Abstract

Spatial Hypertext (SH) has been a long-standing facet of research within the Hypertext field, yet active research is declining despite ongoing interest in the concept. Is this because the question of SH's nature is resolved, or because is needs re-contextualising? This paper summarises SH's history for today's post-Web researcher as well as current SH research, tools and SH's possible future.

CCS Concepts

Human-centered computing → Hypertext / hypermedia

Information systems → Collaborative and social computing systems and tools

Keywords

spatial hypertext, hypertext, AI, XR, sense making, knowledge management, VIKI, VKB, AQUANET, premature formalisation, information triage, Storyspace, Tinderbox, Notecards

1 Introduction

Spatial Hypertext (SH) has been a long-running theme in the Hypertext Conference. At HT'23, in 'Seven Hypertexts' 2, Sect. 4.3 it is noted as underexploited aspect of Hypertext work 3, Sect. 3.5. But looking at reference to DH within in the wider world, the picture looks a little different—see Figure 1. Why might this be?

Figure 1: Google ngram term 'spatial hypertext' 1970–2022.

The term 'Spatial Hypertext' was first coined by Marshall & Shipman in 1993 107, though the roots of SH stem from the late 1980s. The last major SH-centric research program was VKB 149 in 1999, with work on and research using VKB running on until c.2014. The core programs in the SH story are AQUANET, VIKI and VKB, all described in more detail below. However, understanding SH is more than just those three experiments.

Before exploring further, it is worth noting that most working-age people today (2025) left junior school after the Web's public debut (c.1993). Thus, for many readers of this paper, the Web's subset of hypertext features is likely their baseline understanding of the meaning of 'hypertext'—perspective is relevant.

Thus, 'Spatial Hypertext' was coined the same year the (World Wide) Web opened to the public, in 1993. VIKI 110 was launched a year later and was being evaluated at a time when research and public interest in hypertext was pivoting to the fast-growing Web. SH's roots actually stretch back further, to the late 1980s—so, pre-Web. Furthermore, from the published record, the inception of projects is often unclear. This is because papers tended to be written at the end of a research grant, or after it finished, making the narrative doubly retrospective and not always easy to follow. Another factor confusing in hindsight is the scale of content used. Systems in the late 1980s might have hundreds of nodes in a hypertext: those were large hypertexts in their time.

Very few of the systems described can be seen working today (or have video of their use), and early print reproduction of screen images was often poor. Indeed, of the three main SH experimental programs discussed here, only the last (VKB) can still be run (see Figure 2). Bernstein's paper at the SH1 Workshop[^1] asked 'Where Are The Hypertext Systems?' 22, p.1 pointing out that at HYPERTEXT'87 'With the exception of NLS/AUGMENT, the old, established systems were all younger than VIKI is today'. The passage of time means that few of today's (2025) hypertext researchers were 'in the room' when the early SH papers came out and given the over 30-year gap it is useful to re-seam together programs and their surrounding literature, before considering where SH stands today and its possible future.

[^1]: The first of four SH workshops held at the HT Conferences '01–'04: see 160.

1.1 So what then is 'Spatial' Hypertext?

At its simplest, SH is the notion that individual hypertext nodes[^2], drawn as a graph or 'map', can have semantic meaning that derives from either/both their position relative to one another or their appearance. It is also not necessary for there to be explicit linkage between lexia for an SH to be meaningful to its user. A crucial distinction of SH is 'the ability to leave structure implicit and informal' 108, p.90.

[^2]: Nodes, notes, elements, lexia—interchangeable terms for the discrete content elements of a hypertext. Here, 'hypertext' stands proxy for both hypertext and hypermedia.

The apparent rejection of links is just that—apparent. SH does not reject hypertext's links, but simply downplays their role in order to explore the implications of specialised display. A link expressed in a hypertext still exists even if not explicitly visualised.

SH also allows people to express what DeRose refers to as 'extensional structure' 49, p.251, idiosyncratic and dependent on the situation at hand, perceived through context, not computed from content. Ambiguity may be left unresolved without compromising the integrity of the structure' 108, p.90 also footnoting that (my italics): 'In explicit hypertextual linking, links are either there, or they are not. When links are given weights or may exist independently from nodes, the existence of the link still must be specified unambiguously'. This hints at what Halasz has described as 'the tyranny of the link'[^3] 67—something SH set out to circumvent.

[^3]: He notes: 'Basically I would like to claim we need to develop a new conception of hypermedia that includes non-network structures as well as virtual structures on an equal footing with network.'

Although some also ascribe a need for SH to involve a (spatial) parser, this is not explicitly noted as a requirement for a hypertext to be spatial hypertext. That expectation seems to arise from the fact it was a necessary part of some early SH experimental applications, to illustrate computer recognition of human intuition. The human arrangement of a 'map' is an implicit form of spatial parsing, but this was Computer Science research and the wonder of new technology could unintentionally shade out the relevance of merely human input. The role of the parser is generally to recognize and capture emergent structure and/or to suggest formalisations to apply. Importantly, the initial structure is created by the human user.

