Help: Add clarifying text to instrumentation API and Data versions

Help/manual/cmake-instrumentation.7.rst

@@ -133,8 +133,9 @@ CDash using the ``cdashSubmit`` and ``cdashVerbose`` options.
 API v1
 ======
 
-The API version specifies both the subdirectory layout of the instrumentation data,
-and the format of the query files.
+The API version specifies the layout of the instrumentation directory, as well
+as the general format of the query files and :command:`cmake_instrumentation`
+command arguments.
 
 The Instrumentation API v1 is housed  in the ``instrumentation/v1/`` directory
 under either ``<build>/.cmake/`` for output data and project-level queries, or
@@ -277,10 +278,13 @@ Data v1
 =======
 
 Data version specifies the contents of the output files generated by the CMake
-instrumentation API as part of the `Data Collection`_ and `Indexing`_. There are
-two types of data files generated: the `v1 Snippet File`_ and `v1 Index File`_.
-When using the `API v1`_, these files live in
-``<build>/.cmake/instrumentation/v1/data/`` under the project build tree.
+instrumentation API as part of the `Data Collection`_ and `Indexing`_. A new
+version number will be created whenever previously included data is removed or
+reformatted such that scripts written to parse this data may become
+incompatible with the new format. There are two types of data files generated:
+the `v1 Snippet File`_ and `v1 Index File`_. When using the `API v1`_, these
+files live in ``<build>/.cmake/instrumentation/v1/data/`` under the project
+build tree.
 
 v1 Snippet File
 ---------------