Subhierarchies have different roots.

docs/odata-data-aggregation-ext/odata-data-aggregation-ext.html

@@ -4236,7 +4236,9 @@ <h1 id="2-overview"><a name="Overview" href="#Overview">2</a>
 href="#HierarchicalTransformationsPreservingtheInputSetStructure">Hierarchical
 Transformations Preserving the Input Set Structure</a> or be
 service-defined bound functions whose output set is a subset of the
-input set.</p>
+input set. The hierarchy <span class="math inline">\((H&#39;,Q)\)</span>
+can have different <a href="#RecursiveHierarchy">roots</a> than the
+hierarchy <span class="math inline">\((H,Q)\)</span>.</p>
 <h2
 id="62-hierarchical-transformations-preserving-the-input-set-structure"><a name="HierarchicalTransformationsPreservingtheInputSetStructure" href="#HierarchicalTransformationsPreservingtheInputSetStructure">6.2</a>
 Hierarchical Transformations Preserving the Input Set Structure</h2>

docs/odata-data-aggregation-ext/odata-data-aggregation-ext.md

@@ -2586,7 +2586,7 @@ The recursive hierarchy is defined by a parameter pair $(H,Q)$, where $H$ and $Q
 
 The third parameter MUST be a data aggregation path $p$ with single- or collection-valued segments whose last segment MUST be a primitive property. The node identifier(s) of an instance $u$ in the input set are the primitive values in $γ(u,p)$ reached via $p$ starting from $u$. Let $p=p_1/…/p_k/s$ with $k≥0$ be the concatenation where each sub-path $p_1,…,p_k$ consists of a collection-valued segment that is optionally followed by a type-cast segment and preceded by zero or more single-valued segments, and either $s$ consists of one or more single-valued segments or $k≥1$ and ${}/s$ is absent.
 
-The recursive hierarchy to be processed can also be a subset $H'$ of $H$. For this case a non-empty sequence $S$ of transformations MAY be specified as an optional parameter whose position varies from transformation to transformation and is given below. In general, let $H'$ be the output set of the transformation sequence $S$ applied to $H$, or $H'=H$ if $S$ is not specified. The transformations in $S$ MUST be listed in the section on [Transformations Preserving the Input Set Structure](#TransformationsPreservingtheInputSetStructure) or in the section on [Hierarchical Transformations Preserving the Input Set Structure](#HierarchicalTransformationsPreservingtheInputSetStructure) or be service-defined bound functions whose output set is a subset of the input set.
+The recursive hierarchy to be processed can also be a subset $H'$ of $H$. For this case a non-empty sequence $S$ of transformations MAY be specified as an optional parameter whose position varies from transformation to transformation and is given below. In general, let $H'$ be the output set of the transformation sequence $S$ applied to $H$, or $H'=H$ if $S$ is not specified. The transformations in $S$ MUST be listed in the section on [Transformations Preserving the Input Set Structure](#TransformationsPreservingtheInputSetStructure) or in the section on [Hierarchical Transformations Preserving the Input Set Structure](#HierarchicalTransformationsPreservingtheInputSetStructure) or be service-defined bound functions whose output set is a subset of the input set. The hierarchy $(H',Q)$ can have different [roots](#RecursiveHierarchy) than the hierarchy $(H,Q)$.
 
 ## <a name="HierarchicalTransformationsPreservingtheInputSetStructure" href="#HierarchicalTransformationsPreservingtheInputSetStructure">6.2</a> Hierarchical Transformations Preserving the Input Set Structure
 

odata-data-aggregation-ext/6 Hierarchical Transformations.md

@@ -18,7 +18,7 @@ The recursive hierarchy is defined by a parameter pair $(H,Q)$, where $H$ and $Q
 
 The third parameter MUST be a data aggregation path $p$ with single- or collection-valued segments whose last segment MUST be a primitive property. The node identifier(s) of an instance $u$ in the input set are the primitive values in $γ(u,p)$ reached via $p$ starting from $u$. Let $p=p_1/…/p_k/s$ with $k≥0$ be the concatenation where each sub-path $p_1,…,p_k$ consists of a collection-valued segment that is optionally followed by a type-cast segment and preceded by zero or more single-valued segments, and either $s$ consists of one or more single-valued segments or $k≥1$ and ${}/s$ is absent.
 
-The recursive hierarchy to be processed can also be a subset $H'$ of $H$. For this case a non-empty sequence $S$ of transformations MAY be specified as an optional parameter whose position varies from transformation to transformation and is given below. In general, let $H'$ be the output set of the transformation sequence $S$ applied to $H$, or $H'=H$ if $S$ is not specified. The transformations in $S$ MUST be listed in the section on [Transformations Preserving the Input Set Structure](#TransformationsPreservingtheInputSetStructure) or in the section on [Hierarchical Transformations Preserving the Input Set Structure](#HierarchicalTransformationsPreservingtheInputSetStructure) or be service-defined bound functions whose output set is a subset of the input set.
+The recursive hierarchy to be processed can also be a subset $H'$ of $H$. For this case a non-empty sequence $S$ of transformations MAY be specified as an optional parameter whose position varies from transformation to transformation and is given below. In general, let $H'$ be the output set of the transformation sequence $S$ applied to $H$, or $H'=H$ if $S$ is not specified. The transformations in $S$ MUST be listed in the section on [Transformations Preserving the Input Set Structure](#TransformationsPreservingtheInputSetStructure) or in the section on [Hierarchical Transformations Preserving the Input Set Structure](#HierarchicalTransformationsPreservingtheInputSetStructure) or be service-defined bound functions whose output set is a subset of the input set. The hierarchy $(H',Q)$ can have different [roots](#RecursiveHierarchy) than the hierarchy $(H,Q)$.
 
 ## ##subsec Hierarchical Transformations Preserving the Input Set Structure