Interestingly, there is no single short, definitive definition of SH, but general SH papers from 1993 107, 1995 108, and 1999 153 respectively, give the best insight as to the wider context of the description of SH given above. Ironically, that potential ambiguity of meaning has been to SH's benefit, as will be seen, not least because partly it speaks to what is not on the 'page' and to humans' associative sense-making skills. Indeed, back in 1945, Bush's 'As We May Think' noted as much: "The human mind does not work that way. It operates by association."[^4] 41, Sect. 6. Kidd 84 also notes an interesting aspect of mapping information as a scaffold for knowledge workers' learning: once internalised, the source material becomes of less immediate interest.

[^4]: Unproven, even if navigation by association feels intuitive for humans.

Tangential to defining SH but important to informing its approach to eliciting implicit structure is Shipman & Marshall's article 'Formality Considered Harmful' 151 that considered issues of premature vs. incremental formalisation[^5]. One unintentional side-effect of early link-typed systems was the need placed upon the user to consider the intent of a link, and its target before that intent was fully formed, and so encouraging premature formalisation.

[^5]: This work also drew on Shipman's earlier PhD thesis 141. The 1993 Formality paper was later revised and expanded slightly (in 1999) 152.

2 The background to Spatial Hypertext

What may be less clear in hindsight is how transgressive SH's seeming eschewal of links might have appeared back in the early 1990s. Ted Nelson's neologism of 'Hypertext' was of '. . . a body of written or pictorial material interconnected in such a complex way that it could not conveniently be presented or represented on paper.' 122, p.96. Those interconnections were what became termed 'links', and their visibility is something that Nelson himself has always stressed 125 [124, image p1/25].

The 1980s–90s were a time of rapid expansion of hypertext development and research. Pertinent for today's researcher was the fact that most systems then ran on single computers. PCs and workstations were taking over from earlier 'mainframe' computers: merely having a computer was getting easier. Display screens were expensive, physically small, and of low resolution. Colour screens were a rarity. Much of the displayed content was text, partly reflecting the immaturity of displaying image content and partly due to the perceived role of hypertext tools.

For linking, even the very act of traversing (a link) from one node to another was still novel and even confusing, with erstwhile fears of being 'lost in hyperspace' 51, 54 43, p.38. This was also reflected in Landow's consideration of the rhetoric of link-traversal departure and arrival 90. Oddly to today's eye, (hypertext) links were a thing of mystery and not the obvious means of navigation: should I follow this link, what might happen next?

Thus, links and their role (type) were very much to the fore 44, Fig. 8[43, Table 1], not least as there was often little in the way of a graphical overview of the system. The role of link types—an expression of the link's purpose[^6]—increased in 1983 with the arrival of Trigg's TEXNET[^7] 179 and Halascz's Notecards 68. Both these programs were created by staff of Systems Sciences Laboratory (SSL) at Xerox PARC[^8].

[^6]: This is explored by Nelson's link typologies in Literary Machines 124, pp.4/41–4/60 and in Conklin's hypertext survey 43, p.40 44, Sect. 5.2.

[^7]: This drew on his PhD work 173. His link type taxonomy is explained at 19.

[^8]: Xerox's Palo Alto Research Center, in Palo Alto, CA, USA.

Links serve a dual function[107]. Firstly, they give rhetorical structure to a hypertext's overall set of nodes. They offer a literal prompt for, an affordance of, traversal of the hypertext. This might involve following a pre-defined stored path, e.g. Memex's 'trails' 41, scripted documents 190, 191, or 'guided tours' 105, 174. Or, they might involve choice and intuition as in Intermedia 188 or Storyspace 78.

Building on top of Notecards, PARC's Intelligent System Lab built IDE[^9] 76, 129, 138. It added the notion of a graphical Knowledge Structure, allowing visualisation of the domain knowledge to be taught 138, p.209, Fig. 7.9. Within Notecards itself, some structuring of context was possible, primarily via Browser-type cards, and this was leveraged to give 'guided tours' of a hypertext 174. A parallel development was the 'tabletop' card. This allowed a number of cards—and their layout—to be saved, essentially a precursor to today's notion of a saved work space.

[^9]: The Instructional Design Environment.

Other approaches to hypertextual construction and traversal were being tried. Nanard & Nanard expanded the notion of typing further in their MacWeb 120, 121 system—even proposing typed anchors. DeRose, exploring the notion of the link 49, also derived a taxonomy of link types distinguishing intensional links from extensional links. The former follow from the internal structure and content of the nodes compared to the idiosyncratic definition of extensional links.

Taking a differing perspective of the whole, Stotts & Furuta were applying Petri net[^10] principles to the hypertext graph in their Trellis programs 62, 169 using places (notes) and transitions (links) to tease content apart from structure. Van Dyke Parunak's HyperSet 182, 183 explored Set theory as a means of exploring the graph. There was recognition that not all hypertexts were static in representation, so-called 'volatile' hypertexts 29. Fairchild's SemNet 56 looked at using a 3-dimensional view of the hypertext graph as a way of both exposing it to the user and avoiding some of the noise that a densely linked graph has in 2D. Outside the research laboratory, Apple's Hypercard was also following a card-based motif[4].

[^10]: Also known as a place/transition net or 'PT net'

Whilst hypertext traversal via single node-to-node links seemed the most tractable approach, the exact nature of implementing a hypertext was not set as the diverse examples above show. However, the link was a significant component of all these systems.

