Particular to General: a round trip

A Greek philosopher and his disciples by Antonio Zucchi.
From BBC Your Paintings

When you are supposed to produce something that has to be logical and consistent, like, let’s say… an ontology, you are probably expected to have a very theoretical approach to it. Probably, your colleagues imagine you sitting at your desk, dressed like an ancient Greek philosopher, creating categories that describe reality. 

This is definitely a sensible and fruitful approach. It ensures a better level of consistency and it is likely to generate a more solid piece of knowledge modelling. 

Nonetheless, I have the feeling that what is really missing from the existing ontologies on cultural heritage are the specific issues that become apparent only in the very process of modelling or imaging. Even for 3D modellers it is easy to overlook some aspects of the work when they are not actually modelling but just thinking about modelling.
I will need to wear the philosopher's clothes when this phase is finished to make everything more homogeneous and (hopefully) fill the gaps.

So, I have decided to take a different approach: instead of "from general to particular", I’m going in the opposite direction. Looking at what I actually do, I have started drafting what is the information that, in my opinion and experience, is important to express in linked data. 

We can call it a more experimental, or laboratory-style approach.

Deductive and inductive methods are both valuable and needed, maybe at different stages. At the moment, I am completely immersed in the second one. The idea is that it would make the ontology closer to the actual visualisation process, from the research to the production of the output. 

However, the particular-to-general approach has also its drawbacks. I keep changing things when I realise that there are aspects of the process that I had neglected, or not covered in the right way. I add, change or delete attributes very often. Let’s say that I'm working for subsequent refinements. This obviously very much compromises the consistency of my work. I fully expect to spot quite apparent logical gaps only at the end (I bet, just after having submitted my thesis...).

So I am now wearing (ideally) my lab coat and I am fully in the experimental mood. I have started from the relatively easiest of my layers, the one that visualises the Iseum as it might have been in the period before the eruption (but after its restoration). I think I have started identifying quite clearly some of the recurrent processes in virtual archaeology and 3d visualisation.

Of course, everything is at work-in-progress stage: classifications. Concepts. Actually even labels and, generally, names.

What is essential is visible to the eye (if you're in my model)

I hope the ghost of Antoine de Saint-exupery won't haunt me for having played with the wise words of his Fox characters, inverting their meaning. I wasn't suggesting a triumph of shallowness and prejudice, but just introducing a brief premise about my 3D modelling process. 

F. Piranesi's hypothetical restoration of the Iseum (detail)
showing the roof's supporting structure.
From builtindex

I have said that the first phase of my modelling will focus on the present archaeological evidence in situ. I might have called it “what is still there”. The expression is not entirely correct because what I am going to model is actually what we can see of what is there (assuming that we were free to  explore the whole Iseum as much as we like). 

In practice, this means that, for example, I am going to model the Purgatorium's underground space, even though it is not immediately visible and it is not accessible to modern tourists without a permit, but is potentially both visible and accessible.

On the other hand, I won't model what is not visible. To explain ti better, I can use an hypothetical example: let’s imagine that the roof of the Temple had survived. In that case, I would model only the ceiling (which is what an observer could see from inside the Temple) and the external elements such as the tiles or the architrave (which is what an observer could see from the outside of the Temple). But I wouldn’t model the (invisible) supporting structure. 

I am sure that modelling what actually allows a roof to stand (for many centuries!) is of massive interest in the study of architecture and ancient building techniques. 

As I am more interested in how a building was seen and experienced by people (either at as a Roman Temple or as a modern Touristic Attraction), I have decided  to include in my 3D model only what is accessible to the eyes of a human being that is allowed everywhere in the modelled space. 

The matter would be different if the hypothetical roof would be damaged. Then, the internal structure would be visible to visitors and part of their experience (and, therefore, object of my representation).

Everything has (at least) two faces: about walls and normals

At the walls, by S. Bakalovich
from wikipedia

 To explain how I am going to deal with constraints, I will use the simplest, and most common, type of them: walls. Although they often look just as think lines on a plan, walls cannot be represented as flat two dimensional areas. That would contradict our experience and wouldn’t make any sense geometrically, as walls are three dimensional objects with different depth. 

It is possible that at the very beginning of your 3D modelling career you are tempted, quite naively, to simply trace the shape of your walls and extrude them as a solid. In case, the puzzled expression of your supervisor and the question “what is that supposed to be? Minecraft?” will quickly tell you that you’re on the wrong track.

