Randy Miller has published a paper on agile development that discusses the use of 'shadow' applications in an agile modeling and development context, in which he talks in somewhat veiled terms about the use of the Whitehorse design tools.  The term shadow application emerged from discussions Randy and I had at Tech Ed earlier this year as we developed the top-down design approach described in my earlier article.  In the article I show how you can use a shadow application as a placeholder for the behavior of a system and thus design systems top-down. In his paper, Randy take this idea further and suggests the shadow application is actually written or generated, consistent with the code-oriented agile development philosophy.