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7 Prerequisites
7.1 Schema Validation
Tools for XML Schema validation are available and give reliable results. Hence schema validation was not considered a major task for the CityGML QIE, although well-formed
XML document data is required as input for most validation tools.
Schema related problems with the CityGML structure, such as the order of elements in sequences, were not discussed. For example, the order of child elements is different for
_AbstractBuilding in LOD 2 and LOD 3, A change request for the next version of CityGML is suggested cf Section 11.5.
7.2 Definition of a Solid according to ISO 19107
ISO 19107 defines geometric primitives for geodata. A Solid definition is derived from this standard to describe geometric validation criteria of volumetric CityGML objects in
detail. The full definition can be found in Annex A.
7.3 System for encoding of data quality requirements
Suggestions how data quality requirements should be specified in CityGML or in addition to CityGML were discussed and evaluated. The following approaches were
considered.
Add data-quality based conformance requirements that are more prescriptive in a future version of the CityGML standard.
Give additional guidance for implementation in a particular community in documentation separate from the CityGML standard profiling, adding
constraints, documenting conventionsbest practice, implementers’ agreements. Add additional metadata to CityGML modeling constructs used. This could be
implemented in a future version of the CityGML standard or as an Application Domain Extension.
7.4 Specification of data quality requirements and requirement identifiers
For clarity, a validation criteria coding system needs to be defined. Note that every single validation criterion is called a requirement in this document.
The coding system uses the following structure: XX-namespace:YY-ZZZZ
XX is the domain identifier. The following values are allowed:
Copyright © 2015 Open Geospatial Consortium.
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value description
SC Schema Requirements
CO Conformance Requirements
GE Geometry Requirements
SE Semantic Requirements
RI Referential Integrity
YY is the element identifier. It defines the CityGML element upon which the requirement operates. The following values are allowed NB: this is just a first step and needs to be
extended in the future:
value description
bldg:AB Abstract Building bldg:BU Building specific to Building in addition to Abstract Building
bldg:BP Building Part specific to BuildingPart in addition to Abstract Building bldg:BS BoundarySurface
bldg:WS WallSurface bldg:GS GroundSurface
bldg:RS RoofSurface bldg:OFS OuterFloorSurface
bldg:OCS OuterCeilingSurface gml:SO Solid
gml:MS MultiSurface gml:PO Polygon
gml:LR Linear Ring
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ZZZZ is the requirement identifier for the element in the given domain. These identifiers need to be defined by each working group. For example, for conformance requirements,
the identifiers could simply be the number of the conformance requirement from the standard.
7.5 Error codes for geometric errors
