Audiovisual Core Guide

Audiovisual Core Guide

Title: Audiovisual Core Guide

Date version issued: 2023-02-24

Date created: 2013-10-15

Part of TDWG Standard:

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Abstract: The Audiovisual Core is a set of vocabularies designed to represent metadata for biodiversity multimedia resources and collections. This non-normative document provides some background to the aims and uses of the standard.

Contributors: Robert A. Morris, Vijay Barve, Mihail Carausu, Vishwas Chavan, José Cuadra, Chris Freeland, Gregor Hagedorn, Patrick Leary, Dimitry Mozzherin, Annette Olson, Greg Riccardi, Ivan Teage

Creator: GBIF/TDWG Multimedia Resources Task Group

Bibliographic citation: Audiovisual Core Maintenance Group. 2023. Audiovisual Core Guide. Biodiversity Information Standards (TDWG).

1 Introduction

The Audiovisual Core Multimedia Resources Metadata Schema (Audiovisual Core) is a data standard for exchanging data describing biodiversity multimedia resources and collections produced by the GBIF/TDWG joint Multimedia Resources Metadata Task Group (MRTG). The standard consists of four documents. This document is a guide to the aims and uses of the standard. The Audiovisual Core Introduction document provides a brief introduction to the Audiovisual Core Standard. For detailed information about the structure of Audiovisual Core, see the Audiovisual Core Structure document. For term details, see the Audiovisual Core Terms List document.

Acronyms and named institutions and projects are listed in a Glossary in Appendix I.

1.1 Status of the content of this document

All sections of this document are non-normative.

2 Summary

The Audiovisual Core Multimedia Resources Metadata schema (“AC schema”, or simply “AC”) is a set of metadata vocabularies for describing biodiversity-related multimedia resources and collections. The specification is independent of how these vocabularies may be represented for machine use.

Multimedia Resources are digital or physical artifacts which normally comprise more than text. These include pictures, artwork, drawings, photographs, sound, video, animations, presentation materials, and interactive online media including, e.g., identification tools. A multimedia collection is an assemblage of such objects, whether curated or not, and whether electronically accessible or not. For the purposes of this document we regard a collection of multimedia resources itself as a ‘multimedia resource’. Wherever discussion or specification can apply only to a collection or only to a single media resource, we say so explicitly.

Multimedia descriptions are digital records that document underlying multimedia resources or collections. AC is focused on biodiversity-related multimedia resources. It shares terminology and concerns with many well-known and important standards for describing access to resources such as Dublin Core (DC), Darwin Core (DwC), the Adobe Extensible Metadata Platform (XMP), the International Press and Telecommunications Council (IPTC), the Metadata Working Group (MWG) schema, the Natural Collections Schema (NCD), and others. Where there is an exact match to the usage of such standards, AC adopts their identifiers and definitions. Many collections of biodiversity multimedia already have descriptions of their media expressed in DwC or DC. By using those vocabularies where suitable, AC particularly intends to make it easy for such collections to reuse their existing descriptions, augmented where necessary by other terms.

This guide accompanies the normative parts of the AC standard, which are included in two documents: one that describes the structure of the document [1] and a Term List document [2]. The Term List documents a series of terms, each of which is identified by a unique Uniform Resource Identifier (URI), together with normative definitions. In addition, the Audiovisual Core Maintenance Group may develop recommended representations for AC descriptions in several important forms including RDF [3], XML Schema [4], and Comma Separated Values (CSV) [5].

Figure 1 below augments a portion of Figure 2 of the non-normative portion of the NCD document [6]. It shows a number of kinds of biodiversity data-centric resources and illustrates typical user communities, data and metadata standards, and network services that support the discovery, analysis, and integration of data. We extracted from the NCD figure the resources and relationships between them, which we augment with three types not in the main purview of NCD. These are: Observations, Ecological Models, and the focus of this work, Multimedia Resources. Applications exploiting each kind of these resources find utility, or sometimes require the use of multimedia resources to document them. For example, the Biological Heritage Library is a project that provides scanned images of legacy literature at a far greater rate than it can provide digitized versions based on optical character recognition, and these images remain available as sources for any subsequent derived products. Thus digitized legacy literature is documented by the page images. Most scientific literature of course is also illustrated by photographs, graphs, or other artifacts in the purview of the Audiovisual Core. Even the providers of “Molecular DNA” resources sometimes will offer original data as digital images of microarray chips.

