<!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>Return to the Native: From NLS/Augment to HTML 5</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Daniel Yule</string-name>
          <email>yule@cs.dal.ca</email>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>James Blustein</string-name>
          <email>jamie@cs.dal.ca</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Ann-Barbara Graff</string-name>
          <email>abgraff@nscad.ca</email>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Faculty of Computer Science, &amp; School of Information, Management, Dalhousie University</institution>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>Faculty of Computer Science, Dalhousie University</institution>
          ,
          <addr-line>Halifax, NS</addr-line>
          ,
          <country country="CA">Canada</country>
        </aff>
        <aff id="aff2">
          <label>2</label>
          <institution>NSCAD University</institution>
          ,
          <addr-line>Halifax, NS</addr-line>
          ,
          <country country="CA">Canada</country>
        </aff>
      </contrib-group>
      <abstract>
        <p>We present a demonstration of the shopping-list-as-map part of the 1968 NLS system coded in native HTML5 on the WWW. This demonstration is part of a project examining the state of the eld of Hypertext with particular focus on adoption and development of techniques from its early days. This demonstration examines the advances made in hypertext since 1968. Although the WWW has made enormous strides in accessibility, due in no small part to its distributed, scriptable and themable nature, in a real sense, it has only been in the last few years that WWW browsers have been able to reproduce what was demonstrated in 1968's NLS without resorting to plug-ins and extensions. We will compare the capabilities of NLS and the WWW, as well as the di erences in philosophy between the two systems that brought us to this point.</p>
      </abstract>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>MOTIVATION</title>
      <p>The development of HTML5 is the pinnacle of the most
prevalent hypertext system to-date, viz. the WWW.</p>
      <p>We view the development of HTML5 as a case study of
a socio-technical system that authentically provides support
for user practices and behaviours anticipated by the
developers of NLS. What has emerged between the demonstration
of NLS and the recommendation of HTML5 is a system of
standards and a community of users that (mostly) drives
development rather than a prescriptive vision that dictates
a plan.</p>
      <p>The demonstration for ACM Hypertext 2016 is meant to
continue the discussion of the state of hypertext
development and provoke new questions. For example:
does adopting the model that led to the codi cation
of HTML5 elements inevitably mean that otherwise
good ideas will be excluded because they do not t
Corresponding author.
with existing standards or dismissed because users do
not immediately gravitate to them?
how important are interpersonal and social elements
to gaining wide acceptance for novel systems?
2.</p>
    </sec>
    <sec id="sec-2">
      <title>BACKGROUND</title>
      <p>
        In 1968, Douglas Engelbart and his team produced the
rst word processor, outline processor, fully-computerized
hypertext system, graphical user interface, demonstration of
e-presence, and computer mouse [
        <xref ref-type="bibr" rid="ref18">18</xref>
        ]. Several members of
his team would go on to join the newly formed Xerox PARC
and signi cantly in uence the design of modern computer
interfaces. Notably, it has only been in the last few years
that WWW browsers have been able to reproduce that
system without resorting to plug-ins and extensions. Now with
the HTML5 standard much of what was presented in the
user interface to the NLS/Augment system (hereafter NLS)
is to be basic to common WWW browser software.
      </p>
      <p>Our goal in demonstrating the proof-of-concept replica of
part of the NLS demo is to assess progress by comparing
the state of two signi cant hypertext technologies: oNLine
System (NLS) as demonstrated in 1968 and the World Wide
Web (WWW) as represented by the capabilities of HTML5.
Direct comparison of the WWW and NLS is di cult because
their architectures are fundamentally di erent. However,
the comparison is apt because until recently the WWW did
not have native (built-in) support for some of the
functionality of NLS, and indeed the standards around
videoconferencing are still not nalized, although they are implemented
in several major browsers.</p>
      <p>Nonetheless there have been substantial advances between
the demonstration of NLS and the current state of the WWW.
We consider how much advancement there has been in
various areas, and what lessons can be learned from considering
the signi cance of the convergence of the technological
support provided by NLS in 1968 and provided by HTML5 now.
