Interoperability through Web Services: Evaluating OGC Standards in Client Development for Spatial Data Infrastructures

Transcrição

1 GeoInfo 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

2 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

3 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

4 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

5 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

6 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

7 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

8 Implementation Scenario Starting Point

9 Implementation Scenario (2) Starting Point Destination Point

10 Implementation Scenario (3) Starting Point Interest Points Destination Point

11 Implementation Scenario (4) Starting Point Route Destination Point Chosen Interest Point

12 Example Servers and Clients

13 Implemented OGC Services OpenLS Geocoder Service Route Service Web Feature Service Web Catalogue Service Web Map Service

14 Identified Limitations Design and Development of Servers Design and Development of Clients Thin Clients Thick Clients Rich Clients

15 Proposed Non-OGC Services Data Exchange Service (DXS) Client Access Service (CAS) Transaction Control Service (TCS)

16 Data Exchange Service

17 Data Exchange Service

18 Client Access Service Figure 1. Delayed-time communication

19 Client Access Service Figure 2. Client with valid IP Figure 3. Client with no valid IP

20 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);

21 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

22 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

23 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

24 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

25 GeoInfo Interoperability through Web Services: Evaluating OGC Standards in Client Development for Spatial Data Infrastructures Leonardo Lacerda Alves [email protected] Clodoveu A. Davis Jr. [email protected]