2.1 Experience of Notecards

Another factor encouraging the primacy of the link at that time was interest in mapping the structure/logic of (AI) argumentation and business process 45, 101, 102. AI and Machine Learning at that time were also making more deliberate use of decision trees 91, 92, 94. Mapping logic seemed a logical route forward. However, as SSL staff and researchers started to use and report on Notecards 66, 68, 75, 105, 115, 116, 174–178, it became apparent that closely-typed linking of type could hamper users employment of linking, and gaining benefit from their hypertexts.

For all that such formalism offered, some users found making a pre-emptive choice of link types before creating links to be an impediment. For instance, it became apparent that less formal Notecards features like Sketch- and Filebox-type notes allowed organisation without the need to commit to a structure whilst it was still not fully formed 101, 102. Though not explicitly on record, this suggests use of sketch or filebox cards hinted at users trying to avoid premature formalisation. Marshall, in a later (2001) retrospective on Notecards, writes 'much of the use I observed . . . did not involve typed links. Link-typing schemes, if adopted, were frequently abandoned. The automatically maintained hierarchical FileBox links were a far more common way of introducing structure to the hypertext.' 103, p.101

Thus, the formalisation of explicit link typing could actually be detrimental as choice of type could force formalisation before the researcher had a clear feel for structure. How might the user explore the shape of the task without having to guess the structure beforehand?

Also informing the design of these early hypertext systems was the current observation of existing forms of (non-digital) information collection and triage, such as desk organisation 97 and the 'pile' as a metaphor 100. The notion of 'information farming' 15 or 'gardening' arose, echoing human nurturing and husbandry of crops (of information). Hypertext development was also conscious of the need to bridge to existing informational practice. Separately, there was interest in semi-structured communication[98] and systems such as Winograd's Coordinator 186 and Gorry's VNS[^11] 63, 64.

[^11]: Virtual Notebook System, built atop Notecards.

3 AQUANET: holding knowledge in place? (1991)

Mindful of the 'tyranny of the link', PARC SSL's next hypertext experiment was 'AQUANET' (c.1990–92). It attempted to look at the 'knowledge structuring task' using spatial layout to explore and impart semantic meaning to emergent knowledge. It drew upon Germ[^12] 38, gIBIS 40, 45, 46, Notecards, and IDE. Conklin's gIBIS was also of note as it sought to visualise, as a graph, argumentation in business processes.

[^12]: (Graphical Entity Relational Modeling: also see 70.

A primary innovation, with regard to hypertext systems, was that the main display space was 'a large unpartitioned display space' 106, p.58, which was a departure from the multiple window (card) displays of the likes of Notecards or Hypercard. The broad aims were laid out at 104, p.264:

Specifying the elements and connection methods of the problem space.

Being able to model the knowledge structure.

For collaboration, regular updating: 'What You See Is What I Did' (WYSIWID).

Multiple views of the same (data) structure[^13] (citing QOC 96, and SIBYL 91).

Allow combinations of methodologies to structure knowledge (citing Streitz 171).

Allow discussion both about and through the structure, as in Conklin's 'going meta' 45, pp.148–9.

[^13]: q.v. NLS/Augments's viewspecs 55.

The structures offered aimed to support both the Dexter Hypertext Reference Model 69 and frame-based representation (per 33) describing nodes as 'basic objects' and links as relationships. Actual links, as were then the norm, were not included; the visualisation of the display space offering implicit (link) relationships instead. Though AQUANET is often seen as a proto-Spatial Hypertext, in terms of what it set out to do, it was far more structure-oriented than what was to follow. Although the map was free-form, the user was expected to insert objects chosen from a set of pre-defined objects. The freedom of user choice was more in the layout than in the type of object (though the user could define custom objects).

Indeed, it was observations of what had not worked as expected, as much as any success that set in train the notion of SH. It was a subsequent reflective paper 'Two Years Before the Mist' 101 that drew upon these user experiences.

3.1 Reflections on AQUANET (1992)

Study of AQUANET users 106 confirmed earlier observations of how the task of choosing link types was an impediment to work, especially when the problem domain is not yet fully understood. In the AQUANET context, the same issue applied to aims 1 and 2 (list above). Thus, the program actually impeded some of the very tasks it was designed to enable. But this was not a straight failure, as the experience showed that the pinch point was not offering a means for early-stage planning, when the necessary structuring of the problem was not yet fully understood. Marshall & Rogers note:

'Our observations of Aquanet use have led us to reconsider the role of relations in the tool. In designing the tool, we combined a richer, more general form of connection than the link with gIBIS's browser-based mode of navigation and access. Later, we found Aquanet's relations to be less commonly used than the tool's design anticipated, and the structures users built to be more volatile than expected (in the sense described in 29). Thus we find it necessary to both support the interpretation and reinterpretation that takes place in a spatial context without user-articulated relational structures and to assist users in identifying structural regularities that they may choose to formalize.' 106, p.58

Users struggled, early in a task, to define a collection of types to describe the problem domain—the challenge of premature formalisation. It was also found that an assumed top-down schematization of the problems space was not occurring and thus expected abstractions were not occurring. In the same way, users wished to start working from concrete examples and only then working back to generic instances: 'users wanted to manipulate instances in situ in order to define or alter the generic structure of their types.' 101, p.57. A parallel was drawn with users' frustrations learning Smalltalk 126. The Semantic Web's 12 failure to grow to envisaged scale might reflect the same problem of the construction of the data requiring too much structure (or prior knowledge) too early in the process.

