Editing Unified Modeling Language (section)

==== Cardinality notation ====
As with database Chen, Bachman, and ISO [[ER diagram]]s, class models are specified to use "look-across" [[Cardinality (data modeling)|cardinalities]], even though several authors ([[Merise]],<ref>Hubert Tardieu, Arnold Rochfeld and René Colletti La methode MERISE: Principes et outils (Paperback - 1983)</ref>
Elmasri & Navathe,<ref>Elmasri, Ramez, B. Shamkant, Navathe, Fundamentals of Database Systems, third ed., Addison-Wesley, Menlo Park, CA, USA, 2000.</ref>
amongst others<ref>{{cite book
|title=Conceptual Modeling – ER 2004: 23rd International Conference on Conceptual Modeling, Shanghai, China, November 8–12, 2004
|publisher=[[Springer Publishing|Springer]]
|date=October 27, 2004
|series=[[Lecture Notes in Computer Science]] 3288
|edition=2004
|isbn=3540237232
|editor1=Paolo Atzeni
|editor2=Wesley Chu
|editor3=Hongjun Lu
|editor4=Shuigeng Zhou
|editor5=Tok Wang Ling
}}</ref>)
prefer same-side or "look-here" for roles and both minimum and maximum cardinalities. Recent researchers (Feinerer<ref>{{cite thesis
|author=Ingo Feinerer
|title=A Formal Treatment of UML Class Diagrams as an Efficient Method for Configuration Management
|url=https://publik.tuwien.ac.at/files/pub-inf_4582.pdf
|date=March 2007
|location=Vienna
|degree=Doctor of Technical Sciences
|publisher=Technical University of Vienna}}</ref>
and Dullea et al.<ref>{{cite journal
|journal=Data & Knowledge Engineering
|volume=47
|issue=2
|title=An analysis of structural validity in entity-relationship modeling
|author1=James Dullea
|author2=Il-Yeol Song
|author3=Ioanna Lamprou
|date=November 1, 2003
|pages=167–205
|doi=10.1016/S0169-023X(03)00049-1}}</ref>)
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<ref>{{cite conference
|conference=ADC '03: Proceedings of the 14th Australasian database conference
|author=Sven Hartmann
|publisher=[[Australian Computer Society]]
|url=https://dl.acm.org/doi/abs/10.5555/820085.820110
|title=Reasoning about participation constraints and Chen's constraints
|date=January 17, 2003
|pages=105–113}} {{open access}}</ref>
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."