9. Key resolution and the Default data set

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Normally, when retrieving the value associated to a key in a given data set, KeyValue finds the value in the data set containing the key. However, this is not always the case. The process of finding the correct value assigned to a given key is called key resolution .

The most basic way to assign a value to a key is providing the key-value pair as we have seen so far. Additionally, there are three ways to import values from different keys and data sets.

9.1. Importing a value from another key

We can import the value of a key from another key. Moreover, the source key might be in a different data set. For this purpose, instead of providing the value for the key we should put a reference in the following format:

key-name@data-set-name

where key-name is the name of source key and data-set-name is the name of source data set. You can leave either key-name or data-set-name blank to refer to the current key or data set. For instance, on sheet Key resolution and Default data set, key Size in data set Polygon #1 has the same value as Length in data set Small.

Figure 13. Polygon #1 imports key Size from key Length in data set Small.

Data set Polygon #2 imports key Size from data set Large.

Figure 14. Polygon #2 imports key Size from data set Large.

In data set Polygon #3 keys Size and NumberOfEdges have the same value.

Figure 15. Polygon #3 imports key Size from its own key NumberOfEdges.

9.2. Importing all key-value pairs from other data sets

We can import all key-value pairs from one or more data sets into the current one through the key Imports. The value associated to Imports must be a vector of data set names. All key-value pairs in any of these data sets are imported to the data set containing Imports.

Keys assigned locally, either directly or through references, take precedence over imported keys. Data sets assigned to key Imports are processed in the order they appear.

For instance, on sheet Key resolution and Default data set, Polygon #4 imports keys first from Large and second from Polygon #3. Only keys that are not found neither in Polygon #4 nor in Large will be imported from Polygon #3. Therefore, key NumberOfEdges is assigned locally, key Size is imported from Large and isRegular is imported from Polygon #3.

Figure 16. Use of key Imports.

9.3. Importing key-values from Default data set

After searching a key locally and in imported data sets, if the key is still not resolved, then KeyValue makes a last trial searching in a special data set named Default. To make this search effective, Default must have a key Export set to TRUE.

For instance, on sheet Key resolution and Default data set, Polygon #5 imports all keys, but Processor, from Default.

Figure 17. Polygon #5 imports all keys, but Processor, from Default.