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  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>Creating awareness of kinaesthetic learning using the Experience API: current practices, emerging challenges, possible solutions</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Maurizio Megliola</string-name>
          <email>maurizio.megliola@piksel.com</email>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Gianluigi Di Vito</string-name>
          <email>gianluigi.divito@piksel.com</email>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Roberto Sanguini</string-name>
          <email>Roberto.Sanguini@agustawestland.com</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Fridolin Wild</string-name>
          <email>fridolin.wild@open.ac.uk</email>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Paul Lefrere</string-name>
          <email>paul.lefrere@open.ac.uk</email>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>AgustaWestland</institution>
          ,
          <country country="IT">Italy</country>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>Piksel Ltd.</institution>
          ,
          <country country="IT">Italy</country>
        </aff>
        <aff id="aff2">
          <label>2</label>
          <institution>The Open University, Knowledge Media Institute</institution>
          ,
          <addr-line>Milton Keynes</addr-line>
          ,
          <country country="UK">UK</country>
        </aff>
      </contrib-group>
      <fpage>11</fpage>
      <lpage>22</lpage>
      <abstract>
        <p>We describe our use of the Experience API in preparing blue-collar workers for three frequently arising work contexts, including, for example, the requirement to perform maintenance tasks exactly as specified, consistently, quickly, and without error. We provide some theoretical underpinning for modifying and updating the API to remain useful in near-future training scenarios, such as having a shorter time allowed for kinaesthetic learning experiences than in traditional apprenticeships or training. We propose ways to involve a wide range of stakeholders in appraising the API and ensuring that any enhancements to it, or add-ons, are useful, feasible and compatible with current TEL practices and tools, such as learning-design modelling languages.</p>
      </abstract>
      <kwd-group>
        <kwd>Experience sharing</kwd>
        <kwd>xAPI</kwd>
        <kwd>verbs</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>-</title>
      <p>Apprenticeship today often includes the development of ‘kinaesthetic intelligence’,
i.e. the tactile (physical) abilities associated with using the body to create (or ‘do’)
something involving highly coordinated and efficient body movements. Prototypical
examples of this can be found in the fluid and precise motions of skilled dancers,
surgeons, and skilled blue-collar workers. Gardner (2011) links high
bodilykinaesthetic intelligence to “control of one's bodily motions, the capacity to handle
objects skillfully, a sense of timing, a clear sense of the goal of a physical action,
along with the ability to train responses”.</p>
      <p>Becoming a skilled kinaesthetic performer through traditional apprenticeship is
today largely conceptualised to take years, but this golden age of long-cycle training is
quickly disappearing. Professional training environments such as in manufacturing
face the challenge that the world of repetition that enabled long cycles of training to
be cost-justified is increasingly taken over by short-run or personalised production,
11
using advanced factory machinery that does not require physical dexterity (including
teachable robots that can emulate dextrous production-line workers), thereby not only
causing shifts in the demand for skills, but at the same time downsizing the
economically acceptable time-to-competence.</p>
      <p>
        Achievements in interoperability for technology-enhanced learning (TEL) over the
last decade are making it viable to develop TEL-based alternatives to a traditional
apprenticeship. For example, TEL is making it possible to author, exchange, and then
orchestrate the re-enactment of learning activities across distributed tools, using
learning process and learning design modelling languages
        <xref ref-type="bibr" rid="ref2 ref3 ref4 ref5 ref6">(Laurillard &amp; Ljubojevic, 2011;
Fuente Valentín, Pardo, &amp; Degado Kloos, 2011; Mueller, Zimmermann, &amp; Peters,
2010; Koper &amp; Tattersall, 2005; Wild, Moedritscher, &amp; Sigurdarson, 2008)</xref>
        .
      </p>
      <p>What these modelling languages fall short of, however, is the ability to handle
hybrid (human-machine) experiences, to teach machines, or to train people at a distance
– as required, for example, in workplaces that include robots or software agents, or in
workplaces that include distributed participation across companies in a supply chain.
