Appendix A — Data Model

In order to support metadata repair of following the “Fixing Music Data at the Source” principle1, we created a data model that aligns with library (authority) systems like Dublic Core (DCTERMS, DCMI) , the archival standard RiC2, the museum standard CIDOC3, the Europeana Data Model (EDM)4 and HDTO5 for cultural heritage dissemination, and VIAF; furthermore the DDEX6, ISWC7 and ISRC standards of rights management and music distribution or communication to the public; see also Section 2.3.

A.1 Releases

Most users are interested in releases or their contents. People lend releases of music from libraries, listen to releases on streaming services or buy them. If the metadata of a release is wrong, it is likely that the individual revenue earning assets, i.e., the tracks are also documented wrong.

Between 1960 and 2010 the album was the most important release format, arguably in the streaming era it is the single. It is very important that we are able correctly represent all types of releases.

For releases, the most applicable metadata vocabulary is DDEX, the music industry standard that does not exist in ontological form. As we described earlier, we placed some key DDEX expressions in ontological form for interoperability.

A.1.1 Release classes

Release classes
Class Description
musical release The superclass for all releases that make one or more musical sound recordings available to the public or to a defined audience. In DDEX this corresponds to the Release entity, which aggregates metadata about the product and references the recordings it contains. In library and archival contexts it aligns with manifestations such as albums, singles, or other issued carriers. This class serves as the parent for all specific release types in the Open Music Observatory. om:Q232, skcmdb:Q873, fu:Q7074
single A release intended to make one principal sound recording available, regardless of whether additional tracks such as B-sides, alternate versions, or remixes are included. Historically physical singles often contained two recordings (A-side and B-side), while digital singles may contain only one or may include supplementary tracks. In DDEX this corresponds to a Release with ReleaseType=Single. om:Q236, skcmdb:Q886, fu:Q4744 |
album A release that presents a substantial group of sound recordings as a cohesive published unit. The number of tracks may vary, and albums may contain only a few long recordings or many short ones. The defining characteristic is that the release is issued by the rights holder or publisher as an album rather than as a single or compilation. T In DDEX this corresponds to a Release with ReleaseType=Album. om:Q230, skcmdb:Q473, fu:Q4286
compilation A release that aggregates sound recordings originating from multiple sources, such as earlier releases, archival collections, or curated selections. Compilations may be issued for commercial distribution or for scholarly, archival, or thematic purposes, and they may include both previously released and newly issued recordings. In DDEX this corresponds to a Release with ReleaseType=Compilation. om:Q2028, skcmdb:Q2822, fu:Q6595

A.1.2 Release properties

The following properties connect releases as graph nodes to agents, recordings. and identifiers.

Release properties
Property Description
creator The agent or agents credited as the principal creators of the release as presented in catalogue metadata, packaging, or distributor-provided descriptive information. This corresponds to DCTERMS:creator, which is widely used in library and Europeana metadata for high-level authorship statements, and to the presentation-oriented DisplayArtistelement in DDEX. Because such credits may combine performers, ensembles, conductors, or other roles, this property is intended only for descriptive and discovery purposes. Any precise contributor roles, rights-relevant relationships, or distinctions among performer, producer, composer, or other functions should be recorded using has associated agent with an appropriate subject has role qualifier. om:P137, skcmdb:P106, fu:P84
performer An agent credited as a performer on one or more recordings included in the release. This property reflects catalogue or packaging information and may list performers who appear on different tracks throughout the release. It is intended only for high-level descriptive use. Detailed performer information for individual recordings, including specific roles or rights-relevant contributions, should be recorded using has associated agent with an appropriate subject has role qualifier at the recording level. om:P152, skcmdb:P97, fu:P408
has associated agent Links an entity (such as a work, recording, release, event, or archival object) to an agent involved in its creation, performance, production, collection, or other lifecycle activities. This property is used whenever a specific contributor role needs to be recorded, and must be qualified with the subject has role property to indicate the function performed by the agent (for example composer, lyricist, arranger, producer, conductor, performer, or collector). It supports multiple agents and multiple roles and provides the detailed contributor model required for ISWC, ISRC, DDEX, and for provenance descriptions in RiC and CIDOC-CRM. om:P19, skcmdb:P117, fuds:P453
subject has role or has role The qualifier of the property has associated agent which connects the role to the agent (e.g. composer, producer etc.)
record label The imprint or publishing label under which the release is issued, corresponding to the Wikidata property for record label but used with greater rigour to reflect the specific label name printed on the release or supplied by the publisher or distributor. In DDEX this aligns with the LabelName element used to identify the imprint presenting the release. The ISRC Handbook recognises the releasing label as part of the contextual metadata associated with a recording or release but does not define label identity as part of the ISRC code itself. Detailed information about issuing organisations, phonogram producers, reissue labels, or catalogue ownership over time should be recorded using has associated agent with an appropriate subject has role qualifier. om:P163, skcmdb:P144
tracklist Connects a release to the sound recordings it contains and establishes their order within that release. The numerical position of each recording is given using the series ordinal qualifier. This corresponds to the way DDEX represents track sequences using ResourceReference and SequenceNumber elements. The property describes the structure of a specific edition of a release and may differ across reissues or alternate versions. om:P162, skcmdb:P145, fuds:P70
series ordinal A qualifier used with the tracklist property to indicate the numerical position of a recording within a particular release. This property follows the Wikidata convention for ordered membership and corresponds to the sequence number used in DDEX to define track order. It allows different editions or versions of a release to have distinct track sequences.
has time A general temporal property used together with a temporal role qualifier to specify the type of date associated with a release. For example, a temporal role of date of release indicates the publication or distribution date of that particular edition. This structure aligns with DDEX, where release dates are typed elements such as ReleaseDate or OriginalReleaseDate, and with library and archival practice in which dates are associated with specific publication or production events. |
location A general geographic property whose meaning is determined entirely by the location applies to qualifier’s value, such as place of release, place of publication, place of manufacture, or place of reissue. This aligns with library practice, where publication and distribution places are recorded separately, and with CIDOC and RiC-O event-based modelling of publication. The base property provides the geographic link, while the qualifier specifies the role of the location in the lifecycle of the release.
has access point A link or identifier that provides access to information about the release in an external system, such as a library catalogue, digital repository, webshop, or streaming-service landing page. This property supports discovery and interoperability and corresponds to access URLs commonly used in library and archival metadata. It does not express rights or licensing information.
UPC or EAN A GS1 product identifier associated with a specific edition of a release, recorded as a UPC (12-digit) or EAN/GTIN-13 (13-digit) code. In DDEX this corresponds to an ICPN value used to identify a release in commercial distribution channels. UPC and EAN codes apply to releases rather than to individual recordings and may vary across different editions or formats of the same release. om:P161, skcmdb:P140
Spotify album ID A proprietary identifier assigned by Spotify to a release available on its streaming service. This identifier applies only to releases that have been distributed to Spotify and corresponds in DDEX to a proprietary release identifier supplied by a digital service provider. It does not convey rights information and may differ across editions or market-specific versions of a release om:P107, skcmdb:P57, fu:P87.
Discogs artist ID An external identifier assigned by Discogs to a specific edition or pressing of a release. Discogs identifiers may apply to commercial, historical, or archival releases and often distinguish fine-grained variations such as different pressings or formats. In DDEX terms this corresponds to a proprietary release identifier supplied by an external database. The identifier supports reconciliation and discovery but does not express rights information. om:P112, skcmdb:P115, fu:P435

