Managing Harvesting Server and Sets
Your Dataverse Installation as an OAI server
As a harvesting server, your Dataverse installation can make some of the local dataset metadata available to remote harvesting clients. These can be other Dataverse installations, or any other clients that support OAI-PMH harvesting protocol. Note that the terms “Harvesting Server” and “OAI Server” are being used interchangeably throughout this guide and in the inline help text.
If you want to learn more about OAI-PMH, you could take a look at DataCite OAI-PMH guide or the OAI-PMH protocol definition.
You might consider adding your OAI-enabled Dataverse installation to this shared list of such instances.
The email portion of :SystemEmail will be visible via OAI-PMH (from the “Identify” verb).
How does it work?
Only the published datasets in your Dataverse installation can be made harvestable. Remote clients normally keep their records in sync through scheduled incremental updates, daily or weekly, thus minimizing the load on your server. Note that it is only the metadata that are harvested. Remote harvesters will generally not attempt to download the data files associated with the harvested datasets.
Harvesting server can be enabled or disabled on the “Harvesting Server” page accessible via the Dashboard. Harvesting server is by default disabled on a brand new, “out of the box” Dataverse installation.
The OAI-PMH endpoint can be accessed at
http(s)://<Your Dataverse Installation FQDN>/oai.
If you want other services to harvest your repository, point them to this URL.
Example URL for ‘Identify’ verb: demo.dataverse.org OAI
Once the service is enabled, you define collections of local datasets that will be available to remote harvesters as OAI Sets. Once again, the terms “OAI Set” and “Harvesting Set” are used interchangeably. Sets are defined by search queries. Any such query that finds any number of published, local (non-harvested) datasets can be used to create an OAI set. Sets can overlap local Dataverse collections, and can include as few or as many of your local datasets as you wish. A good way to master the Dataverse Software search query language is to experiment with the Advanced Search page. We also recommend that you consult the Search API section of the API Guide.
Once you have entered the search query and clicked Next, the number of search results found will be shown on the next screen. This way, if you are seeing a number that’s different from what you expected, you can go back and try to re-define the query.
Some useful examples of search queries to define OAI sets:
A good way to create a set that would include all your local, published datasets is to do so by the Unique Identifier authority registered to your Dataverse installation, for example:
Note that double quotes must be used, since the search field value contains the colon symbol!
Note also that the search terms limiting the results to published and local datasets are added to the query automatically, so you don’t need to worry about that.
A query to create a set to include the datasets from a specific Dataverse collection:
where NNN is the database id of the Dataverse collection object (to verify the database ID, consult the Dataverse table of the SQL database used by the application or use the View a Dataverse Collection API endpoint).
Note that this query does not provide datasets that are linked into the specified Dataverse collection.
A query to create a set to include the datasets from a specific Dataverse collection including datasets that have been deposited into other Dataverse collections but linked into the specified Dataverse collection:
where NNN is the database ID of the Dataverse collection (to verify the database ID, consult the Dataverse table of the SQL database used by the application or use the View a Dataverse Collection API endpoint). If the Dataverse collection has one or more parent collections, the subtreePaths query has to include the database IDs of each of the collection’s parent collections, up to but excluding the “Root” collection. For example:
where NNN is the database ID of the Dataverse collection containing the desired dataset and AAA and BBB are the database IDs of the parent collections.
A query to find all the dataset by a certain author:
where YYY is the name.
Complex queries can be created with multiple logical AND and OR operators. For example,
(authorName:YYY OR authorName:ZZZ) AND dsPublicationDate:NNNN
Some further query examples:
For specific datasets using a persistentID:
(dsPersistentId:10.5000/ZZYYXX/ OR dsPersistentId:10.5000/XXYYZZ)
For all datasets within a specific ID authority:
For all Dataverse collections with subjects of Astronomy and Astrophysics or Earth and Environmental Sciences:
(dvSubject:"Astronomy and Astrophysics" OR dvSubject:"Earth and Environmental Sciences")
For all datasets containing the keyword “censorship”:
Important: New Solr schema required!
In order to be able to define OAI sets, your Solr server must be upgraded with the search schema that came with release 4.5 (or later), and all your local datasets must be re-indexed, once the new schema is installed.
OAI Set updates
Every time a new harvesting set is created, or changes are made to an existing set, the contents of the set are automatically updated - the Dataverse installation will find the datasets defined by the query, and attempt to run the metadata export on the ones that haven’t been exported yet. Only the datasets for which the export has completed successfully, and the results cached on the filesystem are included in the OAI sets advertised to the harvesting clients!
This is in contrast to how the sets used to be managed in DVN v.3, where sets had to be exported manually before any such changes had effect.
Important: Note however that changes made to the actual dataset
metadata do not automatically trigger any corresponding OAI sets to
be updated immediately! For example: let’s say you have created an OAI set defined by
the search query
authorName:king, that resulted in 43
dataset records. If a new dataset by the same author is added and published, this does not immediately add the extra
record to the set! It would simply be too expensive, to refresh all
the sets every time any changes to the metadata are made.
The OAI set will however be updated automatically by a scheduled metadata export job that runs every night (at 2AM, by default). This export timer is created and activated automatically every time the application is deployed or restarted. See the Metadata Export section of the Admin Guide, for more information on the automated metadata exports.
It is still possible however to make changes like this be immediately reflected in the OAI server, by going to the Harvesting Server page and clicking the “Run Export” icon next to the desired OAI set.