rok commented on code in PR #33925:
URL: https://github.com/apache/arrow/pull/33925#discussion_r1106951957
##########
docs/source/format/CanonicalExtensions.rst:
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@@ -72,4 +72,64 @@ same rules as laid out above, and provide backwards
compatibility guarantees.
Official List
=============
-No canonical extension types have been standardized yet.
+Fixed shape tensor
+==================
+
+* Extension name: `arrow.fixed_shape_tensor`.
+
+* The storage type of the extension: ``FixedSizeList`` where:
+
+ * **value_type** is the data type of individual tensors and
+ is an instance of ``pyarrow.DataType`` or ``pyarrow.Field``.
+ * **list_size** is the product of all the elements in tensor shape.
+
+* Extension type parameters:
+
+ * **value_type** = Arrow DataType of the tensor elements
+ * **shape** = shape of the contained tensors as an array
+
+ Optional parameters:
+
+ * **dim_names** = explicit names to tensor dimensions
+ as an array. The length of it should be equal to the shape
+ length and equal to the number of dimensions.
+
+ ``dim_names`` are used if the dimensions have well-known
+ names and they map to the physical order (row-major).
+
+ * **permutation** = indices of the desired ordering of the
+ original dimensions, defined as an array.
+
+ The indices contain a permutation of the values [0, 1, .., N-1] where
+ N is the number of dimensions. The permutation indicates which
+ dimension of the logical order corresponds to which dimension of the
+ physical tensor (the i-th dimension of the logical view corresponds
+ to the dimension with number permutations[i] of the physical tensor).
+
+ **Permutation is only needed in case the logical order of
+ the tensor is a permutation of the physical order (row-major).**
+
+ When logical and physical order are equal, the permutation will
+ always equal to the original order of dimensions ([0, 1, .., N-1])
+ and therefore doesn't need to be defined.
Review Comment:
```suggestion
and therefore doesn't need to be defined. If permutation is absent
row-major layout is assumed.
```
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