MWG Tags

The Metadata Working Group (MWG) recommends techniques to allow certain overlapping EXIF, IPTC and XMP tags to be reconciled when reading, and synchronized when writing. The MWG Composite tags below are designed to aid in the implementation of these recommendations. As well, the MWG defines new XMP tags which are listed in the subsequent tables below. See http://www.metadataworkinggroup.org/ for the official MWG specification.

MWG Composite Tags

The table below lists special Composite tags which are used to access other tags based on the MWG 2.0 recommendations. These tags are only accessible when explicitly loaded, but this is done automatically by the exiftool application if MWG is specified as a group for any tag on the command line, or manually with the -use MWG option. Via the API, the MWG Composite tags are loaded by calling "Image::ExifTool::MWG::Load()".

When reading, the value of each MWG tag is Derived From the specified tags based on the MWG guidelines. When writing, the appropriate associated tags are written. The value of the IPTCDigest tag is updated automatically when the IPTC is changed if either the IPTCDigest tag didn't exist beforehand or its value agreed with the original IPTC digest (indicating that the XMP is synchronized with the IPTC). IPTC information is written only if the original file contained IPTC.

Loading the MWG module activates "strict MWG conformance mode", which has the effect of causing EXIF, IPTC and XMP in non-standard locations to be ignored when reading, as per the MWG recommendations. Instead, a "Warning" tag is generated when non-standard metadata is encountered. This feature may be disabled by setting $Image::ExifTool::MWG::strict = 0 in the ExifTool config file (or from your Perl script when using the API). Note that the behaviour when writing is not changed: ExifTool always creates new records only in the standard location, but writes new tags to any EXIF/IPTC/XMP records that exist.

Contrary to the EXIF specification, the MWG recommends that EXIF "ASCII" string values be stored as UTF-8. To honour this, the exiftool application sets the default internal EXIF string encoding to "UTF8" when the MWG module is loaded (but this setting does not change automatically via the API).

A complication of the MWG specification is that although the MWG:Creator property may consist of multiple values, the associated EXIF tag (EXIF:Artist) is only a simple string. To resolve this discrepancy the MWG recommends a technique which allows a list of values to be stored in a string by using a semicolon-space separator (with quotes around values if necessary). When the MWG module is loaded, ExifTool automatically implements this policy and changes EXIF:Artist to a list-type tag.

Tag Name WritableDerived FromValues / Notes
City Y IPTC:City
XMP-photoshop:City
XMP-iptcExt:LocationShownCity
CurrentIPTCDigest
IPTCDigest
 
Copyright Y EXIF:Copyright
IPTC:CopyrightNotice
XMP-dc:Rights
CurrentIPTCDigest
IPTCDigest
 
Country Y IPTC:Country-PrimaryLocationName
XMP-photoshop:Country
XMP-iptcExt:LocationShownCountryName
CurrentIPTCDigest
IPTCDigest
 
CreateDate Y EXIF:CreateDate
EXIF:SubSecTimeDigitized
IPTC:DigitalCreationDate
IPTC:DigitalCreationTime
XMP-xmp:CreateDate
CurrentIPTCDigest
IPTCDigest
("creation date of the digital representation" - MWG)
Creator Y+ EXIF:Artist
IPTC:By-line
XMP-dc:Creator
CurrentIPTCDigest
IPTCDigest
 
DateTimeOriginal Y EXIF:DateTimeOriginal
EXIF:SubSecTimeOriginal
IPTC:DateCreated
IPTC:TimeCreated
XMP-photoshop:DateCreated
CurrentIPTCDigest
IPTCDigest
("creation date of the intellectual content being shown" - MWG)
Description Y EXIF:ImageDescription
IPTC:Caption-Abstract
XMP-dc:Description
CurrentIPTCDigest
IPTCDigest
 
Keywords Y+ IPTC:Keywords
XMP-dc:Subject
CurrentIPTCDigest
IPTCDigest
 
Location Y IPTC:Sub-location
XMP-iptcCore:Location
XMP-iptcExt:LocationShownSublocation
CurrentIPTCDigest
IPTCDigest
 
ModifyDate Y EXIF:ModifyDate
EXIF:SubSecTime
XMP-xmp:ModifyDate
CurrentIPTCDigest
IPTCDigest
("modification date of the digital image file" - MWG)
Orientation Y EXIF:Orientation
1 = Horizontal (normal)
2 = Mirror horizontal
3 = Rotate 180
4 = Mirror vertical
5 = Mirror horizontal and rotate 270 CW
6 = Rotate 90 CW
7 = Mirror horizontal and rotate 90 CW
8 = Rotate 270 CW
  
Rating Y XMP-xmp:Rating  
State Y IPTC:Province-State
XMP-photoshop:State
XMP-iptcExt:LocationShownProvinceState
CurrentIPTCDigest
IPTCDigest
 

MWG Regions Tags

Image region metadata defined by the MWG 2.0 specification. These tags belong to the ExifTool XMP-mwg-rs group, and as such they may be accessed without the need to load the MWG Composite tags above. See http://www.metadataworkinggroup.org/ for the official specification.

