The Unified Modeling Language (UML) has far outgrown its initial purpose as a standard visual notation for constructing intuitive, high-level blueprint models of object-oriented software. A series of extension, such as OCL, XMI, ASL, MOF, UML profiles, and different proposed formal semantics, to the language and to its application scope have fedoff each other in synergy. While these extensions constitute a sound starting point to make UML the pivotal element for the Model-Driven Engineering (MDE) and Semantic Web (SW) visions, many other building blocks are still missing, including: (1) Complete formal semantics for UML and OCL; (2) UML inference engine based on such semantics to support model checking and intelligent agent reasoning with UML semantic web ontologies; (3) UML model compilers to fully automate both structural and behavioral code generation from detailed UML/OCL models. In this thesis, we present the MODELOG framework based on a single proposal to address these three issues: it consists of an automatic mapping from fully refined UML/OCL models to the object-oriented logic programs in the Flora-2, an executable and Turing-complete language with a well-defined formal semantics. We developed the MODELOG mapping as model transformations. As source for these transformations, we reused the UML2 and OCL2 metamodels provided by OMG and as target we developed a Flora metamodel. As we experimented and compared two language to implement the transformation: the dedicated transformation language ATL based on OCL, and Flora itself viewed as a model transformation language. As validating case study for MODELOG, we developed the Triangram robotic assembly puzzle. It is an example of planning tasks often executed by agents and it requires a complex class hierarchy together with complex structural and behavioral constraints. The Flora PSM of this puzzle was entirely automatically generated from its UML/OCL model by applying the MODELOG transformations. The main originality of this thesis is twofold. First, it simultaneously tackles various gaps in UML for its new extended role: formal specification language, MDE, semantic web services and agent engineering, Second, it does so without putting forward any new language but only by reusing a theoretically consolidated and efficiently implemented one. In contrast, previous proposals tend be limited to one or two such applications while often proposing new languages. The thesis makes contributions to various fields: For MDE, it shows the feasibility of completely automated full structural and behavioral executable code generation from a UML/OCL PIM, on a non-trivial, complex case study involving automated reasoning; For agile development, it reconcile that the robustness of formal methods with the early testing of fast prototyping, since MODELOG not only generates executable code, but also model checking code from UML/OCL models. For UML and OCL, it provides a fully integrated denotational formal semantics in Transaction Frame Logic on which Flora is based; For logic programming, it provides compositional metamodels of all the languages integrated in the Flora platform that clarify their relations and make them available as source or target language for a variety of MDE tasks such as model checking and fast prototyping; it also provides a way to develop logic programs using the consolidated full-life cycle object-oriented software engineering processes; For agent engineering, it shows how to get combine the complementary strengths of the object-oriented and logic paradigms, the two mostly widely reused in agent-oriented methods; For the semantic web service development, its introduced a highly automated MDE approach allowing to model them visually with UML-based industrial strengths method and CASE tools, and automatically generate their specification in the W3C standard SWSL, which is a XML-enabled variant of Flora