A.1.2.1 Labels

A single release can be associated with several organisations over its lifetime, and these organisations can themselves change through mergers, nationalisation, privatisation, or catalogue transfers. For this reason, the record label property records only the imprint or publisher name as it appears on a specific edition of a release, following library cataloguing and discographic practice. It does not attempt to capture rights relationships or corporate history in the same field.

More detailed relationships are modelled explicitly using has associated agent together with a subject has role qualifier. The original issuing label, a later reissue label, the organisation acting as phonogram producer, and the company delivering the release to a digital service provider can all be represented in this way. These roles may differ from the imprint printed on the object, and they may vary between editions or distribution channels.

Corporate history and succession between labels or production companies are expressed as relationships between the label or company entities themselves. For example, one label may be the predecessor or successor of another, or may have been nationalised into or privatised from a larger organisation. This allows the model to represent cases such as the Tonalit catalogue being absorbed into a state-owned manufacturer and later reissued under the Hungaroton imprint, while still keeping the original Tonalit label attached to the historical release.

This separation between descriptive imprint, rights-related roles, and corporate history preserves accuracy across commercial, archival, and reissued materials and allows the same release or recording to be linked to all relevant organisations without overloading the record label property itself.

A.2 Recordings

Our top level classification is the audio recording. In our music observatory, we mainly store data about audio recordings that contain music. If other audio recordings, such as field notes of an ethnomusicological research or an audiobook, are added, they become part of the publications, not the music collection, and are described using DCTERMS/RiC/CIDOC rather than ISRC/DDEX.

For recordings intended for distribution and communication to the public, we follow ISRC and DDEX.

For recordings not intended for commercial distribution or public communication, but available for research within GLAM institutions under applicable legal permissions, we follow DCTERMS, RiC8, CIDOC9, EDM10, and attach use policies or licences modelled with ODLR or simple licence statements.

Only recordings that fall within the scope of ISO 3901 (ISRC) and the music-focused DDEX profiles are eligible for ISRC assignment. Anything that can have an ISRC under these standards may have one assigned; however, not every audio recording is eligible for an ISRC number (for example, many archival, research-only or purely literary recordings are out of scope, even if technically sound recordings).

