GIS Based Studies in the Humanities and Social Sciences - Chpater 7

7 Data Modelingof Archaeological Sites Using a Unified Modeling Language Teruko Usui, Susumu Morimoto, Yoshiyuki Murao and Keiji Shimizu CONTENTS 7.1 Introduction..................................................................................................99 7.2 Characteristics of Archaeological Information and a Site Survey.....100 7.3 Differences between Japanese and European Techniques in Data Recording and Organizing Archaeological Survey Data....................101 7.4 Object-Oriented GIS and an Archaeological-Information Database......................................................................................................103 7.4.1 Two Kinds of GIS Data Models..................................................103 7.4.2 Standardization of Geographic Information and UML..........104 7.4.3 Data Modeling of Archaeological Information and the General-Feature Model.................................................................105 7.5 European Stratigraphic-Sequence Diagrams Using the Harris Matrix and UML Modeling on Japanese Drawings of Archaeological Features............................................................................108 7.5.1 Class Representing the Archaeological Site (Archaeological Site Class)..............................................................108 7.5.2 Drawing of Archaeological Features and Stratigraphic-Sequence Diagram................................................109 7.6 Conclusion .................................................................................................. 111 References.............................................................................................................112 7.1 Introduction This chapter illustrates a data model for archaeological sites that enables exchange of data among archaeological communities around the world. The first section describes the nature of archaeological site data. The second 99 Copyright © 2006 Taylor & Francis Group, LLC 100 GIS-based Studies in the Humanities and Social Sciences section shows the difference between the Japanese data model and the West-ern data model (i.e., the Harris Matrix model). The third section discusses an object-oriented model for recording archaeological site data in compari-son with the traditional layer-based model. This section also explains the procedure for this modeling and a method of implementing it with the Unified Modeling Language (UML). The fourth section applies the UML to both the Japanese data model and the Harris Matrix model. The sixth section concludes the chapter with remarks on the common data model that can be shared with researchers throughout the world. 7.2 Characteristics of Archaeological Information and a Site Survey Archaeological sites represent evidence of human activities in the past. This evidence can be classified roughly into two categories: namely, archaeological features and artifacts. Postholes and moats are examples of archaeological fea-tures, which exist in a certain location or as a part of the ground, and which are basically not transferable. Stone tools and earthenware come into the category of artifacts, which are transferable. The place in which artifacts and remains are excavated is called an archaeological site. For archaeologists, it is the collected information provided by artifacts and remains at archaeological sites that is the most essential resource to investigate human activities in the past. In archaeology, there are various kinds of surveys, such as distribution surveys, site surveys, trench surveys, and excavation, and the results of those surveys are finalized in reports. During excavation, it is important to record precise positional relationships, configuration and position of remains, and location and direction of artifacts. The drawing of archaeological features, as shown in Figure 7.1, provides spatial information and positional relation-ship of remains and artifacts in a survey report. Thus, Geographic Information Systems (GIS) play a significant role in the management and analysis of archaeological information that contains geo-graphical information (Wheatley and Gillings, 2002). However, there is no standardized procedure by which information is collected, as collection procedures depend on the decisions made by the excavating archaeologists. Whether to interpret an excavated hole as a pillar hole or not is dependent on the knowledge of excavation teams. Further-more, after excavation, the sites are most commonly covered with soil or building constructions, and the information becomes available only in a report, with drawings of archaeological features and photos taken. Informa-tion sharing requires the establishment of standardized recording methods and a database structure reflecting the least subjective interpretation. Stan-dardization is required because of the differences in the approach taken by Copyright © 2006 Taylor & Francis Group, LLC Data Modeling of Archaeological Sites Using a Unified Modeling Language 101 Section of excavation area Different drawing Intrusion Plane feature Different drawing Position of finds Cut features Hachure 566 587 589 X––157050 Y––47505 586 563 592 595 567 Pileup feature 590 593 597 606 575 591 594 599 607 577 569 610 Relation point between drawings (implicit) FIGURE 7.1 Drawing of archaeological features. archaeologists in Japan and Europe in the preservation and recording of archaeological information. 