Tag Name WritableValues / Notes
RegionInfo struct --> MWG RegionInfo Struct
(called Regions by the spec)
RegionAppliedToDimensions struct_ --> Dimensions Struct
(RegionsAppliedToDimensions)
RegionAppliedToDimensionsH real_ (RegionsAppliedToDimensionsH)
RegionAppliedToDimensionsUnit string_ (RegionsAppliedToDimensionsUnit)
RegionAppliedToDimensionsW real_ (RegionsAppliedToDimensionsW)
RegionList struct_+ --> MWG RegionStruct Struct
(RegionsRegionList)
RegionArea struct_+ --> Area Struct
(RegionsRegionListArea)
RegionAreaD real_+ (RegionsRegionListAreaD)
RegionAreaH real_+ (RegionsRegionListAreaH)
RegionAreaUnit string_+ (RegionsRegionListAreaUnit)
RegionAreaW real_+ (RegionsRegionListAreaW)
RegionAreaX real_+ (RegionsRegionListAreaX)
RegionAreaY real_+ (RegionsRegionListAreaY)
RegionBarCodeValue string_+ (RegionsRegionListBarCodeValue)
RegionDescription string_+ (RegionsRegionListDescription)
RegionExtensions struct_+ --> MWG Extensions Struct
(RegionsRegionListExtensions)
RegionFocusUsage string_+ (RegionsRegionListFocusUsage)
'EvaluatedNotUsed' = Evaluated, Not Used
'EvaluatedUsed' = Evaluated, Used
'NotEvaluatedNotUsed' = Not Evaluated, Not Used
RegionName string_+ (RegionsRegionListName)
RegionSeeAlso string_+ (RegionsRegionListSeeAlso)
RegionType string_+ (RegionsRegionListType)
'BarCode' = BarCode
'Face' = Face
'Focus' = Focus
'Pet' = Pet

MWG RegionInfo Struct

Field Name WritableValues / Notes
AppliedToDimensions Dimensions --> Dimensions Struct
RegionList MWG RegionStruct+ --> MWG RegionStruct Struct

MWG RegionStruct Struct

Field Name WritableValues / Notes
Area Area --> Area Struct
BarCodeValue string  
Description string  
Extensions MWG Extensions --> MWG Extensions Struct
FocusUsage string  
Name string  
Type string  
SeeAlso string  

MWG Extensions Struct

This structure may contain any top-level XMP tags, but none have been pre-defined in ExifTool. Since no flattened tags have been pre-defined, RegionExtensions is writable only as a structure (eg. {xmp-dc:creator=me,rating=5}). Fields for this structure are identified using the standard ExifTool tag name (with optional leading group name, and/or trailing language code, and/or trailing # symbol to disable print conversion).

Field Name WritableValues / Notes
[no tags known]

MWG Keywords Tags

Hierarchical keywords metadata defined by the MWG 2.0 specification. These tags belong to the ExifTool XMP-mwg-kw group. ExifTool unrolls keyword structures to an arbitrary depth of 6 to allow individual levels to be accessed with different tag names, and to avoid infinite recursion. See http://www.metadataworkinggroup.org/ for the official specification.

Tag Name WritableValues / Notes
KeywordInfo struct --> MWG KeywordInfo Struct
(called Keywords by the spec)
HierarchicalKeywords struct_+ --> MWG KeywordStruct Struct
(KeywordsHierarchy)
HierarchicalKeywords1Applied boolean_+ (KeywordsHierarchyApplied)
HierarchicalKeywords1Children struct_+ --> MWG KeywordStruct Struct
(KeywordsHierarchyChildren)
HierarchicalKeywords2Applied boolean_+ (KeywordsHierarchyChildrenApplied)
HierarchicalKeywords2Children struct_+ --> MWG KeywordStruct Struct
(KeywordsHierarchyChildrenChildren)
HierarchicalKeywords3Applied boolean_+ (KeywordsHierarchyChildrenChildrenApplied)
HierarchicalKeywords3Children struct_+ --> MWG KeywordStruct Struct
(KeywordsHierarchyChildrenChildrenChildren)
HierarchicalKeywords4Applied boolean_+ (KeywordsHierarchyChildrenChildrenChildrenApplied)
HierarchicalKeywords4Children struct_+ --> MWG KeywordStruct Struct
(KeywordsHierarchyChildrenChildrenChildrenChildren)
HierarchicalKeywords5Applied boolean_+ (KeywordsHierarchyChildrenChildrenChildrenChildrenApplied)
HierarchicalKeywords5Children struct_+ --> MWG KeywordStruct Struct
(KeywordsHierarchyChildrenChildrenChildrenChildrenChildren)
HierarchicalKeywords6Applied boolean_+ (KeywordsHierarchyChildrenChildrenChildrenChildrenChildrenApplied)
HierarchicalKeywords6 string_+ (KeywordsHierarchyChildrenChildrenChildrenChildrenChildrenKeyword)
HierarchicalKeywords5 string_+ (KeywordsHierarchyChildrenChildrenChildrenChildrenKeyword)
HierarchicalKeywords4 string_+ (KeywordsHierarchyChildrenChildrenChildrenKeyword)
HierarchicalKeywords3 string_+ (KeywordsHierarchyChildrenChildrenKeyword)
HierarchicalKeywords2 string_+ (KeywordsHierarchyChildrenKeyword)
HierarchicalKeywords1 string_+ (KeywordsHierarchyKeyword)

MWG KeywordInfo Struct

Field Name WritableValues / Notes
Hierarchy MWG KeywordStruct+ --> MWG KeywordStruct Struct

MWG KeywordStruct Struct

Field Name WritableValues / Notes
Applied boolean  
Children MWG KeywordStruct+ --> MWG KeywordStruct Struct
Keyword string  

MWG Collections Tags

Collections metadata defined by the MWG 2.0 specification. These tags belong to the ExifTool XMP-mwg-coll group. See http://www.metadataworkinggroup.org/ for the official specification.

Tag Name WritableValues / Notes
Collections struct+ --> MWG CollectionInfo Struct
CollectionName string_+ (CollectionsCollectionName)
CollectionURI string_+ (CollectionsCollectionURI)

MWG CollectionInfo Struct

Field Name WritableValues / Notes
CollectionName string  
CollectionURI string  

(This document generated automatically by Image::ExifTool::BuildTagLookup)
Last revised Jul 22, 2013

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