GeoInfo - 2006 Interoperability through Web Services: Evaluating OGC Standards in Client Development for Spatial Data Infrastructures Leonardo Lacerda Alves Clodoveu A. Davis Jr. Information Systems Lab - PUC Minas
Introduction Interoperability between GIS Translation Format standardization Direct interchange: OWS specifications Interoperability using Web Services Industry standards: SOAP, WSDL, XML, etc Spatial Data Infrastructures (SDI) Support to the sharing of efforts to implement and maintain GIS
Background Spatial Data Infrastructures Mainly NSDI Web Services Generic standards to support services OGC Services Mostly for NSDI, while there are a few experiences involving LSDI
Motivation Urban GIS The same set of OGC services, however they are executed in particular ways Urban GIS diffusion requires high-quality and provider-independent GIS clients Additional services can be designed, considering the specific needs of urban users
Our Proposal To assess the role of SOA on the implementation and diffusion of LSDI To evaluate how adequate is the current OWS framework to implement GIS and LSDI clients
Our Proposal (2) To implement a prototype of SDI and GIS using existing urban data To evaluate how adequate are OGC Web services in a real urban context To investigate whether there are any OGC requisites that are not achieved in the development of clients for accessing geographic services
Methodology Definition of a real-world scenario based on an urban context Implementation of a services prototype following OGC's abstract model Assessment of the engineering guidelines for server and client development Composition of infrastructure services to solve existing limitations
Implementation Scenario Starting Point
Implementation Scenario (2) Starting Point Destination Point
Implementation Scenario (3) Starting Point Interest Points Destination Point
Implementation Scenario (4) Starting Point Route Destination Point Chosen Interest Point
Example Servers and Clients
Implemented OGC Services OpenLS Geocoder Service Route Service Web Feature Service Web Catalogue Service Web Map Service
Identified Limitations Design and Development of Servers Design and Development of Clients Thin Clients Thick Clients Rich Clients
Proposed Non-OGC Services Data Exchange Service (DXS) Client Access Service (CAS) Transaction Control Service (TCS)
Data Exchange Service
Data Exchange Service
Client Access Service Figure 1. Delayed-time communication
Client Access Service Figure 2. Client with valid IP Figure 3. Client with no valid IP
Transaction Control Service Abstract: High-level proc = init (mylocation pointofinterest) query Generic: Adapted to LSDI Specific: Adapted to a Device/Client Address a = teleco.getaddressbytel(...,dxs) or coassociation.getaddress(...,dxs) or tourismguide.getaddress(...,dxs) or break; Location l = cityhall.geocoder(dxs.id(a),dxs);
Conclusions In order to become practical for urban use, OGC Web services need to be reinforced with additional features Current limitations would place a large burden on thin and rich clients, such as the ones used in mobile computing
Main results Evaluation of OWS and OpenLS to develop clients Identification of interoperability limitations on generic clients OGC's Abstract Model only Infrastructure services for urban GIS and easier development of GIS clients
Contributions Transparent development of clients: thick, rich, and thin Failure tolerance without overload on the client-side Client may create service chains easier A step forward in a high-level and declarative definition of services
Future Work Clients as GI providers Support of Critical Mission Applications Automatic discovery of GeoSpatial Services A testbed to further studies about privacy, performance, security, and so on
GeoInfo - 2006 Interoperability through Web Services: Evaluating OGC Standards in Client Development for Spatial Data Infrastructures Leonardo Lacerda Alves leonardo@lacerda.eti.br Clodoveu A. Davis Jr. clodoveu@pucminas.br