Annihilation Event – Digital Old Minster, the archaeology of a digital file

From the 22nd to the 29th March 2017 there is a really great event at the Lethaby Galleries near Kingscross St Pancras, London. Called Annihilation Event, it’s billed as having “no singular origin, but many strands and streams.  This is a project about copies, prints, scans, derivations, reconstructions, casts, and virtual models. The 6 day programme in the Lethaby Gallery will bring together a contrary group of artists, archivists, archaeologists, historians, technical experts and theorists from all over Europe.” Go and pay a visit.

I put two annihilation events into constellation here. One was a talk about the ontological status of casting the voids left by Pompeiians in the aftermath of Vesuvius’ eruption in CE 79. The other was the eradication of the Saxon Priory Cathedral of Winchester in 1093/4. I have already blogged and co-authored an article about the finding and restoration of the digital files of the “Old Minster”.  It’s significance is that its the earliest known virtual tour of a constructive solid model (CSG) re-imagination of what was probably the largest building in Europe at the time, before the Normans demolished it and replaced it with the edifice you can visit in the city today.

For this event, I worked with renowned sculptor Ian Dawson based at the Winchester School of Art to create a new instantiation of the Digital Old Minster of Winchester (see figure 1).

 

Figure 1: Digital Old Minster, the archaeology of a digital file, 2017, Paul Reilly & Ian Dawson.

The biography of the Digital Old Minster assemblage not only endures but continues to throw out new threads; this stage moves the 3D print into an art work.

Also in the exhibition, through the help of my collaborators on the original digital restoration project, namely Stephen Todd and Andy Walter, is a VR exhibit of the Digital Old Minster in which some exhibits have been placed. Visitors are invited to explore this exhibition space.

I’m thrilled that parts of our exhibit are in the exhibition and parts of the exhibition are in our exhibit!

Everyone is welcome to visit. Please do!

New life in Old Digital Models

The 3D computer-generated models and animations of the Old Minster of Winchester were remarkable in 1984-6 for producing the earliest animated tour of a virtual archaeological monument. Thought to be lost, thirty years on the original model files were rediscovered buried under layers of now unsupported code and recovered. The models written in a proprietary CSG modeller called Winsom turned up again last spring (2015). The full story of their rediscovery, restitution and recent transmogrification,  written with Stephen Todd and Andrew Walter, will be found – with models and animations- in (Reilly, Todd and Walter 2016).

In short the original models were transcoded from Winsom into an opensource solid modeller (i.e. OpenSCAD), and in modernising the digital Old Minster the original virtual model of the final phase of the Anglo-Saxon Priory Cathedral reimagined prior to its demolition in 1094 has also been translated into a material one in the form of a 3D-print.

Exhibit: WebGL rendering of half section of final phase of ‘Old Minster, Winchester’ re-imagined prior to being demolished in CE 1093/4 (http://programbits.co.uk/minster/minst.html)

Digital assemblages and objects like their physical counterparts gather histories around themselves as they accumulate new significance, connections and meaning throughout their existence (see, for example, Reilly 2015c). The biography of the digital ‘Old Minster, Winchester’ is a case in point. The rediscovery in April 2015 of model definition files, previously thought lost, led to the recovery of the original solid models’ exact geometry. This, in turn, enabled them to be transcoded and then re-presented graphically.  Advances in additive manufacturing technology now enable new kinds of intra-actions with these models, and allows nascent objects, such as cut-away models, inherent in the model files to be instantiated as physical outputs in a variety of different materials and scales (i.e. 3D printed Virtual Heritage ) for further multimodal exploration.

Currently, this apparent potential to align virtual and physical heritage appears to be under-theorised and, if left unaddressed, is set to radically disrupt current best practice in the discipline (see for example Reilly 2015a). Increasingly affordable additive manufacturing represents both an opportunity and a challenge to virtual heritage (Reilly 2015b). On the one hand, 3D printed heritage exhibits the attractive qualities of tangibility and durability, and is amenable to the well-rehearsed processes for curating physical objects. On the other, material instantiations of ‘virtual’ heritage may reintroduce intellectual opaqueness into the models once they are decoupled from the metadata and paradata that previously accorded them the status of being scientifically transparent (see Bentkowska-Kafel, Denard and Baker 2012).  What is at issue here is that like all 3D printable objects, heritage assemblages can be reiterated and, crucially, re-contextualised by anyone, anywhere in the world with access to the web.

