshop I would like to share thoughts on how cooperation on models
actually works in practice and how tools supporting this type of cooperation can
be conceived, while at the same time—from a Janus head perspective—looking at
the structure of this cooperation process on models and taking it as the shared
artefact that the team is actually working on.</p>
    </sec>
  </body>
  <back>
    <ref-list>
      <ref id="ref1">
        <mixed-citation>
          <string-name>
            <surname>Alexander</surname>
            ,
            <given-names>C.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Ishikawa</surname>
            ,
            <given-names>S.</given-names>
          </string-name>
          and
          <string-name>
            <surname>Silverstein</surname>
            ,
            <given-names>M.</given-names>
          </string-name>
          (
          <year>1977</year>
          ).
          <article-title>A Pattern Language: Towns, Buildings, Construction</article-title>
          . Oxford University Press, Oxford, UK.
        </mixed-citation>
      </ref>
      <ref id="ref2">
        <mixed-citation>
          <string-name>
            <surname>Bannon</surname>
            ,
            <given-names>L.J.</given-names>
          </string-name>
          and
          <string-name>
            <surname>Schmidt</surname>
            ,
            <given-names>K.</given-names>
          </string-name>
          (
          <year>1989</year>
          ).
          <article-title>CSCW: Four Characters in Search of a Context</article-title>
          .
          <source>In Proceedings of the First European Conference on Computer-Supported Cooperative Work - ECSCW'89 (Sept</source>
          .
          <fpage>13</fpage>
          -
          <lpage>15</lpage>
          , Gatwick, UK). Elsevier, Dordrecht. pp.
          <fpage>358</fpage>
          -
          <lpage>372</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref3">
        <mixed-citation>
          <string-name>
            <surname>Birnholtz</surname>
            ,
            <given-names>J.P.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Steinhardt</surname>
            ,
            <given-names>S.B.</given-names>
          </string-name>
          and
          <string-name>
            <surname>Pavese</surname>
            ,
            <given-names>A.</given-names>
          </string-name>
          (
          <year>2013</year>
          ).
          <article-title>Write Here, Write Now! An Experimental Study of Group Maintenance in Collaborative Writing</article-title>
          .
          <source>In Proceedings of the Conference on Human Factors in Computing Systems - CHI 2013 (Apr. 27-May 2</source>
          , Paris, France). ACM, N.Y. pp.
          <fpage>961</fpage>
          -
          <lpage>970</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref4">
        <mixed-citation>
          <string-name>
            <surname>Finholt</surname>
            ,
            <given-names>T.A.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Tellioglu</surname>
            ,
            <given-names>H.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Inkpen</surname>
            ,
            <given-names>K.M.</given-names>
          </string-name>
          and
          <string-name>
            <surname>Gross</surname>
          </string-name>
          , T., eds. (
          <year>2012</year>
          ).
          <source>Proceedings of the 2012 International ACM Conference on Supporting Group</source>
          Work - Group
          <year>2012</year>
          . ACM, N.Y.
        </mixed-citation>
      </ref>
      <ref id="ref5">
        <mixed-citation>
          <string-name>
            <surname>Gamma</surname>
            ,
            <given-names>E.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Helm</surname>
            ,
            <given-names>R.</given-names>
          </string-name>
          , Johnson, R. and
          <string-name>
            <surname>Vlissides</surname>
            ,
            <given-names>J.</given-names>
          </string-name>
          (
          <year>1994</year>
          ).
          <article-title>Design Patterns: Elements of Reusable Object-Oriented Software</article-title>
          . Addison-Wesley, Reading, MA.
        </mixed-citation>
      </ref>
      <ref id="ref6">
        <mixed-citation>
          <string-name>
            <surname>Goffman</surname>
            ,
            <given-names>E.</given-names>
          </string-name>
          (
          <year>1959</year>
          ).
          <article-title>The Presentation of Self in Everyday Life</article-title>
          . Doubleday Anchor Books, N.Y.
