# BIM Collaboration Format v2.1 Technical Documentation
- Pasi Paasiala, Solibri (BCF 1.0 / BCF 2.0 / BCF 2.1)
- Juha Laukala, Tekla (BCF 1.0)
- Lassi Lifländer, Tekla (BCF 1.0)
- Klaus Linhard, IABI (BCF 2.0 / BCF 2.1)
- Erik Pijnenburg, Kubus (BCF 2.0)
- Léon van Berlo, TNO (BCF 2.0)
Terms and Abbreviations
GUID Globally Unique Identifier: http://en.wikipedia.org/wiki/Globally_Unique_Identifier IfcGuid Globally Unique ID in the IFC format. This format is used only when referring to components in IFC files.
|BCF||BIM Collaboration Format|
|BCF file||File in BIM Collaboration Format|
|Topic||One topic, such as a problem in the design, described in BCF file|
|GUID||Globally Unique Identifier: http://en.wikipedia.org/wiki/Globally_Unique_Identifier|
- This document describes the BCF format that is used to exchange topics, such as, issues, scenes, etc. between different BIM software.
BCF file structure
A BCF file is a zip containing one folder for each topic with its file extension "bcfzip" for BCFv1.0 and BCFv2.0. The file extension "bcf" is introduced since BCFv2.1. The root of the BCF zip contains the following files.
- project.bcfp (optional)
- An XML file referencing the extension.xsd to a project. The schema for this file is project.xsd.
- An XML file following the version.xsd schema with information of the BCF schema used. The file content should be identical to the contents of bcf.version
Topic folder structure inside a BCFzip archive
The folder name is the GUID of the topic. This GUID is in the UUID form. The folder contains the following files:
- An XML file following the markup.xsd schema that is described below.
- An XML file following the visinfo.xsd schema that is described below.
- Multiple viewpoints are possible since BCF 2.0. Names of these files are not predefined. Note: One viewpoint needs to be be named viewpoint.bcfv even in the case of multiple viewpoints.
- A snapshot related to the topic (for compatibility with BCF 1.0). Multiple snapshots are possible since BCF 2.0. Names of these files are not predefined. Note: One snapshot needs to be named snapshot.png even in the case of multiple viewpoints.
Note: The elements in the XML files must appear in the order given in the schemas and described below.
Project (.bcfp) file
The project file contains reference information about the project the topics belong to.
|ProjectId||Yes||ProjectId of the project|
In addition it has the following nodes:
|Name||Yes||Name of the project.|
|ExtensionSchema||No||URI to the extension schema.|
Markup (.bcf) file
The markup file contains textual information about the topic.
Header node contains information about the IFC files relevant to this topic. It has one attribute, ProjectGuid, which is the project GUID. Header has also a list of File nodes.
Each File node has the following attributes:
|IfcProject||Yes||IfcGuid Reference to the project to which this topic is related in the IFC file|
|IfcSpatialStructureElement||Yes||IfcGuid Reference to the spatial structure element, e.g. IfcBuildingStorey, to which this topic is related.|
|isExternal||Yes||Is the IFC file external or within the bcfzip. (Default = true).|
In addition File has the following nodes:
|Filename||Yes||The BIM file related to this topic.|
|Date||Yes||Date of the BIM file.|
|Reference||Yes||URI to IfcFile.
IsExternal=false “..\example.ifc“ (within bcfzip)
Topic node contains reference information of the topic. It has one attribute, Guid, which is the topic GUID.