What you are supposed to do (or, at least, what I am going to do) is to build two separate surfaces, one for the interior and one for the exterior, without modelling what is in between (i.e. the actual thickness of the wall).

There are a few reasons why I agree it is a sensible approach.

First, walls (as well as every other constraint) may display different material or decorations on the inside or the outside. So, in the model, they will probably have different textures assigned. 

Also, as we were discussing in the other posts, there is a logical (or ontological, in the linked data meaning of the word!) benefit in it. A wall often delimits two different spaces. But, more specifically, one side of it delimits one space and the other side delimits another space (or spaces). For example, the wall that separates the ekklesisaterium from the sacrarium, is the internal southern wall of the ekklesiasterion on one side, but, on the other side, it is the northern internal wall of the  sacrarium.

It may sound confusing at the beginning, but, after you get used to that, it is a simple yet effective convention that has proven his usefulness in my previous models already. I think it will also suit well the RDF modelling and help dividing meaningfully my digital archive.

If there weren’t enough reason to justify a separate management of the two surfaces of a wall (or other constraint), game and VR engines give us another good one: normals. Surfaces are visible only from one view, either from the interior on the exterior. Even if we had a wall with the same identical texture (let’s say a generic masonry), to allow a 360° virtual view of it, we still would need two surfaces: one looking towards the interior and one looking towards the exterior. This is the only way a character (or a camera) can have a realistic view of a virtual building when it is walking into a space as well as when it is walking around it.

Academic guilty pleasures: inventing words and making lists

What I needed in order to start, was a general name to identify everything that is in model. I know that even such an apparently harmless sentence can hyde insidious philosophical controversies. At this stage of my modelling, what I want to represent (both visually and conceptually) is the archaeological evidence, i.e. what can be still seen (and potentially measured) in situ at Pompeii. Further layers of visualisation that involve a bigger amount of speculation and interpretation, will be analysed (and modelled) later on.

Classification of the Greek Orders
from wikipedia

 The terms that I am using are just draft, at the moment. I hope to find something better in the future or even to discover that someone else has already worked out a more convincing naming system and is willing to share it with me.

The word I have chosen for all the components of the model is «element». I think it is abstract and general enough to be associated with pretty much anything (in any 3D model) and it covers logically both the tangible and intangible domains. 

There are no limits to the number of elements in a model or to their size.

After a certain amount of head-banging against the screen of my computer, I think I have identified three different categories of elements. I have tried them against both the Iseum and the House of Orpheus. It seems to me that they kind of work, and cover all the possibilities in a relatively sensible way. But I wouldn’t be surprised if someone pointed out some discrepancy. 

The three groups are:

1) spaces

2) constraints

3) transitions

To be completely honest, this is probably all I need to assign meaningful names to the elements in my 3D model or to catalogue my digital archive of resources. But I thought it was useful to refine the classification a little bit, thinking of a future (potential) higher complexity. 

(The fact that I actually enjoy making lists has absolutely nothing to do with it)

The classification itself, is very likely to be influenced by my 3D modelling experience and by the way I had been taught to approach ancient buildings (especially Pompeian ones) and their components.

Plaster cast of a Pompeian door.
Photo by Günther Einhorn
via Pompeiiinpictures

I call «spaces» the elements that allow activities to happen within them. Very straight forward examples of spaces are all sorts of rooms but also gardens, portici, courtyards, etc...

«Constraints», on the other hand, are elements in which activities cannot take place, and usually serve as boundaries for spaces. The most common type of constraints are walls, but colonnades, podia and roofs will be considered constraints as well. A space is supposed to be delimited on each of its sides, although not all the constraints are tangible. A change in the mosaic pattern can delimit a space, even if there are no walls to mark the separation. To be precise (and slightly pedantic) the tangible constraints can be divided into permeable and impermeable. To the latter clearly belongs plain walls or high gates. To the former, belong colonnades. Although some constraints (such as colonnades) are physically permeable, I suspect that they were not always considered as such in practice. I can hardly imagine someone being allowed to jump down the Temple of Isis’ podium  through the pronaos’ colonnade. However, I will consider only the material qualities to assign the constraint to one or the other category. All the ones we have mentioned so far are permanent constraints (both tangible and intangible), but we know that Romans had temporary ones as well, such as curtains or removable fences. The existence of temporary constraints implies, I guess, the existence of temporary spaces. As I am currently working only on the present archaeological evidence, temporary constraints or spaces are not object of my attention now. 