In such circumstances, how can virtual heritage practitioners adhere to the London Charter’s central principle of accurately conveying to users the status of the knowledge that these new objects represent, such as distinctions between evidence and hypothesis, and between different levels of probability? There is a manifest need for an implementation of the London Charter guidelines focused on ‘virtual-material heritage’ outputs. Clearly, this warrants extensive and critical discussion within the expert community to establish new de facto standards to which such virtual-material outputs should be held accountable.

In the course of this rediscovery project we learned first-hand that 3D computer-based archaeological and cultural heritage models, built with emerging technology, have a very limited shelf-life unless exceptional measures are put in place to sustain them. Consequently, identifying and curating the many landmark virtual objects which have been developed on a huge array of technology bases over the last 30 years will be a weighty challenge for historians and curators wishing to take stock of the inception, early years and key developments in virtual heritage.

Finally, returning to the Old Minster, this virtual heritage model is once again a ‘needy digital object’ calling for an appropriate access and sustainability strategy to be developed (Edmond 2015). The project has returned to the status of a ‘work in progress’.  Moving forward, a number of areas within the model that were originally incomplete (because the virtual tour never visited them) can be developed to agree with the evidence available from the original archaeological, historical and comparative research. In addition to extending the biographical threads pertaining to the Old Minster models, the entangled biographical threads of the modelling technology used to instantiate these geometrically-defined hypotheses are also being drawn out. For example, the Old Minster models are implicated in the development of another reincarnation of Winsom called GOW (Grandson of Winsom) which, hopefully, will soon be released as open source.

References

Bentkowska-Kafel, A., Baker, D. and Denard, H. (eds) 2012. Paradata and Transparency in Virtual Heritage, Digital Research in the Arts and Humanities Series. Farnham: Ashgate.

Edmond, J. 2015. Collaboration and Infrastructure, in: Schreibman, S., Siemens, R. and Unsworth, J. (eds), A New Companion to Digital Humanities. Chichester: John Wiley & Sons, Ltd. DOI: 10.1002/9781118680605.ch4.

Reilly, P. 2015a. Putting the Materials Back into Virtual Archaeology, in: Hookk, D. (Ed.), Virtual Archaeology (Methods and Benefits). St. Petersburg: The State Hermitage Publishers, 2015, 12-21. http://www.academia.edu/15076178/Putting_the_Materials_Back_into_Virtual_Archaeology

Reilly, P. 2015b. Additive Archaeology: An Alternative Framework for Recontextualising Archaeological Entities, Open Archaeology, 1 (1), ISSN (Online) 2300-6560, DOI: 10.1515/opar-2015-0013, October 2015.

Reilly, P. 2015c. Palimpsests of Immaterial Assemblages Taken out of Context: Tracing Pompeians from the Void into the Digital, Norwegian Archaeological Review, DOI: 10.1080/00293652.2015.1086812

Reilly, P., Todd, S. and Walter, A. 2016. Rediscovering and Modernising the Old Minster of Winchester, Digital Applications in Archaeology and Cultural Heritage, 2016. DOI: 10.1016/j.daach.2016.04.001

Conserving the immaterial?

The hollow spaces which mark the final resting places of many hundreds of Pompeiians continues to fascinate and perplex me. These ‘voids’ are powerful testimonies to the final moments of the people who once lived and breathed in these spaces. Devoid of the mortal remains these voids are full of human existence. So what becomes of these spaces when you fill them with liquid plaster (gesso), when the layers are excavated, and the casts lifted?

The context is a void. What is the ontological status of the cast? What has the curator captured and conserved? Significant questions arise: when we fill the voids with material, are these immaterial contexts obliterated by the injected substance (e.g., gesso plaster) used to obtain casts? And, afterwards, when the cast is lifted and the void is ‘restored’, is the context reinstated?  Additionally, if the cast had never been made, and the volcanic deposits simply trowelled away, the void would still be there occupying the same, original, space, but now unbounded and undetectable. Is it still there? I think so.
Another paradox raises its ironic head: excavation in this context is non invasive, at least until the dig ends and the trenches are reinstated. It would seems that it is only when then trenches have been backfilled that these contexts are finally obliterated.

