Use Cases

The following use cases were defined as part of the IFC for GIS project and were used to drive the creation of additional capabilities within IFC.

uc_apply_regulations_or_applications

Captures planning applications that are in place for a physical property or construction and the regulations and waivers (discretionary approvals) that are applicable to an area, a physical property or a construction.

uc_approve_base_model

Provides an approval for the base information provided on top of which the current situation and future planning can be developed. Note that the base model in this case is considered to be equivalent to the base map in current 2D approaches.

uc_check_existing_buildings

Provides for additional information on existing buildings where this cannot be directly derived (or in addition to that which can be directly derived). Additional information provided through this use case is particularly relevant for capturing information in the third dimension within an otherwise 2D representation.

uc_define_allowed_area

Defines the boundary limits of an area within a physical property or other external space within which construction is allowed and provides a test to ensure that an allowed is actually located within the boundary area determined for the containing physical property.

uc_define_coordinate_system

Defines the coordinate system in which coordinates used within a file or database are expressed.

uc_define_footprint

This use case shows the area of ground that is either:

• put forward as being intended for a proposed construction,
• proposed as a modification of an existing construction,
• agreed (fixed) as the actual area for construction,
• used for an actual/completed construction,
• marks the area of a construction that has been removed

uc_define_gis_flow_segment_representation

Consider where an element of a distribution system (of whatever type) is to be represented in a map. The representation of a flow element (and ultimately, it’s grouping within a system) has somewhat different requirements to the specification of a flow segment within an AEC/FM representation. In particular, GIS representations are significantly topological rather than geometric. That is, they show the path and point connection of system elements and not their geometry.

uc_define_grid

Specifies the requirements for the definition and display of a Cartesian grid on a map.

uc_define_land_parcel

Determines the boundary line of a land parcel, to propose changes to a boundary line that already exists and to accept/reject a boundary line or proposed changes. The boundary line of a land parcel is the ‘cadaster’ and requires that the individual lines forming the contiguous boundary be defined and identified. Such lines delineate legal boundaries and ownership.

uc_define_land_use_space

Defines the boundary limits of an area of land having certain properties with regard to its use or restriction of use or physical aspects.

uc_define_line_of_sight

Defines the line of sight from an access road exit onto a public road.

uc_define_map_space

Defines the spatial extents within which geographical information captured within IFC is appropriate. This is to determine equivalence with the concept of a map in geographic terms.

uc_define_services_access

Defines and locates the means of gaining access to relevant points on distribution services for the purposes of inspection and maintenance.

uc_define_survey_points

Defines an array of survey points within a defined area and allocates their X, Y and Z coordinates. Each survey point is given an identifier.

uc_derive_façade_slab_distance

Derives the distance between a point on a façade where it overhangs a foundation slab and a point on the foundation slab.

uc_determine_property_area

Used to determine and allocate the gross and net area of a property. This information is required for existing properties (on the situation map) and should also be identified for new properties (on the situation plan).

uc_display_contour_lines

Displays a contour as a line of constant elevation on a map.

uc_find_distance

Determines the actual physical distance between a construction of interest and a main power distribution cable or the actual physical distance between two constructions.

uc_identify_property_and_construction

Used to determine if an identifier has been assigned to a property or construction and, if not, to ensure that an identification is given. In the case of a construction, it is also determined whether the identifier given is a temporary identifier.

uc_locate_construction

Provides a test to ensure that a construction or proposed construction is actually located within the allowed area for construction for the containing physical property.

uc_place_2d_spatial_shape

This is a general use case that is used for all situations where a 2D spatial shape representation is required. That is, it can be used in geographic information for the specification of construction footprints, external spaces within a land parcel or on a construction site, land parcels, and other geographic spaces.The specification of shape is regardless of whether adjoining shapes have contiguous (shared) boundary entities or are allowed to overlap.

uc_propose_distribution_services

Defines and locates proposed distribution services on a map (situation plan).

uc_set_construction_status

Sets the status of a building or construction in terms of whether it is existing, proposed new construction, proposed modification to an existing construction or planned for removal.

uc_set_north

Sets the north direction for a project or for a geographic map. Within the context of a model, this information is given as a direction relevant to the coordinate context given for the project or map.

uc_set_utilization_extent

For a given property, regulations may specify the maximum percentage area that can be allocated for a construction. This use case allows for assignment of the information defining the percentage area.

uc_show_construction

Used to show all buildings and constructions. It is used for both above ground constructions and below ground constructions, the designation of above/below ground being determined by provision of elevation coordinates.

uc_show_distribution_services

Defines and locates existing distribution services on a map (base map, situation map or situation plan). Distribution services in this context are considered to include the provision of systems up to their point of entry into a construction.

uc_show_geographical_element

Describes features or geographic elements within a map or plan. In this use case, the term geographic element is used to distinguish the idea from features used in geometric modelling. However, the term feature is used with GIS software applications.

uc_show_parking_space

Shows parking spaces that are available or that are proposed for a physical property. The use case deals not only with individual parking spaces, but also with multiple parking spaces that may be required for a proposed construction, including the provision of parking aisles (i.e. aisles giving access to parking spaces) and parking areas (e.g. car parks). It also takes into account parking spaces for bikes and motor bikes.

uc_show_roof

For a particular physical property, determines and captures the area of the roof.

Two roof areas are dealt with in this use case

1. The area of the roof projected onto a 2D horizontal plane which is relevant for massing studies and simplified representations.
2. The total face area of the roof taking into account all individual parts which are relevant

uc_show_terrain

Describes the surface shape of the terrain within an area based on survey information that identifies the elevation of the ground at a set of points.