Last, «transitions» are those elements that connects spaces and, as such, they do not belong to either of the two elements they connect, but are independent. We will consider two kinds of transitions: the ones that allow physical access from one place to the other (such as thresholds or stairs) and the ones that allow visual access from one place to the other (such as windows). Likewise the other two elements, they can be permanent (a stone staircase) or temporary (a ladder). 

Spaces, constraints and transitions can all have «features». Features is used, as the dictionary suggest, to indicate “a distinctive attribute or aspect of something”. 

Features often pertains to the decoration of a space, or a constrain, or a transition. It is easy to identify constraints features, as they are basically contiguous. For example niches in the walls, engaged columns, mosaic floors. But also transitions’ features are usually easy to spot (windows moulding, or doors). Stand-alone features, that have no physical contiguity with any other element (such as altars or herms), will be considered features of the space in which are situated. So, for example, the altar in front of the Purgatorium in the Iseum is a feature of the cavaedium. 

Circular colonnade in the Temple of Vesta, Rome.
Photo by E. Trutat, Bibliothèque de Toulouse

Any element can be divided into sub-elements, according to the level of granularity that the research requires. The sub-elements can be either areas or constraints. For example, in the Iseum, the element space temple can be divided into sub elements pronaos and cella (spaces) and roof and podium (constraints). The Temple also has quite a few transitions: staircases, thresholds, etc...

The same constraint can delimit more than one space, especially when they are subelements of the same space. In the element Temple, constraint roof delimits both sub-elements space pronaos and cella.

It could be argued (especially after a couple of drinks) that the part of a constraint, let’s say a wall, that delimits a space, is conceptually different from the part of it that delimits a contiguous space (such as the wall shared by three of the private rooms in the Iseum). 

In this case, 3D modelling’s logic has stepped forward helping me in two ways. In the first place, reminding me the practicality (even the “materiality” if I can use this word) of the process. Digital 3D models should be optimised for Real Time engines or any other platform that makes them explorable by the users. Therefore it is crucial to keep the number of polygons under control. The less polygons, the faster is the loading process and smoother the character/camera movement.

Also, a limited number of polygons ensures a better control on the file for both the original author and the potential other researchers that want to build on top of it.

On the other hand, I will deal with the conceptual separation of constraints through their internal and external surfaces.

If what I have just written sounds a bit sibylline, I am going to explain myself better in the next post.

Breaking down reality

Greek philosopher Parmenides
image from wikipedia

Dividing the Iseum in its main components and work out a naming convention that made sense in the 3D modelling context as well as in the RDF one, seemed a sensible starting point to me. 

However, reality is a continuum and every attempt to break it down according to our logic(s), and partly to our needs, is bound to result in long hours of discussion, over-consumption of coffee, and a severe headache. The meaning of words and concepts gets challenged over and over again in endless loops, going inevitably back to pre-socratic questions about «being» and «existing». 

The point is that every division and classification is artificial, no matter how much we are fascinated by The Myth of Perfect Consistency or how much we try to be objective.

Objectivity is, probably, a common self-delusion among ontologists. In my opinion, personal and cultural biases can be partly counter-balanced through collaboration and the expression of multiple hypotheses and interpretations. However, at this stage, I have to work on my own in order to produce a proof of concept. So, the best I can do is to record my methodology, so that I can revise it after having received feedbacks.

About naming convention: I was tempted, at the beginning, to use human readable names. I thought it would have made my 3D model much more accessible and easy to look at for other modellers. I had even thought of using Latin to label well identified areas, and more generic names, always in Latin, for the one that have not been identified yet. After discussing it, I have decided to abandon the idea for two main reasons:

Colour map of the elements of the Iseum

1) it is not always so straightforward to label a space. The fact that I am mainly working on the Iseum can be deceptive under this respect. Roman sacred architecture tends to be quite formalised. So there is little to argue if I want to call the pronaos «pronaos». However, it’s not the case for every building in Pompeii. 

A look at my comparative example, the House of Orpheus, proved to be very useful. There are many spaces that do not have an agreed identification, and different scholars refer to them with different names. Not to mention that the upper story(ies) are entirely hypothetical. 

2) Giving a meaningful label means already to make assumptions about the use of a space. And I am trying very hard not to express interpretations at this level. 

In the end, I have opted for a more abstract convention and I will simply use letters (in the English alphabet) to label the components of my model. 

Through RDF triples, I will then express that, for example, room A is type kitchen according to scholar 1 and that the same room A is type storeroom according to scholar 2.

