Unit 7: Use Case #4 – Many-to-Many Mapping
In this unit, we'll examine the final use case involving many-to-many mapping.
Many-to-many mapping explained
The structure map defines the source and target DSD. However, if the mapping is dataflow-specific, the structure map defines the source and target dataflow.
The source DSD/dataflow is the one from which the data will be input into the mapping.
While the mapping rules are bi-directional (data mapped one way can be mapped back again) for more complex mappings, which include regular expression matches or substring matches on the source, it is not always possible to map back again.
Therefore, the source DSD or dataflow should be selected based on where the data is coming from, and the target is where the data is going as a result of the mapping.
Many-to-many mapping
Let's take a closer look at the structure maps, component maps and representation maps used in this use case scenario.
Select each option below to learn more.
- Defines one or more component maps
Each component map:
- Has one or more components from the source DSD, mapping to one or more components in the target DSD
- Can link to a representation map
- Is used to describe how the source values map to the target values
- The linked representation map links to source and target codelists, valuelists, or free text.
- May contain multiple sources and multiple targets
- The number and order of sources and targets to a representation map must match exactly that of the component map. (For example, if a component map has two sources REF_AREA and CURRENCY, then the linked representation map must also have two sources: one for the REF_AREA Codelist and the other for the CURRENCY Codelist.)
- Can include complex rules, such as regular expressions (regex) on source values
- Can even define periods of time for which a mapping relationship is true (For example, if a relationship between source country and target currency is defined then one could map France to the French Franc up until 2002 and then map France to the Euro from 2002 onwards.)
If values do not require mapping, (for example, if source FREQ maps to target FREQ and the values are the same in both the source and target DSD) then the component map should not link to a representation map. The lack of link will inform the system that the value should be copied across verbatim.
What do you know?
Now that we have reviewed the various types of mappings, let's try a question.
When presented with a challenge that is most logically solved by splitting the rules into individual maps or describing the relationship in a single map, what type of mapping is being used to transcode the data?
Select all that apply and then select Submit.
Either many-to-one or one-to many mapping is used to transcode the data when the solution involves either splitting the rules into individual maps or describing the relationship in a single map.
The correct answers are options 2 and 3.
Either many-to-one or one-to many mapping is used to transcode the data when the solution involves either splitting the rules into individual maps or describing the relationship in a single map.
The correct answers are options 2 and 3.
Either many-to-one or one-to many mapping is used to transcode the data when the solution involves either splitting the rules into individual maps or describing the relationship in a single map.
Coming next
In the final unit, a short video on testing.
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