oSIST prEN ISO 7817-3:2026

SLOVENSKI STANDARD
01-april-2026
Informacijsko modeliranje gradenj - Raven informacijskih potreb - 3. del:
Podatkovni model in shema (ISO/DIS 7817-3:2026)
Building information modelling - Level of information need - Part 3: Data model and
schema (ISO/DIS 7817-3:2026)
Bauwerksinformationsmodellierung - Informationsbedarfstiefe - Teil 3: Datenmodel und
Schema (ISO/DIS 7817-3:2026)
Modélisation des informations de la construction (BIM) - Niveau du besoin d’information -
Partie 3: Modèle de données et schéma (ISO/DIS 7817-3:2026)
Ta slovenski standard je istoveten z: prEN ISO 7817-3
ICS:
35.240.67 Uporabniške rešitve IT v IT applications in building
gradbeništvu and construction industry
91.010.01 Gradbeništvo na splošno Construction industry in
general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
International
Standard
ISO/DIS 7817-3
ISO/TC 59/SC 13
Building information modelling —
Secretariat: SN
Level of information need —
Voting begins on:
Part 3: 2026-02-10
Data model and schema
Voting terminates on:
2026-05-05
ICS: 35.240.67; 91.010.01
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Reference number
ISO/DIS 7817-3:2026(en)
DRAFT
ISO/DIS 7817-3:2026(en)
International
Standard
ISO/DIS 7817-3
ISO/TC 59/SC 13
Building information modelling —
Secretariat: SN
Level of information need —
Voting begins on:
Part 3:
Data model and schema
Voting terminates on:
ICS: 35.240.67; 91.010.01
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2026
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
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Published in Switzerland Reference number
ISO/DIS 7817-3:2026(en)
ii
ISO/DIS 7817-3:2026(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Level of information need data schema structure . 2
4.1 General .2
4.2 UML representation of the level of information need structure .3
4.2.1 Specification .5
4.2.2 Prerequisites .5
4.2.3 Georeferencing .5
4.2.4 Specification per object type .6
4.2.5 Object type .6
4.2.6 Alphanumerical information and integration with data template structure (ISO
23387).6
4.2.7 Geometrical information.7
4.2.8 Documentation.7
5 XML representations . 8
Annex A (informative) Usage guide . 9
Annex B (informative) XSD representation .20
Annex C (informative) XML examples .28
Annex D (informative) Sematic web implementation .39
Bibliography .40

iii
ISO/DIS 7817-3:2026(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO [had/had not] received notice of
(a) patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 59, Buildings and civil engineering works;
Subcommittee SC 13, Organization and digitization of information about buildings and civil engineering
works, including building information modelling (BIM), in collaboration with the European Committee
for Standardization (CEN) Technical Committee CEN/TC 442, Building Information Modelling (BIM), in
accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
A list of all parts in the ISO 7817 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
ISO/DIS 7817-3:2026(en)
Introduction
The objective of the level of information need is to define the concepts and principles related to the level of
information need in a structured way.
For a better integration and interoperability between software products and supported workflows, there
is a need for a standardised schema to specify the level of information need according to parts 1 and 2 of
this standard series and in line with ISO standard series 19650, 12006, and 29481, as well as ISO 23386 and
23387.
With this goal in mind, a machine-interpretable representation of the level of information need must be
provided to allow for a vendor-neutral exchange of the specified requirements including the specification of
the relationships between object types within a breakdown structure and the subsequent alphanumerical
information, geometrical information and documentation.
This schema consistently structures information requirements in information containers and databases
and allows the coherent definition of web services. It makes it easier to combine different sets of information
requirements from different actors and across all phases of the life cycle of built assets. It also supports
automated checks of the delivered information against the specified requirements, therefore supporting
the creation, exchange and compliance activities of exchange information requirements in line with the
ISO 19650 series and the ISO 29481 series. The developed schema is applicable on a wide range of exchange
data formats. It can be used in conjunction with the vendor-neutral data exchange format industry
foundation classes (IFC), established in ISO 16739-1, as well as vendor-specific ones, and standards from
other domains, such as CityGML.
With a standardised schema, all stakeholders can exchange specifications of the level of information need
in a structured, interoperable and reproducible yet flexible way. This provides all appointments with a
standardised approach for verification and validation, making the process less error-prone, less time-
consuming and reducing misinterpretations.
The target audience of this document includes:
— Software developers, for embedding the data structure in software, platforms and other applications
— Built environment sector domain experts appointed to describe required information
— Small and medium enterprise practitioners that can use the defined schema and embed it in available
tools for reuse
— Sector practitioners, as they provide the required information
— Authorities, as they review and check relevant submissions
— Research and development personnel, as they support the innovation and continuous development of the
level of information need
— Educational institutions, as the concepts of level of information, information management, and digital
information principles should be merged into education and training programs
— Real estate agents and developers (asset owners), as they need a clearer vision on needed information of
built assets, hence including the level of information need as part of tender documents.