In particular, when it comes to bridging between the virtual and the real world,
between digital and physical experiences, present means are ill equipped for supporting
the capturing, codification, and sharing of hybrid learning experiences.</p>
      <p>Moreover, TEL-focused ways of capturing performance and collecting good
practice are as of today still resource-intensive, placing a barrier to the spread of
innovation and hindering resilience of business.</p>
      <p>That barrier can be somewhat reduced through the use of the present version of the
Experience API (ADL, 2013), and we claim could be further reduced through
possible extensions and complements to the API, the need for which has become apparent
in the TELLME project.</p>
      <p>The Experience API is is a novel interface specification designed to link sensor
networks together to enable the real-time collection and analysis of learning
experiences conducted in different contexts, with the aim of providing better interoperability
between the different types of participating educational systems and devices. Being
precondition to mining and modelling, it forms a centrepiece in the canon of next
generation techniques and technologies for capturing, codification, and sharing of
hybrid learning experiences.</p>
      <p>This paper presents an overview of how the components and concepts of the
Experience API are integrated within the TELL-ME project to foster tracking and analysis
of learning and training in three different manufacturing environments, namely
Aeronautics, Furniture, and Textiles.</p>
      <p>We describe within this contribution, how we deploy an open source Learning
Recording Store to allow for collecting and reporting learning across the various
components of the TELL-ME system. Moreover, starting with the Aeronautics industry, we
define a taxonomy of verbs of handling and motion for capturing in particular
kinaesthetic learning experiences as required in the helicopter industry, when targeting
learning about a defined helicopter model and the connected standard maintenance
procedures.
2</p>
    </sec>
    <sec id="sec-2">
      <title>TELLME Learning Locker</title>
      <p>The ADL Experience API (short ‘xAPI’)1, formerly known as TinCan API, is an
extension of the Activity Streams2 specification, a format for capturing activity on
social networks, created by companies like Google, Facebook, Microsoft, IBM etc.,
that allows for statements of experience to be delivered to and stored securely in a
Learning Record Store (LRS). These statements of experience are typically learning
experiences, but the API can address statements of any kind of experiences a person
immerses in, both on- and offline.</p>
      <p>While the core objects of an xAPI statement (Actor, Verb and Object) derive from
the core Activity Streams specification, the Experience API has many more defined
constructs for tracking information pertinent for the learner (with captured results
such as “score”, “success”, “completion”, “attempt”, and “response”), unlike the
Activity Streams spec which focuses on the publisher.</p>
      <p>In its most basic application, the Experience API allows one system (the activity
‘provider’) to send a message (also known as the ‘statement’) to another system (aka
the ‘Learning Record Store’) about something a user has done. Up until now, this
process has mostly taken place inside the organisation’s Learning Management
System. Anything we wanted to track had to be built as part of the LMS functionality, or
needed tailor-made integration. The Experience API now allows sending and
receiving data between systems about what someone has done in a more openly defined
way (see Figure 1).</p>
      <p>This is important, because via the Experience API, any system can send xAPI
statements using a standard connection method. This process of sending xAPI
statements can happen in systems behind the firewall or openly across the Internet using
secure connections.</p>
      <sec id="sec-2-1">
        <title>1 http://www.adlnet.gov/tla/experience-api/ 2 http://activitystrea.ms/</title>
        <p>Within TELL-ME, we have implemented an instance of the open-source Learning
Locker3 Learning Record Store, a LAMP-based project using MongoDB, PHP, and
AngularJS, to begin collecting learning activity statements generated by xAPI
compliant learning activities and reporting on such data.</p>
        <p>The REST WS interface to the LRS was made available to be used by any
component of the TELL-ME architecture to submit and retrieve xAPI statements. An
example of such xAPI triple submission (with POST), using curl4, is shown below:
curl -X POST --data @example.json -H "Content-Type: application/json"
-user
465ea716cebb2476fa0d8eca90c3d4f594e64b51:ccbdb91f75d61b726800313b2aa9f50
