Gabriele Gattiglia

A PageRank based predictive model for the estimation of the archaeological potential of an urban area

We present the analysis of multi-faceted, GIS managed data for determining the archaeological potential, i.e. a measure of the possibility that a more or less significant archaeological stratification is preserved. We used a sizable number of datasets, in order to consider the problem of estimation of archaeological potential in all of its aspects: archaeological data, building archaeological data, historical data, toponymic data, geomorphological data. As the identification of relations among finds is a key issue for the data mining in archaeological interpretation process, we applied a modified version of the PageRank model, because the criteria for assigning importance to web pages by search engines are similar and based on relations, also. The procedure included a categorization archaeological data, the assignment of initial values of potential to the available data through an automatic procedure, the creation of geomorphological facies maps, the definition of functional areas (i.e. the levels of spatial and functional organization: urban, suburban and rural areas), and the application of the PageRank based algorithm. The model has been applied on the urban area of Pisa, and tested through the data of 14 new cores. The map of archaeological potential consists of the composition of the 7 layers, one for each archaeological period under consideration: Protohistory, Etruscan period, Roman period, Late Roman period, Early Medieval period, Late Medieval period, Modern Age, Contemporary Age. The results, including the archaeological potential map, are to be considered as the first steps towards an automatic, formally definable, and repeatable, approach to the computation of archaeological potential.

Mathematical models for the determination of archaeological potential

The Department of Archaeological Science of the University of Pisa is undertaking the MAPPA project, which is a research project in which archaeologists, geologists, mathematicians will study predictive modelling tools applied to the archaeological potential of an urban area. The project main objectives are: - Enhancing the development in archaeological research by fostering collaboration among different sectors and by developing a common languaxadge. - Creating a model that may be applied to all urban centres in order to facilitate land use decisions. Within this conxadtext, we propose predictive mathexadmatical models, which will have an impact on archaeological hexadritage protection, territorial planning and historical knowledge. - Making raw data from archaeological inxadvestigations available. The project proposes that after acknowledging auxadthorship of the data, the latter shall be made publicly available and easy to consult. Based on the discussions between the mathematical, archaeological and geological teams, an analogy arose between the criteria used for attrixadbuting archaeological potential and those used for assigning importance to web pages by search enxadgines. Indeed, the key issue of the archaeological interpretation process, from an abstract viewpoint, is the identification of the relations that exist among finds, both in spatial terms and in functional terms. In other words, the presenxadce of a particular find near another that has already been discovered could strengthen or weaken the proxadbability that they will form a more complex structuxadre, and so strengthen or weaken the archaeological potential of the area itself. This is exactly the critexadria upon which page ranking algorithms are based, whereby each web page attributes importance to the web pages it points to (via a link) and, in turn, receixadves importance from the web pages it receives a link from. In order to adapt a page rank model to the determixadnation of archaeological potential, variants need to be created: - A three-dimensional grid will model the subsurface of the urban area. A single cell plays the role of a web page, and its importance will be the archaeological potential; - The information available for a cell will be used: in a relative manner, to build the elements of the matrix that, like in page rank models, assigns the transfer of importance among cells; in an absoxadlute manner, providing the absolute value of the archaeological potential; - The matrix controlling the transfer of importance will be constructed on the basis of categories used for classifying the archaeological finds. The categories will characterise the geometry of the distribution of importance; - Geological information will be used in a binary manner, allowing to exclude certain cells from the calculation of archaeological potential. Finally, the MAPPA project will realise an Archaeological Information System able to define the specific nature of archaeological practice, and to manage the heterogeneous data which describe the urban archaeological complexity.