Do you want to pass attributes or features?

If attributes then you can use a wokspacerunner and published parameters in the child workspace.

If features then you will need to write these and read them again in the child workspace. I use FFS as format when I do this. Or a database like PostGIS, sqlite or Excel.

Why do you go for FFS?

This is Safe's internal format. So I do not have to think about specific format limitations, like max characters for a table name, illegal characters for a column name or a geometry type that does not work. FME could already read the data so no need to create another possible bottleneck that will bite you in the future when input data changes from you test / development dataset.

It loads quickly, which makes sense as when you read from a not native format, it will convert it under the hood to FFS for further processing in workbench. I have not retested this recently, but from my experience load time is a big part of the total runtime of a job.

But I might be wrong, so if you have different insights, please share.

Of course the format of choice also depends on specific requirements. Other option is to create a to-do list in a database and use incompleted to-do's as input for a second workspace. If you have very large datasets to process, which you subprocess tile by tile, using this method, you can stop the process without having to do all successfully processed tiles again. This is very nice if your process takes hours to complete and crashes at 80% 🙂

How could I use the workspace runner to read the output attribute from the parent workspace .

And I have different output that I need to read them in child workspace

in the child workspace, a featurereader to read ffs, create a published parameter from the path

in the paren workspace, write the data you need using a featurewriter, send the summary feature to a workspacerunner, select the dataset attribute for the published parameter

now if you run the parent, it will write the ffs, then start the child which will read the ffs based on the published parameter set by the parent

Thanks for ur idea