f562bad66 -H "x-experience-api-version: 1.0.0"
http://demos.polymedia.it/tellme/learninglocker/data/xAPI/statements</p>
        <p>The example above is parameterized by a reference to a JSON file named
example.json: it contains the actual xAPI statement in form of an actor-verb-object triple:
{
}
"actor":{
"objectType": "Agent",
"name": "Gianluigi Di Vito",
"mbox":"mailto:gianluigi.divito@piksel.com"
},
"verb":{
"id":"http://activitystrea.ms/schema/1.0/watch",
"display":{
"en-US":"Watched"
}
},
"object":{</p>
        <p>"id":"http://tellme-ip.eu/media/video/152"
}</p>
        <p>Once statements are logged, they can be queried again, for example, as needed for
constraint validation to check, whether a user actually performed a certain required
action step – then requiring additional constraint checker components.</p>
      </sec>
      <sec id="sec-2-2">
        <title>3 http://learninglocker.net/</title>
        <p>4 curl - command line tool for transferring data w1i4th URL syntax: http://curl.haxx.se/</p>
      </sec>
      <sec id="sec-2-3">
        <title>5 http://adlnet.gov/expapi/verbs/</title>
        <p>6 http://bit.ly/1zGmAzn</p>
        <p>The Learning Locker also allows creating personalized queries by means of its
reporting functions, combining data from both learning activities and workplace
performance, allowing linking of learning activity to performance.</p>
        <p>One important aspect to be considered is the handling of security and the
protection of the privacy of learners. In the Experience API, authentication is tied to the
user, not the content. The user can be any person or thing that is asserting the
statement. The user can be a learner, an instructor, or even a software agent and it can
authenticate with OAuth7, a commonly used access delegation mechanism employed
by many big names such as Google, Facebook, Salesforce, etc. that eliminates the
needs of sharing passwords between applications to exchange data. In this aim, the
Learning Locker supports authentication and it is integrated with OAuth 2.0, exposing
an API which allows 3rd parties to connect to the API via OAuth 2.0.</p>
      </sec>
      <sec id="sec-2-4">
        <title>7 http://oauth.net/</title>
      </sec>
    </sec>
    <sec id="sec-3">
      <title>The &lt;S,P,O&gt; statement vocabulary (Aeronautics industry)</title>
      <p>Each xAPI statement follows the syntax of providing a subject, predicate, and
object. While subjects and objects can vary, predicates (the ‘verbs’) are ideally rather
slowly changing and can be defined in advance.</p>
      <p>From a cognitive linguistic perspective, there is prior work on defining verbs of
motion and handling – and clarifying their relation to the way humans’ cognitively
process them. Roy (2005) explains how humans learn words by grounding them in
perception and action. The presented theories are tested computationally by
implementing them into a series of conversational robots, the latest of which - Ripley - can
explain "aspects of context-dependent shifts of word meaning" that other theories fall
short of. To construct a vocabulary of verbs that is widely understood, easy to learn,
and natural in mapping, the work of Roy provides valuable insights: Roy postulates
17
that "verbs that refer to physical actions are naturally grounded in representations that
encode the temporal flow of events" (p. 391). She further details that the grounding of
action verbs follows the schema of specifying which force dynamics (out of a limited
set) apply and which temporal Allen relations operate (p. 391). Any higher-level
composition of action verbs, so Roy (p.392), can be traced back to and expressed in
terms of these fundamental temporal and force relations.</p>
      <p>This provides an angle for defining and structuring the TELL-ME taxonomy of
verbs of handling and motion: it provides a basis for ordering from fundamental to
composite actions, also defining their similarities. Moreover, it offers insights on how
to map these verbs back to perception: it provides a rationale for how many visual
overlay elements are required for an augmented reality instruction to express a certain
motion verb primitive. For example, a verb 'pick up' requires the overlay visualisation
of a grabbing hand as well as a highlight of the object to be picked up, whereas the
motion verb 'move' consists of both 'pick up' and 'put down' actions, thus requiring
more visual elements to be specified.</p>
      <p>Palmer et al. (2005) further discuss the "criteria used to define the sets of semantic
roles" for building verb classes. It provides insights into the argument structure of
framesets (and so-called role-sets) of verb classes (Palmer et al., 2005, section 3).</p>
      <p>Chatterjee (2001) reviews the cognitive relationship between language and space.
