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Extending the Quality Concept in Geo-Information Processing
3.1 The Context of Business Processes
Recent years have seen considerable change in the geographical information handling and market environments. As a result GI enterprizes have had to rethink their operations, product and service offerings in order to improve performance, stay competitive and expand market niche [31, 18]. Organizational restructuring, business process redesign, deployment of total quality and work ow management systems and quality control procedures (see for example [34, 8, 16]) have thus become commonplace.
The overarching goal is to improve the performance of the business process, hence its products and services. Performance in this context is defined by quality, cost and delay (QCD) [18, 35]. Quality refers to the extent to which the product satisfies user needs also called external quality. The cost of a GI product can be viewed in two ways. First, it can be production cost which is the cost incurred in generation of the product and is directly related to the efficiency of the value chain or business process. It also refers to the price at which the product is made available to the consumer, always considered in the background of perceived quality of the product. Delay is directly related to the responsiveness of the business process and refers to the time it takes to make a product available in the market (time-to-market), and also the time to generate a unit of product. Though the concepts have attracted much interest they are still little developed given the infancy of the markets.
3.2 The Context of Geoprocessing Systems
Enterprizes need exible systems that can be rapidly adapted to changes in their environment and integrated with other systems when the need arises. Enterprize systems support business processes, store, process, manage and analyze business information in pursuance of strategic objectives. Thus an enterprize system will re ect the strategic goals of the enterprize and its organizational structure. The trend in recent years has been towards open distributed systems to support the computing needs of collaborating enterprizes dispersed in space. Distributed systems comprise heterogenous computing elements connected via communication networks and offer better cost/performance trade-offs, improved system availability and reliability, and enhanced resource sharing. Interoper-ability is however a big challenge.
Towards distributed geoprocessing, the OGC has proposed the openGIS services framework (OSF) that defines a set of basic services that can be deployed on the Internet, located and invoked by compliant client applications in a distributed enterprize environment [19]. Basic services canthen be combined together to provide aggregated services or integrated with other services to provide more complex and specialized services (Figure 1). It can be anticipated that as the virtual enterprize becomes the norm and distributed geoprocessing gets pervasive, an increasing number of enterprizes will become reliant on distributed infrastructures for mission critical applications. The ISO (International Standards Organization) and the ITU (International Telecommunications Union) have standardized the reference model for open distributed processing (RM-ODP) to aid the architecting and development of distributed systems and achieve interoperability. The RM-ODP has five viewpoints to enable separation of concerns during design by allowing designers to focuss on facets of the design that are of interest. The enterprize viewpoint captures the purpose, scope and policies for the system being designed. The information viewpoint specifies the information the system holds and the processing it carries out. Evidently, spatial data and its quality are among the concerns of the information viewpoint. The computational viewpoint of the RM-ODP supports distribution through functional decomposition of the system into objects which interact at interfaces. Important quality concerns of the computational viewpoint include portability, modifiability and modularity. The core of OGC work has centered on the definition of specifications for interfaces and protocols for geoprocessing computational objects [1]. The engineering and technology viewpoints focus on the mechanisms,functions and technology choices necessary to realize a distributed system. Several quality concerns can be identified for distributed systems (or any system for that matter) and include performance, availability, reliability, security, usability, modifiability, etc [5] and these qualities are chosen to suit the system requirements and its stake holders.
3.3 The Context of Spatial Data
The classical application of quality concepts in geographical information domains has been to describe aspects of spatial data. For long, data accuracy was the sole concern resulting in elaborate models and techniques to analyze error and its propagation in measurements [17]. With the advent of digital spatial databases and GIS systems, spatial data quality has extended beyond accuracy to include other elements like completeness, consistency, lineage etc. [10].
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