NullAttributeMapper Use Case: Assign Value to Missing Attributes

(FME 2014 build 14234)

From this thread. > Community: Merge and Flag

Assume there are these two tables.
FileA:

Name	Postcode	DOB
Bob	NG1 1AA	01/01/1970
Sue	WP1 1AA	01/01/1990

FileB:

Name	Postcode	DOB
Bob	NG1 1AA	01/01/1970
John	SW1 1AA	01/01/1980

The question was how to merge the tables; the result table must not contain duplicated person's row, and must have additional columns which indicate existence in the original tables.
Required result table should be:

Name	Postcode	DOB	FileAFlag	FileBFlag
Bob	NG1 1AA	01/01/1970	Yes	Yes
Sue	WP1 1AA	01/01/1990	Yes	No
John	SW1 1AA	01/01/1980	No	Yes

In the Community, an excellent solution using the FeatureMerger has been provided. If I created a workspace according to the solution, the first step for merging tables would be like this.

Immediately after the tables were merged, every "FileBFlag" of NotMerged features and every "FileAFlag" of Unreferenced features are <missing>, i.e. not exist. To satisfy the requirement, finally those <missing> attributes should have a specific value - "No".
The subject I think of here is how to assign "No" to <missing> attributes after merging.

One possible way is to use an AttributeCreator with conditional value setting. "Attribute Is Missing" operator can be used in the setting.

There is another way in FME 2014. That is to use a NullAttributeMapper in order to assign "No" to <missing> FileAFlag and FileBFlag.

Both of them work fine, I cannot say which way is better. But the NullAttributeMapper parameter setting looks simpler than conditional value settings in the AttributeCreator.
I would use the NullAttributeMapper if I encountered a similar requirement.

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It's also possible that adding "FileBFlag" (= "No") to NotMatched output and adding "FileAFlag" (= "No") to Unreferenced output in the FeatureMerger using the "Edit Attribute" tool.
If did so, both the AttributeCreator and the NullAttributeMapper would not be necessary no longer, but the process would become difficult to be visible. It's good or not ...