Assembling Cloud-Based Geographic Information Systems: A Pragmatic Approach Using Off-the-Shelf Components - Cloud Computing with e-Science Applications - page 148

Cloud Computing with E-science Applications
Client
Map Control
(Interactive map objects layers)
WKT to Map Plugin Object Parser
(Converts WKT geometric objects such as points and polygons into
appropriate map plugin objects)
Cloud
Web Server (s)
Web Service
(Spatial Data as WKT)
Entity Framework Model
(Spatial Data in WKT, represented as string objects in the models)
Database Server(s) /Cluster
(Spatial Data as Geometry)
FIGURE 7.2
Data representation in the system. Note that our system exchanges data using the Open
GIS Consortium's WKT (Well Known Text) format. (Redrawn from Yonggang Wang, Sheng
Wang, and Daliang Zhou. In Cloud Computing , vol. 5931 of Lecture Notes in Computer Science ,
pages 322-331. Berlin: Springer-Verlag, 2009.)
controls. In addition, the Entity Framework Model in the web application does
not typically support geometry or geography data types. To address this issue,
there has to be a data representation or format for spatial data that can be easily
exchanged between the DBMS geometry/geography data types, the map con-
trol objects, and the appropriate data types in the Entity Framework Model. The
Open GIS Consortium's WKT (well-known text) and WKB (well-known binary)
spatial data formats have been defined to enable such data exchange [19].
Figure 7.2 shows the representation of spatial data in different formats at
different stages of the system, designed to deal with the data incompatibility
problem. It is clear from the figure that the spatial data in the database will
be held in the geometry format as it is easy to convert it into WKT format
using built-in SQL functions.
The Entity Framework Model presents the spatial data in WKT format
to the application and text, and it is stored as a string in the entities. The
web service also deals with spatial data in WKT. One of the most important
elements here is the WKT to the map object parser, which converts WKT
data into appropriate map objects and vice versa. There is no direct way to