Trong các phiên bản trước đó của cuốn sách này, tôi đã nói rất ít về M3, lớp metametamodel. Với những thay đổi UML đã mang lại và phổ biến các công cụ mô hình hóa UML, tuy nhiên, tôi cảm thấy nó là khôn ngoan để khám phá những lớp metametamodel. | 232 Hour 14 FIGURE Modeling metamodeling and metametamodeling in the world of letter-writing. Moving On In earlier editions of this book I said very little about M3 the metametamodel layer. With the changes that UML has brought and the proliferation of UML modeling tools however I felt it wise to explore the metametamodel layer. Although it s not a layer you ll encounter in your day-to-day modeling activities I think you ll understand UML a little better if you re at least familiar with the foundational concepts in this layer. Knowing these concepts might also help you get conversant with a UML modeling tool once you start using one. So take a deep breath and let s journey to M3. To Boldly Go . . . Are you a science fiction fan A devotee of Star Trek perhaps Have you ever wondered how the bizarre inhabitants and exotic life forms from far-off planets all Understanding Packages and Foundations 233 manage to speak perfect English to the crew of the Enterprise And weirdly to each other Sometimes sci-fi writers just ignore the language problem and have all their characters speak English regardless of their worlds of origin. The creators of Star Trek however confronted this problem and came up with the Universal Translator a device that somehow matches up the brain waves of the speaker with the brain waves of the listener to create a matrix of information. The matrix enables the device to quickly turn words phrases and idioms from one language into words phrases and idioms from the other. In that way everybody in the galaxy can talk to everyone else. Why this brief excursion into the linguistics of the final frontier If you substitute applications on widely varying information processing systems for bizarre inhabitants from far-off planets and seamless communication for perfect English you ll pretty much understand one of the early challenges that confronted the Object Management Group Starfleet Command Back in the early 1990s OMG s Prime Directive was to come
