Known Issues

Known Issues of RDF SemSpect Server #

This page contains information about all known issues of the latest release of RDF SemSpect. To report other bugs, request features, or just provide general feedback, you can use the dedicated SemSpect Community GitHub repository.

The context menu of the column headers in the table view has an erratic behaviour #

Some versions of Firefox under Windows have issues in the table view (e.g., opening the context menu of the columns in the table view selects the previous column). Try another version of Firefox or use another browser.

If you have similar issues with another browser or another operating systems, please let us know!

Date filter in the table view does not allow BC dates #

BC dates implementation can vary widely between databases. We did not yet encounter any use case where this is an issue, so we decided to postpone the implementation of the required adapters.

If this is a problem for your use case, please let us know!

Missing resources in persisted views are silently filtered #

When loading saved explorations or SemSpect classes, the backend ignores missing or deleted resources to prevent the view from crashing. Consequently, a shared or saved exploration may appear incomplete without a UI warning.

Delayed Streaming and Broken Pipe Exceptions for GraphDB DataSources #

When using GraphDB as an RDF data source in SemSpect, streaming requests from the repository’s endpoint may experience delays. This issue is accompanied by errors in GraphDB’s logs:

[ERROR] 2026-05-19 15:46:09,789 [http-nio-7200-exec-2 | o.a.c.c.C.[.[.[.[openrdf-http-server]] Servlet.service() for servlet [openrdf-http-server] in context with path [] threw exception [Request processing failed: org.eclipse.rdf4j.http.server.ServerHTTPException: org.eclipse.rdf4j.rio.RDFHandlerException: org.apache.catalina.connector.ClientAbortException: java.io.IOException: Broken pipe] with root cause
java.io.IOException: Broken pipe
  at java.base/sun.nio.ch.SocketDispatcher.write0(Native Method)
	...

The issue occurs when the HEAD request (used by SemSpect to determine the type of URL data sources) fails. This failure triggers a fallback mechanism where SemSpect attempts to determine the content type via other measures.

To test if you are affected execute a HEAD request to your GraphDB repository’s endpoint. If the request fails (returns a non-200 status code), your GraphDB user lacks the necessary permissions.

# If the following command returns a HTTP status code other than 200, your user can't execute HEAD requests.
curl -u "USER:PASSWORD "-I 'http://localhost:7200/repositories/some-store/statements'

To resolve this issue, ensure the GraphDB user accessing the repository has at least write privileges. This resolves the HEAD request failure and allows SemSpect to stream data reliably.