He refers to Jackendoff in postulating that the "conceptual structure of verbs
decomposes into primitives such as ‘movement’, ‘path’ and ‘location’ (p.57).</p>
      <p>From an augmented reality perspective, there is additional prior work of relevance.
Robertson and MacIntyre (2009) provide a review of the state of the art in displaying
communicative intent in an AR-based system. The proposed taxonomy, however,
stays on a level of general applicability across all sorts of augmented reality
applications and is lacking the level of handling and motion required for a particular
workplace, such as required in learning the maintenance of helicopters. The proposed
categories (called ‘style’ strategies) are ‘include’, ‘visible’, ‘find’, ‘label’, ‘recognizable’,
‘focus’, ‘subdue’, ‘visual property’, ‘ghost’, and ‘highlight’ (p.149f). The
communicative goals signified by these styling operations for visual overlays are listed as
‘show’, ‘property’, ‘state’, ‘location’, ‘reference’, ‘change’, ‘relative-location’,
‘identify’, ‘action’, ‘move’, and ‘enhancement’ (p.148). Other than the work in cognitive
linguistics, here, the focus is clearly defined from a technical and not user angle:
helping the user to identify or move an object is on the same level as setting labels.</p>
      <p>In the aeronautical field, maintenance operations must be carried out according to
official documents issued by the design authority of the aircraft. Such document is
called the Maintenance Publication. Usually, it is organised inside the Interactive
Electronic Technical Publication (IETP). The AECMA S1000D (European
Association of Aerospace Constructors S1000D) is an international standard for development
of IETP, utilizing a Common Source Data Base (CSDB). The standard prescribes
rules to name, define, and code everything that is necessary to carry out maintenance
activities in terms of:
• aircraft model;
• systems and subsystems of the aircraft;
• maintenance tasks;
• location of components;
• tools;
• additional documentations;
• miscellaneous.</p>
      <p>Every maintenance task is identified by a unique code referring to the Task
Category (e.g. ‘servicing’, ‘repairs’, ‘package’), the Maintenance Activity within the
category (‘drain’, ‘fill’, ‘remove’, ‘clean’, etc.), and - finally - to the definition which
gives the procedure and data necessary to carry out maintenance tasks on a specific
system or component. The code allows retrieving both procedures and data necessary
to e.g. fill containers with fuel, oil, oxygen, nitrogen, air, water, or other fluids.</p>
      <p>For the TELL-ME taxonomy of verbs of handling and motion the following
preliminary list was compiled by pilot partners, see Table 1. The initial taxonomy
presents the verbs of handling and motion as required in the helicopter industry for a
defined helicopter model and the connected standard maintenance procedures. All the
actions are handled by the actor ‘certified staff’, which therefore has not been
included in the table.</p>
      <sec id="sec-3-1">
        <title>Activity</title>
        <p>Operation
Servicing
Examination, tests Examined (visual)
and checks</p>
      </sec>
      <sec id="sec-3-2">
        <title>Verb</title>
        <p>Loaded
Unloaded
Filled
tolerance check)
Monitored (condition) Product, system, equipment or
component.</p>
        <p>Disconnect,
remove and
disassemble
procedures</p>
        <p>Disconnected
Removed
Disassembled
Opened for access</p>
        <p>Equipment, components, or items.</p>
        <p>Equipment, components, or items.</p>
        <p>Equipment, components, or items.</p>
        <p>Panels or doors (engine bay doors,
landing gear doors, etc.).</p>
        <p>Repairs and locally Added material
make procedures
and data</p>
        <p>Attached material</p>
        <p>Product, equipment, component or item.</p>
        <p>Product, equipment, component or item.</p>
        <p>Unloaded (download Items.
software)
Changed (mechanical Structure, surface.
strength / structure of
material / surface
finish of material)
Assemble, install
and connect
procedures
Package, handling, Removed from Products, systems equipment or
compostorage and trans- (preservation materi- nents,
portation al)
Products, systems, equipment, or
components.</p>
        <p>Moved (when in stor- Products, systems, equipment, or
comage) ponents.</p>
        <p>Material
Damaged product, system, equipment
or component.</p>
        <p>Equipment, components and items.</p>
        <p>Equipment, components and items.</p>
        <p>Equipment, components and items.</p>
        <p>Panels or doors (engine bay doors,
landing gear doors, etc.).