A Permeable Sealed Context and a Stratigraphic Conundrum

Surfaces have a special status in the archaeological record. They present an unique aesthetic peculiar to the trenches. Archaeologists like to photograph and draw them prior to making a new, hopefully equally pleasing, or intriguing, surface when they have finished excavating (aka dematerialising) the context or feature.The contexts themselves, however, are more complex and draw attention to the concept of boundedness; inside and outside.

Boundedness poses some problems to conventional understandings about the nature of the archaeological record in the case of the excavated ‘material’ being composed of interior ‘spaces’. Sometimes a bounded space denotes the inside of a place, such as a painted cave, hypogeum, catacomb, or mine, or the worked insides of a hollow artefact such as a mesopotamian sealed bullae (clay envelops with accounting tokens sealed within). Juxtaposed to these are negative spaces, or voids, delimiting exterior boundaries of a dematerialisation. Immaterial now but, sometimes, still profoundly intransigent, absent presences witnessed as imprints. The classic examples being the poignant ’empty’ moulds at Pompeii, reservoirs full of final dispair; fossilised echos of the final moments  of the people who succumbed to the pyroclastic surges and who were then buried in the ashes of Vesuvius. Conceptually, neither structure, artefact, nor deposit, sitting on the cusp of being either (or neither) positive or negative stratigraphic features, they are sealed contexts. However, stratigraphically, this immaterial assemblage is also simultaneously earlier, co-terminus and later than the volcanic spew. The boundaries of these stratigraphic features present a conundrum.

Boundaries can also be ambiguous in virtual archaeology, and here I’m thinking of 3D printed things. Paradoxically, although the additive manufacturing digital code defining the physical thing is extremely stable, in the sense it doesn’t decay, the encoded entities thus defined are actually very permeable and extensible. Whereas the limits of the physical objects may be clearly defined surfaces, the boundaries of the digital object are drawn by the same file format in which they are encoded, that is the same digital code that marks the content and the voids. Such digital artefacts and assemblages besides being porous are easily networked, replicated, aggregated, augmented, processed or transcoded into other formats (D.M. Berry 2014), and thereby extended. They are also susceptible to new kinds of exploration and analysis. Indeed they can be reconceptualised and recontextualised.

Where does the digital assemblage end (or begin) and the material context begin (or end)?

Husks, Seeds and winter is coming

It’s autumn here and the farmers are still working hard in the countryside to gather in the last of their crops and prepare their fields for the future. The grain harvest looks to be bountiful; winnowed husks given to the winds; the precious seeds meticulously separated, stored and preserved.

Husks and seeds have captured my imagination at the moment. I’m working on a paper which explores some potentialities of additive manufacturing (AM) technologies, e.g., 3D printing, to better inform us about archaeological remains – physical deposits, structures and objects – and the methods archaeologists deploy to ‘record’, ‘restore’ or ‘preserve’ them.

Researchers around the world are doing extraordinary creative things with AM technology. Museum curators, for example, at the Smithsonian in USA , are able to scan exquisite, rare and exciting, materially vibrant objects from around the world and make them available to be rematerialised anywhere else on the planet possessing an internet connection, a web device, and a re-fabrication unit. This is without a doubt a novel, profoundly important, multi-valent arena in the cultural heritage industry in which many new voices can be added to the narrative.

But what are these objects that are being created? They aren’t exactly copies because they can be scaled up or down, reiterated in different materials, at uneven resolutions, features enhanced, and so on. Yes, they resemble the prototype they are based on, but they are not the same. In some ways they are like our autumn husks, empty, devoid of content, or filled with an undifferentiated, but expensive and sterile polymer-impregnated space. On the surface they may be aesthetically pleasing, indeed very cool or sexy. However, more prosaically, like the original object they were based on, they are still subject to decay, mishandling and abuse, and so, ironically, as Victor Buchli (2010) shows, it is the “immaterial code” that the printers use to reprint the object of interest that emerges as the most stable entity in this extended assemblage. Both the old originals and the new originals are mortal. They are potent, but not as virile as those digitally recorded prototypical encoded seeds, immutable, transcendent, and promiscuous, and instantly transportable to any transcultural domain to be reproduced, abused or, possibly, recontextualised.

