Web service approaches for providing enriched data structures to generalisation operators

Abstract

Web service approaches for providing enriched data structures to generalisation operators Abstract Web service technologies can be used to establish an interoperable framework between different generalisation systems. In a previous article three categories of generalisation web services were identified, including support services, operator services and processing services. This paper focuses on the category of support services. In a service-based generalisation system, the purpose of support services is to assist the generalisation process by providing auxiliary measures, procedures and data structures that allow the representation of structural cartographic knowledge. The structural knowledge of the spatial and semantic context and the modelling of structural and spatial relationships is critical for the understanding of the role of cartographic features and thus for automated generalisation. Support services should extract and model this knowledge from the raw data and make it available to other generalisation operators. On the one hand the structural knowledge can be expressed by enriching map features with additional geometries or attributes. On the other hand, there exist various hierarchical and nonhierarchical relationships between map features, many of which can be represented by graph data structures. After a brief introduction to the interoperable web service framework, this paper proposes a taxonomy of generalisation support services and discusses its elements. It is then shown how the complex output of such services can be represented for use with web services and stored in a reusable fashion. Finally, the utilisation of support services is illustrated on four implementation examples of support services that also highlight the interactions with the generalisation operators that use these auxiliary services. Web service technologies can be used to establish an interoperable framework between different generalisation systems. In a previous article three categories of generalisation web services have been identified, including support services, operator services and processing services. This paper focuses on the category of support services. In a service-based generalisation system, the purpose of support services is to assist the generalisation process by providing auxiliary measures, procedures and data structures that allow to represent structural cartographic knowledge. The structural knowledge of the spatial and semantical context and the modelling of structural and spatial relationships is critical for the understanding of the role of cartographic features and thus for automated generalisation. Support services should extract and model this knowledge from the raw data and make it available to other generalisation operators. On the one hand the structural knowledge can be expressed by enriching map features with additional geometries or attributes. On the other hand there exist various hierarchical and non-hierarchical relationships between map features, many of which can be represented by graph da...

Automated processing for map generalization using web services

“…The operators as well as the supporting functions and the iterative processing methods are implemented within the WebGen generalization web services environment that was originally developed with the aim of building a common research platform [8] and later extended by additional functionality [25]. The operators used are true stand-alone services and have no direct interdependencies; the web service interfaces are the only communication and data transfer utility.…”

“…As a third type of generalization service, processing services control the sequencing of the different available operator services [8], [25]. Furthermore, they are also using functionalities offered by support services.…”

“…The implementation was carried out in a web service framework called WebGen [8], utilizing so-called generalization operator services and generalization support services (described in detail in [25]). As a third type of generalization service, processing services control the sequencing of the different available operator services [8], [25].…”

“…Functional decomposition divides a workflow into different tasks as we do by applying the different algorithms onto a building partition in Displacement Aims to achieve sufficient distances between the map features so that they are distinguishable and do not visually coalesce. The algorithm can respect different required minimum distances between buildings and between buildings and roads [25]; uses the triangulationbased proximity graph by [28] Typification Reduces the number of buildings and tries to maintain the arrangement of buildings in a partition. Uses a weighted Delaunay triangulation to replace nearby buildings with a placeholder resembling the more important replaced building [11] Aggregation Aggregates nearby buildings; growing and subsequent shrinking of buffers (dilation and erosion) are used to merge the buildings Shrinking…”

“…Thus, manifold operators with different grades of sophistication (from simple algorithms to sophisticated, context-aware algorithms [30]) can be combined to jointly form a powerful workflow by uniting their strengths. We use a modular service-based architecture that allows the integration of different stand-alone generalization operators even from different generalization systems on different platforms [8], [25]. With this versatile service-based architecture it is possible to build modular generalization processes that can be flexibly extended by introducing additional generalization operators.…”