About identification of elements: In the case of the Iseum, the identification of the main components didn’t seem very difficult to me. The different blocks stands out fairly clearly. Even before making (or agreeing on) assumptions on the use of the spaces, they look pretty much neatly separated from a geometric and structural point of view.

I’m using the first published plan of the Iseum ever published (Saint-non’s one) to illustrate the first division into the main elements. In order to avoid confusion, I have erased from the original map the letter-based naming convention that Saint-Non himself used. Next to the letters, I am listing in the legenda also word labels for the sake of clarity, following a widely accepted convention about the Iseum.

Some of the elements can be divided in sub-elements or grouped in super-elements (the relationship being very easily expressed through properties such as :isPart Of or :hasPart). Some of this relationships are very quickly recognisable looking at the plan. The element C (Temple), for example, can be divided into element H (pronaos) and I (cella). The latter, also contains a sub-element J (cellar). Likewise, space G can be divided in several sub-elements.

Close up of the Temple of Isis

However, buildings are not flat, and spaces are not divided only along an horizontal axis. If we look at a cross-section of the Iseum, then we will notice that the Temple is not only made by pronaos and cella, but also by a podium and a roof. And the Purgatorium has a ground level room as well as an underground one.

Last, we can hypothesise the existence of a second story for at least one of the rooms of the private area, although it isn’t in any plan or blueprint of the Iseum.

So, the whole list of the elements in which I have divided the Iseum is a bit longer than the one showed above, but it is probably not interesting to publish it here.

If reading this post you have started mumbling things like: “do a roof and a room belong to the same category”? “what about stairs?” “what about the altars and the statues?”, I know exactly that feeling and this is why I have spent a few nightly hours searching for some convincing answers (that I will publish soon).

If you love someone, let them go: the House of Orpheus and its dataset

Old undated photograph courtesy of the
Society of Antiquaries, Fox Collection
from Pompeiiinpictures

I was initially planning to work on two examples of Pompeian buildings: the Iseum and the House of Orpheus. I find them both very interesting for different reasons, and I have for them that emotional attachment that 3D modellers develop for the buildings they have been working on.

I have seen them in Pompeii, I have taken measurements and pictures, drawn maps. However, after a more practical approach to my timetable (i.e. looking at an actual calendar), I have suddenly realised that the modelling of the Iseum alone is going to take the entire 2014. There is no really room left for a second model. It wasn’t easy to give up part of my research, but it wasn’t even a choice. Although I am not modelling the House of Orpheus, I think that the amount of data I collected so far on that building (and the related artefacts) can still play a role in my PhD.

I have recently started the very hard task of drafting my ontology for cultural heritage,  having as a main reference my own model of the Iseum. I have quickly discovered how easy it is, in such circumstances, to think of something that turns out to be very much ad hoc for one single case study. Orpheus’ dataset is a good way to double check if my categories work not just for the Iseum, but can be reasonably applied to at least one other Pompeian building (that belongs to a complete different category).

On the one hand the House of Orpheus is a fairly typical Pompeian middle sized household. On the other hand, there is quite a lot of information missing. Only the ground floor survived (while the existence of at least a second floor is strongly suggested by the remains of stairs), and, for a few spaces, there is still no agreement on their use in Roman times. 

Being a more ambiguous context than the Iseum, it points out much more clearly what is the weight of the assumptions in our way to describe (or even look at) an ancient building, and it reminds me that I should try to keep descriptions and interpretations as much separate as possible. 

Lured by the sistrum: the choice of the Iseum

Francesco Piranesi, The Temple of Isis at Pompeii

If you have ever met me in person, it is very likely that I have mentioned the Temple of Isis in Pompeii, at a certain point. Even if you didn’t ask about it. Even if, to be honest, there was little (or no) connection with the conversation topic.
To be precise, the area I’m working on, experimenting with the potentiality of RDF applied to 3D environments, is the Pompeian Iseum. The sacred complex includes, besides the proper temple, other public spaces for the cult, and the private spaces where (probably) the isiac priest(s) used to live.

There are many reasons behind my choice.
First, the digital unification of one of the Iseum’s rooms (the Ekklesiaterium) was the case study for my MA dissertation in Digital Humanities at King’s College London. The Iseum, in fact, has one of the richest and best preserved collections of artefacts and decorations that are exhibited in the Archaeological Museum of Naples. The corpus is so relevant that it has a dedicated space within the Museum itself.