Figure 1. Relationships of Multimedia Resources to primary types of biodiversity resources

3 Audiovisual Core Terms

An Audiovisual Core record is a description, using the Audiovisual Core terms, of a multimedia resource. Two kinds of terms are specified by AC: record-level terms and access-level terms. Record-level terms apply to the media resource being described. Almost all terms are record-level terms. One such term, serviceAccessPoint plays a special role in helping to retrieve the resource that the record describes. A multimedia resource may have more than one serviceAccessPoint, each of which is described by values of one or more access-level terms. The access-level terms provide such things as a web address at which a digital representation of the resource can be retrieved, the size of such a retrieved object, etc.

An Audiovisual Core record is thus a set of terms that conforms to the normative documents, contains at least the four mandatory terms described below, and which provides metadata that describes a single multimedia resource (possibly including a Collection). It usually includes an identifier that may have been assigned to the resource by an external authority or by the provider of the metadata record.

Every Audiovisual Core term has a plain text Name, a URI, and a plain text normative Definition. Terms may also have Usage instructions explaining how the term is used in the context of Audiovisual Core and Notes that provide additional information and examples. URIs for terms conform to the http URI scheme. Informally, one may understand this thusly: an http URI has the syntax of an http URL, but there is no expectation that putting it in a web browser will result in any information being returned to the browser, and if it does, the return may have no relevance.

Because http URIs are rather lengthy, AC documents follow a standard practice of introducing a short prefix comprising a “namespace qualifier” separated by a colon from a mnemonic name closely related to the term’s Name. The namespace of terms borrowed from other vocabularies is that of the original. The namespace of denovo AC terms is In the table of terms, each term entry has a row with the term name. Following the practice of the Darwin Core term list [7], for borrowed terms, this term name is generally an “unqualified name” preceded by a widely accepted prefix designating an abbreviation for the namespace, whereas for denovo AC terms, no such prefix is prepended. It is recommended that implementers who need a namespace prefix for the AC namespace use “ac” wherever feasible. The result is known as a qualified name. For example the normative wiki documentation for the borrowed term dcterms:identifier has URI In this document we will follow the established qualified name convention. In fact, most of the URIs for terms borrowed from external vocabularies (about half of them) do in fact resolve to something in relevant documentation for that external standard. Sometimes it is not precise because the documentation is a PDF document and several (different!) URIs might apparently resolve to the same place.

Examples from the Term List are shown below.

Term Name: dcterms:type
Normative URI:
Label Type
Layer: 1 — Required: Yes — Repeatable: No
Definition: The nature or genre of the resource.
Usage: A full URI preferably from among the type URIs specified in the DCMI Type Vocabulary, Recommended terms are those URIs whose labels are Collection, StillImage, Sound, MovingImage, InteractiveResource, or Text (e.g. . Also recommended are the full URIs of ac:PanAndZoomImage, ac:3DStillImage, and ac: 3DMovingImage. Values MUST NOT be a string, but a URI with full namespace (e. g. from a controlled vocabulary. Implementers and communities of practice may determine whether specific controlled vocabularies must be used. If the resource is a Collection, this item does not identify what types of objects it may contain. Following the DC recommendations at, images of text should be with this URI.
Notes: Following the DC recommendations for the Text type,, images of text should be given as when given as a URI. See also the entry for dc:type in the Audiovisual Core term list document and see the DCMI FAQ on DC and DCTERMS Namespaces,, for discussion of the rationale for terms in two namespaces. Normal practice is to use the same Label if both are provided. Labels have no effect on information discovery and are only suggestions. At least one of dc:type and dcterms:type must be supplied but, when feasible, supplying both may make the metadata more widely useful. The values of each should designate the same type, but in case of ambiguity dcterms:type prevails.
Term Name: ac:reviewerLiteral
Normative URI:
Label Reviewer
Layer: 2 — Required: No — Repeatable: Yes
Definition: String providing the name of a reviewer. If present, then resource is peer-reviewed, even if Reviewer Comments is absent or empty. Its presence tells whether an expert in the subject featured in the media has reviewed the media item or collection and approved its metadata description; must display a name or the literal "anonymous" (= anonymously reviewed).
Notes: Provider is asserting they accept this review as competent. See also ac:reviewer and the section Namespaces, Prefixes and Term Names in the Audiovisual Core Term List document for discussion of the rationale for separate terms taking URI values from those taking Literal values where both are possible. Normal practice is to use the same Label if both are provided. Labels have no effect on information discovery and are only suggestions.