v
DRAFT International Standard ISO/DIS 7817-3:2026(en)
Building information modelling — Level of information
need —
Part 3:
Data model and schema
1 Scope
This document specifies a data model in Unified Modeling Language (UML) and a derived Extensible Markup
Language (XML) schema definition (XSD) for defining the level of information need in software applications
based on concepts and principles given in ISO 7817-1, guidance given in ISO/TS 7817-2, and in compliance
with the principles and data exchange standards of data templates (ISO 23387).
This document defines the exchange format schema in XSD according to the UML data model. It gives
guidelines for the usage and application of the schema.
This document provides the concept of level of information need developed to enable machine interpretability
based on a standardized data structure, carrying information requirements used in the life cycle of assets.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 7817-1, Building information modelling — Level of information need — Part 1: Concepts and principles
ISO/TS 7817-2:2026, Building Information Modelling – Level of information need – Part 2: Guidance for
application
ISO 23387:2025, Building information modelling (BIM) — Data templates for objects used in the life cycle of
assets
ISO 23386:2020, Building information modelling and other digital processes used in construction — Methodology
to describe, author and maintain properties in interconnected data dictionaries
Methodology to describe, author and maintain properties in interconnected data dictionaries
ISO 12006-3:2022, Building construction — Organization of information about construction works — Part 3:
Framework for object-oriented information
ISO 9000:2015, Quality management systems — Fundamentals and vocabulary
ISO 19111:2020, Geographic information — Referencing by coordinates
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 7817-1, ISO/TS 7817-2, ISO 23387,
ISO 23386, ISO 12006-3, ISO 9000, ISO 19111 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp

ISO/DIS 7817-3:2026(en)
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
Document
information and the medium on which it is contained.
[SOURCE: ISO 9000:2015, 3.8.5]
EXAMPLE A door schedule is required within a project.
3.2
Object type
Representation of objects that share common properties.
Note 1 to entry: Using this standard, an object type determines the properties and constraints that apply to all objects
classified under it.
Note 2 to entry: In the context of object-oriented modelling, an object type corresponds conceptually to a “class”.
3.3
Specification
Container element stating requirements following the level of information need schema definition.
[SOURCE: ISO 9000:2015, modified: Exchanged “document” for “container element” and added “following
the level of information need schema definition”]
3.4
Specification per object type
specification (3.3) for an object type (3.2).
Note 1 to entry: Specification per object type elements outline geometrical, alphanumerical and documentation
requirements for specific object types.
EXAMPLE The dimensionality and specific properties can be defined for an object type such as Wall. The object
type has a reference to a dictionary to indicate which classification system the object type belongs to.
4 Level of information need data schema structure
4.1 General
The level of information need data schema is designed to represent the concepts and principles of level
of information need in a machine-readable and structured format. This standard defines the level of
information need data schema using an XML schema definition.
The schema includes a standard XML header. To allow re-usability of data types defined in ISO 23387, the
respective XML schema is imported.
The structure of the level of information need data schema consists of a root element called level of
information need. This element may have one to many (1.*) specification elements. The specification
element consists of the elements prerequisites, georeferencing and specification per object type. The
specification per object type element may have one object type element, as well as one optional element to
describe the alphanumerical information. It also consists of one optional documentation element and one
optional geometrical information element.
Note 1 The object type element used in this schema is defined in ISO 23387. This element is adopted to avoid
inconsistencies by describing object types in varying ways across the industry.
The alphanumerical information also adopts elements from the data structure for data templates described
in ISO 23387 and ISO 12006-3. The adopted elements are property, quantity kind, group of properties,
reference document, dimension and unit. All elements are optional (0.*). Therefore, the alphanumerical

