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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