Abstract
Abstract. A huge amount of geographical datasets are becoming available in distributed environments like Spatial Data Infrastructures (SDI). These datasets are very heterogeneous since they come from different independent sources and surveys and are structured in different formats. In the context of a national SDI that needs to assure an adequate quality level of the data it provides, it is necessary to face the problem of data validation in an uniform way independently from the chosen implementation technology. In this paper we present the tools and methodology for data validation which have been developed to support the construction of the Italian SDI. These tools are conformant to the relevant ISO 19100 and Open Geospatial Consortium (OGC) standards.
Highlights
The GeoUML Methodology (Belussi et al, 2006) and the GeoUML Tools (Belussi et al, 2009) described in this paper have been developed in order to support the management of a geographical Conceptual Schema and to perform the automatic validation of the conformance of a Data Product to a given Conceptual Schema
The GeoUML model consists of the following elements: a. the UML model for class diagrams as defined in (ISO/TC 211, 2005) with some restrictions concerning the use of DataTypes and multiple inheritance b. a profile of the ISO Spatial Schema (ISO/TC 211 2003), called Extended Simple Feature (ESF) c. a set of predefined OCL (Object Constraint Language, the reference language for constraint specification in UML) templates which allow to define spatial constraints referring to the classes and attributes of (a) and to the spatial types of (b) d. a set of additional specialized features
In order to minimize the dependency of the Validator from the physical structure of the input, the architecture of the validator is based on a fundamental component, called the Normalized Database, which is a PostGIS database having an SQL schema which is derived from the Conceptual Schema following the internally defined Normalized Implementation Model; a Reader loads the input dataset into the Normalized Database and performs some controls which depend on the particular input structure, but the main part of the topological controls is done on the normalized database and is independent from the physical structure of the input
Summary
The GeoUML Methodology (Belussi et al, 2006) and the GeoUML Tools (Belussi et al, 2009) described in this paper have been developed in order to support the management of a geographical Conceptual Schema and to perform the automatic validation of the conformance of a Data Product to a given Conceptual Schema. The Data Product to be validated must be implemented using one of several predefined Implementation Models (IM), which transform the Conceptual Schema into a physical structure.
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