ISO/DIS 7817-3:2026(en)
information element acts as a container for properties and groups of properties relating to a specified object
type.
Note 2 The specification per object type, object type, property, quantity kind, dimension, unit, and group of
properties elements in the level of information need schema extend the concept type element from ISO 23387. This
element requires a date of creation attribute, which shall always use the ISO 8601 datetime format.
The documentation element may have zero to many (0.*) required documents. It should be used to describe
the documentation needed for the object type defined within the specification per object type element.
The geometrical information consists of the elements detail, dimensionality, location, appearance and
parametric behaviour. It should be used to describe the geometrical information needed for the object type
defined within the specification per object type element.
The structure of the level of information need structure is shown in the UML model in Figure 1.
4.2 UML representation of the level of information need structure
The level of information need structure representation in Figure 1 uses UML. Figure 1 provides modelling
rules for concepts and their relationship.

ISO/DIS 7817-3:2026(en)
Figure 1 — UML diagram of the level of information need data model

ISO/DIS 7817-3:2026(en)
4.2.1 Specification
The specification element acts as a container for the elements specification per object type, prerequisites
and georeferencing of the specification. The specification element may have many elements specification
per object type (see 4.2.4 and 4.2.5).
The root element of the level of information need may have many specification elements, thus allowing the
definition of required information for separate prerequisites.
Note 1 Varying prerequisites that lead to separate specifications may be different information delivery milestones,
purposes or varying actors.
Note 2 The level of information need data schema works with unique identifiers (UUID).
Note 3 The use of RFC 4122 is recommended.
4.2.2 Prerequisites
Prerequisites are defined in ISO 7817-1. This element acts as a container for the elements purpose,
information delivery milestone, providing actor, and receiving actor and has a UUID.
The prerequisites shall be defined to give a context to the specification, so that actors and purpose of the
required information are clear.
Note Varying prerequisites lead to separate specification elements within the level of information need data
schema. Requirements can be consolidated into one level of information need through multiple specification elements.
The element to define the purpose consists of name, definition, reference document, description, language
region, dictionary reference and UUID. All elements are optional except name and UUID, which are
mandatory.
The element to define the information delivery milestone consists of name, description, reference document,
date and UUID. Name and UUID are mandatory, while all other elements are optional.
The actors are each described by the elements role, description, address, first name, middle name, last name,
affiliation and UUID. The address is restricted to an e-mail address. All elements are optional except the role
and the UUID, which are mandatory.
4.2.3 Georeferencing
The georeferencing element is used to define the required coordinate reference system of the information
container and consists of the (0.1) elements coordinate reference system (CRS) and model coordinate
system (0.*), which are all optional. The coordinate reference system (coordinate reference system type)
element consists of the elements type, datum and vertical datum. The type (coordinate reference enum) is
an enumeration used to describe the type of CRS (projected, engineering, geographic). When the location
information is not known, the value ‘not required’ can be selected.
Example 1 When defining the location e.g., in UTM or Gauß-Krüger, the projected coordinate reference system
(ProjectedCRS) can be selected.
Example 2 When a local Cartesian coordinate reference system has been defined, the value ‘EngineeringCRS’ can
be selected.
Example 3 When defining a geographic coordinate reference system, the value ‘GeographicCRS’ can be selected.
The datum and vertical datum are both datum type elements consisting of one name (string) and one type
(datum registry reference). The datum registry reference consists of a mandatory name, description and a
registry reference (both optional).
Example For defining the datum, well known text (WKT2 according to ISO 19162:2019) or EPSG strings
(following the geodetic registry, ISO 19127:2019) or a customized name can be used.