Besides the conclusions of my dissertation, the Iseum is certainly the groups of buildings in Pompeii I am most familiar with. Moreover, I have already collected a personal archive of digital resources, partly produced by myself (such as digital pictures and measurements) partly found in online repository, partly digitised from printed sources. While researching for my MA dissertation, I obtained access to areas of the Iseum that are usually interdict to the public (such as the interior of the temple, the interior of the ekklesiasterium and the purgatorium) as well as to documents that are relatively rare (such as the original drawings by John Soane, at the Soane Museum and the 1941’s illustrated publication by Elia and the Warbourg Institute). I thought it was a good idea to capitalise the information that I gathered and to produce a 3D visualisation able (among other things) to show and make virtually explorable, parts of the Iseum that are usually unaccessible to the average visitor.

Another reason is that the Iseum was one of the first excavated complex, so it is featured in many accounts, records, watercolours and guide books.

Imaginary interior of the Temple of Isis in the Italian movie
Gli ultimi giorni di Pompeii.
From http://ithankyouarthur.blogspot.co.uk/

In addition, when the place was dug up, the site was still personal property of the Bourbon King and he hired very skilled professional from the Neapolitan Academy of Fine Arts to produce a visual documentation of various features of the building(s) as they were when they had been unearthed. Some of these engravings (now exhibited at the Museum of Naples) are the best information we have about some elements that do not exist anymore.
The fact that the Temple of Isis and the Iseum appear so often in official and unofficial literature about Pompeii, is not merely a matter of “age”.
The temple captured the attention and the imagination of many visitors. Its Egyptianising flavor made it look mysterious, if not slightly sinister. It became quickly an iconic building in Pompeii, and it is featured in many novels (such as the hugely popular Bulwer Lytton’s one) and even peplum movies.

As interpretations and narratives connected to ancient heritage, are part of what I want to represent, the Iseum seemed to  confirm its relevance under this respect too.

The Pompeian Iseum has been very often reproduced. Francesco Piranesi, for example, has studied the place and its architecture in depth. However, it is very seldom shown in its completeness, most of the visual interpretations focusing on the Temple and the Purgatorium alone. My model aims to represent all the different components of the Iseum, (potentially) allowing the investigation of their visual and functional interactions.

On top of these very sensible reasons, there is a more irrational one: the Iseum, in its charming funkiness and lack of symmetry, simply rocks (but I can’t write that in my PhD).

Let's get practical: a digital research journal

After a year spent reading a lot, meeting people, finding out that all my good ideas had already been much better explored by someone else, and, last, after passing the upgrade, I though it was time to start thinking of the practical side of what I am going to do with my 3D visualisation and the RDF ontology.

To prevent the terrifying feeling that hits you at the end of the third year when you are supposed to retire into a cave and spend 6 month writing no-stop (basically degrading all primary needs to a secondary ones), I have decided to take some notes during the process. Hopefully, it will make the process easier and more transparent. They are preliminary thoughts and they are very likely to be a bit green and even clumsy. All going well, they will be refined during the next two years, also thanks to the feedback I receive. So, all comments are very welcome (and actually useful).

An Introduction

Woman with wax tablets (so called "Saffo")
Archaeological Museum of Naples
Wikimedia Commons

I am a PhD student in Digital Humanities and Classics at King’s College London and this is a blog about my research. It is meant to be a digital notebook to fix ideas and share them with colleagues and other people interested in the same topics. 

I study 3D visualisation of archeological heritage, more specifically Pompeian buildings and artefacts. I am focusing on some methodological issues of 3D modelling such as the documentation of the research process and the representation of multiple hypotheses. 

I think that introducing 3D visualisations in the study of the Ancient World would change and enrich our knowledge of the Past, and  I’m trying to find a way to make it possible and easy.

Here I will discuss museum exhibitions, archaeological sites, my own interviews to the public, old and not-so-old accounts of visits to Pompeii and Herculaneum, the image of these places that has been disseminated by cultural products (literature, post cards, movies), touristic guides and official excavation records. 

I will do my best to put together again, logically and visually, things that have been separated many years ago but should be seen and understood together because they complete each other and give sense to each other.

I am interested in the cognitive and emotional relationship that people build with these ancient artefacts and how digital technologies can represent and enhance such a bond. This is a complicated way to say that I want to understand why and how people fall so deeply in love with Pompeii. 

I like to talk, and write, about the idea of «place» and its existence in geography, perception, memory and imagination. And I will probably try to convince you that the best way to engage the audience with the Past is through storytelling. My cunning plan is to actually tell you a lot of stories about Pompeii. You probably won’t believe them at the beginning, but I promise they will be true. Almost all of them.