Objective: Recommendation ITU T Z.109 defines a unified modeling language (UML) profile that maps to SDL 2010 semantics so that UML is able to be used in combination with the ITU T Specification and Description Language. Appendix I includes an (informative) Example language specification for a concrete grammar and its mapping to the UML profile. Coverage: This Recommendation presents a definition of the UML to SDL 2010 mapping for use in the combination of SDL 2010 and UML. Application: The main area of application of this Recommendation is the specification of telecommunication systems. The combined use of SDL 2010 and UML permits a coherent way to specify the structure and behaviour of telecommunication systems, together with data. Status/Stability: This Recommendation is the complete reference manual describing the UML to SDL 2010 mapping for use in the combination of SDL 2010 and UML. It replaces the previous Recommendation ITU T Z.109 that concerned earlier versions of UML and Specification and Description Language. Associated work: Recommendations ITU T Z.100, ITU T Z.101, ITU T Z.102, ITU T Z.103, ITU T Z.104 and ITU T Z.107 concerning the ITU T Specification and Description Language 2010 (SDL 2010).