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Welcome to the OAI interface of the Städel Museum.

The Städel Museum uses the OAI (Open Archives Initiative) interface for data interchange and synchronization. The metadata is regularly updated and can be viewed or harvested. The interface features two different metadata formats: first, a significantly reduced compressed format to assist in identifying the objects with Dublin Core, and, second, LIDO (Lightweight Information Describing Objects) for descriptive metadata.

The metadata is available under the license CC0 1.0.

You now have access to the OAI interface of the Städel Museum. Please save this link for future use.

OAI of the Städel Museum

What is LIDO?

LIDO is an XML-based metadata format and harvesting schema developed by CIDOC (International Committee for Documentation), a working group of ICOM (International Council of Museums). It is intended to increase the global interoperability of museum metadata, allowing for a uniform output format in order to standardize data sharing and harvesting. In LIDO the metadata is sorted into event-based wrappers.

Anyone interested can take a detailed look at the LIDO documentation, download sample records of the collection with in-line comments, or have a look in the section “Metadata Details”. To validate the LIDO schema, please download the appropriate xsd file.

OAI Harvester: Functions and Parameters

To extract large amounts of data from the OAI, the OAI user must implement an OAI harvester that crawls the results using a recursive loop.

The OAI API is HTTP-based and uses GET requests to retrieve XML documents. It supports TLS / SSL and can be accessed using common HTTP clients, e.g.:

curl "https://sammlung.staedelmuseum.de/api/oai?verb=Identify"

The OAI has various subpages that are accessible via the interface. To refine results, you can combine them with different parameters.

 

All pages and parameters at a glance:

Identify

/api/oai?verb=Identify

General information about the OAI interface and the relevant repository: the Städel Museum.

ListRecords

/api/oai?verb=ListRecords

Lists all records available in the OAI, the corresponding command is verb=ListRecords.

Various parameters can be used to select and refine within large result set:

  • The timestamp <datestamp> (see section “Metadata Details”) can be called using from / until; this allows the user to locate all records that have been modified or added within a certain period of time. The argument &from=2020-05-01 therefore returns all results that have been updated after 01.05.2020.

  • The result set can also be qualified using the parameters mentioned under ListSets.

  • Because only 1000 records are only ever displayed on a results page, the resumptionToken for the next 1000 results is shown at the bottom of each results page. The resumptionToken repeats the parameters entered in the search and increases the offset value. For example:

    &resumptionToken={"format":"lido","from":"2020-05-01T00:00:00Z","until":"2020-05-03T17:18:41Z","offset":100,"set":"scope:major"}
    

    A harvester must use a recursive loop to append the resumptionToken located at the bottom of the results to verb=ListRecords to get to the next page. If no further resumptionToken can be found, the loop ends.

Sample requests

/api/oai?verb=ListRecords&metadataPrefix=lido &until=2020-05-01
/api/oai?verb=ListRecords&metadataPrefix=lido&from=2019-12-01&until=2020-05-01
/api/oai?verb=ListRecords&resumptionToken={"format":"lido","from":"2019-08-08T09:32:15Z","until":"2019-12-16T17:18:41Z","offset":1500}
/api/oai?verb=ListRecords&metadataPrefix=lido&set=scope:major &until=2020-05-01

ListSets

/api/oai?verb=ListSets

This is where you can find all available subsets that return a limited selection of data sets. The parameter set indicates in which set the selection is made.

  • &set=scope:major contains all the major artworks in the respective collection departments.

  • &set=scope:graphics contains all works of the Department of Prints and Drawings, in particular those digitally catalogued as part of the German Research Foundation (DFG) project on hand-drawings.

ListMetadataFormats

/api/oai?verb=ListMetadataFormats

The interface applies different data formats to display metadata; the parameter metadataPrefix determines which metadata format is returned.

  • &metadataPrefix=oai_dc returns data in Dublin Core. The format is used to identify and display limited identifying metadata.

  • &metadataPrefix=lido returns data in LIDO; this contains all descriptive metadata, see section “LIDO” or “Metadata Details”.

ListIdentifiers

/api/oai?verb=ListIdentifiers

Lists all unique identifiers present in the OAI and thus enables the harvesting of the unique identifiers within the entire repository. The resumptionToken can also be relevant for the identifiers, allowing for all results to be harvested. More information about the parameter can be found under “ListRecords”.

GetRecord

/api/oai?verb=GetRecord

Finally, there is the possibility to directly call a specific record, using the parameter &verb=GetRecord. For this, the OAI unique identifier for the artwork must be appended to the metadataPrefix argument, e.g.:

&identifier=oai%3ADE-MUS-048017%3A1694&

Whenever a unique identifier contains a colon, it is replaced in the URL by %3A.