ISO/DIS 7817-3:2026(en)
The model coordinate system element (model coordinate system type) has a Boolean element ‘is projected’
to express if the model coordinate system is projected, mapped, distorted or not. Additionally, it includes
one element first coordinate and one element second coordinate as well as height (all decimals). To express
rotation, the elements X axis abscissa and X axis ordinate (both decimals and both optional) can be used.
The scale of model to CRS units can be expressed using the unit scale element and the scale factor between
the model and CRS can be described using the horizontal scale element (decimal, optional).
4.2.4 Specification per object type
The specification per object type element is a child element of the concept type element defined in
ISO 12006-3 (5.3.15) and implemented in the ISO 23387 schema definition. The concept type element
consists of the elements name, definition, reference document reference, description, example, a ‘similar to’
reference, language of creator, country of origin, visual representation, major and minor version, status, a
‘replaced objects’ reference, deprecation explanation, dictionary reference and includes the attributes about,
GUID (refers to a UUID), and date of creation. The concept type element used in the specification per object
type is extended to include exactly one object type, optional alphanumerical information elements (0.*),
geometrical information elements (0.*) and documentation elements (0.*).
4.2.5 Object type
The object type element is a child element of the subject type element defined in ISO 12006-3 (5.3.37) and
implemented in the ISO 23387 schema definition.
4.2.6 Alphanumerical information and integration with data template structure (ISO 23387)
Alphanumerical information is defined in ISO 7817-1. This element is part of the specification per object
type.
The alphanumerical information element consists of the optional elements property, quantity kind, group of
properties, reference document, dimension and unit. These elements are defined in the ISO 23387 schema
definition and in ISO 12006-3 and adopted by the level of information need structure.
The structure defined in ISO 23387 is based on ISO 12006-3 and follows the management rules to author and
maintain properties and groups of properties given in ISO 23386. As ISO 12006-3 supports interconnections
of data dictionaries, elements from the ISO 23387 structure can be composed by concepts from different
data dictionaries. This also applies to the elements used in the level of information need structure. ISO 23387
introduces an additional Uniform Resource Identifier (URI) attribute, which can be used alongside the
UUID. The UUID is mandatory in ISO 12006-3 and may be incorporated into URIs where relevant. UUIDs
are primarily intended for internal references within a data dictionary, while URIs can serve as external
references.
The element property is a concept type according to ISO 12006-3 (5.3.29), that is extended by the mandatory
element data type, the optional element symbol, and the optional reference elements for dimension, unit,
quantity kind, dependent on, and is specialization of, as defined in ISO 23387.
The element quantity kind is a concept type according to ISO 12006-3 (5.3.30), that is extended by the
optional element dimension reference, where references (UUID, URI) can be applied.
The element groups of properties in the level of information need structure consists of the two elements
group of properties and group of properties reference. The latter allows to reference groups of properties
in existing libraries following ISO 23387. The group of properties element allows defining the properties in
the level of information need specification and grouping them. This element is an abstract element within
the ISO 23387 structure. It is a subject type according to ISO 12006-3 (5.3.37). The subject type is a child
element of the concept type element, that is extended by the elements ‘has part ref’ and ‘is subtype of ref’,
both of which are reference types. The subject type is extended by the element has property reference,
where references (UUID, URI) can be applied, as defined in ISO 23387.
The element reference document is a concept type according to ISO 12006-3, that is extended by the elements
date of publication, author, ISBN, publisher, and URI, as defined in ISO 23387.