The principal namespace qualifiers for term URIs in this document are

  • dcterms: and dc: The DCMI vocabulary documented at

  • dwc: The Darwin Core vocabulary described at

  • Iptc4ampExt: Geographic extensions to IPTC with namespace documented in

  • ac: Terms in the namespace not derived from other controlled vocabularies. The normative definitions of these documents can be found in the Audiovisual Core Term List document

  • xmp: The Adobe XMP vocabularies with namespace documented in Section 8.4 of

  • xmpRights: The Adobe XMP rights vocabulary with namespace documented in Section 8.5 of

  • photoshop: Adobe XMP additional properties with namespace documented at

  • exif: the Camera and Imaging Products Association Exchangeable Image File Format vocabulary with namespace documented at

4 Motivation and Rationale

Many valuable multimedia resources exist that have no information stored in databases. Some may have a web presence and others not. Even those available online may not be adequately discoverable by search engines, or may be lost in the noise of images from unreliable sources. A brief descriptive record as defined by the Audiovisual Core standard can act as the “business card” for a multimedia resource, providing enough information to identify and locate media resources by researchers, aggregators, decision makers, educators, or the general public.

The standard enables the aggregation of multimedia resource descriptions from many sources and facilitates resource discovery, including establishing relationships among multimedia resources in several locations. AC records can also be used as an aid for multimedia resources management processes, allowing an institution to take a step back and see which collections are most in need of conservation or would benefit from a higher priority for item-level cataloguing.

Among important uses identified by the Task Group, which are facilitated by the metadata, are:

  1. Discovery;

  2. Evaluation of fitness-for-use prior to fetching a resource (especially relevant for off-line resources);

  3. Use of metadata records as potential taxon occurrence evidence, or other biological inferences such as evidence for species interactions, habitats, and phenotypic variation;

  4. Identification aids;

  5. Easing the burden of multimedia resource providers and producers to gather and serve resources contributed by a wide variety of producers and custodians, particularly those with little or no IT expertise or support.

To ensure that the barriers to use are as low as possible, only four properties of an Audiovisual Core record are considered to be mandatory:

  1. Identifier (dcterms:identifier): An arbitrary code that is unique for the resource, with the resource being either a provider, collection, or media item. Whereas the identifier must be globally unique for providers and collections (e. g. a URI), identifiers for media items may be unique only within the context of a collection or provider. In fact the standard strongly recommends but does not require an Identifier for media items, though it does so for a provider or collection.

  2. Type (dcterms:type): Any dcmi type term from may be used. Recommended terms are Collection, StillImage, Sound, MovingImage, InteractiveResource, and Text.

  3. Metadata Language (ac:MetadataLanguage): Language of description and other metadata (but not necessarily of the image itself)

  4. Copyright Statement (dcterms:rights): Information about rights held in and over the resource. A full-text, readable copyright statement, as required by the national legislation of the copyright holder. On collections, this applies to all contained objects, unless the object itself has a different statement. When available, it is also recommended to provide the Copyright Owner using xmpRights:Owner

In addition it is strongly recommended to provide a concise title of the resource, using dcterms:title

5 Existing Standards

The Audiovisual Core intends to provide metadata that describe either media resources themselves or collections of them. There are several well-known or newly emerging standards that address these concerns, so one may ask: why not simply use them? In fact, AC does exactly that in about half of its 80 elements, almost all of which are optional. Indeed, as shown above, most of the mandatory terms come from external controlled vocabularies. However, all existing controlled vocabularies, most notably the widely used Dublin Core, present very few opportunities to provide media resource content metadata that is specifically biologically relevant. Use of the Dublin Core alone would make it difficult to do media resource discovery with high precision. Thus, one consequence of using Dublin Core alone would be that queries will not be selective enough. By contrast the Darwin Core TDWG standard [8] has more support for some such concerns, but little about important intellectual property rights issues, or ways to express relationships between alternate versions of media resources (e.g. different resolution versions). In turn, neither of these controlled vocabularies has mechanisms for capturing technical metadata, such as EXIF, which the imaging systems themselves, or metadata embedding tools, such as Adobe Photoshop(tm) and the GIMP open source image editor, can insert into media files and streams. To address this, and in furtherance of the above goals, the Audiovisual Core should be regarded as a synthesis of DC, DwC, and, where those are inadequate, some forward looking metadata standards that the camera manufacturers are presently planning to support within the cameras themselves, much as they now use EXIF [9]. Where any of these standards suffice, AC metadata terms and definitions are those of such standards. In some instances, we find that none of these address concerns that our experience suggests are held by a wide variety of image contributors, especially those with limited access to sophisticated IT staff or to Digital Librarians. The AC schema might be regarded as an extension to the union of small subsets of several accepted standards (together with a framework to insure that use of metadata from these standards can be understood by people and machines as referring to the same resource). Put another way, much of AC may be viewed as a wrapper around DwC, DC, XMP, and IPTC [10].