2.1</p>
    </sec>
    <sec id="sec-3">
      <title>Two Hypertext Systems</title>
      <p>The goals of NLS | as described by Engelbart in the 1968
demonstration | and those of the WWW | as described by
Berners-Lee in contemporary publications | are strikingly
similar.</p>
      <p>
        According to notes accompanying a video recording of the
demonstration NLS was `a tool for navigating through
[information] structures and examining them in ways that would
be too complex otherwise' [
        <xref ref-type="bibr" rid="ref22">22</xref>
        ].
      </p>
      <p>
        Similarly, Berners-Lee [
        <xref ref-type="bibr" rid="ref7">7</xref>
        ] writes that he thought `suppose
all the information stored on computers everywhere were
linked' and then `suppose I could program my computer to
create a space in which anything could be linked to
anything' [7, p 4].
      </p>
      <p>
        Engelbart speaks in terms of augmenting human
cognitive abilities through technology and evolving practices [
        <xref ref-type="bibr" rid="ref18">18</xref>
        ],
whereas Berners-Lee speaks of linking information, but both
had a vision of enabling humans to navigate information.
2.1.1
      </p>
      <p>NLS</p>
      <p>
        NLS was created by a small group of people and intended
for use by other information professionals like them. There
were no formal user studies or needs analysis. The initial
idea came from Engelbart but many of the innovations and
details came from other members of the group [
        <xref ref-type="bibr" rid="ref11">11</xref>
        ].
      </p>
      <p>
        NLS was a monolithic system running on a single
timeshared computer. It used an embedded markup language.
NLS was the rst computer system with a graphical user
interface (GUI). NLS's GUI used a mouse, chorded keyboard,
and a screen that could display multiple independent
rectangular regions which could include text, static graphics,
and video. One particularly interesting achievement shown
in the 1968 demonstration was the combination of an
interactive map and multi-level hierarchical shopping list that
could be altered in real-time [
        <xref ref-type="bibr" rid="ref22">22</xref>
        ].
      </p>
      <p>
        In terms of the Needs-Satisfaction Curve of a
technology [
        <xref ref-type="bibr" rid="ref21">21</xref>
        ] NLS was a high-tech product; that is to say, it
delivered less than the median customer of a commercial
product would need. According to Norman, `When
technology reaches the point that it satis es user needs,
consumers no longer seek the best technology; they seek the
most convenient one, the one with the most satisfactory user
experience, the lowest cost, and the highest reliability' [21,
p. 251]. Clearly, NLS was not yet at that point to be broadly
accepted as a consumer commodity, but neither was it
intended as such. To reach the level of consumer commodity,
improvements would be needed in both the software
technology and other factors a ecting users' experience such as
the hardware interface and the widespread availability of
computers. However what we will see, after a discussion
of HTML5, is that the conceptual underpinnings and
fundamental technology that we believe today's users want was
already present in NLS, although it may have been concealed
behind the unfamiliar and complex interface.
2.1.2
      </p>
      <p>The World Wide Web</p>
      <p>
        The WWW was conceived by Tim Berners-Lee. In 1995,
he and Robert Cailliau shared ACM's System Software Award
for their work in bringing about the WWW [
        <xref ref-type="bibr" rid="ref2">2</xref>
        ].
BernersLee [
        <xref ref-type="bibr" rid="ref5">5</xref>
        ] credits Cailliau with many essential, but non-technical
advancements which made the WWW possible. Technology
alone is insu cient to ensure successful development.
Today's WWW runs on many hardware platforms. Of
particular interest today are interfaces on desktop and laptop
computers (with screens at least 14"-diagonal and high
resolution colour graphics), and small-screen devices (such as
smartphones). At its simplest, the WWW is composed of
browsers for displaying content, and servers for transmitting
that content to browsers. Although there are many protocols
involved in that process, the `HyperText Markup Language`
(HTML) is an essential piece, encoding a hypertextual
representation of documents to be transmitted from server to
browser. There have been many changes (both de facto and
de jure) to HTML over the years since it was rst codi ed
in an Internet Engineering Taskforce (IETF) RFC [
        <xref ref-type="bibr" rid="ref4">4</xref>
        ]. In
2000, the markup language was re-cast into XHTML using
the extensible markup language (XML) to make the
language easier to adapt to changing conditions [
        <xref ref-type="bibr" rid="ref25">25</xref>
        ]. The next
year, Berners-Lee and others publicly initiated an e ort to
move the WWW in a new direction with the creation of the
Semantic Web project [
        <xref ref-type="bibr" rid="ref6">6</xref>
        ] which would build on XHTML.
