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Version 1 is available at https://api.deutsche-digitabledigitale-bibliothekebibliothek.de
Version 2 is available at https://api.deutsche-digitabledigitale-bibliothekebibliothek.de/2
The data behind the two versions is identical.
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The Search API has been reduced to include only the generic search endpoint. The other endpoints of the Search API were tailored to speciffic specific functionalities of the DDB frontend and were no longer needed. The Search API endpoint now also supports POST requests in addition to the previously supported GET requests so allow longer queries.
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The endpoints under /items are about the same as in version 1. There are very minor changes to the AIP model used, mainly due to the fact that other XML libraries are used internally. The only substancial change regarding the content is teh the fact that the object source is no longer inlined into the AIP.
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Furthermore, starting from Backend 7.3 it is also possible to save search queries for logged in users, details on this can be founf found at Saved Searches API