Ontologically fecund, but winter is coming

Additive Archaeology, epistemological cleavers and ontological chisels

Early this morning, I walked down a mountain through olive groves, with the pre dawn breeze wafting me gently on, to catch a bus from the SE Cretan town of Makrigialos which took me to ancient and modern Irepetras, Europe’s most southerly port city, and from there onwards to Heraklion Airport from where I’ll post this missive. It was a beautiful scenic route, taking in sections of both of Crete’s impossibly sapphire-blue south and north coasts, and a pass though island’s eastern massifs, gorge riven, and pine forested, and of course ancient groves filled with contemporary olives. The shaded coolness of the air conditioned buses provides a stark contrast to the solar sintered landscapes through which the the bus is wending its way. En route I passed by the Minoan impregnated places of Vasaliki, Gournia and Malia. The past endures here. It’s persistent.

So, a journey to sit back and reflect.

This is the second time I’ve been to the island this year. I was talking at a conference in March, held in Rethymnon, another beautiful city; ancient, persistently Venetian. The inaugeral conference of ‘Computer Applications in Archaeology – Greece’ was very inspirational. I contributed some thoughts on ‘Additive Archaeology’ a term I coined with my friend and colleague Gareth Beale to explore the potential impact of additive manufacturing, most commonly seen in 3D printing, in archaeology. We argued it had potential for a new kind of ‘virtual archaeology’, another term I coined in another millennia which has become, bizarrely, at least to me, strangely persistent.

While travelling, I reflect on some of the things I’ve read over the last weeks. You see, I’ve been on holiday and I’m heading home to UK where I’ll soon join a team of archaeologists conducting field work at the Iron Age hillfort on Moel y Gaer, Bodfari in North Wales. I’m interested in the material persistence of archaeological assemblages, or entities, and how they emerge through interaction with other entities, including archaeologists, theories, interpretations and tool kits. For as Chris Fowler sums it up,”whereas the present is fleeting, the past is what endures: fleeting moments are entangled within an unfolding past” (Fowler 2013, 245).

The theorists I have been reading reflect a major shift in thinking by some parts of the archaeological community. Jones and Alberti (2013, 16) for example argue for “a reorientation from questions of an essentially epistemological nature — what constitutes archaeological knowledge and how do we go about securing it — to concerns of an ontological kind. What are archaeological entities and what is the real character of archaeological thought and practice?” This latter approach, known variously as a post interpretive or non representionalist position, draws attention to the fluid ecosystem of polytemporal relationships arising beween all the perpetually interacting agents implicated through archaeological research practices ( e.g., theories, archaeoloists, institutions, materials, technologies, instruments, techniques, and methodology). The corollary according to Fowler (2013, 235) is that since all this knowhow and wherewithal “is equally real, copresent and entangled, it is impossible to separate reality from theory or interpretation and test one against the other”. Put another way, there aren’t archaeological facts ‘out there’ awaiting discovery, no stable singularities ready to be clove off with epistemological cleavers. Rather, all these elements are relational, real but conditional. They are chiseled out and sculptured. In the words of Jones and Alberti (2013, 29) “[r]ather than interpreting the meaning of the artifacts they excavate through contextual analysis, archeologists shape and compose the assemblages that they excavate; through this process of composition, interpretation and evaluation arises”.

At CAA Greece, and later in the spring at CAA Paris, we highlighted how when a new technology is introduced into archaeology, the change in practice often makes explicit the craft knowledge, that invisible tacit knowledge, characterised by Bruno Latour as ‘black boxed’. Through such windows of time, of practice, we are given another chance to reassess those techniques, methods, tools, truths and theoretical assumptions before they are again reified within the instruments, technology and praxis of contemporary archaeology, time, in other words, to reflect on the ontological multiplicity, these ‘new’ multifaceted, ‘extended objects’ which emerge when we look at things from a ‘new’ perspective, and thereby make a new translation, a new instantiation. All our previous notions, theories, measurements, facts, and assumptions are still intact, we have just added some new dimensions to what was there previously. As Fowler (2013, 242) puts it: “Each time we instantiate a network, assemblage, or phenomenon, it is different: a unique configuration. Yet, I would argue, many of the components, actants, intra-actions, and so on do endure in similar ways from one instantiation to the next. One assemblage bleeds into others. These “new” assemblages are not exactly the same as the previous instantiations, but some of their properties seem to endure from one set of relations to another.”

