Class Definitions Introduction
The classes and their definitions appearing within the NHS data standards logical data model are listed in alphabetical order.
Each listed class contains a 'Description' tab that link to its nationally agreed definition, an 'Attributes' tab that links to a list of its attributes, a 'Relationship' tab that links to a list of its relationships it has with other classes and a 'Data' tab if a data element also exists for it.
The 'Where Used' tab provides a list of all the Model View, Central Return and Data Set diagrams that the class is included in. Each diagram is a sub-set of the logical data model but does not contain an exclusive set of classes. Thus the same class can appear in more than one diagram.
Each attribute name or class name which appears in the definition text, attribute list or relationships is in uppercase. Where the name also appears in blue indicates that it is clickable and if clicked on will display the definition for that class or attribute. In the same way, if a 'data' tab is present and clicked on then the information for the data element will be displayed.
The following information may be shown against an attribute:
|Keys||The unique identifier of an class element may include one or more attributes. These are known as key attributes and are shown with 'K' before the attribute name. Attributes are sequenced with the key attributes first. |
|Optionality||Optional attributes are those which may not exist for all occurrences of the class. For example, the END DATE of a CONSULTANT EPISODE (HOSPITAL PROVIDER) will not be known until the episode is finished. They are marked with an 'O' before the attribute name.|
The following information is shown for each relationship:
|Keys||The unique identifier of a class may include one or more relationships to other classes. These are indicated by 'K' before the relationship description. Relationships are sequenced with the key relationships first. |
|Description||The nature of the relationship is indicated by 'must be' if the relationship is mandatory and by 'may be' if the relationship is optional. ||Where relationships from one class to others are mutually exclusive, then 'or' appears at the beginning of the description between the second and subsequent exclusive relationships. Mutually exclusive relationships are shown on diagrams by a short straight line cutting across the relationship.|