In effect, though AQUANET could hold knowledge in place, the act of systematising the problem to get to that point proved harder than expected, tempering success. Whilst AQUANET may have had issues with its intended structuring task, it usefully illustrated the effects of premature formalisation that SH later explored. AQUANET's users created spatialised text in preference to using its relational model for semantically and graphically expressing interconnections.

In the final analysis 106, Sect. 5, the authors clearly show that whilst the program's shortcomings were addressable, more meaningful insights had occurred in that the hard-edged structure familiar to (software) engineering work was not as well suited to the structuring of emergent knowledge. As Trigg had found 175, p.106—not all use of the hypertext can be effected within the hypertext alone nor via a single presentational view. More successful were the aims for assisting collaboration which did not present problems.

3.2 Spatial Hypertext takes its name (1993)

At HYPERTEXT '93, Marshall & Shipman's paper 'Searching for The Missing Link' drew on the lessons of AQUANET, but with a looser framing, examining 'the role of structures in hypertext and some ways and reasons that hypertext become implicitly structured.' 107, p.217. It focused on structure not simply as a means of traversal but as a rhetorical or semantic basis for hypertext; it asked of structure:

Where does it lie? Is it inferred from content (as suggested by Superbook's tools 52), or is it defined by context?

How it is constrained? Is it truly ad hoc or is does the cognitive model of the activity 172 impose limits?

How is it conveyed? Is structure laid out by the system 29 or flow straight from the user's head?

An important new consideration drew on the authors' paper on formality 151[^14]. The formal mechanisms of existing hypertext systems could struggle to express the sheer uncertainty of the connections at the early stage of sense-making. One hope was that parse-able factors like distance and collocation might hint at emergent structure. 'In practice, people experience difficulty trying to articulate why they've linked two things (or even deciding if what they're trying to express is a node or a link)' 107, p.219.

[^14]: This drew in turn on Shipman's PhD 141. The article was formally published, with minor edits in 1999 152

In considering links—a construct AQUANET side-steps—the authors mention DeRose's notion of 'implicit vs. extension' 49 as well as other approaches to implicit links in PERSEUS 119, Assistant 187, IDE 76, PHIDAS 112. This is juxtaposed with Nelson's transclusional StretchText 124, Tufte's sidenote presentational style 180, and with 'spatialised text' as described by Bolter 34.

To investigate link-less structure, tests were conducted on eight mature projects created in Notecards, AQUANET, and VNS 145. Although Notecards had a strong node-and-link model, it was evident that some users circumvented this by spatialising text into diagrams in sketch-type cards 107, Fig.1, thus creating structure outside the hypertext. For VNS, there was a stronger set of references (linking) but still with structure deriving from spatial layouts. Interestingly, despite AQUANET having no formal drawing mechanism, the overall map allowed for the emergence of distinct groupings partly aided by the patterns of re-use of formal structural elements used to contain information. In all the specimen programs, there was structure evident in a place where hitherto it had not been expected.

After consideration of visible structures that might be parsed, such as aggregates, lists, bounding lines, and arrows, a specimen parser was built and tested, with a summary concluding that 'that automatic perception of implicit spatial structure is possible, and that it can identify several useful kinds of hypertext constructs.' 107, p.224. This formalised the notion of expressing hypertextual connections without explicit linkage, using a parser ('recognition algorithm') to surface possible structure in analysed documents. Implementing the latter lead to VIKI (see Section 4), the first program able to describe itself as a Spatial Hypertext system.

Thus was Spatial Hypertext introduced, albeit without any close formal definition. SH was noted as extending the more normal node-link structure, rather than acting in opposition to or replacement of it. Reflecting challenges of incremental formalisation, there was also recognition that 'any sort of heuristic recognition should be guided by human interaction.' 107, p.227. The '93 paper's sections on the 'how' and 'why' of implicit structure 107, p.219, expressed in contrast to hypertext linking norms, also speak to the emergent sense of what SH is. In a subsequent 1999 SH paper 153, the authors also emphasised distinctions between 'document-centered' and 'map-based' (SH) hypertext systems and implications of the latter.

4 VIKI—parsing structure (1994)

Introduced at ECHT'94, VIKI made use of the parser tested in the previous year's SH paper (see previous section) as well as other spatial parsing work at PARC 117, 139. Having established the concept of SH, VIKI deliberately set itself apart from the linking of earlier hypertext systems 110, Sect. 2, focusing on representing overall structure rather than navigation. Of note too is that section's discussion of browser-based systems (VIKI, Storyspace, AQUANET, MacWeb, Sepia 170, gIBIS) vs. document-based systems (WWWeb 11, HOS 157, OVAL 99 and PHIDAS). Whilst permissive and prescriptive linking systems can also expand their linking approach (e.g. Storyspace's Link Apprentice tool 14), it was felt that eventually the sheer number range of link types could make system navigation hard to use or visualise. The SH approach let the location and visual style indicate emergent structure. Not stated but implicit was that such an approach suited early-stage hypertexts still under construction, rather than a mature system where structure should have stabilised.

