<P> After the first release a task force was formed to improve the language, which released several minor revisions, 1.3, 1.4, and 1.5 . </P> <P> The standards it produced (as well as the original standard) have been noted as being ambiguous and inconsistent . </P> <P> As with database Chen, Bachman, and ISO ER diagrams, class models are specified to use "look - across" cardinalities, even though several authors (Merise, Elmasri & Navathe amongst others) prefer same - side or "look - here" for roles and both minimum and maximum cardinalities . Recent researchers (Feinerer, Dullea et . alia) have shown that the "look - across" technique used by UML and ER diagrams is less effective and less coherent when applied to n - ary relationships of order strictly greater than 2 . </P> <P> Feinerer says: "Problems arise if we operate under the look - across semantics as used for UML associations . Hartmann investigates this situation and shows how and why different transformations fail .", and: "As we will see on the next few pages, the look - across interpretation introduces several difficulties which prevent the extension of simple mechanisms from binary to n - ary associations ." </P>

What are the three types of components in uml