A.2.1 Recording classes

Recording classes
Class Explanation
audio recording Superclass for all recorded sound (musical or non-musical), including field recordings, interviews, audiobooks, and musical performances. Matches DCTERMS:Sound and EBUCore:AudioObject, and corresponds to FRBRoo concepts for recorded sound (e.g., F26 Recording). These recordings are all E73 Information Object items in CIDOC. The term is also compatible with the broad DDEX “Resource” notion but has no direct ISRC or DDEX equivalent. This class does not imply eligibility for ISRC, and is the level at which GLAM-style rights and ODLR-modeled use policies may apply to any audio object, including those outside the music domain. om:Q117, skcmdb:Q269, fu:Q21.
music audio recording A subclass of audio recording whose primary content is musical. This class separates musical sound recordings from other kinds of audio such as audiobooks, interviews, or spoken-word field notes, which are treated under publications and described with DCTERMS, RiC, or CIDOC. This is an internal OMO semantic category used as the branching point for commercial, archival, demo, and pre-release musical recordings. It has no direct equivalent in ISRC or DDEX, although it roughly corresponds to DDEX Resources with UseType = Audio where the content is musical. om:Q118, skcmdb:Q2417, fu:Q4832.
archival music recording A non-commercial musical audio recording created, collected, or deposited for archival, research, or documentary purposes. It is not intended for public communication or commercial distribution and therefore is not eligible for ISRC assignment in its archival state. Rights and access are governed by institutional use policies or licences, modelled with ODLR or similar statements. This class aligns with description practices in DCTERMS, RiC, and CIDOC-CRM rather than ISRC or DDEX. In some cases archival recordings may later be communicated to the public, but this requires a rights investigation; if eligible and intended for release, the object should be reclassified as a pre-release recording before becoming a commercial sound recording. om:Q122, skcmdb:Q2416, fu:Q4412
sound recording (music) A musical sound recording that has been publicly communicated or commercially released (for example through physical media, download, streaming services, or broadcast). Recordings in this class are within the commercial domain and therefore eligible for ISRC assignment under ISO 3901, although the ISRC may have been assigned earlier at the pre-release stage. Once a pre-release recording becomes publicly available, it is reclassified as a sound recording (music). This class corresponds to the audio Resource used within DDEX releases and covers the recordings that form the content of published releases. Audiobooks and other non-musical spoken-word recordings are excluded. om:Q119, skcmdb:Q280, fu:Q121
demo recording (music) A musical recording created for demonstration, pitching, rehearsal review, or internal artistic or production purposes, and not originally intended for public communication or commercial release. Demo recordings are not eligible for ISRC assignment while in this category and are not described using DDEX. If a demo recording later enters a commercial production workflow, it should be reclassified as a pre-release recording; if it is deposited with a GLAM institution for research or heritage preservation, it should be reclassified as an archival music recording. om:Q121
pre-releaserecording (music) A recording designated for future release. This recording may or may not yet have an ISRC assigned. Once publicly released, it becomes a commercial sound recording. ISRC should be assigned (at any point) in the production workflow, even before mixing or mastering, provided the recording is uniquely identifiable. This aligns with DDEX PreRelease models and ISRC. Once it is released, it must be reclassified sound recording (music).

A.2.2 Alignment of archival recordings with DCTERMS, RiC, and CIDOC-CRM

Archival music recordings are part of the cultural heritage domain rather than the commercial music distribution domain. Because of this, they are best described using metadata models developed for archives, libraries, and museums. A recording such as Tšitšōrlinki, tšitšōrlinki (archival recording) (fu:Q4169) would be mapped as follows.

In all three ontologies, an archival music recording such as fu:Q4169 is treated as:

  • an E73 InformationObject arising from a specific recording event

  • held or curated within an archival or museum context

  • governed by institutional or community rights

  • non-commercial unless explicitly reclassified after rights clearance

These mappings allow interoperability between OMO and GLAM metadata systems without invoking ISRC or DDEX models.

DCTERMS alignment

DCTERMS or DCMI Metadata Terms is resource-centric and provides simple descriptive properties suitable for digital audio held in GLAM collections. It is mainly used in libraries and in some scientific repositories, but the Europeana Data Model is also derived from it.

Example mapping:

This expresses descriptive, contextual, and rights metadata without implying commercial release.

RiC (Records in Contexts) alignment

Records in Context describes archival entities, their provenance, and their relationships. It replaces earlier, but widely used archival standards like ISAD(G). While most archives do not use yet RiC, RiC provides a conceptual model to translate archival metadata into a graph. Therefore we use RiC with backward compatibility possibilities to ISAD(G) and other prior archival standards.

Example mapping for fu:Q4169:

  • Record Resource = the archival recording itself

  • Record Set = the archival collection, fonds, or subfonds where the recording belongs

  • Activity = the recording event (e.g., fieldwork session)

  • Event = the event that was recorded

  • Person or Group = performers, collectors, recordists

  • Place or PlaceName = recording location

  • Temporal Relation = various qualified event like recording date, transcription date, digitisation date.

  • A rightsholder Agent can be linked with hasOrHadIntellectualPropertyRightsHolder.

  • RiC-Relation:

    • was created by (fieldworker / performer)

    • was recorded at (place)

    • is part of (archival collection)

    • has rights holder (institution, community, or individual)

    • has access conditions (institutional policies)

RiC allows documenting complex provenance: who recorded it, in what context, and under what permissions.

CIDOC-CRM alignment

CIDOC-CRM models cultural heritage objects and their events.

Typical mapping for fu:Q4169:

CIDOC expresses the event-based provenance: what happened, who participated, and what physical/digital carriers exist.

A.2.3 Recording properties

The following properties connect the music recordings to releases, various agents or authoritative identifiers.