The latest, potentially disruptive technology on the archaeological horizon called, generically, additive manufacturing, but popularised and hyped now as 3D printing, has been around longer than virtual archaeology, and encompasses a set of far more mature technologies that have long since passed over the peak of inflated expectations, through the trough of disillusionment, and are steadily advancing up the slope of enlightenment to the stable plateau of productivity, according to industry analysts (Gartner 2013). 3D printing is already causing fundamental changes to our interactions with the finds record and other archaeological assemblages. The Smithsonian museum, for example, has embarked on the ambitious X3D project, which aims to digitalise all 137 million iconic items in its collection, and make them available for 3D printing anywhere in the world. In so doing, we should note, they are also making them available for transcultural discourses within ethnographic archaeologies, in the sense of Castañeda and Mathews (2008). Imagine, if you will, that we might also print, the ‘context’ (assemblage, constellation, entity) in which these artefacts were ‘discovered/recovered/re purposed’ – materially vibrant translations imbued with more cognitive depth, more memories.

Additive manufacturing is just one technology enabling the spirit of virtual archaeology to generate new challenges to transform archaeological practice positively. Printing artefacts, monuments and cultural landscapes is established technologically, and is already starting to disrupt both transcultural and disciplinary discourses and narratives as direct access to these e-cultural entities by almost anyone, almost anywhere, to aggregate and disaggregate, to materialise and rematerialise them in any transcultural space, effectively disintermediates the opinions, interpretations and ‘authority’ of archaeologists and cultural resource managers. A richer multivalent archaeology is emerging. The implications of this abbreviated, and much truncated, thesis for archaeology are immense. Releasing the spirit of virtual archaeology thus will add a further technological nuance to the debate on the ontology of archaeology (e.g., Hamilakis 2014). Additive manufacturing provides a credible challenge to current archaeological practice, if we persist.