Since the overwhelming portion of the AC metadata fields are optional, a resource provider that can already serve Dublin Core metadata, could essentially serve little else but that, plus a suitable globally unique identifier to tie all the metadata to the same object. Similarly, a provider describing image content entirely with Darwin Core terms might have little more to do. However, both such providers would find that value-added services such as metadata-indexers and caching aggregators and would be less likely to keep references to their media resources and metadata than if they had richer metadata. This gives a clear strategy for providers to increase the utility of their multimedia resources with little or no impact on their IT cyberinfrastructure services. They may need only to update mappings between their internal field names and the metadata terms specified by AC, as personnel become available to do so. As more resources become available to record additional metadata, and as community annotation mechanisms arise to support this, they can add the additional metadata at a pace determined by their own resources. If harvesters of the metadata monitor the (optional) Metadata Date property (xmp:MetadataDate), the updated metadata can automatically be pulled by those value-added services, and more queries will return the provider’s metadata and references to its media resources.

6 Common Concerns with Other Biodiversity Information Standards

The Audiovisual Core regards Collections of Multimedia Resources themselves as a kind of Resource. Many types of Collections are describable in the pending TDWG Natural History Collections (NCD) proposed standard. If a provider wishes only to provide for discovery of a multimedia Collection without regard to discovery of and access to its contents (other than sub Collections), it will often be immaterial whether NCD or AC metadata, or both, are served. This is all the more so if the NCD CollectionIdentifier and the Audiovisual Core Identifier have the same value. While Audiovisual Core Collection types are richer than NCD types, it is an open question whether Audiovisual Core’s variety in this case is useful.

There is substantial overlap with use of Darwin Core terms, notably with respect to taxonomic, geographic, and temporal coverage of the data being described by the metadata record. We use DwC terms for most of those metadata and the entirety of the Darwin Core geolocation vocabulary are included by reference. GPS point locations increasingly common in image data created by cameras is easily mapped to the ‘verbatim’ locality terms of Darwin Core.

7 Concerns Not Emphasized in Other Biodiversity Information Standards

Some of the concerns mentioned here are also those of bibliographic metadata such as the Dublin Core. These are, however, not explicitly of detailed concern in existing TDWG biodiversity standards, and some are not adequately addressed by DC. Some such concerns are below.

Size: Individual multimedia resources such as images, and especially video and sound are very large compared to specimen records, observation data, or species descriptions. The main consequence of this is that multimedia metadata must support use cases for which humans or software agents can, without fetching the resource, attempt to assess the fitness of the underlying media resource for the desired use, typically by use of a search based on a fine-grained controlled vocabulary. However, without hit-and-miss natural language searches, it is not possible, even using both DC and DwC, for a metadata provider to answer a request of the form “Supply me with sizes and URL access points for still images of Dictyophora indusiata and which have Spanish metatdata available.

Intellectual Property Rights: DwC describes physical objects, whose ownership is generally governed by property laws not considered part of the Intellectual Property Rights corpus of law. Some impending standards about scientific literature address these, but rarely are publication reproduction permission issues as varied as for multimedia, which have a history of being treated as creative works of art, not necessarily as facts.

Provenance: For any scientific data, it is clearly important to know how and when the data may have been changed from its original gathering. This is particularly important for media, which are commonly edited for one or another purpose. If carelessly done, this may destroy some if the modified object’s utility. No TDWG standards or proposed standards seem very robust about provenance, including Audiovisual Core, which provides only the Derived From property in order to provide a reference to another resource. This is somewhat akin to the NCD DerivedCollection term, which identifies a Collection record as having been produced by a query to another Collection. However, that apparently does not identify the source collection or the query. A future version of Audiovisual Core will add more provenance terms.

