1. External. It's the individual user view of data. Different levels of users may have different view of the same database. Normally, the end user do not care about the subset if the database.
2. Conceptual. It's the enterprise user view of the whole enterprise. It's the most stable of all three views. The database includes all the information and conceptial view is the community view of the database.
3. Internal. It's about the actual physical data storage. There're 3 apects should be considered: allocation of storage,access paths, miscellaneous. Thus, the efficiency of data is important for this level.
Three-Schemes Architecture
DBMS Software:
IntelliVIEW It's an analytics and reporting end-to-end solution for enterprise. The enterprise can create report by IntelliVIEW Designer, and analyze the report by IntelliVIEW Report Analyzer. The software provides a mix for traditional reporting.
Arbutus Connect It's a solution for data access. The software connect the Windows, web and server applications to non-relational data sources
CONNX It's a data access, integration, and management tools . It helps the company extend the value and life of the existing systems. It provides SQL for access to both relational and non-relational data sources.
Reference
WikiAnswers (2008) Descripe the architecture of a DBMS in terms of 3 schema architecture?
http://wiki.answers.com/Q/Descripe_the_architecture_of_a_DBMS_in_terms_of_3_schema_architecture
Capterra (2009) Database Management Software Finder
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