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33
Enterprise
Data Warehouse (e.g., Oracle)
L Marketing
ET Systems
MS Access
(Department ODB
Application) C (A Transform
PI) ETL
OD
BC
(A PI ) L
System A's Data ET
Subset of Customer Data
Census
Data
System B's Data
Web
Services Marketing
Analyses
GIS Web GIS
Server
Spatial
Data
Manager
World Wide Web System C's Data Replication
Processes
GIS Data
GIS Data Mart
Replicated
GIS Data Mart
Remote GIS
Desktop / Mobile
Application
Figure 4-2. Data access and integration.
Data Oriented Integration Techniques Web services can be written which access the data in the
warehouse as needed by web users. The web interface and
· File transfer web services are designed such that the data organization
· Extract, transform, and load (ETL) and required access are hidden from the web user.
· Data replication Web services logically unify disparate data sources where
necessary.
Software or Service Oriented Integration Techniques RPC/API integration involves one system that supplies in-
formation via a call from another system. RPCs and APIs de-
· Web services fine how external applications can call a system and specify
· Remote procedure call integration/application program- what information it wants returned from the system. RPCs
ming interface (RPC/API) and APIs are often provided by a commercial application
and can be provided by custom applications.
File transfers are simple data exchanges where a file from Each integration methodology has advantages and disad-
the source data mart is directly consumed by the target data- vantages. In practice, multiple methods will often be used to
base/data warehouse, or the source system writes a file in a interact with the data warehouse or with specific source/
specific format for the target database/system to consume. In target systems that participate in the warehouse. Figure 4-2
some cases, the source file is copied and placed in another depicts various data access methods using the data warehouse
location for the target system to use. as a central repository.
The ETL method uses data extraction from the source data
mart, processing of the data to transform it into the format
Implementing Enterprise Data
expected by the target system, and then loading the resulting
Management and Integration
data into the target database.
Data replication involves a more sophisticated source and This section describes a strategy and a process for data
target database management system. The data in the source management and integration that will result in more and bet-
system can be replicated for use in a target system. Updates to ter data being available for marketing and other functions
the data can be made in both systems. Changes originating in within the organization. Following this strategy would bene-
one system will be synchronized in the other. fit most of the transit organizations interviewed and would
