Towards a Specification-based Quality Guarantee for Geo Raster Web Services

Geo raster web services provide access to detailed and rich sets of geospatial information used in multidisciplinary earth system science research, such as solar, atmosphere, ocean, cryosphere, solid earth, and biosphere research. However, the heterogeneity of services deployed in these disciplines tends to weaken the interoperability of today’s highly multidisciplinary earth system science research. Several syntactical and semantic approaches have been investigated, such as similarity assessment, inconsistency resolution and standardization, to overcome this heterogeneity obstacle. Among them, standardization is a promising approach, which has the potential to achieve interoperability by combing methods of best practices and making them generally accepted within communities at large. Families of geo service standards have been developed and maintained by international organizations, such as the Open Geospatial Consortium (OGC) and the International Standardization Organization (ISO). To ensure the interoperability of implementations which claim to adhere to those standards, conformance testing programs have been set up by some of the standardizing bodies. For instance, the OGC has set up a conformance testing program with open test for each OGC standard. This constitutes a more comprehensive conformance testing in the field of geo web services than human inspection and closed source approaches. The approach follows a specification-based black box approach. This approach organizes specification requirements as assertions and groups them by functional modules. However, there is no methodology to coherently classify these assertions; neither the maturity of derived tests nor their completeness can be proven based on this approach. The goal of this thesis is to establish a model to evaluate an existing standardization approach and to evaluate the extent to which the specification itself supports the evaluation of confidence in service implementations, tests and test results. We propose a Request Parameter Relationship Analysis approach to master service testing complexity and maturity. Deductive reasoning is used to address reference output adoption according to the corresponding conditional statements and service facts. By addressing the relations among individual conformance statements, we propose the integrated dependency and goal model. We present a sequential evaluation schedule and prove the stable status in an isolated testing environment. These approaches provide a basis for analyzing service compliance, test maturity, and the validity of global statements. As our study example, we use the OGC WCS standard series as it offers a suitably formalized model for conformance testing. These approaches are applied to a real-life application, concretely testing the OGC WCS 2.0 geo service standard. The outcomes of this thesis contribute to the development of specifications, services and test suites for several standards whose normative conformance tests are specified using our approach. As a result, improved interoperation of geo raster web services under evolving implementations is expected in the future.