Learning from AQUANET, VIKI used three pivotal requirements: '(1) interaction must be informal; (2) users must have access to a variety of representational modes; (3) additional structure must be available on demand, either through the development of types from examples and prototypes, or through recognition of implicit structure.' 110, pp.15–16.

Rather than use predefined structures to help shape the layout of the hypertext, VIKI took the opposite approach. Now the users would lay everything out, and a parser would assist them by deriving structure. This fostered emergent structure and avoided premature formalisation: use of structure or abstraction in VIKI would always be done at the user's initiative.

To assist the user, three fundamental types of element were offered: objects, composites, and collections. Objects were the basic constructional blocks (lexia) and were semi-structured, allowing the user the choice as to how content was added to them. Composites would consist of two or more objects in a particular visual or spatial configuration. A collection was an arbitrary spatial arrangement of objects, composites, or other collections. A flexible system of object types was available to allow for consistent styling of groupings of similar elements. Visual nesting of elements, on the map but with an implicit hierarchy, was allowed. Following Boxer 50 and Pad 128, VIKI used a spatial navigation metaphor.

The parser, at the users invitation, could suggest new collections based on the detected layout of the selected elements. The assumption was that this would assist the user with generating empty structures for new content, as a productivity accelerator. Note that the parser was not creating the layout of items, but parsing it to suggest recognised and emerging structures. The parser also drew on Shipman's Hyper-Object Substrate (HOS)[^15] 141, 157.

[^15]: HOS included agents to examine text content included in the hypertext and recommend the addition of particular attribute/value tuples and inter-object relations.

Reflecting the newly available world Wide Web, VIKI could also link outwards to the Web to avoid internal replication of content already available (online) elsewhere. As there was an intention for group rather than individual use, 'note' objects were offered to enable meta-communication by group members indicating their intent in incremental formalisations made to the map.

Through this set of features, VIKI was able to test a more permissive SH environment that gave the user more agency in the organisation and styling of information. By not forcing a defined structure, elucidation could be imparted whilst still allowing some information to remain tacit 130. VIKI essentially validated the notion of SH as set out by the 1993 SH paper.

4.1 Building on VIKI's insights

VIKI's use led to a number of papers reporting insights gained from its use, notably Marshall & Shipman's 1995 paper 'Spatial Hypertext: Designing for Change' 108. On linking, it notes:

Instead of providing a mechanism for defining specific links between objects, VIKI focuses on the relationships that can be noted visually and spatially. These relationships may either remain implicit, or be recognized by structure-finding algorithms that automatically analyze spatial layout and visually salient properties of the constituents of a space. (108, p.95)

They also noted that as well as SH surfacing the potential relationship of nodes, it could also 'conceptualise a reader's growing sense of meaning' 108 (citing Kaplan & Moulthorp[83]).

The 1995 paper 'Finding and Using Implicit Structure in Human-Organized Spatial Layouts of Information' summarised four discrete spatial primitives observed being used in VIKI 156, p.348, Fig. 4:

lists: aligned objects of the same type.

stacks: overlapping objects of the same type

composites: repeated arrangements of alignment between objects of different types

heaps: overlapping objects of different types

Of note is that these primitives do not express an explicit reason for their association, such as the use of a categorised link type might enforce. Rather, they allow for capturing implicit and possibly impermanent relationships.

Acknowledging the rapid growth of the Web as a resource, VIKI was updated to improve its ability to draw information via web links for further triage within the program. In 'Spatial Hypertext and the Practice of Information Triage' 109, p.124, Marshall & Shipman reflect on the Web's relevance, noting 'We can see this trend realized in Web workspaces like VIKI, Eastgate's Web Squirrel 16, or the Web Forager 42. The reader is transformed into a gatherer, as Rosenberg suggests 135' (original inline references updated). In this triage role, they mention Joyce's notion of 'successive attendings' and his observation that the 'the value of what we collect is not as much embodied in what it is as in how we found it and why we keep it.' 80. This matches SH's approach of privileging display of context over detailed content. They further state: 'subjects' organizational strategies changed over the task's duration as they became more familiar with the material'. That reflected the cumulative effect of 'successive attendings' and underlined the need for nurturing emergent structure in tasks involving structuring, such as is offered by SH tools like VIKI.

The web access improvements in VIKI led to work on generating web-based presentations 146, itself drawing on Shipman et al.'s prior work with Walden's Paths 154, Zellweger's scripted paths 191, and Trigg's 'Guided Tours and Tabletops' 174.

Shipman & Marshall's 1999 SH paper 'Spatial Hypertext: An Alternative to Navigational and Semantic Links' 153, contextualised their web-based work in VIKI: 'Additionally, systems like Web Squirrel 16, D-LITE 47, Web Forager 42, and Data Mountain 133 provide workspaces for analysis and interpretation similar to that of VIKI.' (original inline references updated).

An impact of increasing the amount of data being added to SH layouts was the problem of being able to display enough of a large SH to work on it without loss of spatial context. One approach to resolving this was an experimental fisheye view added to allow for greater information density 155.

