Archeologia e Calcolatori 4 - 1993

The development of computer applications in archaeology involves a complex trend in order to define, before undertaking any implementation, a conceptual framework of computable functions, archaeological objects and data models. This conceptual framework allows the definition of a global information system, well adapted to the various archaeological problems. After that definition, it is easier to develop a long-term and evolving software architecture, integrating the best packages of the market.

Encoding problems are often neglected, in archaeological as in other humanities related research, because of their apparent triviality. Encoding is assumed to be the reproduction in an “electronic alphabet” (be it the ASCII code or a second level language like SGML) of something written on paper. On the contrary, the encoding process begins with the recognition, choice and declaration of the elements of reality which we are going to submit to an electronic process. As a consequence, we must examine very carefully the substance of the logical and formal passages that we undertake. This article tries to show the difference between many kinds of encoding and the significance of encoding in archaeology, in comparison with other opinions, mainly by J.-CI. Gardin and F. Djindjian.

This paper provides a short summary of some recent results in intrasite spatial analysis in Prehistoric archaeology and, in particular, in Paleolithic archaeology where, as it is well known, intrasite spatial analyses have been applied for at least twenty years. Starting with some “classic” examples of 80’s (the Magdalenian site of Pincevent, the ethnoarchaeological analysis of the Mask site in Alaska), and a short illustration of the techniques applied (correspondence analysis, k-means cluster analysis, unconstrained clustering, factor analysis, etc.), some of the most recent applications are described: the Mesolithic Barmose I site in Denmark, studied by H. Blankholm, and the Middle Pleistocene site of Grotte Vaufrey in South West France (Dordogne), where the intrasite spatial analysis has been performed by J. Simek. We then discuss the relationship between the “quality” of the quantitative procedures used in the data analysis, which is in general of an outstanding level, and the “reliability” of the archaeological interpretation. A major conclusion is that the problems arising in the archaeological interpretation (a good example of which is Grotte Vaufrey) are much more connected with the choice of variables in the quantitative analysis, than with the different algorithms employed: we thus recommend to the archaeologists (and not to the computer scientists involved in the research) the basic selection and choice of the essential variables derived from the data.

In this paper I have tried to build a computational theory. In other words, a “theory” implemented in a computer program. When using a computational theory we try to solve scientific problems, that is to say, we do not retrieve data units, but we “instantiate” a solution for the problem. I have formalised the concept of an “archaeological problem” in the following way: how is an artefact (or set of artefacts) used by a community in a specific context. The task is then to evaluate the social uses of a specific set of artefacts (Final Situation or State) in terms of: a) their description, and b) all information available about the social, cultural or chronological context and about the human community who produced those artefacts (Initial Situation or State).We may then represent problem solving knowledge as a list of discrete and closed units. Those declarative units are successive states of the problem. We substitute equations for explicit sets of propositions. We can implement a set of answers and a set of decision rules for each one. The resulting program looks like a complex database and not like a mathematical procedure, and we may consider the problem-solving mechanism as a sequential search in a preexisting problem space, using a finite number of particular decision rules. Some interesting work has been done in mathematical representation of archaeological theories, but such approaches have not been very successful, maybe because social sciences cannot be exclusively represented by mathematical models, or because archaeologists are incapable to communicate between themselves using mathematical expressions. As a consequence, archaeologists tend to express their theories by means of linguistic sentences, which is inadequate, given the fact that natural language obstructs objectivity. A representation in terms of logical propositions appears then as the best representation tool available to build social theories. Artificial Intelligence scientists are now exploring this possibility. In this paper I propose an analogy between the structure of archaeological (and social sciences) theories and the mechanism of Turing Machines: given some empirical data (observation of the archaeological record) and a knowledge-base (constituted by high-level concepts and their middle-range correlates), we have to explain the particular case (the archaeological record) by means of the knowledge-base (the theory). The logical mechanism is modus ponens.

The article describes the transformation of a number of procedures for archaeological data processing into Excel (Macintosh and MS Dos versions) macro-programming language. Automatic seriation is dealt with first. The general principles of the two best known algorithms - the reciprocal averaging method and P. Ihm’s correspondence analysis - are discussed. The Excel programme text is then presented and commented. After detailed analysis of the comparative merits of the two algorithms, a number of general remarks of a methodological nature are made about problems posed by seriation and particularly by automatic seriation techniques. The article then turns to the construction of incidence (presence/absence) tables and co-occurrence matrices. Here again, general principles are discussed before presentation of the programme text and comments on the macro. The last macro presented carries out replacements of cell contents. The conclusion contains some general methodological remarks about Excel and the writing of macro-programmes in Excel’s macro-programming language.

Multivariate discriminant analyses were applied to the chemical composition data of four groups of fictile archaeological findings from the lagoon of Venice. Three groups are constituted of ceramic fragments of different manufacture, local and imported Byzantine originating from different epochs, from the Middle Ages to the Renaissance. The fourth group is formed of special Middle Age bricks (“altinelle”). Our aim was to first find the chemical characteristic of each group and, on this basis, to classify other unidentified findings. After having verified the structure of the four groups by means of PCA analysis, three discriminant canonical variates were determined: the relative weights of the original variables represent their discriminant power. The groups were also analysed in pairs and their relative discriminating variables were found. Discriminant function on the basis of the three new variates were calculated for each of the four groups and used for their verification. Finally a quadratic PCA analysis was applied to the first two variates of each group allowing, by means of recognition of their geometric form, to also identify non-linear relationships.