Recording properties
Property Explanation
creator The principal credited artist, group, or other agent named on the recording as presented in the source metadata (for example on a CD cover, LP label, or catalogue entry). In library practice this corresponds closely to DCTERMS:creator, which intentionally reflects the ambiguity of such statements. On commercial recordings this often aligns with the and ISRC:Main Artist11. or the DisplayArtist in DDEX, but the value may also reflect broader or ambiguous catalogue information, especially in classical music. Detailed contributor roles such as composer, conductor, lyricist, arranger, producer, or featured performer should be expressed using the has associated agent property with a subject has role qualifier. om:P137, skcmdb:P106, fu:P84
performer An agent credited as performing on the recording, such as a vocalist, instrumentalist, conductor, or ensemble. This property expresses the basic performer relationship as it appears in catalogues, liner notes, or DDEX Resource metadata. It refers specifically to participation in the recorded performance, not to authorship of the underlying work. More detailed role information, such as soloist, conductor, featured performer, or instrumental role, should be provided using the has associated agent property with the subject has role qualifier. om:P152, skcmdb:P97, fu:P408
has associated agent Links an entity (such as a work, recording, release, event, or archival object) to an agent involved in its creation, performance, production, collection, or other lifecycle activities. This property is used whenever a specific contributor role needs to be recorded, and must be qualified with the subject has role property to indicate the function performed by the agent (for example composer, lyricist, arranger, producer, conductor, performer, or collector). It supports multiple agents and multiple roles and provides the detailed contributor model required for ISWC, ISRC, DDEX, and for provenance descriptions in RiC and CIDOC-CRM. om:P19, skcmdb:P117, fuds:P453
subject has role or has role The qualifier of the property has associated agent which connects the role to the agent (e.g. composer, producer etc.)
title The title of the recording as it appears in catalogue metadata or on the release from which the recording originates. This property may be recorded in multiple languages, each with its own language code, and may include translated or alternative titles where appropriate, for example in classical or traditional repertoire. It is conceptually aligned with dcterms:title, and with the ResourceTitle element in DDEX, although without requiring specific title types. This property refers only to the title of the recording itself, not to the title of the underlying musical work. om:P41, skcmdb:P114, fu:P391,
duration The playing time of the recording, expressed as a time value (for example in seconds or using an ISO 8601 duration format). This corresponds to the duration element used in DDEX Resource metadata. Duration may be exact or, in the case of archival material, approximate where only partial information is available. om:P66, skcmdb:P62, fu:P99
genre The musical genre or style associated with the recording. This may be taken from a controlled vocabulary used in commercial music metadata, from DDEX genre classifications, or from specialised archival or ethnographic genre schemes. Multiple genre values may be recorded where appropriate. This property refers to the genre of the recorded performance, which may differ from classifications applied to the underlying musical work. om:P36, skcmdb:P139, fu:P452
language of work or name This property corresponds to the Wikidata property for indicating the language associated with a work or recording. In the context of sound recordings it refers specifically to the principal language used in the recorded performance, typically the language of sung or spoken content. It does not refer to the language of the recording title, which is indicated using language-tagged literals, nor to the language of the underlying musical work, which may be recorded separately at the work level. For instrumental recordings this value may be omitted, or the value “instrumental music (no language)” may be used. om:P33, skcmdb:P37, fuds:P80
location A general property linking a recording to a geographic place. The specific meaning of the location is always determined by the value of the qualifier location applies to, such as place of recording, place of release, place of collection, thematic location, or place of creation. This avoids ambiguity between technical recording locations, descriptive subject locations, and other geographic associations. The ISRC country code must not be interpreted as a recording location, and if recorded for analytical purposes it should use its own qualifier. The base property serves as a simple place link, while all semantic detail is expressed through qualifiers.
ISRC The International Standard Recording Code assigned to a musical sound recording in accordance with ISO 3901. This identifier uniquely identifies a specific recording and follows the ISRC format (country code, registrant code, year of reference, designation code). Only recordings intended for public communication or commercial exploitation are eligible to receive an ISRC. An ISRC may be assigned at any point in the production workflow once the recording is uniquely identifiable. Archival or non-commercial recordings normally do not carry an ISRC unless they are reclassified for commercial release. In DDEX metadata an ISRC is provided as a ResourceIdentifier with IdentifierType = ISRC. om:P136, skcmdb:P59, fu:P90
appears in order on or appears on Connects a recording to a release on which it is included. When used with a series ordinal qualifier, it expresses the position of the recording within the release’s track sequence. This corresponds to the way DDEX represents resources within releases, where each recording is listed as a ResourceReference with an associated sequence number. A recording may appear on multiple releases, possibly with different sequence positions. om:P156, skcmdb:P141, fu:P474
Spotify track ID A proprietary identifier assigned by Spotify to a track available on its streaming service. This identifier applies only to recordings that have been distributed to Spotify and is not used for archival, demo, or other non-commercial recordings. In DDEX terms it corresponds to a proprietary identifier supplied by a digital service provider. Use of this identifier is subject to Spotify’s terms of service. om:P106, skcmdb:P56, fu:P86
Apple track ID A proprietary identifier assigned by Apple Music to a track available through its streaming or download services. This identifier is used only for recordings that have been distributed to Apple Music and does not appear on archival, demo, or other non-commercial recordings. In DDEX this corresponds to a proprietary identifier supplied by a digital service provider. Use of this identifier is subject to Apple’s media terms and conditions.
MusicBrainz recording ID An identifier assigned by the MusicBrainz database to a recording. MusicBrainz identifiers may be applied to commercial, archival, demo, or unreleased recordings, and provide a stable open identifier for interoperability with external music metadata sources. In DDEX this corresponds to a proprietary identifier supplied by an external database rather than a digital service provider. om:P109, skcmdb:P60, fu:P91
is recording of Links a sound recording to the musical work that it realises or performs. This property expresses the relationship between a specific recorded performance and the underlying abstract work, whether the work is formally identified by an ISWC or represented as a traditional, anonymised, or locally defined musical work. In DDEX this corresponds to the reference from a Resource to a Work, and in ISWC–ISRC workflows it provides the essential connection between the work identifier and the recording identifier. In archival and ethnographic contexts it may link recordings to non-notated or culturally defined works. om:P122, skcmdb:P108, fu:P456

The is recording of property is recording of expresses the essential relationship between a particular sound recording and the musical work that it realises. In the context of ISWC and ISRC this link is fundamental, because ISWC identifies abstract musical works and ISRC identifies the recordings that embody those works, and the two systems rely on such connections for rights management, repertoire tracking, and distribution of royalties. In DDEX this relationship corresponds to the way a Resource representing a recording refers to the underlying Work in ERN and related messages, enabling digital services to associate a performance with the correct composition.