5 Convergent Evolution I: Storyspace (1987)

Developed by Bolter, Joyce & Smith, Storyspace 35, 78 predates SH by almost a decade, having started development in 1984 and was first shown publicly in 1987 at the first Hypertext conference. Whilst SH was not on the minds of Storyspace's creators, there was an intent to give users a place to play and explore with the relation of their notes. The app offered an overall outline structure, whilst its map view allowed a per-outline-container view where the user could arrange their notes ('writing spaces'). Joyce noted:

'More particularly, [the structure editor] involved combining the relatively familiar and efficient hierarchical data structure known as the tree with the less familiar but more robust data structures known as networks or graphs' (Markle 81, p.13, via 87).

Differing from the link-less nature of systems like VIKI, Storyspace draws any links on the map (if needed). There is no parser controlling the layout, which is manually arranged by the user, although some placement assistance features are offered. Despite this, the map experience still fosters SH's sense of emergent structure and the serendipity of contingent positioning.

Joyce also described the notion of 'constructive' (creating) vs. 'exploratory' (reading) hypertext 79, pp.40–42[^16] 31. This is not touched on in the early SH papers, but their exploratory [sic] work chimes with the freedom of Joyce's constructive category. Storyspace's presentational duality of discrete tree and graph views echoes Smith's Writing Environment (WE) 162. Bernstein's 'Architecture for Volatile Hypertext' 29 also explores how Storyspace embraces the challenge of the impermanent structure when making constructive hypertexts.

[^16]: A reprint of the unavailable original 77.

VIKI's creators make reference to Storyspace—see 110, Sect. 2—but do not adjudge it to be an SH tool. Note though, with hindsight, that at that time VIKI was trying to prove the point of meaningful SH without any explicit links. By contrast, Storyspace's 'map view' combined a spatial layout of nodes (like an SH) whilst also showing any links between them. Whilst links were the necessary—and intentional—means of navigation the map still offered a perspective only later formalised as SH.

6 Visual Knowledge Builder (VKB) (1999–2014)

Figure 2: VKB v1.0 beta (on Win98 under VirtualBox v7).

Building on experience from VIKI, at HYPERTEXT '01, Shipman and colleagues presented VKB 149 (also see 144, 147) as a visual workspace for collecting, organising, and sharing information. The design of VKB also incorporated experiences with information authoring and sharing from the Virtual Notebook System 145 and with information representation and formalisation from their previous HOS system 141, 158.

Whereas earlier SH systems had run on PARC's workstations—far more powerful than the PCs of their day, VKB ran under Windows OS on ordinary PCs[^17]. Significantly, SH had broken free of research-grade equipment and was now running on consumer-grade OS and hardware.

[^17]: VKB was written in Java and ran on Windows 98 & NT.

Whilst VIKI had already proved the basic case for SH, VKB identified further emergent SH issues 149, p.113:

the difficulty of interpreting changing visualizations

the visualization interfering with visual source information

the inability to express cross-space interrelations

the lack of means for expressing publishable information spaces

For all tht SH offered, the last item is of particular note and not really resolved by this last of the main SH experiments. Whilst SH is a powerful approach to information triage and initial structure, its 'flattened' state—notwithstanding nested elements—does not necessarily indicate the best approach to the linear narrative needed for most forms of publishing (output). Even digitally native documents still embrace the linearising constraints of paper, even though such documents may never actually be printed. This issue has been addressed, in part, by Tinderbox (see Section 7). The task of writing, as distinct from initial data input, is discussed in Section 4.2 of Shipman et al.'s 'Emergent Structure in Analytic Workspaces' 148.

A further innovation in VKB was its navigable history. Hypertext tools had long had a history list of nodes/objects selected or edited. A novelty in VKB was to allow the user, via a scrubber control, to move back to a particular past snapshot of the system, or watch the emergence of structure replayed snapshot by snapshot. That feature enabled SH users both to find a given state and to (re)view the emergence of structure in the SH. Additionally, links could be added to point to a particular saved snapshot of the SH, though it was noted that the benefits of the latter 71 had yet to be fully explored and established 143. The history scrubber also exposed the time axis of the document for the reader 95 147, pp.163-4. Kim & Shipman revisited this in a VKB v3 10, 86.

In VKB the 'Suggestion Manager' exposed the parser to the user. Invoking the feature results in a number of suggestions relating to the visual layout and styling of the SH, see 159, Fig. 1. The parser is not significantly altering the layout of the SH, but rather surfacing and enhancing apparent emergent structure. Importantly, as with AQUANET and VIKI, the human user controls the overall 'map' of the content of the SH.

To address the issue of SH map size vs. display size, VKB included a 'Miniature Space' navigation overview window that indicated the currently visible area of the whole SH map (used to investigate information triage in SH 9).

With VKB developed, Shipman's research group used it to investigate information triage 9, 85, 113, 127, 150. MASH (Multi-model Adaptive Spatial Hypermedia) 57, 60 saw experimental joining in of SH with Adaptive Hypertext, using VKB as the authoring environment. MASH debuted in conjunction with WARP 58, a web-browser-based dynamic SH presentation, again using VKB as the SH authoring component. Further work was also undertaken on improved spatial parsers for VKB/WARP 59. VITE 72–74 drew on VKB for a visualisation space for structured data (contrasting generally ad hoc input to SH). VKB itself iterated through three major versions over 15 years.