2.2
      </p>
    </sec>
    <sec id="sec-4">
      <title>W3C’s and WHATWG’s Divergent Views</title>
      <p>
        Progress continued within the WWW Consortium (W3C)
on developing a new (and incompatible) version of XHTML
to support the expansive ideas represented by the
Semantic Web. However, in 2004 at the W3C Workshop on Web
Applications and Compound Documents a schism developed
which led to the formation of the Web Hypertext
Application Technology Working Group (WHATWG) [
        <xref ref-type="bibr" rid="ref10">10</xref>
        ].
According to the WHATWG [26], `Apple, Mozilla and Opera were
becoming increasingly concerned about the W3C's direction
with XHTML, lack of interest in HTML and apparent
disregard for the needs of real-world authors.' WHATWG was,
and may still be, driven by a pragmatic concern for what
today's programmers (writing browser software and webpages)
are doing, whereas the XHTML 2 group idealistically tried
to create a system based on what should be done.
2.3
      </p>
    </sec>
    <sec id="sec-5">
      <title>One Track — HTML5</title>
      <p>The divergent paths of development ceased when the W3C
agreed not to pursue development of XHTML 2 but to
instead join the e ort by the WHATWG to standardize
existing practices.</p>
      <p>
        HTML5 is a descriptivist approach of standardizing
existing practices (working from the bottom-up) rather than
being guided from the top-down by a prescriptive vision. The
main principles which guide the development of HTML5 are:
to be backwards compatible; to de ne error handling more
rigorously; and to evolve towards greater in-built support for
the types of WWW-based applications we see today [
        <xref ref-type="bibr" rid="ref16 ref24">16, 24</xref>
        ].
The selection of markup elements (e.g. navigation, header,
footer) was based on an analysis of the use of CSS class
attributes from over two billion webpages collected by web
crawlers [16, p. 6].
      </p>
      <p>HTML5 is a standardization of not only the markup
language used to describe the page, but also the Application
Programming Interfaces available to JavaScript running on
the page. It is not a monolithic entity, but an evolving
collection of standards in varying states of readiness and
implementation. It includes native support for
drag-anddrop, video, remote procedure calls (a la Ajax), drawing,
data storage, geolocation, graphical widgets for new kinds
of input and output, and more.</p>
      <p>HTML5 now provides (natively) almost everything that
was in NLS. No previous version of HTML was able to
support all that functionality natively.
3.</p>
    </sec>
    <sec id="sec-6">
      <title>DEMO: HTML5 SIMULATING NLS</title>
      <p>The accompanying demonstration (see Figure 1) uses the
HTML5 standard as implemented by the Firefox browser.
We show a working model of the dynamic shopping cart
with associated 2D map like that demonstrated in 1968 and
referred to above. The map is implemented using the canvas
element. The nested hierarchies are represented by ordered
lists which are manipulated in memory through the DOM
and ECMAscript. The lists of locations, etc. are displayed
to users in menus. We use the localStorage API for storing
data persistently (i.e., so it is retained between sessions).</p>
    </sec>
    <sec id="sec-7">
      <title>CONCLUSION</title>
      <p>Our conclusion is in three parts: what seems not to have
changed, what has, and predictions.
4.1</p>
    </sec>
    <sec id="sec-8">
      <title>Running on the treadmill</title>
      <p>Although, hardware and network performance have
improved tremendously since 1968, many of the capabilities of
NLS were not matched by the WWW until very recently.