Within CIDOC-CRM the correspondence is expressed through the distinction between the conceptual musical work, treated as an E28 Conceptual Object, and the recorded performance, treated as an E73 Information Object brought into being by a performance or recording activity. CIDOC models this as an information object created through an event that actualises or realises a conceptual work, which parallels the conceptual grounding of the property in OMO/SKCMDb. RiC-O follows a similar approach, where the recording is a record resource and the work is an intellectual or cultural entity represented or instantiated by that resource, allowing the relationship to be documented even when the work has no formal composer attribution or ISWC registration.

In library and archival practice the relationship is equally important because it connects a recording to the abstract musical content that a catalogue or finding aid describes. This applies both to well-defined notated works in Western art music and to traditional, anonymous, or community-defined works in ethnographic and archival collections. The property therefore provides a consistent modelling mechanism across commercial, archival, and scholarly contexts, allowing all these systems to express the same conceptual link in ways compatible with their respective standards.

A.3 Works

The work model in the Open Music Observatory describes the abstract musical content that may be realised in performance, embodied in recordings, and made available through releases or published scores. In this sense it follows the same conceptual boundaries used in library science, rights management, cultural heritage description, and commercial music metadata, even though these traditions express the concept in different ways. In FRBR and the Library Reference Model the work is the abstract intellectual creation that precedes any performance or manifestation. In CIDOC-CRM this corresponds to a E28 Conceptual Object that becomes realised through events that produce performances and recordings.

In the Records in Contexts ontology it aligns with an IntellectualEntity whose existence is distinct from the record resources that document or embody it.

In DDEX the same notion appears in the Work entity, which may be accompanied by descriptors such as titles, contributors, genre, identifiers, and proprietary references. In the ISWC standard the musical work is the registered abstract composition that connects to authorship shares, rights, and society-level administration.

The creator of a work is always an intellectual author. This may include a composer, lyricist, librettist, or another contributor who is recognised under authorship rules such as those defined by CISAC in connection with ISWC registration. The role is equivalent to the intellectual authorship sense of dcterms:creator, without implying performance. In CIDOC-CRM the creator is an actor associated with a conceptual production activity, and in RiC-O it is an agent responsible for the creation of an intellectual entity. DDEX differentiates the roles of authors and performers in the WorkDescriptor, and the ISWC standard treats these authorship roles as central to rights management. The OMO model retains this clarity by reserving creator for authorship and describing all other contributions through the has associated agent property, qualified with subject has role.

A.3.1 Work classes

Class Explanation
intellectual work The superclass for all conceptual works, including musical works. Aligns with LRM Work, CIDOC E28 Conceptual Object, and RiC-O IntellectualEntity. Used for any abstract content realised in performances or recordings.
musical work A subclass of intellectual work representing a musical composition or culturally defined musical entity. This includes composed works, traditional works, anonymous folk works, and musical structures with or without notation. Aligns with the ISWC domain and the DDEX Work entity. om:Q138, skcmdb:Q270, fu:Q20
song A subclass of musical work intended for vocal performance, including popular songs, art songs, folk songs, and traditional sung repertoire. Corresponds to vocal musical works in FRBR/LRM and ISWC practice. om:Q155, fu:Q23

A recording is linked to the work it realises using the is recording of property, and the work maintains the reciprocal link through has recording. This mirrors the ISWC–ISRC relationship in rights management, where a registered work may have multiple registered recordings. DDEX models the same relationship when a Resource references the underlying Work in release metadata. FRBR/LRM treats recordings as manifestations of performances that are expressions of the work, and CIDOC-CRM distinguishes between the performed event, the recording event, and the resulting information object, all of which may be tied back to the conceptual object representing the work. In RiC-O the recording is a record resource that documents or embodies the intellectual entity. By modelling the link explicitly, OMO ensures consistency whether the context is commercial distribution, archival preservation, or library cataloguing.

Works may be discovered or accessed through published or manuscript scores, represented by has score, or through external catalogues and digital repositories via has access point. This aligns with FRBR distinctions between expression and manifestation, where a score is a manifestation of the work’s notated expression, and with CIDOC-CRM where scores may be described as information carriers linked to the conceptual content they represent. In RiC-O these relationships connect the intellectual entity to the record parts or representations that document it. The model accommodates published identifiers such as ISMN and ISBN, allowing connections to library catalogues and authority files.

Identifiers play a central role in interoperability. ISWC identifies the abstract musical work under ISO 15707 and is managed within CISAC’s global registration system. ISMN identifies printed music, while older scores may carry ISBNs. MusicBrainz Work IDs support integration with open linked music graphs. These identifiers allow OMO to interoperate with rights societies, libraries, archives, and public knowledge bases without altering their respective practices.

NoteLocal content and heritage

The property is heritage of originates from the Heritage Digital Twins Ontology, where heritage attaches cultural objects to communities or cultural identities. In OMO the property is used in a dual manner that distinguishes ethnolinguistic heritage from national or regulatory heritage. Ethnolinguistic heritage refers to cultural belonging defined by language or community identity. For example, music classified as heritage of Hungarians refers to works connected to Hungarian-speaking communities regardless of national borders, and heritage of Slovaks encompasses works relevant to Slovak ethnolinguistic identity whether they originate in Slovakia, Hungary, or Serbia.