In Shipman's 'Seven Directions for Spatial Hypertext Research' 142, Direction #6 'Writing & Designing Spatial Hypertexts' acknowledges the creator and user are often the same (group of) people. For them, any ambiguity of presentation is offset by the user's ongoing familiarity with the work. Not so for the general reader. This is similar to the problem of creating 'publishable' SH information spaces.

7 Convergent Evolution II: Tinderbox (2001)

Having taken over development of Storyspace in 1990, and with the experience of Hypergate 13, 14, 32 and Web Squirrel 16, 17, in 2001 Eastgate created Tinderbox 23, 24—incidentally contemporaneous to VKB. Reflecting the interim arrival of the Web and an erstwhile interest in blogging, Tinderbox—as compared to Storyspace—moved from being a self-contained hypertext app[^18] to a general 'toolbox for notes', albeit with the same hypertextual core. Storyspace's views, most notably the map view, were retained and since enhanced with further views[^19] 27, 30. The design allows the user multiple concurrent views, of the same underlying data[^20], to visualise their notes' relationships. Tinderbox has also continued to enhance the visual affordances of the map view 25, 30.

[^18]: By comparison, Storyspace is both the authoring app and the reading tool, though a stand-alone reader app was offered.

[^19]: Currently, there are 10 discrete view types.

[^20]: q.v. NLS/Augments's viewspecs 55.

Tinderbox's flexible support for export echoes a need expressed in the conclusions of Trigg's survey of Notecards users 175, p.106—not all hypertext-based work can be effected solely within the hypertext. VKB also noted the challenge of expressing publishable information spaces 149, p.113. The relationship of hypertexts with other media forms is not new. Moulthorp noted: 'This paper begins by asking why hypertext researchers publish their work in print and compose their hypertexts from previously printed sources 118.

Bernstein's two books on Tinderbox 26, 28 explore his design ideas and the origins of the program. An explicit link to earlier SH experiments is that VIKI cited as a key influence 26, p.165. It is also clear that this essentially SH tool—at least within its map view—draws as much on the literary/creative side of hypertext as it does upon pure computer science. Happily, the only SH tool currently available to the general public thus represents both expressions (evolutions) of SH.

8 Spatial Hypertext Since VKB

Similar to later use of VKB, Buchanan et al.'s 'Garnet' 39 used SH as a means to explore digital libraries. (2004). Solis and collaborators merged the concept of SH with that of wikis 93 to make 'ShyWiki' 164–167. Here, discrete wiki articles could be arranged on an SH map. A difficulty experienced was with new users understanding the templating system used to generate structured content 163. This seems to echo earlier SH experiences with AQUANET where it was the design and choice of structures to be used in the SH rather than the overall SH experience that impeded use. (2008–12).

'Emberlight' 111 was an experiment using a Tinderbox file as the back-end to a web display offering both an outline and an (SH) map (2010). Given advances in what more web browsers can now do, this approach remains interesting. In context, Tinderbox's poster concept [28, Ch.11] reverses this by using embedded web browser rendering in map objects obviating the need for building new app-native views (2023). In part, this approach draws on the ideas of van Dam's DASH 181, 189 (2019–to date).

Reprising his earlier influential 'Patterns of Hypertext' 18, Bernstein's 'Can we talk about Spatial Hypertext?' 25 offered an enriched syntax for the representational talkback of SH, moving beyond simple styled boxes of text (2011).

Kolb, writing from a perspective of philosophy, saw value in SH as it related to scholarly writing 88 and in 'Other Spaces for Spatial Hypertext' 89 he drew a connection between useful SH as evolved both via VIKI/VKB and Storyspace/Tinderbox. The case for non-link-based meaning in hypertext having been made by former, SH co-existing with (visible) links seems less odd than when AQUANET was trying to escape the 'tyranny of the link'.

Atzenbeck and colleagues at iisys (Hof, DE) have continued SH work in the context of recommender systems and AI. A three-tier Component-based Open Hypermedia base (CB-OHS) base 8 (2017) underlies their 'Mother' 6 system. Pertinently, the system involves three parsers. A spatial parser observes the arrangement of nodes in the display plane, a visual parser looks at the visual styling similarities of nodes and a temporal parser (Schedel 140) watches the temporal sequence of user interaction with nodes. The latter reflects a more dynamic view of the temporal axis compared to that seen in the likes of VKB. Examples of their 'Mother' system are seen in active decision making 5, story brokering 137, video selection 131, end-user development 136.

9 Spatial Hypertext Today (2025)

Aside from Eastgate's and iisys's work, SH is little in evidence today, the more so outside the research lab. We might ask "Where are all the spatial hypertexts?" (q.v. 20)—why such a dearth of material?

The Twine authoring tool 61, though Web in lineage, does make use of a spatial layout to assist in the narrative construction. Tapestries[^21] 168 (in late beta) is interesting as, whilst not overtly hypertextual in construction, is essentially an SH as the salience of a tapestry comes from the appearance and juxtaposition of its elements.

[^21]: Its team draws on long experience of e-publishing, stretching back to e-book CDs.

