What functions should be performed by ideal DDL ?

An ideal DDL should perform the following functions :

1. It should identify the types of data division such as data item, segment, record and data-base file.
2. It should give a unique name to each data-item-type, record-type, file-type, database and other data subdivision.
3. It should specify the proper data types.
4. It should specify how the record types are related to make structures.
5. It may define the type of encoding the program uses in the data items (binary, character, bit, string etc.). This should not be confused with the encoding employed in physical representation.
6. It may define the length of the data items.
7. It may define the range of values that a data-item can assume.
8. It may specify means of checking for errors in the data.
9. It may specify privacy locks for preventing unauthorized reading or modification of the data.
10. A logical data definition should not specify addressing, indexing or searching techniques or specify the placement of data on the storage units, because these topics are in the domain of physical, not logical, organization.