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Modelling Databases

Figure 1 shows the types of metadata that describe databases.

Figure 1

Figure 1: Database metadata

The structure of a database schema consist of a number of database tables and database views. The difference is that the database table has its values stored in the database whereas the database view is a set of values that are derived from accessing other database tables using a query.

The structure of both the database tables and database views are describes by database columns.

Database columns have a types that represent a single value. This can be stored, or derived using a query. If the column presents the unique for a row within the table, it can be decorated with the PrimaryKey classification. If a column contains values that are the primary key of another table then the two columns can be linked using the ForeignKey relationship.

Figure 2 shows the open metadata types used to represent the metadata created through this service.

Figure 2

Figure 2: Database open metadata types for databases

A database schema is represented using the DeployedDatabaseSchema entity, the database table is represented using the RelationalTable entity and the database column is represented using the RelationalColumn entity. A database view is a RelationalTable entity with the Calculated Value classification attached.

If a DatabaseManager is defined, any Database created is automatically linked to it using the ServerAssetUse relationship. When a DeployedDatabaseSchema is created for the Database, the service automatically inserts the DataSetContent relationship. (The database schema is a DataSet over the database which is a type of DataStore).

When a RelationalTable is created for the DeployedDatabaseSchema, the service automatically inserts the Schema relationship, RelationalDBSchemaType entity and AttributeForSchema relationship in between the DeployedAPI entity and the RelationalTable entity.

The SchemaType for a RelationalTable is RelationalTableType. The schema attributes for RelationalTable and RelationalColumn also use the TypeEmbeddedAttribute classification method for defining the schema type.

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