        </mixed-citation>
      </ref>
      <ref id="ref7">
        <mixed-citation>
          <string-name>
            <surname>Gross</surname>
            ,
            <given-names>T.</given-names>
          </string-name>
          (
          <year>2013</year>
          ).
          <source>Supporting Effortless Coordination: 25 Years of Awareness Research</source>
          . Computer Supported Cooperative Work:
          <source>The Journal of Collaborative Computing</source>
          <volume>22</volume>
          ,
          <fpage>4</fpage>
          -
          <lpage>6</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref8">
        <mixed-citation>
          <string-name>
            <surname>Gross</surname>
            ,
            <given-names>T.</given-names>
          </string-name>
          and
          <string-name>
            <surname>Marquardt</surname>
            ,
            <given-names>N.</given-names>
          </string-name>
          (
          <year>Sept</year>
          .
          <year>2010</year>
          ). Creating, Editing, and
          <article-title>Sharing Complex Ubiquitous Computing Environment Configurations with CollaborationBus</article-title>
          .
          <source>Scalable Computing: Practice and Experience - Scientific International Journal for Parallel and Distributed Computing (SCPE) 11</source>
          ,
          <issue>3</issue>
          . pp.
          <fpage>289</fpage>
          -
          <lpage>303</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref9">
        <mixed-citation>
          <string-name>
            <surname>Hutchins</surname>
          </string-name>
          , E., ed. (
          <year>1995</year>
          ).
          <article-title>Cognition in the Wild</article-title>
          . MIT Press, Cambridge, MA.
        </mixed-citation>
      </ref>
      <ref id="ref10">
        <mixed-citation>
          <string-name>
            <surname>Kaptelinin</surname>
            ,
            <given-names>V.</given-names>
          </string-name>
          and
          <string-name>
            <surname>Nardi</surname>
            ,
            <given-names>B.A.</given-names>
          </string-name>
          <string-name>
            <surname>Activity</surname>
          </string-name>
          <article-title>Theory: Basic Concepts and Applications</article-title>
          .
          <source>Presented at Tutorial #11 at the Conference on Human Factors in Computing Systems - CHI'97 (Mar</source>
          .
          <fpage>22</fpage>
          -
          <lpage>27</lpage>
          , Atlanta, GA).
          <year>1997</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref11">
        <mixed-citation>
          <string-name>
            <surname>Marca</surname>
            ,
            <given-names>D.</given-names>
          </string-name>
          and
          <string-name>
            <surname>Bock</surname>
          </string-name>
          , G., eds. (
          <year>1992</year>
          ).
          <article-title>Groupware: Software for Computer-Supported Cooperative Work</article-title>
          . IEEE Computer Society Press, Los Alamitos.
        </mixed-citation>
      </ref>
      <ref id="ref12">
        <mixed-citation>
          <string-name>
            <surname>Martin</surname>
            ,
            <given-names>D.</given-names>
          </string-name>
          and
          <string-name>
            <surname>Sommerville</surname>
            ,
            <given-names>I.</given-names>
          </string-name>
          (Mar.
          <year>2004</year>
          ).
          <article-title>Patterns of Cooperative Interaction: Linking Ethnomethodology and Design</article-title>
          .
          <source>ACM Transactions on Computer-Human Interaction 11</source>
          ,
          <issue>1</issue>
          . pp.
          <fpage>59</fpage>
          -
          <lpage>89</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref13">
        <mixed-citation>
          <string-name>
            <surname>Nardi</surname>
            ,
            <given-names>B.A.</given-names>
          </string-name>
          (
          <year>1996</year>
          ).
          <article-title>Context and Consciousness: Activity Theory and Human-Computer Interaction</article-title>
          . MIT Press, Cambridge, MA.
