leave @n=0 implicit and add a corresponding remark

Author: nolda

P5/Source/Guidelines/en/AI-AnalyticMechanisms.xml

@@ -1215,7 +1215,7 @@ sake of readability).
       last, tenth, column can be used for miscellaneous information, such as
       whether or not there is space to add after the token when joining them.
       Empty columns are marked with <code>_</code>. Note that, by convention,
-      the index for the unrepresented, <soCalled>virtual</soCalled> root node
+      the index for the unrepresented, <soCalled>virtual</soCalled>, root node
       is 0.</p>
     <p>A graphical rendition of this example is given below in terms of an
       annotated dependency graph.</p>
@@ -1233,17 +1233,17 @@ sake of readability).
       <ident type="class">att.linguistic.dependency</ident> classes, the
       above example can be encoded as follows:
       <egXML xmlns="http://www.tei-c.org/ns/Examples">
-        <s n="0">
+        <s>
           <w n="1" head="2" deprel="nsubj" pos="PRON" lemma="they">They</w>
           <w n="2" head="0" deprel="root" pos="VERB" lemma="buy">buy</w>
           <w n="3" head="2" deprel="obj" pos="NOUN" lemma="book" join="right">books</w>
           <pc n="4" head="2" deprel="punct" pos="PUNCT" lemma=".">.</pc>
         </s>
       </egXML>
       Here, the <att>n</att> attribute represents the node index of the
-      tokens marked up with <gi>w</gi> and <gi>pc</gi> elements; the node
-      index <val>0</val> for the root is given on the parent <gi>s</gi>
-      element. Dependency relations are encoded by means of <att>head</att>
+      tokens marked up with <gi>w</gi> and <gi>pc</gi> elements; the
+      index <val>0</val> for the <soCalled>virtual</soCalled> root node is left
+      implicit. Dependency relations are encoded by means of <att>head</att>
       attributes of <gi>w</gi> and <gi>pc</gi> elements in terms of the node
       index of their syntactic head. Labels for the types of the dependency
       relation are provided as the value of the <att>deprel</att> attributes on
@@ -1277,7 +1277,7 @@ sake of readability).
     <p>For convenience, those additional arcs are rendered as curves.</p>
     <p>The above example may be encoded as follows:
       <egXML xmlns="http://www.tei-c.org/ns/Examples">
-        <s n="0">
+        <s>
           <w n="1" head="2 4" deprel="nsubj nsubj" pos="PRON PRP" msd="Case=Nom|Number=Plur" lemma="they">They</w>
           <w n="2" head="0" deprel="root" pos="VERB VBP" msd="Number=Plur|Person=3|Tense=Pres" lemma="buy">buy</w>
           <w n="3" head="4" deprel="cc" pos="CCONJ CC" lemma="and">and</w>

P5/Source/Specs/att.linguistic.dependency.xml

@@ -24,7 +24,7 @@
   <exemplum xml:lang="en">
     <p>Universal Dependency (UD) annotation of the English sentence <q>They buy books.</q>.</p>
     <egXML xmlns="http://www.tei-c.org/ns/Examples">
-      <s n="0">
+      <s>
         <w n="1" head="2" deprel="nsubj" pos="PRON" lemma="they">They</w>
         <w n="2" head="0" deprel="root" pos="VERB" lemma="buy">buy</w>
         <w n="3" head="2" deprel="obj" pos="NOUN" lemma="book" join="right">books</w>
@@ -36,7 +36,7 @@
     <p>Universal Dependency (UD) annotation of the English sentence <q>They
       buy and sell books.</q>.</p>
     <egXML xmlns="http://www.tei-c.org/ns/Examples">
-      <s n="0">
+      <s>
         <w n="1" head="2 4" deprel="nsubj nsubj" pos="PRON PRP" msd="Case=Nom|Number=Plur" lemma="they">They</w>
         <w n="2" head="0" deprel="root" pos="VERB VBP" msd="Number=Plur|Person=3|Tense=Pres" lemma="buy">buy</w>
         <w n="3" head="4" deprel="cc" pos="CCONJ CC" lemma="and">and</w>
@@ -47,7 +47,13 @@
     </egXML>
   </exemplum>
   <remarks xml:lang="en" versionDate="2025-03-13">
-    <p>The following table summarises the serialisation choices for the CoNLL-U format in TEI XML.
+    <p>In the UD examples above, a <att>head</att> value of <val>0</val> by
+      convention refers to an unrepresented, <soCalled>virtual</soCalled>, root
+      node. The corresponding <att>deprel</att> value is <val>root</val>. (For
+      discussion, cf. section <ptr target="#AILADEP"/>.)</p>
+  </remarks>
+  <remarks xml:lang="en" versionDate="2025-03-13">
+    <p>The following table summarises the serialisation choices for UD’s CoNLL-U format in TEI XML.
       <table cols="3">
         <row role="label">
           <cell>CoNLL-U column</cell>