National or regulatory heritage refers to classifications used in local content regulation, cultural policy, or territorial reporting. Heritage of Hungary includes works created in Hungary, works by minority communities within Hungary, and in some contexts works published or produced in Hungary, because national regulations treat these categories inclusively. By using qualifiers, the model can describe both the community-significance dimension and the regulatory-significance dimension without conflating them.

This alignment enables the OMO work model to operate coherently across commercial, scholarly, and heritage-oriented contexts. Commercial systems rely on ISWC and DDEX; libraries use DCTERMS, MARC, VIAF, and published identifiers; archives use RiC-O and event-based provenance; museums use CIDOC-CRM to link conceptual objects to performances, recordings, and documentation; community heritage frameworks use classificatory properties such as is heritage of. By maintaining a clear abstract concept of the work and linking it to recordings, scores, agents, and heritage dimensions, the model allows diverse systems to interoperate without compromising the integrity of their respective traditions.

A.3.2 Work properties

Property Explanation
creator The intellectual authors of the work: composers, lyricists, librettists, or other creators recognised under ISWC/CISAC authorship rules. Aligns with the authorship meaning of dcterms:creator and the CISAC Work roles. Does not include performers or producers. Specific roles should be assigned using has associated agent + subject has role.
has recording Links a musical work to the sound recordings that realise or perform it. Mirrors the Work–Resource relationship in DDEX and is parallel to ISWC–ISRC associations in rights management. om:P115, skcmdb:P107, fu:P457
has score Connects the work to its notated manifestations (printed score, manuscript, digital edition). Aligns with library practice, FRBR Manifestation/Expression, and CIDOC’s E84 Information Carrier for notated material.
is curated member of Indicates that the work belongs to a curated collection, repertoire list, anthology, ethnographic corpus, or thematic grouping. Useful for scholarly and GLAM contexts.
is heritage of (local to) Connects the work to an ethnolinguistic group, cultural heritage community, or national tradition. Supports policy use cases such as local content quotas, intangible heritage classification, etc.
has access point A link to a catalogue entry, archival description, or other external resource describing the work. Mirrors the meaning of an access point at the release/recording levels without implying rights or licences.
ISWC The International Standard Musical Work Code assigned according to ISO 15707. Identifies the abstract work independently of any recording or release. May be stored but not publicly displayed if required by CISAC policies.
MusicBrainz Work ID A stable open identifier for the musical work in the MusicBrainz database. Useful for interoperability across open music metadata ecosystems.

A.4 Music Sheets

The music sheet classes in the Open Music Observatory describe notated representations of musical works, whether they are printed publications, digital editions, or manuscript sources. In the current model these classes are treated as subclasses of a broader category of publications. This is a pragmatic choice that allows textual and notational materials to be handled within a unified interface, separate from sound recordings and audiovisual items. Although this means that manuscripts become grouped with publications, even though they were never formally published, this approach supports a coherent user experience and can later be refined without affecting the underlying semantic relationships.

A.4.1 Music sheet classes

Printed music sheets correspond closely to the concept of a manifestation in the FRBR and Library Reference Model, where the printed score or part is a physical or digital embodiment of an expression of the work. In this sense an ISMN identifies the published score and an ISBN may appear for older scores printed before the adoption of ISMN. DCTERMS can describe both printed and digital editions through properties such as title, creator, publisher, date, and identifier. Europeana practices similarly treat printed scores as text-based cultural heritage objects that carry bibliographic descriptions and link back to the abstract musical work.

Manuscript scores and handwritten sources present a different case. These items are not publications in the bibliographic sense and belong more naturally to archival or museum domains. In CIDOC-CRM a manuscript score would be an Information Carrier, generally described as an E84 Information Carrier, whose content is an E73 Information Object representing the notated music.

In RiC-O the manuscript appears as a Record Resource within a specific fonds or collection, accompanied by provenance relationships that explain who created it, when, and under what circumstances. Despite their different status, both printed and manuscript scores correspond to notated expressions of the musical work, and treating them within one superclass allows the model to present them together in a practical interface.

Music sheet classes
Class Desciption
publication A textual or notational resource that presents intellectual content in a fixed form. This includes printed or digital books, articles, and music scores. Manuscript materials are included for practical reasons, allowing all text and notation resources to be handled through the same interface even when they have not been formally published. Corresponds to FRBR Manifestation, CIDOC-CRM Information Carrier, and RiC-O Record Resource.
music sheet or printed music sheet A notated representation of a musical work, either printed or digital. This includes scores, parts, and lead sheets issued as published editions. Identified by ISMN or ISBN where applicable.
manuscript sheet A handwritten or otherwise unpublished notated source that documents a musical work. This includes composer manuscripts, archival copies, and field-transcribed notation. Corresponds to archival record resources in RiC-O and information carriers in CIDOC-CRM.

The relationship between a musical work and its notated representations is captured in OMO by the has score property. This establishes a link from the abstract work to one or more physical or digital manifestations, aligning with FRBR’s distinction between work, expression, and manifestation, and with CIDOC-CRM’s event and carrier-based descriptions. The same property can connect a work to a modern scholarly edition, a historical printed part, or a manuscript source found in an archive. The unified modelling of these materials allows digital publications, library holdings, and archival manuscripts to operate within the same structural framework while retaining the ability to differentiate provenance, publication status, and material form.