4</p>
      </sec>
    </sec>
    <sec id="sec-4">
      <title>Conclusion and outlook</title>
      <p>In this contribution, we have presented an overview of how the concepts of
Experience API can be applied in a manufacturing environment, precisely in the Aeronautics
industry. In the context of the TELL-ME project, three different taxonomies of verbs
of handling and motion were prepared or are currently being prepared by the pilot
partners, one of which has been described in this paper (from the helicopter industry).
An instance on the open-source Learning Locker Learning Record Store was made
available to any TELL-ME component, allowing them storing and retrieving xAPI
statements about the workers activities.</p>
      <p>For the future development, we intend to add preliminary taxonomies for the other
two industry sectors, further mature them, and address issues related to the analytics
and statements interpretation, going further ahead in understanding data and how to
find meaning from it (with the help of statistical analysis). In addition, we plan to
explore how to extend (keyword: ‘constraint checker’) or complement the Experience
API to handle emerging challenges such as the need to consider the ergonomics and
learning needs of human-robot workspaces. This will involve conversations and
collaborations with multiple stakeholders, such as TEL vendors and users, standards
bodies, and participants in robotics projects and projects involving or affected by
automation – as envisioned for the Factory of the Future projects.</p>
    </sec>
    <sec id="sec-5">
      <title>Acknowledgements</title>
      <p>The research leading to the results presented in this contribution has received
funding from the European Community’s Seventh Framework Programme
(FP7/20072013) under grant agreement no 318329 (the TELL-ME project). The authors would
like to express their gratitude to the partners who have been involved in the related
research work in TELL-ME.</p>
    </sec>
  </body>
  <back>
    <ref-list>
      <ref id="ref1">
        <mixed-citation>
          1.
          <string-name>
            <surname>Gardner</surname>
            ,
            <given-names>H.</given-names>
          </string-name>
          (
          <year>2011</year>
          )
          <article-title>: Frames Of Mind: The Theory of Multiple Intelligences</article-title>
          , Basic Books, first published in
          <year>1983</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref2">
        <mixed-citation>
          2.
          <string-name>
            <surname>Laurillard</surname>
            ,
            <given-names>D.</given-names>
          </string-name>
          ;
          <string-name>
            <surname>Ljubojevic</surname>
            ,
            <given-names>D.</given-names>
          </string-name>
          (
          <year>2011</year>
          ):
          <article-title>Evaluating learning designs through the formal representation of pedagogical patterns</article-title>
          , In: Kohls &amp; Wedekind (Eds.):
          <article-title>Investigations of Elearning Patterns: Context Factors, Problems, and Solutions, IGI global</article-title>
          .
        </mixed-citation>
      </ref>
      <ref id="ref3">
        <mixed-citation>
          3.
          <string-name>
            <given-names>Fuente</given-names>
            <surname>Valentín</surname>
          </string-name>
          , L. de la; Pardo,
          <string-name>
            <given-names>A.; Delgado</given-names>
            <surname>Kloos</surname>
          </string-name>
          ,
          <string-name>
            <surname>C.</surname>
          </string-name>
          (
          <year>2011</year>
          ):
          <article-title>Generic service integration in adaptive learning experiences using IMS learning design</article-title>
          ,
          <source>In: Computers &amp; Education</source>
          ,
          <volume>57</volume>
          :
          <fpage>1160</fpage>
          -
          <lpage>1170</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref4">
        <mixed-citation>
          4.
          <string-name>
            <surname>Mueller</surname>
            ,
            <given-names>D.</given-names>
          </string-name>
          ;
          <string-name>
            <surname>Zimmermann</surname>
            ,
            <given-names>V.</given-names>
          </string-name>
          ;
          <string-name>
            <surname>Peters</surname>
            ,
            <given-names>J.</given-names>
          </string-name>
          (
          <year>2010</year>
          )
          <article-title>: ISURE: Guideline for the integration of instructional models with open educational content in IMS Learning Design</article-title>
          , deliverable
          <year>d5</year>
          .
