nodes with optional inputs

Is there a way to create a node with one or more optional inputs? We are running up against this in a couple of places. My reading of code so far suggests that this isn't possible, but what have I overlooked?


the current version of KNIME has no such feature. All ports must be connected and predecessor nodes must be executed before a node itself is executable.

We do have a new workflow manager in the works, though, that will be able to accept open ports,making them effectively optional. But a new version with this manager will not be out until the end of this year.

- Peter.

Excellent. I am looking foward to another great release of Knime!

I also need the ability to have optional input to a node.
When would the new workflow manager be available in 2008 ?


I'm not sure what I was smoking when I posted the new workflow manager will be available end of "this" year (and it was 2007 back then when I wrote it)...
It is going to be available in the near future.
- P.

Hi Peter,
thanks for your encouraging info. Sounds promising for me too.
Could you please anticipate other new fetaures of upcoming workflow manager.

I'm missing a possibility to make node configuration parameters variable. This is useful, when you want to run an algorithm several times with different settings. Environment variables could be a solution.
Can you foresee something of that kind?


Yes, we do forsee environment variables in the near future. V2.0 will have those but I doubt that all nodes will support them for their internal parameters. So if you are talking about your own nodes using them, fine, if you are counting on all KNIME nodes making use of env vars you may need to wait for a subsequent version.

- Michael

Thanks Michael. Great news!
I dare to ask a question, which is normally disliked.
Are there any hints regarding the timelines except "near future"?


That's an excellent question.

(we are in the midst of testing and finetuning our own, internal, buggy release of the new version right now).

berthold wrote:
(we are in the midst of testing and finetuning our own, internal, buggy release of the new version right now).

Sounds promissing )
Good luck!

Despite a few search attempts, I’ve been unable to find a description of how to designate an input as optional. When I encountered “The documentation of this class is mostly missing and will be fixed in future versions” (in Java doc for PortType), I wondered whether it was premature to contemplate using optional input ports? Is this functionality available? Stable? Subject to revision?


Hello, all.

Are there any possibilty to reinforce development of some most useful features in KNIME? May be donations or etc?

BR, Valery Otryvankin

Hi Keith & Valery,

@Keith: Your question regarding optional ports is fair given Peters comment from 27 Aug 2007. The new workflow manager does not support optional inports and such feature is not planned, either. Sorry for the confusion – we should be more careful when talking about planned features and timelines.

@Valery: Supporting KNIME is always welcome. This can be in form of plain donations but also in form of sponsored node development. In fact, we have done this quite a few times in the past. Some nodes in the data preprocessing category were sponsored (there are others, check out This is not necessarily constrained to new nodes, this can also be general KNIME functionality (e.g. we have funds that allow us to to allocate resources for adding Undo/Redo functionality to KNIME, available in v2.1) or for high-priority bug fixing. Can you contact us at for details?


:frowning: Most of my plans for KNIME 2.x revolved around optional inputs. For me they provided a means of layering on more sophisticated options without complicating the implementation by adding ‘basic’ and ‘advanced’ nodes which provided different levels of functionality. Specifically, I had envisaged the use of ‘drug-like’ profiles or in KNIME terminology models which when available and desirable could be used to limit which molecules were selected for synthesis, purchase, testing etc in a pharmaceutical research environment. (Obviously, the millions of molecules which are being considered are too many to contemplate placing in KNIME tables, they have to reside on disk - as do the outputs).

I need to have a re-think…