standardization efforts. The result of this work, UML 1.1, was submitted to the OMG in August 1997 and adopted by the OMG in November 1997. 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. The standards it produced (as well as the original standard) have been noted as being ambiguous and inconsistent. Cardinality notation 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 al.) 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. 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." UML 2 UML 2.0 major revision replaced version 1.5 in 2005, which was developed with an enlarged consortium to improve the language further to reflect new experience on usage of its features. Although UML 2.1 was never released as a formal specification, versions 2.1.1 and 2.1.2 appeared in 2007, followed by UML 2.2 in February 2009. UML 2.3 was formally released in May 2010. UML 2.4.1 was formally released in August 2011. UML 2.5 was released in October 2012 as an "In progress" version and was officially released in June 2015. Formal version 2.5.1 was adopted in December 2017. There are four parts to the UML 2.x specification: The Superstructure that defines the notation and semantics for diagrams and their model elements The Infrastructure that defines the core metamodel on which the Superstructure is based The Object Constraint Language (OCL) for defining rules for model elements The UML Diagram Interchange that defines how UML 2 diagram layouts are exchanged Until UML 2.4.1, the latest versions of these standards were: UML Superstructure version 2.4.1 UML Infrastructure version 2.4.1 OCL version 2.3.1 UML Diagram Interchange version 1.0. Since version 2.5, the UML Specification has been simplified (without Superstructure and Infrastructure), and the latest versions of