|Guid||No||Guid of the topic|
|TopicType||Yes||Type of the topic (Predefined list in “extension.xsd”)|
|TopicStatus||Yes||Type of the topic (Predefined list in “extension.xsd”)|
In addition it has the following nodes:
|ReferenceLink||Yes||List of references to the topic, for example, a work request management system or an URI to a model.|
|Title||No||Title of the topic.|
|Priority||Yes||Topic priority. The list of possible values are defined in the extension schema.|
|Index||Yes||Number to maintain the order of the topics.|
|Labels||Yes||Tags for grouping Topics. The list of possible values are defined in the extension schema.|
|CreationDate||No||Date when the topic was created.|
|CreationAuthor||No||User who created the topic.|
|ModifiedDate||Yes||Date when the topic was last modified. Exists only when Topic has been modified after creation.|
|ModifiedAuthor||Yes||User who modified the topic. Exists only when Topic has been modified after creation.|
|DueDate||Yes||Date until when the topics issue needs to be resolved.|
|AssignedTo||Yes||The user to whom this topic is assigned to. Recommended to be in email format. The list of possible values are defined in the extension schema.|
|Description||Yes||Description of the topic.|
|Stage||Yes||Stage this topic is part of (Predefined list in “extension.xsd”).|
BimSnippet is an additional file containing information related to one or multiple topics. For example, it can be an IFC file containing provisions for voids.
|SnippetType||No||Type of the Snippet (Predefined list in “extension.xsd”)|
|IsExternal||Yes||Is the BimSnippet external or within the bcfzip.
(Default = false).
|Reference||No||URI to BimSnippet.
IsExternal=false “..\snippetExample.ifc“ (within bcfzip)
|ReferenceSchema||Yes||URI to BimSnippetSchema (always external)|
DocumentReference provides a means to associate additional payloads or links with topics. The references may point to a file within the .bcfzip or to an external location.
|Guid||Yes||Guid attribute for identifying it uniquely|
|IsExternal||Yes||Is the Document external or within the bcfzip.
(Default = false).
|ReferencedDocument||Yes||URI to document.
IsExternal=false “..\exampleDoc.docx“ (within bcfzip)
IsExternal=true “https://.../ exampleDoc.docx“
|Description||Yes||Description of the document|
Relation between topics (Clash -> PfV -> Opening)
|RelatedTopic/GUID||Yes||List of GUIDs of the referenced topics.|
The markup file can contain comments related to the topic. Their purpose is to record discussion between different parties related to the topic. Comment has also the Guid attribute for identifying it uniquely. In addition, it has the following nodes:
|Date||No||Date of the comment|
|Comment||No||The comment text|
|Viewpoint||Yes||Back reference to the viewpoint GUID.|
|ModifiedDate||Yes||The date when comment was modified|
|ModifiedAuthor||Yes||The author who modified the comment|
The markup file can contain multiple viewpoints related to one or more comments. A viewpoint has also the Guid attribute for identifying it uniquely. In addition, it has the following nodes:
|Viewpoint||Yes||Filename of the viewpoint (.bcfv)|
|Snapshot||Yes||Filename of the snapshot(.png)|
|Index||Yes||Parameter for sorting|
Viewpoints are immutable, therefore they should never be changed once created. If new comments on a topic require different visualization, new viewpoints should be added.
Visualization information (.bcfv) file
The visualization information file contains information of components related to the topic, camera settings, and possible markup and clipping information.
The components node contains a set of Component references. The numeric values in this file are all given in fixed units (meters for length and degrees for angle). Unit conversion is not required, since the values are not relevant to the user. The components node has also the DefaultVisibility attribute which indicates true or false for all components of the viewpoint.
Components element contains the following properties.
ViewSetupHintsto describe the visualization settings that were used in the application creating the viewpoint
Selectionto list components of interest
Visibilityto describe default visibility and exceptions
Coloringto convey coloring options for displaying components
Selection element lists all components that should be either highlighted or selected when displaying a viewpoint.
BCF is suitable for selecting a few components. A huge list of selected components causes poor performance. All clients should follow this rule:
- If the size of the selected components is huge (approximately 1000 components), alert the user and give him the opportunity to modify the selection.
Visibility element states the components
DefaultVisibility and lists all
Exceptions that apply to specific components. The components in the
Exceptions have the opposite visibility than `DefaultVisibility.
BCF is suitable for hiding/showing a few components. A huge list of hidden/shown components causes poor performance. All clients should follow these rules:
- If the list of hidden components is smaller than the list of visible components: set default_visibility to true and put the hidden components in exceptions.