9.1 Spacial, or 'Spacialised', Hypertext?

Today, Google Scholar finds c.650 results for papers mentioning 'spatial hypertext'. Brief perusal shows that most reference is tangential to SH, although spatiality of content is still generally the point of interest (and the reason for mention of SH). The wider discussion appears to be of (default: 'false') presentation of text/media. As SH's progenitors never chose to define SH too tightly, these other perspectives are too easily dismissed as 'not Spatial Hypertext'. Now that deliberately hypertextual tools are a rarity, subsumed by a more Web-based perspective, the edge of SH is harder to place.

For instance, 'The Itinerary of King John' 48, a mash-up of digital map, timeline, and textual sources, was not built as an SH but really—potentially—it is. Brath's Visualising with Text 37, based on his thesis 36, when considered alongside VIKI or VKB, shows how much more SH could be doing, even with 'just' text. Yet technology alone is not the crux. Contrast Aigner et al.'s tech-oriented Visualization of Time-Oriented Data 1 against the richness of Rosenberg & Grafton's pre-digital Cartographies of Time 134.

We should also be careful not to mistake an apparent focus on text in older SH's apps as intentionally exclusive of other media, and be mindful of the limitations of the technology of their time. A contemporary issue for both VIKI and VKB was how better to manage non-textual information. This suggests benefit in being more open in our interpretation of the 'what' of spatial hypertext. SH's unspoken part—about the dangers of premature formalisation and over-commitment to structure before warranted—remains just as pertinent even in this wider context as with text alone.

Happily, the Hypertext Conference has long looked across all disciplines. If cross-pollination waned, the reconnection that started at HT'19 7 appears healthy once more. This is good timing, as a recent increase in interest from the Digital Humanities presents an opportunity for SH to help with effective visualisation of their work 82, 184, 185.

Artificial Intelligence. Projects at iisys (see above) are already making use of SH with AI/ML in the context of recommender systems. The recent concept of Model Context Protocol[^22] for Large Language Models (LLMs) offers an interesting new potential for such AI to communicate with SH tools and offer new ways to combine SH views, parsers, and AI.

[^22]: https://modelcontextprotocol.io/introduction (Accessed April 14, 2025).

Extended Reality (XR). At an ECHT'92 keynote, Bolter talked about 'Virtual Reality and the Future of Hypertext' 34 and spatialised text. Since then, capability of XR has improved massively in terms of hardware and software, so XR[^23] is no stranger to Hypertext. The entirely constructed nature of XR loosens some previous limitations for SH, not least in scope and scale. At the more extreme end is the potential to work with spatial arrangements in using non-Euclidean space 114. Non-SH experiments with hypertext are already happening in XR 192.

[^23]: eXtended Reality: a portmanteau term for VR, AR and MR.

XR appears a good medium to expand on SH's capability for problem exploration and information triage. Eidloth, Atzenbeck & Pfeiffer's 'Stepping into the Unknown' 53 has explored this potential, reflecting ideas Simpson imagined in 'Beyond the Plane: Spatial Hypertext in a Virtual Reality World' 161 (1996).

10 Conclusions

Whilst Spatial Hypertext's heyday may appear to be in the past, SH as a means of sense- and knowledge-making remains relevant today, although, as 'Seven Hypertexts' notes, 'Spatial Hypertext has become dormant' 3, Sect. 3.5. I would suggest the issue faced is twofold: a lack of SH tools and a lack of clarity as to how and where to build SH practice into existing work practice.

Scope. It can be seen from its genesis that SH's strength is in exploration of a problem space and elucidation of its potential structure and breadth. But, having made an SH, what can we then do with just the SH result? Is the result meaningful to others, or do we have a beautiful 'mind palace' of use only to its maker(s)? Thus, a challenge for proponents of SH is to make clear what problems it addresses better than other processes, and in what context to use it. SH is a software-mediated experience, and certainly, without SH tools, the analytically assistive power of SH is hidden from a wider audience.

Tools. As noted in Section 9, programs like Tinderbox still offer an SH experience within a wider feature set, but most SH systems described here either are no longer usable or are restricted to a research setting. An early beta of VKB survives, but Tinderbox and Storyspace (now on a common codebase) are the only two publicly available, current, SH tools—albeit for macOS only.

In considering a role for SH, I think Kidd's 1994 observation on knowledge work triage still holds true:

'My explanation is that once informed (ie, given form) by some written material, these workers have no particular need to retain a copy of the informing source. However, if a piece of written material has not yet informed them, then they cannot sensibly tile it anyway because its subsequent use or role in their world is still undetermined, I conclude that the valuable marks are on the knowledge worker rather than on the paper or on the electronic file. . . ' ('Marks in The Water' 84, via 156)

This chimes with this author's experience of using SH tools for over two decades: it is the practice of using an SH environment which is as valuable as using a particular SH tool. But it is having such SH tools that enables and unlocks that experience. Working via SH assists with the contextualisation of new knowledge.

Spatial Hypertext deserves not to whither away. It is to be hoped research on SH will continue.

Acknowledgments

I would like to acknowledge the insights of Cathy Marshall and Frank Shipman in preparation of this paper, not least for their perspective as 'creators' of SH. My thanks to Mark Bernstein for help in re-contextualising some early SH facts, and to Silas Hooper. The paper's peer reviewers also gave helpful input and supplied some missing pieces.

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