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\section{Changes from Previous Versions}

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\subsection{Changes from WD-2019-03-20}
\begin{itemize} 
  \item Section 1.2: added clarifying text on the distinction between Quantity, Coordinate, and Measurement in the IVOA models.
  \item Updated URLs for vocabularies
  \item Appendix B: changed 'Class' to 'ObjectType' to better align with the VO-DML description.
  \item Appendix C: brought initial vocabulary content in line with URL content.
\end{itemize}
\subsection{Changes from PR-2019-08-30}
\begin{itemize} 
  \item Migrate CoordSys element to include both CoordSpace and CoordFrame concepts.
  \item Coordinate element to reference CoordSys, rather than CoordFrame and CoordSpace.axis
  \item Removed specialized Coordinate types linked to standard spatial coordinate spaces, replace with Point
  \item Corrected multiplicity of SpaceFrame.planetaryEphem
  \item Corrected URLs for vocabularies ('http' not 'https')
  \item Corrected LaTex for TCG and TCB records to fix display 
\end{itemize}