- If the list of visible components is smaller or equals the list of hidden components: set default_visibility to false and put the visible components in exceptions.
- If the size of exceptions is huge (approximately 1000 components), alert the user and give him the opportunity to modify the visibility.
This element contains information about the default visibility for elements of certain types (
OpeningsVisible). These flags have the following logic when applied to spaces: When a viewpoint has no spaces visible, set the value of
SpacesVisible to false. If there are any spaces visible in the viewpoint, set the value to the same as
DefaultVisibility. The DefaultVisibility flag decides whetever to export the hidden or the visible spaces. The logic applied to spaces is also applied to
The visibility is applied in following order:
- Apply the
- Apply the
- Apply the
Coloring element lists colors and a list of associated components that should be displayed with the specified color when displaying a viewpoint. The color is given in ARGB format. Colors are represented as 6 or 8 hexadecimal digits. If 8 digits are present, the first two represent the alpha (transparency) channel. For example,
40E0D0 would be the color <span style="color:#40E0D0;";>Turquoise. More information about the color format can be found on Wikipedia.
BCF is suitable for coloring a few components. A huge list of components causes poor performance. All clients should follow this rule:
- If the size of colored components is huge (approximately 1000 components), alert the user and give him the opportunity to modify the coloring.
A component has the following attributes:
|IfcGuid||No||The IfcGuid of the component|
|OriginatingSystem||Yes||Name of the system in which the component is originated|
|AuthoringToolId||Yes||System specific identifier of the component in the originating BIM tool|
This element describes a viewpoint using orthogonal camera. It has the following elements:
|CameraUpVector||No||Camera up vector|
|ViewToWorldScale||No||Scaling from view to world|
This element describes a viewpoint using perspective camera. It has the following elements:
|CameraUpVector||No||Camera up vector|
|FieldOfView||No||Camera’s field of view angle in degrees.|
FieldOfView is currently restricted to a value between 45 and 60 degrees. There may be viewpoints that are not within this range, therefore imports should be expecting any values between 0 and 360 degrees. The limitation will be dropped in the next schema release.
Lines can be used to add markup in 3D. Each line is defined by three dimensional Start Point and End Point. Lines that have the same start and end points are to be considered points and may be displayed accordingly.
ClippingPlanes can be used to define a subsection of a building model that is related to the topic. Each clipping plane is defined by Location and Direction.
A list of bitmaps can be used to add more information, for example, text in the visualization. It has the following elements:
|Bitmap||No||Format of the bitmap (PNG/JPG)|
|Reference||No||Name of the bitmap file in the topic folder|
|Location||No||Location of the center of the bitmap in world coordinates|
|Normal||No||Normal vector of the bitmap|
|Up||No||Up vector of the bitmap|
Since BCF 2.0 is compatible with version 1.0, there are some ambiguities in the implementation. The following agreements are written to clarify the implementation.
One to Many Mapping between Viewpoints and Comments
The schema would allow to have many to many mapping between viewpoints and comments. This is not allowed. A viewpoint can have multiple comments, but a comment can only refer to one viewpoint.
Status and VerbalStatus to be Phased out
Status and Verbal Status of Comment will be phased out and replaced by TopicStatus and TopicType in Topic.
When interpreting BCF 1.0 files use the following logic:
- use Status of most recent comment as value of TopicType
- use Verbalstatus of most recent comment as TopicStatus.
When interpreting BCF 2.0 or higher files: VerbalStatus and Status on comment level should all be neglected if TopicStatus and TopicType are present in Topic.
When writing BCF 2.0 or higher files:
- write the current type and status to Topic's TopicType and TopicStatus
- write Status and VerbalStatus at Comment level for backward compatibility.
.BCFZIP encoding guide
Software tool vendors are encouraged to follow the following guidelines to ensure that the .BCFZIP files produced by their software can be correctly exchanged with other tools.
Use forward slash as path separator
The forward slash (“/”) should be used as a path separator rather than the backslash (“\”). Windows developers should consult the following MSDN page when attempting to follow this guideline: https://msdn.microsoft.com/en-us/library/mt712573(v=vs.110).aspx
Create directory (folder) entries in the zip file's central directory
When creating the zip archive make sure to create directory (folder) entries in the .BCFZIP file’s central directory.