Disciplinary Grand Challenge: Additive Archaeology

In a previous blog, I outlined how virtual archaeology was originally conceived as an approach by which technology could be harnessed, in order to achieve new ways of documenting interpreting, annotating and narrating primary archaeological materials and processes, by inviting practitioners to explore the interplay between digital and conventional archaeological practice. As such, it wasn’t just about ‘what was’ or even ‘what persists’, it was also a generative concept allowing for creativity and improvisation including ‘what might come to be’. Here, I want to share some more ideas which have crystallised out through discussions with my friend and colleague Gareth Beale, at the University of York, UK. (N.B. More in press)  To begin, let’s as it were remove our gaze off the broad landscape of virtual archaeology and concentrate our senses on one exciting and potentially  disruptive virtual archaeology technology which seems to us to offer greater cognitive depth: additive manufacturing (AM). 3D printing, or rapid prototyping, is one form of AM experiencing a great deal of hype at the moment. However, AM more generally, encompasses a set of far more mature and for archaeologists, more profoundly relevant technologies. At a very high level, the huge array of available AM technologies can be loosely classified into three families (for a full treatment refer to  H. Lipson & M. Kurmar’s  ‘Fabricated: the new world of 3D printing’. Wiley. 2013). Selective extrusive printers in essence squirt, squeeze or spray pastes or powders through nozzles, syringes and funnels of all sizes to build up objects by depositing materials in layers. Selective binding printers by contrast, fuse, bind or glue materials together, again in a layers. The aforementioned technologies can, in one sense, be seen as producing analogue printing or additive manufacturing outputs using digital controllers. Currently at the cutting edge is true digital assembly using pre-manufactured physical objects. We can think of them as Lego blocks. However, precise assembly of billions of small physical voxels made in different and multiple materials remains a huge computational and fabrication challenge.  Of course, hybrids, deploying multiple print heads, deploying various different fabrication methods, could also be configured. Lipson and Kurmar summarise the evolution of additive manufacturing as three episodes of gaining control over physical mattercontrol over geometry, composition, and behaviour. First is an unprecedented control over the geometry, or shape, of objects. 3D printers can already fabricate objects of almost any material in any shape. Next is control over the composition of matter. We have already entered into this new episode where we go beyond just shaping external geometries to shaping the internal structure of materials with unprecedented fidelity, with the possibility of printing multiple materials including  ‘entangled components’ which can be co-fabricated simultaneously. The final stage is control over the behaviour of materials, where they envisage programmable digital materials – made of discrete, discontinuous units – which are designed to function in a desired way, such as spongy, transparent, rhinoceros-shaped, in shades of grey and blue – perhaps even embedded with nano devices. Voxel-based printing affords the notion of different types of physical voxels. Imagine, if you will, a library of archaeologically-defined material voxel types. Control over shape provides a bridge between existing 3D modelling formats and the ability to re-purpose them as 3D printed physical objects. Existing point clouds, terrain and solid models,indeed any system that can output STL format files can be 3D printed. By way of example, a 3D-printed map of the cone, crater, and summit of Mount St. Helens, Washington, USA, is available on Shapeways.com in three sizes!  Geologists are already 3D printing stacks of geology (i..e., stratigraphy) from north eastern GermanyAlthough these examples produce solid objects made only in a single material, with the same density throughout, they nevertheless communicate in a very tangible fashion. In fact, makers print all kinds of materials: from bread dough, chocolate, and other food-based materials with their pronounced olfactory characteristics (which, incidentally, introduces another cross-sensory modality into the mix), to gypsum, sand, soil, terracotta, metal alloys, plastics and polymers. At a somewhat higher level of technological sophistication, and, commensurately funding, modern industrial additive manufacturing technologies span a wide spectrum of applications across a very broader range of scales: from bioprinting living ink; replacement body parts and prosthetics; manufacturing textiles; ceramics; glassware; jewelry; furniture; weapons; vehicle components: and innumerable parts and fixtures, including 3D printer components. Crucially, they can also combine multiple entangled materials. Stepping back and opening the aperture of the nozzle somewhat,  let’s look at some more examples at a much larger scale. For example, Midwest Studios 3D printed a highly detailed architectural model for a new Carmelite foundation, designed as a classic French gothic monastery, in Wyoming, USA, using the architect’s CAD files. In Europe, Hansmeyer and Dillenburger, Swiss architects, created and 3D printed an ultra-modern, gothic-like, human-scale, immersive space dubbed the ‘Digital Grotesque’.  Both NASA and the European Space Agency are exploring the feasibility of building future moon-bases using fabricators exploiting local materials (i.e., regolith or lunar soil). Of course, at the moment, these projects require the use of (crucially) terrestrial simulants, in other words materials with the same necessary material properties.Becoming more speculative, more aspirational, let’s now explore some facets of additive manufacturing pertaining to materialisations of virtual archaeologies that might come to be. As additive manufacturing evolved from producing primarily single-material, homogenous shapes to producing multi-material geometries in full colour with functionally graded materials and microstructures, it created the need for a standard interchange file format that could support these powerful new features. The response was the Additive Manufacturing File format (AMF), an open standard for describing objects for additive manufacturing processes such as 3D printing. What is striking about the AMF format is that it encapsulates the typical recording sheet used on a modern archaeological excavation, but does so in much finer spatio-compositional (i.e. both macro-morphological and micro-morphological) detail. Image If we did recast our recording method to generate contexts described in an AMF-like format, we suggest that archaeology would be a step closer to aligning the virtual and physical worlds, and a step closer towards the possibility of rematerialising archaeological entities found in the field. What is to stop us from recording our excavations in such a way so as they can be refabricated? Current methods are clearly deficient. Here, by the way, we are not suggesting that all excavation should be 3D printed. We submit that if we recorded in such a way that we could rematerialise, or refabricate, our excavations in 3D then we would have improved substantively our practice. Some will argue that current procedures are adequate for current needs. We counter, that in a uniquely destructive discipline, are we not ethically obliged to strive for superior recording practices? We contend that AM provides a credible challenge to traditional archaeological practices (e.g.in recording). With this in mind, we call for disciplinary grand challenge for this generation of archaeologists, to fabricate an excavation, that is an excavation – rematerialised geometrically and compositionally accurate – whereby the curious can explore iteratively, reflexively, and comprehensively, the disaggregation and reassembly of archaeological entities encountered through archaeological intervention in such a manner as to engender a constant, multivalent, hermeneutic cycle between analysis and synthesis. We envisage that in striving to meet this challenge, the discipline will establish elements of an exemplary platform for strategic innovation, affording the development, and structured introduction of innovative and distinctly archaeological approaches through technology. In so doing we create a catalyst for increased innovation, strength of purpose, and direction in digital archaeology.