The classification of music sheets as publications therefore serves both practical and conceptual purposes. It supports the workflow in which textual and notational materials are managed separately from sound and audiovisual content, and it maintains compatibility with established bibliographic and archival ontologies.

Future refinements to the publication hierarchy can introduce a clearer separation between published scores and unpublished manuscripts without altering their fundamental relationships to works, agents, or collections. For now the model provides a coherent and interoperable way to represent all forms of notated music, ensuring that they can be linked to musical works and contextualised within the broader cultural heritage ecosystem.

A.4.2 Music sheet properties

Music sheet properties
Property Description
creator The intellectual author of the notated content, typically the composer or lyricist of the musical work. Does not include performers or editors. Corresponds to dcterms:creator and authorship roles in FRBR and RiC-O.
title The title of the music sheet as it appears in the edition, catalogue entry, or archival description. May be recorded in multiple languages. Corresponds to dcterms:title and normal title practices in library metadata.
has score Links the music sheet to the musical work that it represents. Allows multiple manifestations or manuscript sources to be associated with the same abstract work.
publisher The entity responsible for issuing the printed or digital music sheet. Corresponds to dcterms:publisher and to publisher relationships in library cataloguing.
has time The date on which the music sheet was published or first made available in its present form. For manuscript sheets this may be the date of creation if known. The full path is represented by: has time property with qualifier temporal relation and the value date of publication
is curated member of Indicates that the work belongs to a curated collection, repertoire list, anthology, ethnographic corpus, or thematic grouping. Useful for scholarly and GLAM contexts.
is heritage of (local to) Connects the work to an ethnolinguistic group, cultural heritage community, or national tradition. Supports policy use cases such as local content quotas, intangible heritage classification, for example, the ECCCH HDTO ontology.
has access point A link to a catalogue entry, archival description, or other external resource describing the work. Mirrors the meaning of an access point at the release/recording levels without implying rights or licences.
location The physical or digital holding location of the item when applicable, such as a library, archive, or collection. The location applies to qualifier specifies whether the location refers to the holding institution or the place of publication.
edition statement? Information describing the edition, revision, or version of the music sheet. Common in printed scores to distinguish revised editions, urtext versions, or scholarly editions.
material or format? The physical or digital format of the item, such as print, manuscript, facsimile, digital score, or part. Corresponds to material description practices in library and archival metadata and to CIDOC-CRM carrier types.
ISMN Identifier for published notated music (printed scores). Applies to manifestations, but recorded here to support linking between work and published sheet resources.
ISBN Identifier for older printed music publications when ISBNs were used prior to the introduction of ISMN as a distinct standard.

A.5 Agents

Agents are the people, groups, or organisations involved in the creation, performance, production, distribution, or documentation of musical works, recordings, releases, and publications. Different metadata traditions describe agents in different ways. Rights management systems such as ISRC and ISWC require precise distinctions between performers, composers, producers, and other contributors. Library cataloguing frequently records only a creator or contributor statement based on what appears on a publication or catalogue entry, even if such statements are ambiguous. Archives may describe materials at the level of a fonds and attribute provenance to an estate, an organisation, or a collecting activity rather than to individual creative agents. The OMO model allows all three traditions to coexist by separating the class of the agent from the role the agent performs and by using role-qualified relationships when precision is required.

DDEX defines DisplayArtist as the credit that should be presented to users at the release level. DisplayArtist is a presentation and marketing field rather than a rights or authorship classification. It may represent a group of artists, a conductor and orchestra, a solo performer, or an aggregated credit such as Various Artists. The ISRC Main Artist, by contrast, is a recording-level performer designation defined in Annex E of the ISRC Handbook and refers specifically to the primary performing artist or group contributing to the recorded performance. A release can therefore have a DisplayArtist that does not match the ISRC Main Artist of any of its tracks.

The OMO model reflects this separation by treating creator as a general catalogue credit and reserving detailed performer, producer, or authorship information for role-qualified relationships through has associated agent.

Agent classes
Class Explanation
creator (artist) The main agents associated with the creation of the release, equivalent to DCTERMS:creator and DDEX:Artist. The MainArtist is a subclass of DDEX:Artist, and a mandatory field of ISRC. In case of classical music, the evolving standards clarifies the MainArtist is the performer, and the composer is a new class. Ambiguous from a copyright management point of view, and we aim not to use this as a qualifier, however, we connect various artists with the creator property for easier finding the music. The qualifier can be used when we do not know the role of an agent.
composer Equivalent with composer (Q36834), an agent who is credited as author of a musical work
arranger Equivalent with music arranger (Q1643514)
lyricist Equivalent with lyricist (Q822146) who may be an author specialised in song lyrics or opera librettos, or a poem whose words are used in vocal music.
producer An agent responsible for the (mastered) production of the recording. Near equivalent with record producer (Q183945) with the exception that we aim to record those producer(s) who have sound recording rights. Often several people are credited in participating in the production role but usually only the main producer has rights.
performer An agent who is a credited performance on the live or recorded performance. A subclass of the DDEX:Artist class. We aim to find those performers who may be credited with performer’s right; sometimes session musicians may have contributed to a performance whose role is based on work-by-hire and have no performer’s right.
Role classes
Property Description
creator alias (main artist) A general class for agents credited in a catalogue, metadata feed, or publication as responsible for the creation of a release or recording. It corresponds to dcterms:creator and to the DDEX Artist class used in DisplayArtist statements. It does not imply a specific authorship or performance role. Detailed contributions should be recorded using role-qualified properties.
composer An agent credited as the author of a musical work. This corresponds to composers in ISWC registration, to work authors in DDEX WorkDescriptors, and to intellectual authors in library and archival metadata.
lyricist An agent credited as the author of song texts, librettos, or poems used in vocal compositions. This aligns with ISWC lyricist roles and with standard authorship roles in bibliographic metadata.
arranger An agent who prepares or adapts a musical work or traditional melody for performance or publication. In rights management this may count as authorship depending on the jurisdiction and degree of creative contribution.
producer An agent responsible for the production of a sound recording, particularly the entity holding neighbouring rights in European law or sound recording copyright in jurisdictions such as the United States and the United Kingdom. A single recording may list many production-related credits, but the rights-bearing producer is usually a smaller subset of these contributors.
performer An agent credited as performing on the recording or release, such as a vocalist, instrumentalist, conductor, or ensemble. This property expresses the basic performer relationship as it appears in catalogues, liner notes, or DDEX Resource metadata. It refers specifically to participation in the recorded performance, not to authorship of the underlying work. More detailed role information, such as soloist, conductor, featured performer, or instrumental role, should be provided using the has associated agent property with the subject has role qualifier.

