Abstract
The design of a Web-geographical information system, Web-GIS (Worboys & Duckham, 2004; Zhong Ren & Ming Hsiang, 2003), strongly requires methodological and operational tools for dealing with information distributed in multiple, autonomous and heterogeneous data sources, and a uniform data publishing methodology and policy over Internet Web sites. In this article we describe the experience of the Politecnico di Milano group in the activities of requirement analysis and conceptual design of the DEAFIN Web-GIS (Schreiber et al., 2003), whose objective is to provide a common environment for comparison of information about available vacant industrial sites coming from different regional data sources. Heterogeneity and Web availability requirements have been taken into account in the system architecture design; the system is thus conceived as a federated Web-based information system, apt to manage and provide access to all the regional relevant information in an integrated and complete fashion. Furthermore, since the data available by a given region partner can be both spatial and alphanumeric, a Web-GIS is defined for each regional component system.
TopBackground
The DEAFIN (development agencies and their impact on foreign direct investments) project has been launched with the purpose of allowing companies and investors to get a comprehensive information framework about areas located in European regions suited for potential investments. The aim is to make the regional data about possible investment areas homogenous and comparable, and internationally accessible. Potential investors need both a survey and a detailed view of vacant sites in different locations in order to compare different opportunities and decide their convenience. Quite naturally, such requirements call for a federated information system (FIS), which grants local sites a great deal of autonomy while enabling interoperation by means of a global integrated conceptual schema, that is, the federated data schema. Furthermore, owing to the capillarity of the end-user locations and to the need of a simple and widely known interface, Web-based access is mandatory. To define the functional specification of the system, the following activities have been carried out:
- •
analysis of the requirements of a distributed Web-based information system relying on a common conceptual database schema of the regional information that was initially (almost completely) available on paper support;
- •
conceptual design of the DEAFIN FIS, centered on the conceptual design of the federated conceptual database schema. The regional databases must be built according to the federated schema and then made accessible via the Web. The availability of data on the Web allows potential investors to navigate in the DEAFIN site according to various and customizable criteria, based on a benchmarking model developed within the project.
TopThree regional administrations from Germany, Italy, and Sweden were involved. The project started with a data-gathering phase, aimed at collecting requirements about data and processes managed at the partner Public Administrations. A questionnaire-based tool was circulated to collect common information to be stored in the FIS.
The basis of the questionnaire is a set of the data categories managed in Public Administration information systems. The relevant data categories concern land use plans (master and regional or specific), territorial services, industrial vacant sites, mobility data, statistical and social-economic data, base cartography data, and information on cadastral units data. Information on vacant industrial sites is the main focus of the investigation. For each category, the questionnaire collected the data characteristics reported in Figure 1.
Figure 1. Summary of data characteristics collected in the data-gathering phase
Key Terms in this Chapter
ER (Entity-Relationship) Diagrams: The most widely used model to express the database conceptual schema.
Web-GIS: A GIS system empowered with a Web-based interface.
Extensible Markup Language (XML): Markup language proposed by the World Wide Web Consortium [W3C] for data and documents interchange.
Wrapper: A software tool to extract content from data sources and perform data format translation.
Federated Information System (FIS): An information system is named federated when it supports interoperation among several autonomous and possibly heterogeneous information systems, by means of a shared global data schema.
Geographical Information System (GIS): Information system storing geographical data along with alphanumeric and spatial components. GIS systems also provide the data structures and algorithms to represent and efficiently query a collection of geographical data.
Mediator: A software component providing a uniform integrated interface to process and execute queries over data stored in multiple, heterogeneous data sources.