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After running features through a transformer that does uses a Group By, is there a simple way to determine which destination features came from which source features? The best I could come up with is some combination of SpatialRelator and FeatureMerger, to do a spatial join on the result.

Edit: For example, I have a source dataset that feeds into a BUFFERER, that I set a group-by attribute on. For each BUFFERER output feature, I wish to associate it somehow with the subset of original features that donated themselves to it. Unfortunately I don't believe the BUFFERER has a List attribute in FME Desktop 2011. How would I do this?

Edit edit: bufferer, not dissolver.

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Isn't there a attribute that you can expose that is called fme_basename or fme_filename or something like that? Couldn't you maybe expose that, toss it into a variable and then call it later? Don't have access to FME right now or I'd test it out. – Chad Cooper Apr 28 '11 at 16:54
@Chad: I'm looking for the specific source polygons within a dataset, not just the source dataset as a whole. – Dave Rafkind May 20 '11 at 12:37

Using the List feature you can keep source features

FMEpedia is a excellent resource for this information.

specifically for you

"Using a list. Many transformers have a list option so you can keep track of source attributes by keeping all the values. "

just create a list of source datasets before you set it in the groupby.

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BUFFERER has no list attribute. – Dave Rafkind May 20 '11 at 12:37

The fme_feature_type attribute contains the value of the feature's original feature type (feature class, table name etc.).

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I'm looking for specific polygons, not just the name of the source dataset. – Dave Rafkind May 20 '11 at 12:37

I think what you are looking for is the filterTypeFilter transformer. Give it a try.featureTypeFilter

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I'm looking for specific source polygons, not the name of the source dataset. – Dave Rafkind May 20 '11 at 12:41

Rather than SpatialRelator and FeatureMerger, I would use the Aggregator and FeatureMerger. The Aggregator would let you use the same group-by as the Bufferer, but with the ability to create a list. Then the FeatureMerger would let you merge that list onto the buffered features. Of course there would need to be an ID of some sort to enable the merging.

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This is the best answer so far. Unfortunately I also want the effect of having run the bufferer, which means I have to do the provenance assocation after the bufferer (bufferer and amalgamator will result in differently membered-groups) which means the amalgamator won't have any effect. – Dave Rafkind May 20 '11 at 12:41

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