====== Inheritance in datasheets ======
Inheritance is an essential notion in the creation of a set of DS, to avoid repeating itself. This makes it possible to inherit characteristics of a parent DS, and even to rewrite on some, and even to make it possible not specifying "everything again" when we realize a set of DS have common characteristics.

For example, imagine an object ''my object'' that can have four characteristics A, B, C and D, having between 0 and 10 as values.
One could have:
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<code=xml my_object01>
A = 2
B = 3
C = 4
D = 5
</code>
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<code=xml my_object02>
A = 2
B = 3
C = 4
D = 9
</code>
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One sees that A, B and C are identical in the two different objects, one could thus simplify the task by making a parent DS:
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<code=xml my_object>
A = 2
B = 3
C = 4
</code>
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Then we call it the other two:
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<code=xml my_object01>
parent = my_object
D = 5
</code>
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<code=xml my_object02>
parent = my_object
D = 9
</code>
</WRAP>
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In addition to not allowing repeating itself, it allows to pass on any change in a "parent" to all of his/her children.

One can nevertheless decide to specify a difference(with respect to the "parent"), which makes it possible to modify a common characteristic.
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<code=xml my_object03>
parent = my_object
B = 7
D = 5
</code>
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In DS, parenting is done through the call:

<code=xml>
<PARENT Filename="xxxx.sitem"/>
</code>

It is advisable to organize the [[en:rcdsnomenclature | DS nomenclature]] in order to be able to identify it quickly, and also to quickly identify a parent of a complete card.. by doing it like this:

   * Put an underscore "_" at the beginning of parents' names to make them come up first in a directory listing;
   * Use underscores "_" for name fields, like for example the code shipped with RC.
This lets you know which parameters are populated and which ones are absent if the nomenclature is explicit.


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Of course, a parent DS can call one or more parents, etc.
\\ Attention to inheritances in cascade(as in CSS).
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{{tag>datasheet }}