Per http://plantuml.com/ru/ie-diagram
the following notations are supported:
Entity01 }|..|| Entity02
Entity03 }o..o| Entity04
Entity05 ||--o{ Entity06
Entity07 |o--|| Entity08
However, if you try using another valid line type - "~", "~~" or "~~~" instead of "--" or "..", PlantUML will fail. Is that a defect? Here is the failing snippet:
http://www.plantuml.com/plantuml/uml/SoWkIImgAStDuKhEpot8pqlDAr5mLAZcgaNYEm7vG04kBaU5cfgw_1e59oukXzIy5A0k0000