Networking capabilities are one of the only exceptions to
this observation.</p>
      <p>One lesson that can be extracted from the legacy of NLS
is that people cannot be directed to do things in prescribed
ways even if the vision is eventually borne out, given that the
features demanded by users of the WWW were very similar
to those rst envisioned by Englebart 50 years earlier.</p>
      <p>Without Englebart's grand vision, the ideas behind HTML5
might not have existed at all. It took fty years for the world
to change enough that Englebart's original ideas could
become widespread. However, HTML5 is not a grand vision; it
simpli es what has already been done. Perhaps in another
50 years, we will nally catch up to the promise of XHTML2
and the semantic web By contrasting NLS and HTML5 it is
apparent that we (the hypertext/WWW programming
community) have not done much more than executing the vision
of the original founders.</p>
      <p>
        Just as the WWW could not be successful without
Cailliau's non-technical contributions so future progress will be
impossible without engaging many people [
        <xref ref-type="bibr" rid="ref18 ref3">3, 18</xref>
        ]. We
cannot rely solely on visionaries in standards bodies to drag the
rest of us along to `the next \Big Thing"'. People must also
be ready to accept it.
4.2
      </p>
    </sec>
    <sec id="sec-9">
      <title>Substantial progress</title>
      <p>
        At the rst Hypertext conference, Halasz [
        <xref ref-type="bibr" rid="ref14">14</xref>
        ] challenged
the community to solve seven major issues with hypertext.
The list and progress towards solutions has been a recurrent
theme at the conference. In 2007, Goble [
        <xref ref-type="bibr" rid="ref13">13</xref>
        ] showed how,
within parts of the WWW, all of the issues have at last been
resolved.
      </p>
      <p>Competing interests led to standards (some good, others
not so good) that have led to improved e ciency in
developing across many platforms, and have often driven
development.</p>
      <p>
        Engelbart's ideas that led to the development of NLS,
although recognizing that `communications is an integral
part of the design' [18, p. 87] were more aligned with Bush's
memex [
        <xref ref-type="bibr" rid="ref9">9</xref>
        ] than the modern conception of social media and
e-commerce. The modern Semantic Web and the Web of
Linked Data [
        <xref ref-type="bibr" rid="ref15">15</xref>
        ] are considerably more advanced in scope
and depth than their early precursors in NLS. However, we
believe that it has fallen victim to the same problem that
NLS did decades before, of being too far ahead of the curve.
4.3
      </p>
    </sec>
    <sec id="sec-10">
      <title>Predictions</title>
      <p>
        If the experience from 1968 until the present is a
reliable predictor then we expect that prescriptive approaches
to systems will be di cult to sustain. Popular demand will
dictate where the money and research goes, and
entertainment is what is usually popularly demanded [
        <xref ref-type="bibr" rid="ref17">17</xref>
        ].
      </p>
      <p>
        Where should we be going? For real improvements in
the state of the user-based WWW (not the Web of Linked
Data) we should mine features from earlier systems that
were seen as too complicated, computationally expensive,
autocratically organized, or unusual at the time of their
release. Of course, some of this has already been done: for
example innovations from Microcosm [
        <xref ref-type="bibr" rid="ref12">12</xref>
        ] have been ported
to the WWW, Trellis [
        <xref ref-type="bibr" rid="ref23">23</xref>
        ] and VIKI [
        <xref ref-type="bibr" rid="ref19">19</xref>
        ] have inspired parts
of StorySpace and Tinderbox [
        <xref ref-type="bibr" rid="ref8">8</xref>
        ].
      </p>
      <p>If any new ideas are to be considered a success, they must
be measured by the balance they strikes between prescriptive
and descriptive impulses.</p>
    </sec>
    <sec id="sec-11">
      <title>Acknowledgements</title>
      <p>This article was inspired by a lengthy conversations with
Douglas Engelbart and Carole Goble, and was fuelled by
comments from Dame Wendy Hall and Lynda Hardman.
Hermann Maurer provided valuable clari cations and a
different perspective. The initial versions of the software were
developed by Trevor Hrenko under the direction of James
Blustein. Their help is gratefully acknowledged. This work
is supported by a Discovery grant from NSERC.
[26] WHATWG. What is the WHATWG? in FAQ
WHATWG Wiki. http://wiki.whatwg.org/wiki/FAQ#
What is the WHATWG.3F. Accessed 2011-09-07.
TM</p>
    </sec>
  </body>
  <back>
    <ref-list>
      <ref id="ref1">
        <mixed-citation>
          [1]
          <string-name>
            <given-names>Keith</given-names>
            <surname>Andrews</surname>
          </string-name>
          , Frank Kappe, and Hermann Maurer.
