What are in the Catalog

There are two kinds of objects defined in the Catalog.   They are:

Data objects are the objects that are diagnosed by the Catalog Doctor.  Let us first look at an overview of the data objects in the Catalog:

A connection defines the raw database information from which the Catalog gets the raw data.  For example, it specifies the driver such as JDBC-ODBC Bridge, the Data Source name (when the driver is a JDBC-ODBC bridge), the user ID, and the password for connecting to the raw data.   As the figure illustrated above, the Connection is the gate to the raw database.

Mapped objects of tables or views in the raw database that a connection refers to.

Mapped objects have mapped names that are probably different from their names in the raw database.  The Catalog stores the information about the real tables/views mapped, such as the name, qualifier, and owner, etc.

Since tables/views are only mapped objects, they could be mapped and remapped.   That is, the information of the real tables/views stored in the catalog is changeable.  This is useful when you change the connection,  from an Access database to an Interbase, you only need to re-map all the tables/views in the catalog rather than creating a new       catalog.

Mapped objects of columns in the raw database that the table/view refers to.  We will refer to the fields of a table/view in the Catalog as DB-Fields.

You can specify a new name for the fields (mapped field names)which is different from the name of the real columns in the raw database.

Fields store information (such as column name, SQL type etc.) about the real columns they map to.

Fields can also be mapped and remapped.

A Parameter is a variable whose value is an input value at the run time.  Please refer to the document on Catalog for more information.

Formula and summary are objects to be computed at the run time.  They only depend on the information from DB-Field and Parameter, rather than the real columns that DB-Fields refers to.  So formulas and summaries are independent from the raw database.  This means when a connection is changed ( from Access database to Interbase ), you don’t need to re-create the formulas and summaries.  However, if you re-map a DB-Field, formula and summary will generate errors.

DB-Field, formula,summary as well as parameter are all called mapping fields.  They share the same naming domain.

Query is a higher-level object in the Catalog.  Its concept is similar to that in the database.  The columns a query can select include DB-Field, formula, and computed column.  The table/view it can select from are mapped tables/views defined in the Catalog.  So the query is also independent from the raw database too.  Please refer to the Catalog document for more detailed information on the Query object.

As illustrated by the figure above, data objects in the Catalog are constructed one after another:  In a Query the Connection is the basic object, the Table/View comes next, and then comes the DB-Field together with the Parameter, and then the Formula together with the Summary.  In other words, the changes of a Formula won’t change the validity of any DB-Field, but it may change the validity of a Query.  It is extremely important to know how the Catalog Doctor works.