Frequently Asked Questions

What is my <>?

Unless explicitly specified, please use

Can I access the DSL API using my ReadCube account?

Unfortunately no, this is currently not possible.

How can I get support?

Please send an email to Please provide as much information about your problem as possible, mainly:

  • What are you trying to do and what problem are you facing.

  • What is the exact error message, full body and headers.

  • Describe how can we reproduce the problem.

  • Any additional details, such as possible network proxies, firewalls, any additional details that might be relevant for reproducing the issue.

What is the proper Content-Type and encoding information?

The DSL does not expect any specific content type or encoding information. UTF-8 and JSON is always assumed, with the exception of /dsl.json, where the requests are DSL queries, not JSON input.

Similarly, the DSL always returns valid JSON objects, encoded in UTF-8.

I’m getting “Something went wrong” bubble after running a query in the user interface, or alternatively getting HTTP 500 Internal Server Error when using API access.

This error is usually raised when the query is either too long (ie. has too many or clauses in the filter) or it returns too much data(such as returning all fieldset). Try to rewrite the query using different filters, for example using in operator. Try returning less records.

What does it mean “Query is too long or complex.”?

This error usually happens in these circumstances:

  • An entity filter (e.g. returns too many results. In this case the user should try to make entity filters more specific. For instance, instead of filtering publications by researcher’s first/last name, it is better to either use authors search (ie search publications in authors for "<first name> <last name>"), or run a query to researchers source first (ie search researchers for "\"<first name> <last name>\"") to obtain the researcher ID and then filter on publication using this ID instead.

  • The query contains too many filters, such as too many and/or conditions. This could also occur when using in filter with too many values.

Are there any guidelines regarding query length/complexity?

To achieve optimal query performance, we recommend to stick to the following general principles:

  • Number of items used in in filter clause: up to 400, example: search publications where id in [...]

  • Number of boolean filter conditions: up to 100, example: search publications where field1 = value and field2 = value

  • Number of boolean full text clauses: up to 100, example: search publications in authors for "\"Alan Turing\" OR \"Stephen Hawking\""

What is the difference between old-style FOR codes and the new ones?

As of version 1.18, we implemented a new methodology to assign Fields of Research (FOR) categories to publication documents. The new methodology is improving both the precision and recall of the FOR categorization. The API now provides both the 4-digit and the respective 2-digit codes via the single field category_for.

Do all author/investigator affiliations include GRID and GeoNames identifiers?

No. Identifiers are automatically extracted from person affiliations text, so they can be missing in some cases. Also, these identifiers are the result of separate data mining processes, so some affiliations may include a GeoNames country or city code, but not a GRID ID.