8 Multimedia Resource Descriptions

The term Multimedia Resources encompasses a wide variety of objects of interest to biologists and the communities with whom they interact for research, education, and public service. Some instances of multimedia are familiar. These include:

  • Still images from cameras, scanners, or medical and industrial imaging devices

  • Movies with or without sound

  • Audio recordings

In some of the above cases, these resources may exist in electronic or non-electronic form or both. The electronic form may be analog or digital, the latter being more amenable to storage and exchange with computers. The digital form may have been born digital, i.e. originally captured as a digital object, or it may have been created from a non-digital object. As with biological specimen records, publications, field notes, experimental data and other artifacts of the practice of science, there is a large quantity of such material that has not yet been digitized, yet which may be available, albeit with greater expense and inconvenience than digital resources. These analog (including paper) resources still require descriptive metadata to promote discovery and to ascertain fitness-for-use. At least as important, some of the metadata is itself of scientific and educational use even if the object is not conveniently accessible. Evidence for georeferenced taxon occurrence is one such use.

Audiovisual Core metadata also can describe resources less often thought of as multimedia objects. These include:

  • Interactive software applications, either on the web or available for stand-alone use

  • Taxonomic identification keys

  • Collections of multimedia resources

  • Web sites not otherwise falling into one of the above categories

9 Audiovisual Core Records

The normative Audiovisual Core metadata record specification is independent of the way in which those records are rendered into electronic form. MRTG intends to publish specifications for such rendering represented in, represented in XML constrained by an XML-Schema, and represented in plain text as comma separated values (CSV). Sections 4.4 to 4.5 of the TDWG Standards Documentation Specification describe how basic term metadata should be expressed in machine-readable forms such as RDF serializations. A future task group might develop a more semantically rich machine-readable ontology following the procedures listed in Section 4 of the TDWG Vocabulary Maintenance Specification.

The language of the normative Audiovisual Core specification is English, but this in no way constrains applications from using labels or content of the metadata in local languages. Because its language is English, each metadata item in the normative document has an English label (which might, for example be part of a user interface), but these, too, are not required to be used by applications, although their use is strongly encouraged, at least in documentation.

As mentioned earlier, an Audiovisual Core metadata record is a set of terms describing the underlying multimedia resource that the record describes. Each term is identified by a Uniform Resource Identifier (URI). These are URIs of the attribute, not of the underlying resource, and they simply specify which term is being provided. There are many URI schemes, some of which have been registered with the Internet Assigned Names Authority (IANA). All Audiovisual Core term URIs, conform to the http URI Scheme. This is chosen because this widely used URI scheme uses the familiar internet URL syntax as its URI syntax. But this familiarity gives rise to a common misconception, namely that pasting the URI into a browser URL line, or providing it to some other application that respects the http protocol, should result in the application returning some information about the object identified by the URI. Such behavior is usually called resolution (or, more technically, resolution and dereferencing) of the URI and is in no way guaranteed for Audiovisual Core term URIs. Where possible, we in fact try to make http URIs be resolvable, with the information returned being documentation for how the metadata attribute identified by that URI is defined or use. To reiterate: for Audiovisual Core term URIs, any such resolution will never contain information about the underlying multimedia resource being described. For this reason, few human-centric Audiovisual Core applications should ever present the URIs to users, nor use them as linking mechanisms. (One possible exception is an application for assigning metadata to multimedia resources, where such a use may provide a thesaurus entry aiding the user in the semantics of the metadata property. However, the incidental nature of the resolution, and its lack of guaranteed long term persistence, makes even this approach one that should be considered with extreme caution.) Finally, note that some external controlled vocabularies are defined in PDF or other documents that do not have URL links directly to each defined term. In these cases, any resolution available from the normative document may only link to the beginning of the document, leaving it necessary to search in the document for the referenced definition.