During the last few years we have witnessed the development of research on trade amphorae, in particular with the help of archaeometric techniques and quantitative processing of analytical data. In this context we can quote the research project carried out by the authors, which focuses on the amphorae of Spanish origin found in Venetia. The study is articulated in two main parts: the first one concerns morphometric analysis of the amphorae by means of their photogrammetric restitution and the comparison between the diverse forms using geometric indexes calculated on the coordinates of the points measured on outline of the vase. The second one concerns the characterisation of the amphorae by means of the chemical-mineralogical analysis of the paste, with the aim of reconstructing their exact provenance. The historical-archaeological purpose of the project, the first results of which concern the amphorae from the Tomba di Giulietta in Verona, is the assessment of trade exchanges between Venetia and Betica.

Computer simulation of natural phenomena is one of the most attractive and modern subjects for image synthesis. Simulation is the result of many processes, computed with mathematical models, which can be visually represented on a graphic screen. The synthetic image of the model generated can then be compared with other available information, and thus the image becomes an instrument for furthering knowledge. Two problems exist in the visual simulation of natural environments and 3D navigation. The first one is the construction of a reliable and detailed Digital Elevation Model (DEM or Digital Terrain Model, DTM); the second one, closely tied to ambient simulation, is terrain rendering, that is, the reproduction of the colour vision in the observer. DTM’s can be generated from isoliner or regular point data, using classical models (linear interpolation and Kriging) or fractal models (Brownian interpolation). In this example the aim is to create a landscape model (including archaeological sites) using a DTM and satellite or aerial images; these applications involve the following steps: acquisition of isolines from cartographic maps at any reasonable scale; DTM generation; digital image classification to determinate the pixel distribution map for the DTM; image synchronization (digital aerial photographs or satellite images synchronized with the DTM); texture mapping and generation of 3D images. In practical terms, the texture mapping involves the overlaying of the original image point by point on the DTM: the result is a realistic and significant landscape 3D image. This kind of simulation is especially useful to enhance the geomorphological characteristics of the landscape in connection with its evolution and the ancient settlement. Inside the image the researcher can move, navigate and explore, as in the real world. The example described concerns the Etruscan town of Marzabotto in the Reno Valley (Bologna). A realistic and representative 3D image was achieved which includes important topographical and geomorphological information about the archaeological site and the Reno Valley, the natural resources, and the correlation between the Reno river and the Etruscan town. A digital vertical aerial photography was overlayed on the DTM of this area, generated from cartographic isolines and contour lines. The processing consists of different steps: the first one is the digitisation of the aerial photograph (scale 1:30.000), in order to create a numeric input for part of the Valley of Reno, including the archaeological area and the DEM model with a topographical sample. The aerial photograph was digitised using a CCD camera and converted into a numeric format in raster file (RGB 24 bit plane, resolution 595 x 394 pixels). It was aligned with the DEM model using a regular grid with a resolution similar to the one of the digital image. Special hardware (SGI workstation) was used for the final rendering; the polygon rendering did not follow the usual texture mapping technique, but instead a geometric texturing was produced (one polygon per pixel). This technique allows a lower sampling noise (antialiasing) without heavy software interpolation. In this way the only problem is related to the dependence on the graphic library GL which is implemented either on a Silicon Graphics or RISC 6000 IBM platform.

Between 1989 and 1992, studies and experiments on automatic systems for the acquisition, calculation and management of archaeological data relating to the Carta Archeologica d’Italia (Forma Italiae) were carried out. The different phases of application confirmed the methodological assumptions originally outlined in the first issue of this journal: from the use of a GPS system to locate the archaeological survey station, to the exploitation of particular functions of commercial geodetic software, and to the strengthening of the value of an approach whose “natural” end consists in creating a Geographic Information System for archaeology.

This paper illustrates the computing section of a Strategic Project for the development of research methods applied to the study and safeguard of the archaeological heritage of southern Adriatic Italy. The project was launched by the Italian National Research Council and the University of Lecce. The computing section has as its objective the creation of a system for the management of data pertaining to antique settlements that guarantees the integration of three information supports: alphanumeric, cartographic and photographic. These supports contain data deriving from two interacting research systems: field survey and excavation. The cartographic data is varied: large scale maps, area and site plans, detailed plans of single monuments, stratigraphic sections and feature and layer plans. Software used consists of a relational database and a specific digitised mapping system. The system permits the acquisition of raster images. A global user-friendly interface which permits maximum navigation is in the process of completion. We foresee the principal field of application being the analysis of spatial distributions of artefacts and ecofacts as a basis for synchronic and diachronic cultural analysis.

Quantitative studies of Attic figured pottery have interested many scholars as the existing vases represent only a modest percentage of the whole Athenian production, and their number is liable to change after any new excavation. Traditional systems of analysis confuse the pattern of ancient trade: near to the peaks of single cities, we have a total absence of data from areas that we would believe to be centres of a lively trade. The research conducted by the Institute of Archaeology of Catania University attempts to highlight the “commercial context” of the distribution of Attic pottery; data processing is based on a file divided in 13 areas and 47 sub-areas. The file follows the possible routes from East to West. The appendix describes the file of the Painter of Paris Gigantomachy, based on the vases assigned to him by J.D. Beazley. The painter’s production is analysed through three points of view: number and provenience of vases; provenience of shapes; provenience of subjects.

The first part of the article deals with the problem of the relationship between the business world and the world of learning. In particular the author confirms the fundamental role of humanistic disciplines in the contemporary world and the necessity of the business world to recover their formative power. The second part of the article underlines archaeological trends as a “discipline” that can question the business world. The examination of computerised research undertaken up till now in the archaeological field of study shows a double purpose: the progress of scientific knowledge and the safeguard of cultural heritage. Among recent developments, the increase in the sectors devoted to didactics and the diffusion of knowledge are underlined.