          <article-title>2 of the iCoper consortium</article-title>
          .
        </mixed-citation>
      </ref>
      <ref id="ref5">
        <mixed-citation>
          5.
          <string-name>
            <surname>Koper</surname>
            , R.; Tattersall,
            <given-names>C.</given-names>
          </string-name>
          (
          <year>2005</year>
          )
          <article-title>: Preface</article-title>
          , In: Koper, Tattersall (Eds.):
          <article-title>Learning Design: A handbook on modelling and delivering networked education and training</article-title>
          , Springer: Berlin.
        </mixed-citation>
      </ref>
      <ref id="ref6">
        <mixed-citation>
          6.
          <string-name>
            <surname>Wild</surname>
            ,
            <given-names>F.</given-names>
          </string-name>
          ;
          <string-name>
            <surname>Mödritscher</surname>
            ,
            <given-names>F.</given-names>
          </string-name>
          ;
          <string-name>
            <surname>Sigurdarson</surname>
            ,
            <given-names>S.</given-names>
          </string-name>
          (
          <year>2008</year>
          )
          <article-title>: Designing for Change: Mash-Up Personal Learning Environments</article-title>
          , In: eLearning Papers,
          <volume>9</volume>
          (
          <year>2008</year>
          ).
        </mixed-citation>
      </ref>
      <ref id="ref7">
        <mixed-citation>
          7.
          <string-name>
            <surname>Dillenbourg</surname>
            ,
            <given-names>P.</given-names>
          </string-name>
          (
          <year>2011</year>
          )
          <article-title>: Design for Orchestration</article-title>
          , In: Dillenbourg (Ed.): Trends in Orchestration: Second Research &amp;
          <source>Technology Scouting Report, deliverable d1</source>
          .
          <article-title>5 of the STELLAR consortium</article-title>
          .
        </mixed-citation>
      </ref>
      <ref id="ref8">
        <mixed-citation>
          9.
          <string-name>
            <surname>Roy</surname>
            ,
            <given-names>D.</given-names>
          </string-name>
          (
          <year>2005</year>
          ):
          <article-title>Grounding words in perception and action: computational insights</article-title>
          ,
          <source>In: TRENDS in Cognitive Sciences</source>
          ,
          <volume>9</volume>
          (
          <issue>8</issue>
          ):
          <fpage>389</fpage>
          -
          <lpage>396</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref9">
        <mixed-citation>
          10.
          <string-name>
            <surname>Palmer</surname>
            ,
            <given-names>M.</given-names>
          </string-name>
          ;
          <string-name>
            <surname>Gildea</surname>
            ,
            <given-names>D.</given-names>
          </string-name>
          ; Kingsbury,
          <string-name>
            <surname>P.</surname>
          </string-name>
          (
          <year>2004</year>
          ):
          <article-title>The Proposition Bank: An Annotated Corpus of Semantic Roles</article-title>
          , In: Computational Linguistics,
          <volume>31</volume>
          (
          <issue>1</issue>
          ):
          <fpage>71</fpage>
          -
          <lpage>106</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref10">
        <mixed-citation>
          11.
          <string-name>
            <surname>Chatterjee</surname>
            ,
            <given-names>A.</given-names>
          </string-name>
          (
          <year>2001</year>
          )
          <article-title>: Language and space: some interactions</article-title>
          ,
          <source>In: TRENDS in Cognitive Sciences</source>
          ,
          <volume>5</volume>
          (
          <issue>2</issue>
          ):
          <fpage>55</fpage>
          -
          <lpage>61</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref11">
        <mixed-citation>
          12.
          <string-name>
            <surname>Robertson</surname>
            ,
            <given-names>C.</given-names>
          </string-name>
          ;
          <string-name>
            <surname>MacIntyre</surname>
            ,
            <given-names>B.</given-names>
          </string-name>
          (
          <year>2004</year>
          ):
          <article-title>Adapting to Registration Error in an Intent-Based Augmentation System</article-title>
          , In: Ong, Nee (Eds): Virtual and Augmented Reality Applications in Manufacturing, Springer: London.
        </mixed-citation>
      </ref>
    </ref-list>
  </back>
</article>