Since 2008, as part of a European project, we
develop a collaborative web platform dedicated to
urban facility management. Our Urban Information
Model (UIM) approach combines both BIM and GIS
using semantic modelling to access global
knowledge of a complete urban environment,
including sets of buildings and urban objects that
compose this environment. This approach is based
on a semantic architecture using ontology evolution
mechanisms (Gruber, 1993). We have developed a
specific 3D-viewer making possible semantic
management of Level of Details (LoDs) according to
user profile and context. The multi-representation
introduced in our architecture adds to the traditional
LoD the notion of Contextual LoDs (C-LoDs). A C-
LoD is not only displayed depending on the distance
between the view point and the object as it is usually
the case. The representation is chosen according to
other criteria that depend on user (like the business
process to which he is attached), external criteria as
day/night or weather, or even of the object itself.
The semantic management drives streaming
processes which extract the semantic and 3D
representations of urban objects from a relational
database.
2 SIGA3D OVERVIEW
Our proposal is based on a semantic architecture
articulated in 6 levels (Figure 1). The import/export
level is dedicated to the parsing of various file
formats required to model the UIM from different
sources (GIS/BIM). The data model level makes it
possible the combination of geometrical data and
semantics. The level "contextual view" associates
user profiles and business rules to build contextual
LoDs. The connection level is mainly dedicated to
the streaming process between the databases and the
interface. The interface level displays the urban
environment into a 3D digital mock-up coupled with
a semantic tree of urban elements.
The innovative part of this architecture is mainly
contains in the data model level and contextual
views level. This part is the base of our semantic
LoD proposal. The first data model level part is
architecture of graphs representing the ontology,
allowing the context management and versioning of
the data (CMF for Contextual Model Framework).
Graphs operators are also defining to facilitate the
implementation of changes in conceptualization.
Figure 1: SIGA3D Architecture.
Information about reference systems for space
and time (CRS and TimeZone) are also managed in
this part. The other part defines a unified syntax-
based knowledge representation based on the
languages OWL, RDFS, and rules RuleML, SWRL
and described in this document in an expressive way
with description logic. It is called DMF (Data Model
Framework). DMF also contains operators for the
management of space and time and the definition of
local contexts that allow us to conduct a multi-
representation of data. The goal of this part is to
provide models used in inference engine to infer and
to check the data modelled by the CDMF modelling
operators.
3 DATA MODEL FRAMEWORK
The Data Model Framework is made of operators to
construct urban data models. These operators allow
the description of classes and properties that can be
used to define complex concepts using operators of
intersection, union, involvement, etc ...
The spatial data and especially georeferenced
coordinates do not make sense without the
knowledge of the coordinate reference system. This
information will appear in the next layer of our
architecture that manages the context of model
graph, to unify the management of coordinates. The
same kind of information is provided for time, with
the management of Time zones (Gutierrez et al.,
2007).
The management of local contexts, which allows
multi-representation, is done in this part by defining
new stamped operators, corresponding to the dmf
operators defined above. For example, script 1
defines three local contexts, designer,
structureEngineer and achievementDate. Script 2
3DEngine
DataLayer
Semantic LayerGeometric Layer
Semantic Viewer
SIGA3DInterface
SIGA3DConnexion
Streaming
SIGA3D
Contextual Views
View ManagementTool
ProfilManagementTool
SIGA3D Data
ModelFramework
SIGA3D
Import/Export
IFCDWG/DXF/DGN/GML
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