Associated to each Audiovisual Core property is its value. The datatype of this value is also specified in the normative document. Datatypes can include free text, specific literals taken from a controlled vocabulary specified in the normative document, or a number of other datatypes specified and described in the normative document. In the case of a controlled vocabulary, it is important to note that whatever an application may present in a user interface, any Audiovisual Core metadata interchange should use the literals from a specified controlled vocabulary when one is specified, even if the record is declared to be a record in a different language than that of the controlled term. An important example is the Type metadata field, which is recommended to come from the corresponding vocabulary from Dublin Core, augmented by some recommended in the normative document. (We also add to that an optional field Subtype.) Similarly, agents answering Audiovisual Core metadata queries MUST be able to consume and respond to queries framed with the controlled vocabulary. Nothing in the normative document prevents an Audiovisual Core data provider from asserting it has no records with a given controlled term, nor from internally mapping between a controlled vocabulary and its internal attributes, whose names may well be in a language other than English. Only a small number of Audiovisual Core properties take values in a specific, English-based controlled vocabulary. This will become relevant only for metadata interchange. Of the mandatory terms, only Type has any such requirements.

An Audiovisual Core record consists minimally of the four mandatory fields (Identifier, Type, Metadata Language, and Copyright Statement).

In some cases, some metadata terms are necessarily related to others (e.g. various versions of an image must be associated the “main” version). However, spreadsheets and other flat sources of contributor metadata are regarded as particularly important, and in many of these it is difficult to represent such structural relationships. Consequently an Audiovisual Core record is itself mainly flat, the exception being the object of a property named hasServiceAccessPoint. This object itself has further properties that describe how to fetch the actual media described by the AC record. One consequence of this is that, for some purposes, a metadata Provider might have to make several metadata records available about the same underlying resource, because the representation-neutral Audiovisual Core specification does not provide for “subproperties” on its properties, or for relations in most cases. An important case surrounds multilingual metadata. Because each metadata record is in a fixed language specified by the Metadata Language property (this is the language of the record, not the multimedia resource, in case it should have one), a Provider might have to offer several metadata records about the same multimedia resource. The values of the four required terms must be provided in every metadata record, even if repeated in other metadata records describing the same resource. At the date of this writing, the normative document does not provide a mechanism for identifying a metadata record that might be overarching, in the sense that its optional terms may be regarded as defaults for any not specified in other records about the same resource. This point is under discussion on the MRTG Wiki.

Many items may be repeated in an Audiovisual Core record, but some may not, as indicated in the normative document. For example the Modified item corresponds to a date at which the media resource was modified and may be repeated to reflect the history of the resource. By contrast, Date Available is a single date or a single range of dates at which the underlying resource became, or will become, available.

10 Implementation and Compliance

Audiovisual Core is defined in a way that is as representation-neutral as possible. It provides natural language definitions of classes, properties and instances that are identified by URIs and it makes recommendations on the use and content of properties from other vocabularies.

The URIs defined here may be used across a number of technologies, such as namespaces in XML Schema-valid table documents, RDF, and column headings in comma delimited text files.

This approach facilitates:

  • Embedding of Audiovisual Core data within other standards such as descriptions of specimens or literature.

  • The extension of Audiovisual Core records with other data types such as the extensive geographic controlled vocabularies of the Open Geospatial Consortium (OGC)

  • Cross walking between technologies such as a Comma Separated Value file, an RDF graph, an XML document and a JSON object.

The Audiovisual Core representation-neutral normative standard itself does not provide an off-the-shelf, self validating exchange format. Multiple such exchange formats meeting different requirements can be defined and this standard allows mapping between them.

11 Further Information

  • Audiovisual Core Maintenance Group Charter

  • Discussion of the Audiovisual Core takes place at

  • Register for the mailing list at This email list tracks all discussion about the content of TDWG standards.