Sample requests

/api/oai?verb=GetRecord&metadataPrefix=lido&identifier=oai%3ADE-MUS-048017%3A2442

Details and Special Features of Metadata

  • The OAI identifier identifies each object using the Städel Museum’s ISIL number DE-MUS-048017 and the object number of the individual artwork. This creates an internationally unique identifier for each object, e.g. “DE-MUS-048017:2442”.

    This identifier is found first of all in the header of each object as <identifier>, second of all in the <lido:lidoRecID>, and thirdly in the <lido:objectPublishedID>.

  • The <datestamp> of an object indicates when it was last modified. For example, all records that have been modified since the last retrieval can be found and harvested (see ListRecords parameters in the section “OAI Harvester”).

  • The object number forms the unique identifier and maps to the object in the Städel. It can be found in the <lido:workID lido:type="Object ID"> and is part of the string that makes up the OAI identifier.

  • Some artworks in the collection have an object number that differs from the inventory or accession number (which is derived from the historical inventorying of the collection). This number is not a unique identifier of the artwork in the museum, and instead only refers to a subset within collection holdings. It is found in <lido:workID lido:type="Inventarnummer">.

  • The permalink to an object in the Städel’s Digital Collection is found in the <lido:objectWebResource> of the <lido:relatedWorksWrap>. It is made up of the root element https://www.staedelmuseum.de/go/ds/ and the artwork’s object number (without spaces or periods).

  • The image corresponding to the record is found in <lido:linkResource> within the <lido:resourceWrap>. It is available for download under the license CC BY-SA 4.0. Please note the following copytight when using images in any way: “CC BY-SA 4.0 Städel Museum, Frankfurt am Main”.

  • For the best possible integration and subsequent use and remixing, the images are trimmed before the alpha channel or, in the case of works on paper from the Department of Prints and Drawings, trimmed into a rectangular shape and placed against the background.

  • The metadata are available in German and in English and they can be used separately through the marker xml:lang="de" or xml:lang="en".

  • LIDO data is organized into events. <lido:eventSet> has different <lido:eventType>, which indicate the area the following information belongs to.

    • The <lido:eventSet> with the type “Work conception” provides information about the creation of an artwork.

    • The <lido:eventSet> with the type “Acquisition” contains information about the acquisition of the object.

    • The <lido:eventSet> with the type “Designing” contains information about pictorial invention (whether the work is a copy after or imitation of another artwork, or if a preliminary drawing exists, for example).

  • Elements that begin with lido:display[...] combine content from several individual fields that have been merged for better display. For the correct information given in the authority file, please use the individual fields.

  • Some objects return more than one artist’s name: this may reflect a collaboration between two or more artists, but also past attributions which are no longer valid. For this reason you should pay attention to the <lido:attributionQualifierActor> whenever more than one <lido:eventActor> exists.

  • In order to standardize the metadata (particularly in regard to proper nouns such as artist and subject names, geographical information, and other keywords), links to the Deutsche Nationalbibliothek’s Integrated Authority File GND (Gemeinsame Normdatei) have been added in many places. These can be recognized by lido:source=https://d-nb.info/ and provide the link to the corresponding entry in the authority file.

  • The keyword tags used by the Digital Collection can be found in <lido:objectRelationWrap> and are divided into the following categories:

    • The <lido:subjectConcept> with the <lido:conceptID> “Motivgattung” relates to a genre-like term and forms the uppermost category in the hierarchy under which a work is classified.

    • The next level in the set hierarchy is the <lido:subjectConcept> with <lido:conceptID> “Motiv”, which represents various general subjects or themes of an artwork.

    • The <lido:subjectConcept> with <lido:conceptID> “Bildelement” contains all pictorial motifs presented in detail in the artwork.

    • <lido:subjectConcept> with a <lido:conceptID> with the specification https://iconclass.org/[...] represents an Iconclass term. Iconclass is a classification system for the cataloguing, description, and retrieval of subjects represented in images. Here whole object genres are summarized in one identifier. For example the IconclassID “25I1” with the link https://iconclass.org/25I1 stands for vedute or city views.

    • <lido:subjectActor> contains all the subjects or figures presented in the artwork (e.g. biblical figures).

  • In the case of multipart works (such as altarpieces / series of prints / painting cycles), the respective individual records hierarchically reference parental records and vice versa. These references can be found under <lido:relatedWorksWrap>. In such a case, each individual work <lido:relatedWork> contains both the permalink of the Digital Collection <lido:objectWebResource> and its <lido:objectID>. <lido:relatedWorkRelType> describes how the two relate to each other, e.g. “altarpiece”, “inner face, left-hand shutter”, “verso”, etc.