A.5.1 Roles

Roles specify the function an agent performs in relation to a work, recording, release, publication, or event. In the OMO model, roles are never stored as subclasses of agents but always as qualifiers on the has associated agent property. This allows a single agent to perform multiple roles without ambiguity and supports detailed rights management, library cataloguing, and archival provenance descriptions.

Role classes
Property Explanation
creator alias (main artist) A descriptive credit used at the release or catalogue level. It may include composers, conductors, performers, or ensembles and is not restricted to rights-relevant roles.
has associated agent qualified with composer role Indicates that the agent is the author of the musical work.
has associated agent qualified with lyricist role Indicates that the agent is the author of the lyrics or text of the work.
has associated agent qualified with arranger role Indicates that the agent is credited with arranging or adapting the work.
has associated agent qualified with producer role Indicates that the agent is responsible for the production of the recording and may hold neighbouring rights or sound recording copyright.
performer or has associated agent qualified with performerrole Indicates that the agent contributed to the recorded performance.

The composer creates the musical work. In the event-based CRM mapping:

E65 Creation → P14 carried out by → E21 Person
E21 Person → P94 has created → E28 Conceptual Object

A performer is an
E21 Person or an E74 Group, linked via P14 carried out by to the performance E7 Activity

A.5.2 Agent properties

Role and agent properties
Property Explanation
has associated agent Links an entity to an agent participating in its creation, performance, production, distribution, or documentation. The relationship must be qualified with subject has role to specify the agent’s function. om:P19, skcmdb:P117, fuds:P453
(subject) has role A qualifier for has associated agent that specifies the particular role performed by the agent. om:P20, skcmdb:P118, fuds:P463
performer Records an explicit performance contribution when a simple performer property is needed instead of a role-qualified relationship. om:P152, skcmdb:P97, fu:P408
record label The organisation credited as the imprint or label responsible for issuing a release. This refers to descriptive imprint information rather than rights ownership. |Equivalent to record label on Wikidata. For details see Releases earlier.
date of birth Birth date of the agent, recorded when permitted by applicable data protection regulations.
date of death Death date of the agent, recorded when permitted by applicable data protection regulations.
ISNI The International Standard Name Identifier assigned to the agent. om:P92, skcmdb:P41, fu:461
VIAF cluster ID The Virtual International Authority File identifier for the agent. om:P91, skcmdb:P40, fu:P60
IPI Name Number The Interested Parties Information Name Number used for CISAC rights administration for composers, lyricists, and arrangers. om:P100, skcmdb:P42
Spotify Artist ID A proprietary identifier used by Spotify for artists. om:P101, skcmdb:P43, fu:P61
MusicBrainz Artist ID The identifier assigned to the agent in the MusicBrainz database. om:P103, skcmdb:P45, fu:P62
Discogs artist ID The identifier assigned to the agent in the Discogs database. om:P105, skcmdb:P116, fu:P476

  1. See Fixing Music Data at the Source in (Antal 2025), and the European Parliament’s resolution (European Parliament 2024).↩︎

  2. Records in Contexts–Conceptual Model (International Council on Archives Expert Group on Archival Description 2023)↩︎

  3. Definition of the CIDOC Conceptual Reference Model (Bekiari et al. 2024)↩︎

  4. Europeana Data Model (Europeana 2017)↩︎

  5. Heritage Digital Twin Ontology (HDTO). First Draft. (ECHOES Ontology Task Force 2025)↩︎

  6. DDEX is a standards setting organisation focused on the creation of digital value chain standards to make the exchange of data and information across the music industry more efficient. See <https://ddex.net/>.↩︎

  7. International Standard Musical Work Code (ISWC). ISO 15707:2022 (ISO 2022)↩︎

  8. Records in Contexts–Conceptual Model (International Council on Archives Expert Group on Archival Description 2023)↩︎

  9. Definition of the CIDOC Conceptual Reference Model (Bekiari et al. 2024)↩︎

  10. Europeana Data Model (Europeana 2017)↩︎

  11. See International Standard Recording Code (ISRC) Handbook 4th Edition, 2021, International ISRC Registration Authority, particularly Annex E. (International ISRC Registration Authority 2021)↩︎