12 Appendix I: Glossary

DC Dublin Core. Metadata element set that is a standard for cross-domain information resource discovery.
DCMI Dublin Core Metadata Initiative. The organization engaged in developing Dublin Core metadata standard.
DwC The Darwin Core is a TDWG standard for representation of specimen records. It has been in wide use for several years in a number of nonstandard, sometimes inconsistent, versions. A recently adopted standard version is at
EOL Encyclopedia of Life. Information about many species.
EXIF A widely used tagging format for digital image metadata that is often embedded in the image files, particularly by modern digital cameras. Many image rendering applications can read and display EXIF data. See for a history and description.
GBIF Global Biodiversity Information Facility. Interoperable network of biodiversity databases and information technology tools.
IANA Internet Assigned Names Authority. Specifies the forms of, and registers instances of, names of various protocols in use on the internet. See especially information on the IANA http URI scheme.
IPTC IPTC is a mature standard from the International Press and Telecommunications Council. Its Intellectual Property Rights support finer-grained controlled vocabularies than DC, providing better machine processing for discovery and fitness-for-use. The current version is a vocabulary for XMP.
JSON JavaScript Object Notation. Lightweight data-interchange format.
Morphbank A specimen image repository.
MWG The Metadata Working Group is an industry consortium (Adobe, Apple, Canon, Microsoft, Nokia, and Sony) organized to specify how to exploit the Adobe Extensible Metadata Platform, XMP, for embedding metadata into common image file formats in several widely used controlled vocabularies. Although MWG's thrust is mainly toward consumer applications, over two dozen open source and commercial software products and platforms support XMP and Adobe has placed a Developers' Toolkit under an open source license.
NBII The former U.S. National Biological Information Infrastructure. Its image library, the Library of Images From the Environment (LIFE), was at or If LIFE is reconstituted in any form, there might be a link there.
NCD Natural Collections Description is a draft data standard designed to describe collections of physical objects such as specimens. It can accommodate collections of media objects, but cannot relate them to descriptions of the objects themselves.
OGC Open Geospatial Consortium. Provides standards for geospatial data representation and exchange.
RDF Resource Description Framework. Lightweight ontology system to support knowledge exchange online.
TDWG Taxonomic Databases Working Group. Now known as the Biodiversity Information Standards (TDWG), it is an international working group that develops standards and protocols for sharing biodiversity data.
URI Unique Resource Identifier. Generic term for linking web resources including URLs.
XML Extensible Markup Language. A simple flexible text format playing an increasingly important role in the exchange of a wide variety of data on the Web.
XMP Adobe Extensible Metadata Platform (XMP) is a framework for embedding metadata into media files. Adobe provides a BSD-licensed open-source XMP developer’s toolkit which includes documentation about how to represent metadata in XMP. The XMP specification itself is licensed by Adobe under a "Public Patent License" by which Adobe grants everyone the right to make XMP-compliant components of their applications, but it reserves the right to withdraw the license in case such a compliant component infringes "Essential Claims" of any patent. See for download information. See also MWG in this table.

13 Appendix II: Audiovisual Core Development History

The Audiovisual Core Multimedia Resources Metadata Schema (Audiovisual Core) standard is the culmination of work on multimedia resource descriptions carried out by Key to Nature, the NBII Digital Image Library, Morphbank, and others, together with input from a number of other stakeholder communities including Encyclopedia of Life (EOL), the Biodiversity Heritage Library (BHL) and the University of Massachusetts-Boston. The Global Biodiversity Information Facility (GBIF) commissioned the ‘Multimedia Resources Task Group (MRTG)’ in March 2008 and the group was approved in December 2009 by Biodiversity Information Standards (TDWG) as the ‘Joint GBIF-TDWG Task Group on Multimedia Resources in Biodiversity’.

Participants in drafting the schema (in alphabetical order)

  • Mr. Mihail-Constantin Carausu, Danish Biodiversity Information Facility (DanBIF), Copenhagen, Denmark

  • Dr. Vishwas Chavan, Global Biodiversity Information Facility, Copenhagen, Denmark

  • Mr. Chris Freeland, Missouri Botanical Garden, St. Louis, USA

  • Dr. Gregor Hagedorn, JKI, Federal Research Institute for Cultivated Plants, Berlin, Germany

  • Prof. Robert A. Morris, University of Massachusetts at Boston, USA

  • Dr. Dimitry Mozzherin, Encyclopedia of Life, Woods Hole, USA

  • Dr Annette Olson, American Association for the Advancement of Science

  • Prof. Greg Riccardi, Florida State University, Tallahassee, USA

  • Dr. Éamonn Ó Tuama, Global Biodiversity Information Facility, Copenhagen, Denmark

The standard was developed by the Joint Task Group to fit with the suite of standards-based data management resources being developed by GBIF.

Funding was provided by the Global Biodiversity Information Facility.

Grateful thanks go to Woods Hole Marine Biological Laboratory and the Encyclopedia of Life for hosting one of the meetings. This document, including some narrative is adapted from a corresponding document produced by the TDWG Natural Collections Descriptions (NCD) task group.

