Combine the dried tomatoes and water in a small pot and bring to a boil over high heat. Reduce heat to low, cover, and simmer for 2 minutes or until the tomatoes are soft and the liquid is absorbed. Set aside to cool to room temperature.
Cook the pasta al dente according to package directions. Drain, rinse with cool water and drain again.
Put the cooked pasta in a medium sized bowl. Add the tomatoes, chicken, artichoke hearts, olive and scallions; toss to mix well. Pour 1/4 cup of the dressing over pasta mixture, and toss to mix well. Cover the pasta mixture and refrigerate for at least 2 hours.
When ready to serve, place the romaine in a large bowl and add the pasta mixture, the remaining dressing, and, if desired, the walnuts. Toss to mix well. Sprinkle the Parmesan cheese over the salad and toss again. Serve immediately.