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Added unfinished draft of hypertext post Getty Ritter 8 years ago
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1 \meta{("some-hypertext-features"
2 "beyond wikis: hypertext stuff"
3 ("hypertext"))}
4
5 For many people, the word 'hypertext' brings to mind HTML and
6 wikis. Hypertext encompasses a wide range of systems, artifacts,
7 and approaches, from choose-your-own-adventure books to experimental
8 literature, from Twine games to HyperCard, and so forth. But—for
9 very good reason—HTML has become ubiquitous, and with it, its
10 approach to hypertext.
11
12 On the other hand: previous decades included a lot of experimental
13 hypertext systems which pushed out into interesting different
14 directions that aren't as common in modern hypertext systems.
15
16 Here are just a handful of features of older hypertext systems:
17
18 \h2{Typed Nodes}
19
20 In HTML, every page is a soup of information. Pages are structured
21 from the point of view of the \em{markup}, but not really from
22 the hypertext-level view of the page: an HTML page can be edited
23 to include more information or less information, and there isn't
24 really a way of distinguishing them.
25
26 Some other systems distinguish nodes based on what "type" of node
27 they are, which often gives them more structure: for example,
28 we could build up a hypertext system for describing places
29 in which there is a specific sort of node that describes a "city".
30 Instead of \em{just} being a mass of formatted text and links, it
31 would have a set of specific fields: the name of the city,
32 the population, its area, its location, and so forth.
33
34 Some values of these fields could be links, but those links
35 could also stipulate the sort of thing they link to: a city
36 might have a field telling us what country it is in, and our
37 system could prevent us from accidentally filling in that field
38 with anything other than a country.
39
40 Certain historical hypertext systems used nodes of this type:
41 for example,
42 \link{http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.438.8515&rep=rep1&type=pdf|Aquanet}
43 took its node descriptions directly from Common Lisp descriptions
44 of objects, so that each field corresponded to an instance
45 variable (or \em{slot}, in Common Lisp parlance) of an object.
46
47 \h2{Typed Links}
48
49 In HTML, a hyperlink usually doesn't mean anything in particular
50 to a computer. It usually means something to a \em{reader}, but
51 the semantics aren't necessarily conveyed in a machine-readable
52 way.
53
54 This isn't always true: for example, some hyperlinks are annotated
55 to let the computer know that \em{this} link is to the next page
56 in a sequence, while \em{this} link is to the previous, or other
57 roles. But some other hypertext systems took that notion even
58 further, allowing for documents that conveyed more
59 precise information about their hypertext structure.
60
61 For example, you can imagine a hypertext system which describes
62 places, and has links with specific geographical and spatial
63 connotations: a link could specify in a machine-readable way
64 that a given place \em{contains} another place, and use
65 this link to link the \em{Italy} node to the \em{Rome} node,
66 and in turn the \em{Rome} node to the \em{Coliseum} node.
67
68 In doing so, you not only build up a hypertext structure with
69 richer affordances for navigation, but also with richer affordances
70 for \em{automated reasoning}. I could, for example, query my
71 hypertext system by asking, "What are other places that are
72 contained within the same place that contains the Coliseum?"
73
74 Numerous old papers on hypertext systems consider the problem of
75 attempting to build and reason about arguments, and usually
76 start from the
77 \link{https://en.wikipedia.org/wiki/Toulmin_method|Toulmin model of reasoning}.
78 Systems that include typed links could represent relationships
79 like \em{is-a-fact-that-supports} directly as links, so a user
80 could query the system by asking, "What are all the nodes that
81 are supporting facts for this thesis?"
82
83 \h2{Link Arity And Direction}
84
85 In HTML, a link is one-way: if I include a link in document A which
86 leads to document B, I won't necessarily have a link back. There
87 are various ways of synthesizing backward edges: by including
88 smarts in the browser (e.g. the 'back' button) or in particular
89 applications (e.g. a wiki's 'what links here' feature) or by
90 cross-application mechanisms (e.g. 'pingbacks' in WordPress or
91 other CMS systems), but none of these are inherent in the HTML
92 mode.
93
94 Some other hypertext systems include links that are \em{inherently}
95 two-directional. These systems build up stronger interconnectedness
96 between nodes, because there are no "dead-end" paths: you can always
97 at least move back the way you came, and creating a new node
98 also creates a backwards path. In a system with typed links, this
99 also means you can have links with swapped semantics: creating
100 a \em{contains} link from \em{Italy} to \em{Rome} is the same
101 operation as creating a \em{is-contained-in} link from \em{Rome} to
102 \em{Italy}.
103
104 Even more extreme, some hypertext systems include links that
105 join together more than two nodes. This doesn't make a whole lot
106 of sense in something like HTML, where a link doesn't necessarily
107 connote any particular "meaning", but in a system with typed
108 links, we can imagine a link that brings together multiple nodes
109 with a different denotation for each: in our hypothetical
110 geographic system, we could have a ternary link that represents
111 \em{is directly between x and y}.
112
113 In the most extreme, you could imagine a system that treats
114 n-ary links as n-ary predicates.
115
116 The aforementioned Aquanet system contained not just typed nodes but
117 also typed n-ary links, which were there called \em{relations}.
118
119 \h2{Spatial Hypertext}
120
121 In HTML, pages are identified by names. Organization is largely
122 done by creating other pages that name things together. For
123 example, I could create a web site in which I build up index
124 pages that describe how I structure my site. URLs originally
125 also mapped to hierarchical folder structures, and it's common
126 for people to treat them in a similar way today, but by no
127 means is that obligatory on the modern web.
128
129 Some historical hypertext systems took a different approach: each
130 node was identified with a location in a spatial field, so navigating
131 a piece of hypertext could involve not just links that 'took you'
132 to other nodes, but also following spatial paths which connected
133 nodes positioned on or along those paths.
134
135 Different spatial hypertext systems took different approaches to
136 this: some of them allowed the user to move nodes around, which
137 could be useful in editing the document. Others took the conceptual
138 relationship between nodes as expressed in the hypertext and
139 extracted a spatial system from that, building up 'maps' to
140 help a reader navigate an otherwise abstract structure.
141
142 Some
143 systems would even work in the opposite way: allowing the users
144 to position nodes spatially, and then inferring information
145 about the conceptual structure of those nodes from the common
146 spatial patterns produced by users. This was the approach
147 of the
148 \link{http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.76.5062&rep=rep1&type=pdf|Viki}
149 system.
150
151 There's actually a very good example of a modern spatial hypertext
152 editing system: \link{|Twine}
153
154 \hr{}
155
156 Many of the features I've described are structural, and it's pretty
157 obvious in retrospect that HTML and Wikis impose far less structure
158 than many other hypertext systems. In many ways, this is to their
159 advantage: an HTML page can mean anything you want it to, and an
160 HTML link can also be used for any purpose.
161
162 On the other hand, this also makes certain operations infeasible or
163 even nonsensical: a more structured hypertext system can perform
164 operations by looking at the shape or structure of a collection of
165 nodes or links, and can perform computer-aided reasoning. This is
166 one of the reason why the Toulmin method showed up so often in
167 past hypertext research: you were building up relationships between
168 data in ways that you \em{and your system} could both reason about.
169