          <article-title>The Hyper-G network information system</article-title>
          .
          <source>Journal of Universal Computer Science</source>
          ,
          <volume>1</volume>
          (
          <issue>4</issue>
          ):
          <volume>206</volume>
          {
          <fpage>220</fpage>
          ,
          <string-name>
            <surname>April</surname>
          </string-name>
          <year>1995</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref2">
        <mixed-citation>
          [2]
          <string-name>
            <surname>Assoc</surname>
          </string-name>
          . for Comput.
          <source>Machinery (ACM)</source>
          . http://awards. acm.org/award winners/cailliau 5353144.cfm,
          <year>1995</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref3">
        <mixed-citation>
          [3]
          <string-name>
            <given-names>Thierry</given-names>
            <surname>Bardini</surname>
          </string-name>
          and
          <string-name>
            <given-names>Michael</given-names>
            <surname>Friedewald</surname>
          </string-name>
          .
          <article-title>Chronicle of the death of a laboratory: Douglas Engelbart and the failure of the knowledge workshop</article-title>
          . In Ian Inkster, editor,
          <source>History of Technology</source>
          , volume
          <volume>23</volume>
          , pages
          <fpage>191</fpage>
          {
          <fpage>212</fpage>
          . Continuum Press, London,
          <year>2003</year>
          . http://www. friedewald-family.de/Publikationen/hot2002.pdf.
        </mixed-citation>
      </ref>
      <ref id="ref4">
        <mixed-citation>
          [4]
          <string-name>
            <given-names>T.</given-names>
            <surname>Berners-Lee</surname>
          </string-name>
          and
          <string-name>
            <given-names>D.</given-names>
            <surname>Connolly</surname>
          </string-name>
          .
          <source>Hypertext markup language - 2.0. RFC</source>
          <year>1866</year>
          , Network Working Group of Internet Engineering Taskforce,
          <year>November 1995</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref5">
        <mixed-citation>
          [5]
          <string-name>
            <given-names>Tim</given-names>
            <surname>Berners-Lee</surname>
          </string-name>
          .
          <article-title>Robert Cailliau's role in Frequently asked questions by the Press - Tim BL</article-title>
          . http://www. w3.org/People/Berners-Lee/FAQ.html#Cailliau.
        </mixed-citation>
      </ref>
      <ref id="ref6">
        <mixed-citation>
          [6]
          <string-name>
            <given-names>Tim</given-names>
            <surname>Berners-Lee</surname>
          </string-name>
          ,
          <string-name>
            <given-names>James</given-names>
            <surname>Hendler</surname>
          </string-name>
          , and
          <string-name>
            <given-names>Ora</given-names>
            <surname>Lassila</surname>
          </string-name>
          .
          <article-title>The Semantic Web</article-title>
          . Scienti c American, May
          <year>2001</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref7">
        <mixed-citation>
          [7]
          <string-name>
            <given-names>Tim</given-names>
            <surname>Berners-Lee</surname>
          </string-name>
          and
          <string-name>
            <given-names>Mark</given-names>
            <surname>Fischetti</surname>
          </string-name>
          .
          <article-title>Weaving the Web: The Original Design and Ultimate Destiny of the World Wide Web by Its Inventor</article-title>
          . Harper San Francisco, rst edition,
          <year>1999</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref8">
        <mixed-citation>
          [8]
          <string-name>
            <given-names>Mark</given-names>
            <surname>Bernstein</surname>
          </string-name>
          .
          <article-title>Can we talk about spatial hypertext</article-title>
          .
          <source>In Proc. 22nd ACM Conference on Hypertext and Hypermedia</source>
          ,
          <source>HT '11</source>
          , pages
          <fpage>103</fpage>
          {
          <fpage>112</fpage>
          ,
          <year>2011</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref9">
        <mixed-citation>
          [9]
          <string-name>
            <given-names>Vannevar</given-names>
            <surname>Bush</surname>
          </string-name>
          .
          <article-title>As we may think</article-title>
          .
