The Multiple Feature Attribute Support functionality has been added to the AttributeCreator in FME 2013 SP2, it realizes accessing freely to attributes of backward / forward features in a sequence of features. Using this functionality, for example, the Fibonacci sequence can be created easily by a Counter and an AttributeCreator with the settings like:
Count Output Attribute: _fibonacci
Count Start: 0
<Mutliple Feature Attribute Support>
Number of Prior Features: 2
<Attribute To Set>
Attribute Name: _fibonacci
Test Condition: 1 < @Value(feature._fibonacci)
Output Value: @Evaluate(@Value(feature[-2]._fibonacci)+@Value(feature[-1]._fibonacci))
After this, using an AttributeAccumulator and a ListConcatenator, got a correct Fibonacci sequence: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, ...
The point is that we can access any attributes of prior / subsequent features with the syntax of feature[n].<attribute name>. n is an integer value which indicates the relative position of a feature based on the position of the current feature in the sequence. Negative n means a prior feature, positive n means a subsequent feature, and naturally 0 means the current feature. The range of available n value will be determined according to "Number of Prior Features" and "Number of Subsequent Features" parameters.
Does the Fibonacci sequence seem useless?
Great! Multiple Feature Attribute Support in AttributeCreator FME 2013 SP2
In FME 2013 SP3, we don't need to use the syntax of feature.<attribute name> for the current feature attribute. Just <attribute name> indicates the current feature attribute in condition expressions. For example:
Test Condition: 1 < @Value(_fibonacci)
Next: Use Case of Multiple Feature Attribute Support