        </mixed-citation>
      </ref>
      <ref id="ref14">
        <mixed-citation>
          <string-name>
            <surname>Nolte</surname>
            ,
            <given-names>A.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Prilla</surname>
            ,
            <given-names>M.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Rittgen</surname>
            ,
            <given-names>P.</given-names>
          </string-name>
          and
          <string-name>
            <surname>Oppl</surname>
          </string-name>
          ,
          <source>S. Call for Papers: Workshop "MoRoCo - Models and their Role in Collaboration" at ECSCW</source>
          <year>2013</year>
          . http://moroco2013.files.wordpress.com/
          <year>2013</year>
          /05/moroco-2013
          <source>-call.pdf</source>
          ,
          <year>2013</year>
          . (
          <issue>Accessed 7</issue>
          /5/2013).
        </mixed-citation>
      </ref>
      <ref id="ref15">
        <mixed-citation>
          <string-name>
            <surname>Perry</surname>
            ,
            <given-names>M.</given-names>
          </string-name>
          (
          <year>2003</year>
          ).
          <article-title>Distributed Cognition</article-title>
          . In Carroll, J.M., ed.
          <source>HCI Models</source>
          ,
          <article-title>Theories, and Frameworks - Towards a Multidisciplinary Science</article-title>
          . Morgan Kaufmann Publishers, San Francisco, CA. pp.
          <fpage>193</fpage>
          -
          <lpage>223</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref16">
        <mixed-citation>
          <string-name>
            <surname>Rodden</surname>
            ,
            <given-names>T.</given-names>
          </string-name>
          (
          <year>1991</year>
          ).
          <article-title>A Survey of CSCW Systems. Interacting with Computers 3, 3</article-title>
          . pp.
          <fpage>319</fpage>
          -
          <lpage>353</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref17">
        <mixed-citation>
          <string-name>
            <surname>Schirmer</surname>
            ,
            <given-names>M.</given-names>
          </string-name>
          and
          <string-name>
            <surname>Gross</surname>
            ,
            <given-names>T.</given-names>
          </string-name>
          (
          <string-name>
            <surname>Oct</surname>
          </string-name>
          .-
          <source>Dec</source>
          .
          <year>2011</year>
          ).
          <article-title>Lightweight Editing of Distributed Ubiquitous Environments - The CollaborationBus Aqua Editor</article-title>
          .
          <source>International Journal of Distributed Systems and Technologies (IJDST) 2</source>
          ,
          <issue>4</issue>
          . pp.
          <fpage>57</fpage>
          -
          <lpage>73</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref18">
        <mixed-citation>
          <string-name>
            <surname>Schmidt</surname>
            ,
            <given-names>K.</given-names>
          </string-name>
          (
          <year>2011</year>
          ).
          <article-title>Cooperative Work and Coordinative Practices - Contributions to the Conceptual Foundations of Computer-Supported Cooperative Work (CSCW)</article-title>
          .
          <source>SpringerVerlag</source>
          , Heidelberg.
        </mixed-citation>
      </ref>
      <ref id="ref19">
        <mixed-citation>
          <string-name>
            <surname>Schuemmer</surname>
            ,
            <given-names>T.</given-names>
          </string-name>
          and
          <string-name>
            <surname>Lukosch</surname>
            ,
            <given-names>S.</given-names>
          </string-name>
          (
          <year>2007</year>
          ).
          <article-title>Patterns for Computer-Mediated Interaction</article-title>
          . Wiley, N.Y.
        </mixed-citation>
      </ref>
      <ref id="ref20">
        <mixed-citation>
          <string-name>
            <surname>Sommerville</surname>
            ,
            <given-names>I.</given-names>
          </string-name>
          (
          <year>2007</year>
          ).
          <article-title>Software Engineering 8</article-title>
          .
          <string-name>
            <given-names>Pearson</given-names>
            <surname>Education</surname>
          </string-name>
          <string-name>
            <surname>Limited</surname>
          </string-name>
          , Harlow, England.
        </mixed-citation>
      </ref>
    </ref-list>
  </back>
</article>