I compressed the poem, "She Sells Sea Shells". I was able to get 25.84%. However, as I tried to add additional repeated patterns to the dictionary, the compression percentage went down.
My heuristic boiled down to the following steps:
1. I looked for repeated phrases first and added them to the dictionary
2. As I added phrases and/or words to the dictionary, I monitored the Compression %.
3. If something I put in reduced the compression rate, I took it out of the dictionary.
4. I continued compressing with additional repeated words.
Reminding the students that trial and error is okay and that it will add to the challenge of these activities.