          <source>The Atlantic</source>
          ,
          <year>1945</year>
          . As reprinted by Nelson [
          <volume>20</volume>
          ].
        </mixed-citation>
      </ref>
      <ref id="ref10">
        <mixed-citation>
          [10]
          <string-name>
            <given-names>Tantek</given-names>
            <surname>Celik</surname>
          </string-name>
          .
          <source>HTML5 Now. New Riders</source>
          ,
          <year>2011</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref11">
        <mixed-citation>
          [11]
          <string-name>
            <given-names>Christina</given-names>
            <surname>Engelbart</surname>
          </string-name>
          .
          <article-title>A lifetime pursuit</article-title>
          . http://www. dougengelbart.org/history/engelbart.html,
          <year>2008</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref12">
        <mixed-citation>
          [12]
          <string-name>
            <surname>Andrew</surname>
            <given-names>M.</given-names>
          </string-name>
          <string-name>
            <surname>Fountain</surname>
          </string-name>
          , Wendy Hall, Ian Heath, and
          <string-name>
            <surname>Hugh</surname>
            <given-names>C. Davis. MICROCOSM:</given-names>
          </string-name>
          <article-title>An open model for hypermedia with dynamic linking</article-title>
          . In N. Streitz,
          <string-name>
            <given-names>A.</given-names>
            <surname>Rizk</surname>
          </string-name>
          , and J. Andre, eds,
          <source>Hypertext: Concepts</source>
          ,
          <source>Systems and Applications</source>
          , pages
          <volume>298</volume>
          {
          <fpage>311</fpage>
          . Cambridge U. Press,
          <year>1992</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref13">
        <mixed-citation>
          [13]
          <string-name>
            <surname>Carole</surname>
            <given-names>A.</given-names>
          </string-name>
          <string-name>
            <surname>Goble</surname>
          </string-name>
          .
          <article-title>The return of the prodigal web</article-title>
          .
          <source>In Proceedings of the Eighteenth Conference on Hypertext and Hypermedia</source>
          , HT '
          <fpage>07</fpage>
          , New York,
          <year>2007</year>
          . ACM.
        </mixed-citation>
      </ref>
      <ref id="ref14">
        <mixed-citation>
          [14]
          <string-name>
            <surname>Frank</surname>
            <given-names>G.</given-names>
          </string-name>
          <string-name>
            <surname>Halasz</surname>
          </string-name>
          . Re ections on Notecards:
          <article-title>Seven issues for the next generation of hypermedia systems</article-title>
          .
          <source>In Proceedings of the ACM Conference on Hypertext, HYPERTEXT '87</source>
          , pages
          <fpage>345</fpage>
          {
          <fpage>365</fpage>
          , New York,
          <year>1987</year>
          . ACM.
        </mixed-citation>
      </ref>
      <ref id="ref15">
        <mixed-citation>
          [15]
          <string-name>
            <given-names>Wendy</given-names>
            <surname>Hall</surname>
          </string-name>
          .
          <article-title>From hypertext to linked data: The ever evolving Web</article-title>
          .
          <source>In Proceedings of the 22nd ACM Conference on Hypertext and Hypermedia</source>
          , HT '
          <fpage>11</fpage>
          , New York,
          <year>2011</year>
          . ACM.
        </mixed-citation>
      </ref>
      <ref id="ref16">
        <mixed-citation>
          [16]
          <string-name>
            <given-names>Bruce</given-names>
            <surname>Lawson</surname>
          </string-name>
          and
          <string-name>
            <given-names>Remy</given-names>
            <surname>Sharp</surname>
          </string-name>
          .
          <source>Introducing HTML5</source>
          . Peachpit Press,
          <year>2010</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref17">
        <mixed-citation>
          [17]
          <string-name>
            <given-names>Andrew</given-names>
            <surname>Marantz</surname>
          </string-name>
          .
          <article-title>The virologist: How a young entrepreneur built an empire by repackaging memes</article-title>
          .
          <source>The New Yorker, 05 January</source>
          <year>2015</year>
          . http://www.newyorker. com/magazine/2015/01/05/virologist.
        </mixed-citation>
      </ref>
      <ref id="ref18">
        <mixed-citation>
          [18]
          <string-name>
            <given-names>John</given-names>
            <surname>Marko</surname>
          </string-name>
          .
