Data Modelling

Data modelling is a phrase used to describe the tools and the process of identifying entities required for a database, the relationship between those entities and the attributes of those entities. In fact data modelling is all of the processes required for the design of the database prior to building it. Data modelling tools include:

 

 

Data dictionaries: A data dictionary is a comprehensive description of each field in a database set out in a table. A data dictionary would normally include a field name, data type (text {this includes numbers that are read like text such as telephone numbers}, numeric {these are numbers that could potentially be added or subtracted}, Boolean, date, time, currency), field size (and optionally, a description of that field) Schematic Diagrams: these are tools, which enable the database designer to create a graphical layout of the database showing entities, attributes and relationships. They help to identify which data should be included and to normalise the data used. Normalisation of data: This is the process of organising data into tables so that the results are unambiguous and leads to a reduction in data redundancy. First Norm Form (1NF)- moving data into separate tables where each table holds similar data in order to remove redundancy. Each table is given a primary key. This is the most common form. Domain/key Normal Form (DKNF): a key uniquely identifies each row. A domain is the set of permissible values for each attribute. Enforcing key and domain name restrictions ensures there are no problems in modifying data. DKNF is a final level of normalisation that most designers aim to achieve.