Provides the database schema encapsulation.
Package Specification
The classes in this package provide a database independent abstraction 
of database access for a variety of catalogs.
 
To provide an alternative implementation for an existing catalog, you
need to:
  - extend the {@link org.griphyn.vdl.dbschema.DatabaseSchema} class.
  
- implement the appropriate {@link org.griphyn.vdl.dbschema.Catalog} 
    child interface.
To provide an addition catalog implementation, you need to extend the 
{@link org.griphyn.vdl.dbschema.Catalog} interface. In the next step, 
you will need to provide an implementation as before.
Currently, several concrete catalogs are implemented in Chimera:
  - The Provenance Tracking Catalog {@link org.griphyn.vdl.dbschema.PTC}
  
- The Virtual Data Catalog {@link org.griphyn.vdl.dbschema.VDC}
  
- An extension of the VDC {@link org.griphyn.vdl.dbschema.Advanced}
  
- Joining attributes to Virtual Data objects {@link org.griphyn.vdl.dbschema.Annotation}
Related Documentation
For overviews, tutorials, examples, guides, and tool documentation,
please see:
@see org.griphyn.vdl.dbdriver
@see org.griphyn.vdl.annotation