ISPRS, Vol.34, Part 2W2, “Dynamic and Multi-Dimensional GIS”, Bangkok, May 23-25, 2001 
Service-ID 
Location 
Páramete 
& Type 
• Type 
Input 
data 
schema 
table 
Output 
data 
schema 
table 
Data Schema Table: 
Field-ID 
Type 
Available 
operators 
Constrains 
Type 
Table 1 Data model for services 
Data service is specified by its identification, location of the 
service provider (i.e. URL), parameters available to the service, 
category of the service and the data set. Function service uses 
a similar data structure as data service, with an additional 
column that specify the schema of its output data. Data schema 
table specifies the data input to a service, this is particularized 
by operators and corresponding constraints. A single data set 
corresponds to a record in the table. The table is used for the 
input data to a data service and for both input and output data 
for function service as well. 
6. APPLICATION EXAMPLES 
This section gives an application example to illustrate the 
operation of the proposed Spatial Information Marketplace. 
Supposes that there are two data service providers and one 
function service providers in the Marketplace. Information of the 
catalog is shown as below: 
Service Table (Data service): 
Service-ID 
Location 
Parameter & 
Type 
Type 
Data 
schema 
table 
A 
http://a.com 
(Return, string) 
Data 
1 
B 
http://b.com 
(Return, string) 
Data 
2 
Service Table (Function service) 
Serv 
ice-l 
D 
Locati 
on 
Parameter, 
& Type 
Type 
Input 
data 
schema 
table 
Output 
data 
schema 
table 
C 
http:// 
c.com 
(Color, Look 
up Table) 
eMapping 
3 
4 
Data Schema Table 1: 
Field-ID 
Type 
Available 
operators 
Constrains Type 
X 
Real 
Equal, <, > 
10000-30000 
Y 
Real 
Equal, <. > 
10000-30000 
Zoom level 
Integer 
Equal 
1-8 
Language 
String 
Equal 
Chinese / 
English 
Data Schema Table 2. 
Field-ID 
Type 
Available 
operators 
Constrains Type 
Address 
String 
Equal 
No + Street + 
Building Name 
Language 
String 
Equal 
Chi / Eng 
Zoom level 
Integer 
Equal 
1 - 10 
Data Schema Table 3: 
Field-ID 
Type 
Available 
operators 
Constrains Type 
~X1 
Real 
Equal 
10000 - 30000 
Y1 
Real 
Equal 
10000-30000 
X2 
Real 
Equal 
10000-30000 
Y2 
Real 
Equal 
10000 - 30000 
Land Use 
String 
Equal 
A, B, C, D, E, All 
Data Schema Table 4: 
Field-ID 
Type 
Available 
operators 
Constrains Type 
Filename 
Image 
NA 
NA 
Suppose the requesting language is implemented using Active 
Server Page (ASP) in the Marketplace. Structure of the RSL is 
known as: 
Data service: 
http://sericeprovide.asp?”Service=”&”Name of Service 
provider” & “Data” & “Operantl” & ”Operator1” & “Constraint 
1" & “Parameter” & “Parameter Type 1” & “Value 1” 
Service, Data and Parameter are the keywords to delimitate the 
three components of a statement of the language. Within the 
component of Data, each filtering element is grouped by three 
elements: “Operant", "Operator", and “Constraint”. 
Function service: 
http://sericeprovide.asp?”Service=”&”Name of Service 
provider” & “Data" & “Operantl” & "Operatorl” & “Constraint 
1” & “Output Data” & “Operantl” & "Operatorl” & 
“Constraint 1” “Parameter" & “Parameter Type 1” & “Value 
1” 
There are three requests to the services and the corresponding 
RSL statements are: 
Request 1: 
Retrieve the map at X=1000 and Y=2000, zoom level at 5, 
language is English, and return the map in Shape file format. 
Requesting language 1: 
http://a.com/mapquervservice.asp?”Service-’&’’a”&"Data”&’’X" 
&”-’&”1000”&"Y”&’’=’’&”2000”&”ZoornLever&’’=”5”&”Lanquaqe” 
&"="Enqlish"&”Parameter”&”Retum”="Shape” 
Request 2: 
Retrieve the map with address “123, ABC Street”, language is 
English, and return the map in JPEG format. 
Requesting language 2: 
http://b.com/mapquervservice.asp?”Service=”&"b"&”Data”&”Ad 
dress”&"="&"123 ABC Street”&”Lanquaqe”&"=”&”English”&’’P 
arameter”&”Return”&’-"&”jpq” 
Request 3 
Product the Land Use map for area within (1000, 1000) and 
(2000,2000). Draw the map based on a lookup table 
(lookuptable.txt). Return the map as “landuse.jpg” 
Requesting language 3: 
http://c.com/functionservice. asp?Service=”c’’&”lnputData”&"X1 
1000”&“Y1 ”&"="&”1000''&“X2"&"="&”2000”&“X2"&”=”&” 
2000"&”Landuse”&”=”&"AH"&"Parameter”&"Color”&"=”&“lookup 
table.txt”&”OutputData"&"landuse.jpg” 
7. CONCLUSIONS 
Spatial Information Marketplaces will be the most popular way 
of using GIServices in near future. The approach not only 
provides actual economic benefits to both users and vendors of 
GIS, but also follows the mainstream in information technology 
(IT). This paper describes the architecture for the marketplace, 
as well as a data model and requesting language for generic 
services. The authors concludes the paper by giving key 
technical barriers in the development of the Spatial Information 
Marketplaces: 
• Multiple server structure: Current standard in geographic 
information interoperation is not comprehensive enough 
for the use in the Spatial Information Marketplace. For 
example, OGC is now investigating the cascading server 
for multiple WMS server structure, this approach is not