The SYSFOREIGNKEY view is provided for compatibility with older versions of Sybase IQ that offered a SYSFOREIGNKEY system table. However, the previous SYSFOREIGNKEY system table has been replaced by the ISYSFKEY system table, and its corresponding SYSFKEY system view, which you should use instead.
The SYSFOREIGNKEY view is a SQL Anywhere consolidated view. See "SYSFOREIGNKEY compatibility view (deprecated)" in SQL Anywhere Server – SQL Reference.