Directed Acyclic Graph Information

SQL with Trees and Graphs

http://www.artfulsoftware.com/mysqlbook/sampler/mysqled1ch20.html

MySQL Stored Procedure of Dijkstra’s Algorithm

http://www.artfulsoftware.com/infotree/queries.php?&bw=1059#766

http://www.codeproject.com/KB/database/Modeling_DAGs_on_SQL_DBs.aspx

More on Nested Tree Model

http://dev.mysql.com/tech-resources/articles/hierarchical-data.html

http://articles.sitepoint.com/article/hierarchical-data-database/2