Example of a zip file with directory entries (Correct)
Archive: correctly_encoded_file_with_directory_entries.bcfzip Length Date Time Name --------- ---------- ----- ---- 217 2015-02-18 09:12 bcf.version 0 2015-02-18 09:12 bff0f7ed-6b0d-4aad-ab28-401cc1db7f6e/ 1782 2015-02-18 09:12 bff0f7ed-6b0d-4aad-ab28-401cc1db7f6e/markup.bcf 565 2015-02-18 09:12 bff0f7ed-6b0d-4aad-ab28-401cc1db7f6e/viewpoint.bcfv 181641 2015-02-18 09:12 bff0f7ed-6b0d-4aad-ab28-401cc1db7f6e/snapshot.png --------- ------- 184205 5 files
Example of a zip file without directory entries (Incorrect)
Archive: incorrect_file_without_directory_entries.bcfzip Length Date Time Name --------- ---------- ----- ---- 35525 2015-02-25 09:28 742b0df3-9a99-4da3-95ad-171e282f8122/snapshot.png 681 2015-02-25 09:28 742b0df3-9a99-4da3-95ad-171e282f8122/viewpoint.bcfv 1057 2015-02-25 09:28 742b0df3-9a99-4da3-95ad-171e282f8122/markup.bcf 119 2015-02-25 09:28 bcf.version --------- ------- 37382 4 files
How to verify
On windows 7 using 7zip and the windows command prompt
- Download and install 7zip from http://www.7-zip.org/download.html
- On the start menu type ‘cmd’ and select cmd.exe
- Execute the following:
“c:\Program Files\7-Zip\7z.exe" l $PATH_TO_BCFZIP
7-Zip  9.20 Copyright (c) 1999-2010 Igor Pavlov 2010-11-18 Listing archive: E:\BIM\bcf files\bulkExport_1topic.bcfzip -- Path = #### Path to the bcfzip file Type = zip Physical Size = 183599 Date Time Attr Size Compressed Name ------------------- ----- ------------ ------------ ------------------------ 2015-02-18 09:12:40 ..... 217 161 bcf.version 2015-02-18 09:12:40 D.... 0 0 bff0f7ed-6b0d-4aad-ab28-401cc1db7f6e 2015-02-18 09:12:40 ..... 1782 632 bff0f7ed-6b0d-4aad-ab28-401cc1db7f6e\markup.bcf 2015-02-18 09:12:40 ..... 565 336 bff0f7ed-6b0d-4aad-ab28-401cc1db7f6e\viewpoint.bcfv 2015-02-18 09:12:40 ..... 181641 181678 bff0f7ed-6b0d-4aad-ab28-401cc1db7f6e\snapshot.png ------------------- ----- ------------ ------------ ------------------------ 184205 182807 4 files, 1 folders
On Unix or Linux shell
- Start your favourite shell and execute the following:
$ unzip -l $PATH_TO_BCFZIP
Archive: /mnt/engineering/BIM/bcf files/bulkExport_1topic.bcfzip Length Date Time Name --------- ---------- ----- ---- 217 2015-02-18 09:12 bcf.version 0 2015-02-18 09:12 bff0f7ed-6b0d-4aad-ab28-401cc1db7f6e/ 1782 2015-02-18 09:12 bff0f7ed-6b0d-4aad-ab28-401cc1db7f6e/markup.bcf 565 2015-02-18 09:12 bff0f7ed-6b0d-4aad-ab28-401cc1db7f6e/viewpoint.bcfv 181641 2015-02-18 09:12 bff0f7ed-6b0d-4aad-ab28-401cc1db7f6e/snapshot.png --------- ------- 184205 5 files
Additional Document Properties
If any Xml file in an imported BCF container contains additional or unknown properties, BCF clients shall ignore them and not produce errors. This is to allow BCF implementations the freedom to add additional functionality. Client implementations are not required to preserve these properties.