          <article-title>What the Dormouse Said: How the Sixties Counter-culture Shaped the Personal Computer Industry</article-title>
          .
          <source>Penguin Books</source>
          ,
          <year>2005</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref19">
        <mixed-citation>
          [19]
          <string-name>
            <surname>Catherine</surname>
            <given-names>C.</given-names>
          </string-name>
          <string-name>
            <surname>Marshall</surname>
          </string-name>
          ,
          <string-name>
            <surname>Frank M. Shipman</surname>
          </string-name>
          , III, and
          <string-name>
            <surname>James</surname>
            <given-names>H.</given-names>
          </string-name>
          <string-name>
            <surname>Coombs</surname>
          </string-name>
          . VIKI:
          <article-title>Spatial hypertext supporting emergent structure</article-title>
          .
          <source>In Proceedings of the 1994 ACM European Conference on Hypermedia Technology, ECHT '94</source>
          , pages
          <fpage>13</fpage>
          {
          <fpage>23</fpage>
          , New York,
          <year>1994</year>
          . ACM.
        </mixed-citation>
      </ref>
      <ref id="ref20">
        <mixed-citation>
          [20]
          <string-name>
            <surname>Theodor</surname>
            <given-names>Holm Nelson. Literary</given-names>
          </string-name>
          <string-name>
            <surname>Machines</surname>
          </string-name>
          .
          <source>The Distributors</source>
          , 702 South Michigan,
          <source>South Bend IN 46618 USA, 90.1 edition</source>
          ,
          <year>1990</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref21">
        <mixed-citation>
          [21]
          <string-name>
            <surname>Donald</surname>
            <given-names>A.</given-names>
          </string-name>
          <string-name>
            <surname>Norman</surname>
          </string-name>
          . The Invisible Computer:
          <article-title>Why good products can fail, the personal computer is so complex, and information appliances are the solution</article-title>
          . MIT Press,
          <year>1998</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref22">
        <mixed-citation>
          [22] Stanford University Libraries.
          <source>Doug Engelbart</source>
          <year>1968</year>
          demo. http://sloan.stanford.edu/MouseSite/ 1968Demo.html,
          <year>1968</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref23">
        <mixed-citation>
          [23]
          <string-name>
            <given-names>P.</given-names>
            <surname>David</surname>
          </string-name>
          Stotts and
          <string-name>
            <given-names>Richard</given-names>
            <surname>Furuta</surname>
          </string-name>
          .
          <article-title>Trellis: A system for writing and browsing Petri-net-based hypertext</article-title>
          .
          <source>In Proceedings on Advances in Petri Nets</source>
          <year>1990</year>
          , APN
          <volume>90</volume>
          , pages
          <fpage>471</fpage>
          {
          <fpage>490</fpage>
          , New York,
          <year>1991</year>
          . Springer-Verlag New York, Inc.
        </mixed-citation>
      </ref>
      <ref id="ref24">
        <mixed-citation>
          [24]
          <string-name>
            <surname>Anne</surname>
            <given-names>van Kesteren</given-names>
          </string-name>
          and
          <string-name>
            <given-names>Maciej</given-names>
            <surname>Stachowiak</surname>
          </string-name>
          .
          <article-title>HTML design principles</article-title>
          .
          <source>W3C Working Draft, WWW Consortium</source>
          ,
          <year>2007</year>
          . http://www.w3.org/TR/2007/ WD-html
          <string-name>
            <surname>-</surname>
          </string-name>
          design-principles-
          <volume>20071126</volume>
          /.
        </mixed-citation>
      </ref>
      <ref id="ref25">
        <mixed-citation>
          [25]
          <string-name>
            <surname>W3C HTML Working</surname>
          </string-name>
          <article-title>Group</article-title>
          .
          <article-title>XHTML 1.0 The Extensible HyperText Markup Language (second edition): A reformulation of HTML 4 in XML 1.0</article-title>
          .
          <source>Technical report, WWW Consortium</source>
          ,
          <year>2002</year>
          .
        </mixed-citation>
      </ref>
    </ref-list>
  </back>
</article>