7.3 Differences between Japanese and European Techniques in Data Recording and Organizing Archaeological Survey Data Survey systems and data-recording techniques are significantly different in Japan and Europe. In Europe, the differences of stratification are classified into units of stratification based upon stratigraphy, and each unit of strati-fication is precisely surveyed with repeated observations of stratigraphic sequences. Then, the remains are objectively reported in a stratigraphic sequence diagram, generally called a Harris Matrix (Harris, 1989). Figure 7.2 shows a Harris Matrix diagram. From the aspect of information recording, it has superiority in the adoption of the minimum unit based on types of soil, which is least influenced by arbitrary decisions of excavation teams. The numbering 115 to 153 in Figure 7.2 indicates the relationship of stratigraphic sequences during excavation. The recording method enables archaeologists to reproduce excavation processes with possible interpreta-tions. In contrast, repeat processes are unobtainable after excavation by the Japanese recording methods shown in Figure 7.1. Copyright © 2006 Taylor & Francis Group, LLC 102 GIS-based Studies in the Humanities and Social Sciences Harris matrix’s stratigraphic sequence diagram Boundary surface of stratum 115 115 131 131 141 Cut feature 132 132 Solid of stratum 141 153 153 115 ~ 153 Unit of stratification FIGURE 7.2 Harris Matrix’s stratigraphic structure and sequence diagram. On the other hand, Japanese archaeologists first identify a feature surface, which becomes the basis of the survey, and each piece of the remains is examined based upon geological transitions relative to the feature surface. The result is reported in the drawing of archaeological features. Compared to the European stratigraphic technique, objective reporting on remains in the upper layers is basically left out of the Japanese surveys, because infor-mation recording is determined on site. In Japan, extensive surveys mostly take place in a relatively hot and humid environment, and such techniques enable archaeologists to retain efficiency of surveys and maintain quality. The boundary of stratification has significant meaning in archaeology, and its two-dimensional diagram is considered a plainer representation of remains. The clarification of the relationship between stratigraphic sequence diagrams and drawings of archaeological features enables database devel-opment and integration of archaeological information collected in both Japan and Europe. Consequently, archaeological information sharing could become feasible, allowing for the shared use of archaeological information to proceed worldwide. For that purpose, we propose that it is critical to articulate the relationship between the Harris Matrix stratigraphic-sequence diagram and the Japanese drawing of archaeological features, and to define a schema for an archaeo-logical-information database to identify the context and structure of archae-ological information. However, the layer structure in the existing GIS model has no flexibility to fully incorporate association and definition of archaeo-logical information. Given that fact, we consider that instead of the layer-based model, it is beneficial to adapt the feature-based GIS data model to object-oriented GIS technology — a rapidly advancing technology. Copyright © 2006 Taylor & Francis Group, LLC Data Modeling of Archaeological Sites Using a Unified Modeling Language 103 7.4 Object-Oriented GIS and an Archaeological-Information Database 7.4.1 Two Kinds of GIS Data Models Existing GIS has a database structure derived from paper maps, which require overlaying of several outlines, showing such features as buildings, roads, and administrative boundaries. In a similar way, GIS adopts the same layer structure, and geographic spaces are represented with the over-lay technique. As shown in Figure 7.3, general database structure supports layers consisting of geometric and attribute databases, ensuring the col-lated data is merged and combined in a spatial index. The layer-based data model has an interlayering relationship problem, which can be significant. For instance, in the electricity-management system, electric line (line), power pole (point), and power plant (polygon) layers are created and manipulated in electricity flow and facilities. In this layer-based data model, realistic situations often occur. For example, the electricity line remains even if a particular pole in the layer is erased. Since the mid-1980s, a more robust, feature-based data model has been operational, superseding the layer-based data model (Tang et al., 1996). This development has been accelerated by the object-oriented, technological advance leading to the standardization of geographical information by the International Organi-zation for Standardization (ISO) Technical Committee (TC 211, Geographic ID = 1 Telegraph pole (point) ID = 1 Power line (line) Attribute table ID 1 ID 1 ID = 1 Power station (polygon) ID 1 FIGURE 7.3 The structure of a layer-based data model. Copyright © 2006 Taylor & Francis Group, LLC ... - tailieumienphi.vn