ISO/DIS 7817-3:2026(en)
The element dimension is a concept type according to ISO 12006-3 (5.3.18), that is extended by a series of
exponents as defined in ISO 23387.
The element unit is a concept type according to ISO 12006-3 (5.3.40), that is extended by the elements
symbol (optional), dimension, scale, base, coefficient, and offset, as defined in ISO 23387.
Note ISO 23387 allows both the definition of user-defined values using the possible values element and
referencing to a dictionary elsewhere. When defining elements, e.g., properties it is recommended to either reference
an already defined property or define a new one within the level of information need specification.
4.2.7 Geometrical information
Geometrical information is defined in ISO 7817-1. This element is part of the specification per object type.
The geometrical information element consists of the optional elements detail, dimensionality, appearance,
and parametric behaviour. All elements are defined in ISO 7817-1. The provided elements allow asset owners
and users to define project-specific geometrical information.
Note 1 The description of each value may be defined separately by asset owners or national bodies.
The detail element is defined by the optional elements dictionary, shape assembly, shape representation,
shape influence and UUID. The dictionary consists of a reference (URI, UUID).
Note 2 The dictionary reference within the detail element can be used to reference established modelling
definitions by asset owners or national bodies.
The shape assembly and shape representation elements consist of an enumeration each, where one of the
values according to the decision trees established in ISO/TS 7817-2 can be selected. The shape influence
consists of the optional elements inside geometry, connections, openings, operating and clearance zones,
and features. All elements consist of an enumeration each, where one of the values according to the decision
trees established in ISO/TS 7817-2 are accepted. Actors can also define a threshold dimension as established
in ISO/TS 7817-2 for the shape influence which includes a dimension, unit and definition.
The dimensionality element is defined by an enumeration to describe the dimensionality of the required
object type using four values (0-3). The values refer to 0D-dimensional, 1D-dimensional, 2D-dimensional
and 3D-dimensional.
The absolute location information is defined in the georeferencing element, so it applies to the entire
specification it is defined for (see 4.2.3).
The relative location is described in the location element within the geometrical information, where the
position information can be selected from an enumeration and an indicative object can be given for relative
positioning.
The appearance element accepts different values to define the appearance of an object type. It consists of an
enumeration each, where one of the values according to the decision trees established in ISO/TS 7817-2 are
accepted.
The parametric behaviour element accepts the values requested and not requested, as established in
ISO/TS 7817-2.
4.2.8 Documentation
Documentation is defined in ISO 7817-1 as a set of required documents.
NOTE The intention of asking for documentation is to define the list of required documents and not to define their
content.
This element is part of the specification per object type. It relates to an object type element, an alphanumerical
information element and a geometrical information element.
The documentation element acts as a container for required documents. Required documents consist of
the elements name, reference document, description, format and have the attributes type, form, content

ISO/DIS 7817-3:2026(en)
and a UUID. All elements and attributes are optional except for the name and UUID, which are mandatory.
The reference document consists of a reference (URI, UUID). The format consists of a format name, format
version and a format definition. The format definition also consists of a reference (URI, UUID).
5 XML representations
An XML Schema Definition (XSD) is included in Annex B. Examples of XML instances based on this XSD are
included in Annex C. A usage guide is included in Annex A.

ISO/DIS 7817-3:2026(en)
Annex A
(informative)
Usage guide
This usage guide supports implementers of the level of information need XML schema. It explains the
available data structures and gives examples of how they can be used to encode the defined requirements.
The XML schema defined in the ISO 7817-3 relies heavily on the structures defined in the Data Template norm
ISO 23387. Those structures are only explained as far as necessary in this guide, so for further information
please consult ISO 23387 directly. When constructs from ISO 23387 are used in the examples below, they
are indicated with the dt prefix.
Note 1 The XML examples in this guide (Annex A) use simplified, skeletal structures with ‘.’ placeholders to clearly
show the underlying XML structure. These examples are not complete valid XML documents, but rather illustrative
templates. For complete, working examples, please refer to Annex C.
Note 2 Many elements in the level of information need schema extend dt: ConceptType from ISO 23387, which
requires a dateOfCreation attribute. Elements requiring this attribute include: SpecificationPerObjectType,
ObjectType, Property, QuantityKind, Dimension, Unit, and GroupOfProperties. It is recommended to always include
dateOfCreation="." (ISO 8601 datetime format) when creating these elements.
Fundamental data structure
The root of a level of information need document is of the LevelOfInformationNeed type, which is a container
for multiple Specification instances.
Definition example:

.
.
...

The Specification type has one Prerequisites child that defines in which context the specification
shall be applied, multiple SpecificationPerObjectType children, which contain the information about the
requirements, and an optional GeoReferencing child which provides information about the georeferencing
to be used.
Definition example:

.
.
.
.

