Can WFS-T replace SQL ?

Background With the advent of rich internet applications (RIA’s), part of processing has been transferred from the server to the client. However, many geo-spatial applications still require serverside access to a geodatabase to select and manipulate data using SQL. It would be profitable if these actions could be handled by an out of the box serverside component, thus eliminating the need for the development of a custom serverside component. Can OGC standards like WMS and WFS play a role here? Since WFS-T provides select, insert, delete and update methods much like SQL, it was decided to investigate whether the WFS-T implementation specification could replace SQL when developing complex geo-spatial applications. Or is SQL still needed? Method To answer this research question, this approach was tested during the development of several tailor made internet GIS applications: - a wheater and crop growth monitoring system; - a discussion support system for the water domain; - a national cultural heritage portal. Results Filtering and manipulating serverside data by WFS-T using the OpenGIS Filter Encoding Standard (FES) fullfills the needs to a large extent. Almost all of the desired functionality is there. There is one major limitation: FES lacks the ability to define a filter expression based on a joined table. Dependant on the implementation a work around may be available. Xml-schemas support 1-to-many relationships. They can be implemented as a joined table, which as a result can be queried. For larger datasets - a couple of ten thousand records or more - WFS-T tends to end up with a bad performance. Larger datasets should be processed serverside. Downloading large amounts of data and processing them clientside is too time-consuming. Compared to SQL WFS-T has less possibilities to influence the serverside performance. So for performance reasons SQL stays inevitable to handle larger datasets

Systematic planning and cultivation of agricultural fields using a geo-spatial arable field optimization service: Opportunities and obstacles

This paper describes a geo-spatial arable field optimization service (GAOS) and an assessment of users' experiences after three years of experimental operation. The service was developed in close cooperation with farmers. It allows farmers to optimize the locations of tracks within their fields, explore different options and download these to commercial Global Navigation Satellite System-guided steering systems. GAOS runs as a web service using standards defined by the Open Geospatial Consortium and is being operated by a group of farmers who received a few hours of training. The objective of optimization is to maximize efficiency by avoiding both inefficient turns and discontinuous swaths. Where applicable, released space is converted into field margins that meet environmental objectives and potentially generate additional income. The system provides dedicated functionality for geometrical operations, such as uploading and splitting of fields, merging and splitting of field edges, and manual editing of reference lines in the headlands. Acknowledged beneficial features include reduced expenditures on time and wasted resources and support for planning spraying paths. Given its complexity, most farmers preferred specialists to operate the system rather than operating it themselves. Future development should aim for simpler operation and full support for interactive coverage planning as well as computational optimization

Using Semantic Web technologies to Improve Accesibility to SDI's

In this paper we will focus on the use of semantic web technologies to support easy, user-oriented access to SDIs, and on the specific issues that occur because of the spatial nature of data. A key-register for the soil and subsurface domain is being set up to provide access to soil and subsurface data to users with a wide variety in background and an equal large variety in vocabularies. The data models the data is stored in are defined in professional terminology. An infrastructure was designed and developed, that provides a semantic shell on top of an OpenGIS based spatial data store for soil and subsurface information. A first version of a web application (BRON portal) has been developed to support (end) users to pose a query related to the soil and subsurface domain in the language of their own specific domain (e.g. environment, agriculture, hydrology) and to their level of expertise (e.g. professionals, policy-makers, inexperienced). The semantic shell translates user questions to the underlying datasets terminology with the use of a domain ontology and relevant information is retrieved from a catalogue. The relevance of the retrieved information can be evaluated by the users based on the metadata and by previewing the spatial dataset (available as a service) in a map viewer. In the future, the portal also needs to provide functionality for disclosing individual features of the datasets (as WFS). Querying these datasets by building an ontology guided query will be a challenge