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.
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.
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.
/api/oai?verb=Identify
General information about the OAI interface and the relevant repository: the Städel Museum.
/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.
/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
/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.
/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”.
/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”.
/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
.
/api/oai?verb=GetRecord&metadataPrefix=lido&identifier=oai%3ADE-MUS-048017%3A2442
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.