Prerequisites
The Prerequisites element defines the context in which a level of information need specification shall be
applied. It establishes the transaction framework by specifying who needs what information, when, and
for which purpose(s). According to the schema, a level of information need specification always describes
a specific transaction between two actors (providing and receiving) for one specific purpose. These
transactions can be applied to the overall tendering process but also to sub-transactions, e.g., between a
main and sub-contractors.
ISO/DIS 7817-3:2026(en)
The Prerequisites consist of four required elements:
Purpose: Defines why the information is needed. This includes a name and optionally a definition, description,
reference documents, description, language, region, and dictionary references.
InformationDeliveryMilestone: Specifies when the information is needed. This includes a name, optional
description and reference documents, and optionally a specific date/time.
ProvidingActor: The actor who provides the information. Includes their role, and optionally name,
affiliation, description, and contact address (e-mail, restricted by a pattern).
ReceivingActor: The actor who receives the information. Same structure as ProvidingActor.
Definition example:


.


.

dt:GUID="." >
.


.


Note 1 If specifying requirements for different actors or different purposes is needed, users should create separate
level of information need Specification instances rather than trying to consolidate them into one prerequisites
element.
Note 2 Consolidation of varying prerequisites is possible in one level of information need specification through
separate specification elements.
Specification per object type
The SpecificationPerObjectType element is the core container that defines what information is required
for a specific type of object (e.g., a wall, door, or bridge abutment). It binds together the object type definition
with the three aspects of information requirements: alphanumerical, documentation, and geometrical.
Each Specification can contain multiple SpecificationPerObjectType elements – one for each type of
object that needs to be delivered. For example, a handover specification might include separate requirements
for walls, slabs, windows, doors, etc.
The structure consists of:
ObjectType: Defines which type of object these requirements apply to (required)
AlphanumericalInformation: Specifies which properties are needed (optional)
Documentation: Defines what documents must be provided (optional)
GeometricalInformation: Specifies the required geometrical aspects (optional)
Definition example:

.
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ISO/DIS 7817-3:2026(en)
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Note The SpecificationPerObjectType extends the dt:ConceptType from ISO 23387, which is why it can
have Name and Definition elements to describe the specification itself, in addition to the ObjectType it applies to.
Object Types
The ObjectType element identifies what type of object the requirements apply to. It uses the
dt:ObjectTypeType from ISO 23387, which extends the concept system and allows for rich semantic
definitions with multilingual support.
Key considerations:
— Identity: Each ObjectType should have a dt:GUID for internal referencing within the level of information
need specification.
— Definition vs. Reference: The level of information need data schema covers two main approaches:
— Inline definition: Defining the object type directly within the level of information need specification
with Name, Definition, and other metadata
— External reference: Referencing an existing object type definition from an external resource, such as
a library or standard, using dt:ReferenceDocumentRef
— Multilingual support: Object types can have multiple names and definitions in different languages, which
is essential for international projects. For further information, consult ISO 23387
— Versioning: Object types can include version information (dt:MajorVersion, dt:MinorVersion) and
status (dt:Status) to track evolution over time.
Note 1 For further information, consult ISO 23387.
Inline definition example:

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External definition example:

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dt:referenceURI=”https://identifier.buildingsmart.org/uri/buildingsmart/ifc/4.3/class/IfcC
olumn”/>
Note 2 Using dt:ReferenceDocumentRef allows linking to well-known classifications (like IFC classes, UniClass,
or other industry standards) while still maintaining its own GUID for internal references and optionally providing a
local name or additional metadata.
Alphanumerical Information
ISO/DIS 7817-3:2026(en)
The AlphanumericalInformation element specifies which properties and groups of properties are required
for the object type. It serves as a container for property requirements and their supporting definitions.
The structure can contain:
— Property: Individual properties that must be provided (inline definitions or references). Properties can
specify data types, constraints, and reference units, dimensions, and quantity kinds.
— QuantityKind: Definitions of quantity kinds (e.g., "length", "mass", "pressure") used by inline
property definitions
1 0 0
— Dimension: Physical dimension definitions (e.g., L M T for length) used by inline units and quantity
kinds
— Unit: Unit definitions (e.g., meter, kilogram) used by inline property definitions
— GroupsOfProperties: A wrapper element containing collections of related properties, either defined
inline (GroupOfProperties) or referenced externally (GroupOfPropertiesRef)
— ReferenceDocument: Links to external property dictionaries or standards (e.g., buildingSMART Data
Dictionary); Optional
Definition example:
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