diff --git a/BDNS_Specification_naming_syntax.md b/BDNS_Specification_naming_syntax.md
index 7972114..6a25350 100644
--- a/BDNS_Specification_naming_syntax.md
+++ b/BDNS_Specification_naming_syntax.md
@@ -111,8 +111,65 @@ For BIM workflows, the validation procedure shall include the following tests:
 
 `[A-Za-z0-9_$]{22} `([IFC base 64](https://standards.buildingsmart.org/IFC/DEV/IFC4_2/FINAL/HTML/schema/ifcutilityresource/lexical/ifcgloballyuniqueid.htm) format)
 
+### Device/Asset type (asset.type)
 
 
+#### Definition
+
+The device or asset type is a human-generated identifier that is unique for a type of assets to the building. It combines a standard abbreviation for device/asset types and a numerical ID that is unique to each specific device/asset type.
+
+#### Originator
+
+Generated by the BIM operator, design team, project team or facilities team, depending on project stage.
+
+#### Format
+
+```
+<X><Z>
+```
+
+where:
+
+`X `= <type_abbreviation> (alphabetic characters only, variable length, between 2 and 6 characters)
+
+`Z `= <asset_type_incremental_number> (variable length, unique integer numbers by asset type in each building, non zero padded)
+
+The type abbreviation shall be according to the [Building Device and Asset Abbreviation Registry](https://github.com/theodi/BDNS/blob/master/BDNS_Abbreviations_Register.csv).
+
+The format is composed of a 2 to 6 uppercase alphabetical characters long type abbreviation according to the name abbreviation (`X`) and a variable length character numeric sequence that is unique to the building (`Z`) for each asset type. No leading zeros are allowed in the asset type incremental number to avoid ambiguity.
+
+Only uppercase alphabetic characters and numeric characters are allowed, according to the regular expression below. There is no separator character between the type abbreviation and the incremental number for the `asset.type`.
+
+If there is only one asset type per abbreviation, the asset type incremental number can be omitted.
+
+#### Examples
+
+Asset type example for a lighting fixture asset type: `LT3`
+
+Asset type example for an air handling unit asset type: `AHU10`
+
+Asset type example for a distribution board asset type: `DB7`
+
+Asset type example for a lighting fixture asset type when there is only one type: `LT`
+
+Asset type example for an air handling unit asset type when there is only one type: `AHU`
+
+Asset type example for a distribution board  asset type when there is only one type: `DB`
+
+
+#### Validation tests
+
+The validation procedure shall include the following tests:
+
+1. Regular expression matching to validate the name format.
+2. Uniqueness of the name across all asset types in the building.
+
+##### Regular expression matching
+
+```
+[A-Z]{2,6}(?:[1-9][0-9]*)?
+```
+
 ### Device/Asset role name (asset.name)
 
 
@@ -130,12 +187,22 @@ Generated by the BIM operator, design team, project team or facilities team, dep
 <X>-<Y>
 ```
 
+or
+
+```
+<XZ>-<Y>
+```
+
 where:
 
 `X `= <type_abbreviation> (alphabetic characters only, variable length, between 2 and 6 characters)
 
 `Y `= <building_unique_incremental_number> (variable length, unique integer numbers by building, non zero padded)
 
+`Z `= <asset_type_incremental_number> (variable length, unique integer numbers by asset type in each building, non zero padded)
+
+The use of the `Z` field is optional, only in case there is a need to include `asset.type` definitions.
+
 The type abbreviation shall be according to the [Building Device and Asset Abbreviation Registry](https://github.com/theodi/BDNS/blob/master/BDNS_Abbreviations_Register.csv).
 
 The format is composed of a 2 to 6 uppercase alphabetical characters long type abbreviation according to the name abbreviation (`X`) and a variable length character numeric sequence that is unique to the building (`Y`). No leading zeros are allowed in the building unique incremental number to avoid ambiguity.
@@ -153,6 +220,11 @@ Name example for an air handling unit: `AHU-3`
 
 Name example for a distribution board: `DB-2`
 
+Name example for a lighting fixture including an asset type: `LT3-375`
+
+Name example for an air handling unit including an asset type: `AHU10-46`
+
+Name example for a distribution board including an asset type: `DB3-21`
 
 #### Validation tests
 
@@ -165,10 +237,9 @@ The validation procedure shall include the following tests:
 
 
 ```
-[A-Z]{2,6}-[1-9][0-9]*
+[A-Z]{2,6}(?:[1-9][0-9]*)?-[1-9][0-9]*
 ```
 
-
 ## Physical device/asset labels
 
 Physical device/asset labels shall contain the following items:
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