The value of Object Type Library (OTL)

Knowing how, when, and what decisions were taken and who has responsibility for them, is of crucial importance to any infrastructure project.

An OTL, Object Type Library, is the unambiguous description of built environment concepts – both physical and spatial - from which this information is derived.

The contents of an OTL apply to the entire lifecycle of a project and include all sub-sectors in construction and groundwork, both residential and non-residential building, as well as the spatial (geo) environment.

Definition OTL:

Defining OTL, the INTERLINK report Information Management for European Road Infrastructure using Linked Data | Investigating the Requirements’ (final issue: March 31, 2017) states:

‘An object type library (OTL) is a library with standardised object-types names (e.g. road, viaduct) and properties or specifications. An object is described with its object-type data, geometry data and metadata, Metadata are data (or information) about the data of objects. Metadata are needed because each object type has its own properties. How the object types are grouped is called an ontology. The OTL can be linked to a data dictionary, with the definitions of object-types.’

Within an OTL, assets are described with the standardised language, syntax and semantics required for a reliable information exchange.

Example of an OTL:

Using the Millau Viaduct cable-stayed bridge in France as an example of an object type. An instance of this object type would be a data object carrying the relevant data about this bridge (see image).

The relevant object type data for such a bridge would depend on who is looking for the information:

• For a designer, it could be the number of pylons, the number of spans, the spans lengths and the deck material.
• A contractor may find a web link to a construction specification.
• For an asset manager, the relevant data could be the expected residual life of the structure and the time to the next inspection of the bearings.
• For the bridge inspector, it could be the access route for inspecting the pylons.

Objects can carry or reference graphical data, non-graphical data and metadata. An example of metadata for the Millau Viaduct object could be when and by whom the object data was last revised.

The OTL defines the data structure and the variables to be populated at different stages of an asset's life, often in the context of associated open data standards.

Examples of OTL are:

• CB-NL, Concepten Bibliotheek (Concept Library), BIR Bouw Informatie Raad (Building Information Council, The Netherlands.
• OTL-Rijkswaterstaat, The Netherlands, can be found at: https://otl.rws.nl/publicatieomgeving.
• OKSTRA, ObjektKatalog für das STRaßen- und Verkehrswesen, Germany.