13.1 Timeline

2006, November TDWG Image Interest Group initiated

2008, March GBIF commissions Multimedia Resources Task Group (MRTG)

2008, June GBIF Multimedia Resources Task Group met in Copenhagen, Denmark

2008, August GBIF Multimedia Resources Task Group meeting in Woods Hole, USA

2008, October TDWG Image Interest Group met in Fremantle, Australia at the ‘TDWG Annual Conference 2008’

2008, December Joint GBIF-TDWG Task Group on Multimedia Resources in Biodiversity commissioned

2009, February GBIF Multimedia Resources Task Group met in Copenhagen, Denmark to refine the metadata schema

2009, March GBIF – TDWG Multimedia Resources Metadata Schema (MRTG) ver. 0.4414 drafted and opened for informal comment, evolving through v 0.9

2010, February Schema v 0.9 submitted to TDWG for internal Review

2010, July TDWG Internal Review 1 completed

2010, November v1.0 submitted to TDWG Executive committee with response to Internal Review 1. Proposed Standard renamed Audiovisual Core Multimedia Resources Metadata Schema (AC).

2011, June Response to Internal Review 2 under way.

2011, September Responses to Internal Review 2 and 3 completed and submitted to TDWG Executive Committee

2011, November Prepared responses to “Review g” and “Review h” and to some comments of the Review Manager, Steve Baskauf. Prepare submission for permission to have public comment.

January-November 2012 Further preparation for submission for permission to have public comment

13.2 Document revision history


  • Harmonized document to the fact that Subtype is optional in normative v0.7

  • Fix mismatched parentheses, extra spaces, missing spaces, etc.

ACv1.0 docv1.0

  • Harmonized to v1.0: replace “MRTG” with “Audiovisual Core” where used as name of schema. Correct minor typos. Add “dcterms” as prefix.

ACv1.0 docv1.0

  • Further replacement of MRTG with “Audiovisual Core” or “AC”.

AC v1.0 docv 1.2

  • Address Internal Review 2 comments

  • Fix mismatched parentheses, extra spaces, missing spaces, etc.

AC v1.0 docv1.3

  • Remove requirement to have Copyright Owner provided.

AC v1.0 docv1.4

  • Clean up citations of six mandatory elements instead of five.

AC v1.0 docv1.5

  • Replace “” with “” to reflect move of normative wiki. Remove some unused Glossary terms. Update docv to 1.5

AC v1.0docv1.6

  • Remove dcterms:title from mandatory list. Add description of it as strongly recommended. Add mention of xmpRights:Owner in Copyright Statement item in the mandatory list. Change to “four” the references of “five” mandatory elements or remove the count altogether where text becomes unambiguous. Mention acterms namespace. Correct Iptc4xmpExt namespace to Update docv to 1.6.

AC v1docv1.7

  • Clarify relation of this document to the normative docs. Set major major text to left-align, unjustified.

AC v1.0docv1.8

  • Remove mention of crosswalks since no longer in normative termlist.

  • On p. 5 force URL of DwC terms into footnote.

  • Improved language about use of literals with dcterms.

C v1.0docv1.91

  • Various minor grammar and punctuation corrections.

  • Reconciliation to current normative docs.

AC v1.0docv1.92

  • More minor grammar fixes.

AC v1.0docv1.93

  • Fixed inconsistent internal version references to current version. No substantive or grammatical changes. Note that v1.92 was submitted to TDWG executive committee with request for permission to hold public review.

AC v1.0docv1.94

  • Change references from species-id wiki to gbif terms wiki. Adjust Fig 1

AC v1.0docv1.95

  • Correct “hasAccentPoint” to “hasAcccessPoint”. Remove text suggesting this is a draft

14 Endnotes









[9] The Metadata Working Group (MWG, is an industry consortium (Adobe, Apple, Canon, Microsoft, Nokia, and Sony) organized to specify how to exploit the Adobe Extensible Metadata Platform, XMP ( for embedding into common image file formats metadata in several widely used controlled vocabularies. Although MWG’s thrust is mainly toward consumer applications, over two dozen open source and commercial software products and platforms support XMP and Adobe has placed a Developers’ Toolkit under an open source license. Along with proposals for standard serializations of the representation-neutral Audiovisual Core schema, MRTG intends to propose a TDWG Best Practice for embedding such serializations in multimedia files using XMP.

[10] IPTC is a mature standard from the International Press and Telecommunications Council ( Its Intellectual Property Rights supports finer grained controlled vocabularies than DC, providing better machine processing for discovery and fitness-for-use.