Searching for and importing bibliographic and authority data

With SRU (Search/Retrieve via URL), you can use search indices and search terms to conduct systematic searches of the German National Library’s data and subsequently import it into your own environment. The results of the search are provided in a defined XML format.
Queries are formulated in the retrieval language (Contextual Query Language).

The SRU standard was published by the Library of Congress and is a further development of the Z39.50 protocol.

An overview of all available metadata as well as the different options of obtaining data is given here.

Standards of SRU interface

SRU protocol: Version 1.1
Retrieval language CQL Context Set Version 1.2, Conformance-Level 2

SRU functions

SRU encompasses the basic functions:

• Explain: Self-description in XML standard format, including information on

  • Catalogue
  • Indices and supported sorting parameters
  • Data formats

• Search/Retrieve: Search query

  • Retrieval language: CQL (Contextual Query Language)

  • Boolean operators (and, or, not) are supported. An index must be entered for each search term, otherwise the search is carried out in the default index WOE.

    Syntax of a search query: ... index%3Dsearch term%20or%20index%3Dsearch term ...

  • Help in formulating a CQL search query

• Sort: Sorting the result set

  • the sort parameter is not supported in SRU version 1.1 but as part of CQL Context Set version 1.2. For which indices the sorting parameter is supported is available in the catalogue-specific SRU-Explain, in the specification sort=“true“, a combination is not possible.
    Syntax of a search query: sort.descending or sort.ascending

Access requirements

The SRU interface can be accessed free of charge and without registration.

Available catalogues

Formats

Detailed information on the formats available is given here.

Terms of use and provision

Detailed information on terms of use and provision is given here.

Practical examples

SRU-query for the bibliographic data of a specific edition or calendar week of the New Release Service or a series of the Deutschen Nationalbibliografie: Queries for the calendar week must follow the pattern: YYseriesCW in the „WVN" index (e. g. 24N05 or for Series A, Edition 05 of year 2024 = 24A05). The calendar week requires two digits, weeks 1 through 9 starting with 0.

Example:
https://services.dnb.de/sru/dnb?version=1.1&operation=searchRetrieve&query=WVN%3D24A05&recordSchema=MARC21-xml

The following qualifications are possible:

The Asterisk *is a placeholder for any number of characters and must be placed directly behind the value.

Examples of SRU requests:

Tp* (Person)

https://services.dnb.de/sru/authorities?version=1.1&
operation=searchRetrieve&
query=WOE%3DRupp%20Elisabeth%20and%20BBG%3DTp*&
recordSchema=MARC21-xml

Ts* (Subject term)

https://services.dnb.de/sru/authorities?version=1.1&
operation=searchRetrieve&
query=WOE%3DMarketing%20and%20BBG%3DTs*&
recordSchema=MARC21-xml

Subject headings can be obtained by qualifiying the search with „COD=s“:

https://services.dnb.de/sru/authorities?version=1.1&
operation=searchRetrieve&
query=WOE%3Dsozialistenkongress%20and%20COD%3Ds&
recordSchema=MARC21-xml

URL coding

In URL-Encoding umlauts are coded using UTF-8 and with a prefixed % sign (percent encoding).
Example: Lower case ö in UTF-8 = C3 B6. With prefixed % sign = %C3%B6.

In order to use "=" in a query (... query=dc.title=musik ...) the guidelines recommend replacing the second "=" by "%3D" (... query=dc.title%3Dmusik ...) and replacing special characters (e. g. diacritical marks with UTF-8 hexadecimal) in the search key (Standard).
Spaces e.g. before and after Boolean operators should be replaced by %20 (... SW%3DKRAFTWERK%20not%20SW%3DROBOTER ...), depending on client.

Number of data records returned per request

Standard (default): 10 data records per response
Maximum: 100 data records per reply if ...&maximumRecords=100 specified (possible values 1 to 100)
Call of further data records: ...&startRecord=101 (possible values 1 to 99,000)

Frequently asked questions (FAQ)

Contact

schnittstellen-service@dnb.de

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