Terminology

Definitions

This terminology area gives definitions and examples of the specialist terms commonly used within the DNF documentation.

The DNF Expert Group reserves the right to modify definitions if there is a strong case for doing so.

Term Definition
Abstraction Process of selecting only those Real World Objects and the Attributes and behaviours of those objects which are relevant to a particular application
Application Reference Layer Aggregation of Application Reference Objects forming a partial or complete coverage of an area. Example Notes
Example

Index of land title extents
Notes

Need not exhaust space nor have national coverage
Application Reference Object Geographic Object which is referenced by a Business Object in an application. The Application Reference Object can refer to one to many DNF Reference Objects Example Notes
Example

Basic Land & Property Unit (BLPU) in a land & property gazetteer; a street in a highways maintenance application.
Notes

Class or instance depends on the context, assume class unless otherwise stated
Attribute Property of a class of objects Notes
Notes

By convention attributes are named. An instance within a class can hold a value within a defined range of values. In the case of a geographic object attributes may describe, for example, the geometrical, topological, or thematic characteristics
Business Object Object which is processed by an application and needs to be located relative to a Geographic Object Example Notes
Example

EXAMPLE Planning application referenced to a land parcel, census record referenced to a house, ecological record referenced to a Site of Special Scientific Interest
Notes

Business is used a wide sense here to relate to any data and objects which are non-geographic. It is not specific to commercial data and can relate to any data such as environmental data that needs to be located
Coordinate Reference Position of a Geographic Object given using coordinates Example
Example

National Grid Eastings and Northings
Cross-Referencing Mechanism for holding links between objects which may be expressed through the use of identifiers. Example
Example

The Unique Property Reference Number (UPRN) of a Basic Land and Property Unit (BLPU) cross-referenced to an OS MasterMap Topographic Area
Data Quality Element Component of the information used in documenting the quality of a dataset Example
Example

Positional accuracy
Data Quality Schema Model used to define and relate the Data Quality Elements
Digital National Framework (DNF) Industry standard for integrating and sharing business and geographic information from multiple sources
DNF Ancillary Geometry Lines or areas used to qualify the relationship between an Application Reference Object and a DNF Reference Object where the spatial relationship is not coterminous. Example Notes
Example

Additional line geometry created where a title extends beyond the physical boundary of a land parcel as represented by the DNF Reference Object
Notes

The geometry must be compatible with that of the DNF Reference Base and snap to it

DNF Association The relationship between an Application Reference Object and one-to-many DNF Reference Objects. Notes
Notes

This is a spatial relationship which can be simply expressed through cross-referencing or with more complexity. It may be qualified by the addition of other attributes and metadata and may include DNF Ancillary Geometry
DNF Coordinate Position Point on the Earth's surface defined by a coordinate value derived using a Spatial Referencing System Using Coordinates and used in the context of DNF Notes
Notes

May be a two or three dimensional coordinate
DNF Positioning System System for referencing position in time and space in the DNF Reference Base
DNF Reference Base Framework of reference made up of DNF Reference Objects which occupy the area of interest and to which Application Reference Objects may be related
DNF Reference Framework Aggregation of DNF Reference Base and Application Reference Layer
DNF Reference Object Geographic object that forms part of the DNF Reference Base which may be referenced by other objects. Notes
Notes

Currently, DNF Reference Objects are derived from OS MasterMap Topography but they could be derived from other sources
DNF Reference Object Geometry Representation of a DNF Reference Object as geometric primitives (points, lines and areas) defined by coordinates based on a recognised spatial referencing system Notes
Notes

If the DNF Reference Object is derived from OS MasterMap then the spatial referencing system will be based on the National Grid
DNF Topographic Identification Scheme Scheme for identifying Geographic Objects used in a DNF context
DNF Unique Identifier Means of uniquely identifying Geographic Objects using a registered prefix and a local identifier which can be used in a DNF context
Feature Abstraction of real world phenomena Notes
Notes

1 A feature may occur as a type or an instance. Similar instances of particular phenomena can classified together as a type 2 Object is used in preference to feature in DNF except in reference to data classification and feature cataloguing where the term
Feature Catalogue Catalogue containing definitions and descriptions of classes of geographical objects or Feature types Notes
Notes

Feature and object regarded as synonymous in this context
Geographic Object Abstraction or application view of a real world object which has a fixed and identifiable location on the Earth's surface Example Notes
Example

Building, street, land parcel
Notes

Typically represented in data by points, lines or areas

Geometry Primitive Geometric object representing a single, connected part of space e.g. point, line or polygon
Geometry Type Class of geometry Example
Example

Point, Line, Area
Information Service Any system that operates on DNF Reference Objects, Application Reference Objects or Business Objects
Location Identifiable geographic place
Metadata Element Component of information used in documenting the metadata of a dataset, Feature or object
Metadata Schema Model used to define and relate the Metadata Elements used to document data resources
OSMM Topographic Object Geographic Object that is derived from a subset of Feature class instances in OS MasterMap Topography where these are abstractions of real world objects Notes
Notes

Not all instances of all feature classes in OS MasterMap Topography are candidate objects
Position Point fixed in relation to the Earth's surface which is defined by coordinates Notes
Notes

Coordinates may describe the position in two or three dimensions
Real World Object Something which has existence, whether concrete or otherwise, and is definable in some way through its attributes and behaviour. Notes
Notes

In the context of DNF real world objects will usually refer to Geographic Objects or Business Objects. Whereas the former will have a concrete existence, the latter may not be tangible objects e.g. a planning decision
Reference Relating of business information to defined Geographic Objects which can be uniquely identified by address, set of characters or position Notes
Notes

This is a specialisation of a general term when used in a DNF context

Representation In the context of DNF, the depiction of a Geographic Object using Geometric Primitives defined by coordinates based on a Spatial Referencing System Using Coordinates Notes
Notes

Other forms of representation are possible such as images but these are currently not within scope of DNF
Spatial Referencing System Using Coordinates Means of locating objects on the earth’s surface using coordinates
Standard Reference Object Geographic Object that forms part of a reference base with a maintained coverage to a consistent national specification.
Taxonomy System of classification of things
Temporal Reference System Means of date and time referencing

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