" The Standard Model The Standard Model contains both fermionic and bosonic fundamental particles. Fermions are particles which possess half-integer spin and obey the Pauli exclusion principle, which states that no fermions can share the same quantum state . Bosons possess integer spin and do not obey the Pauli exclusion principle. Informally speaking, fermions are particles of matter and bosons are particles that transmit forces. For a detailed description of the differences between fermions and bosons, see the article on identical particles. In the Standard Model, the theory of the electroweak interaction (which describes the weak and electromagnetic interactions) is combined with the theory of quantum chromodynamics. All of these theories are gauge theories, meaning that they model the forces between fermions by coupling them to bosons which mediate (or "carry") the forces. Girl Hot Model The Lagrangian of each set of mediating bosons is invariant under a transformation called a gauge transformation, so these mediating bosons are referred to as gauge bosons. The bosons in the Standard Model are: Unsolved problems in physics: Parameters in the Standard Model: What gives rise to the Standard Model of particle physics? Why do its particle masses and coupling constants possess the values we have measured? Does the Higgs boson predicted by the model really exist? Why are there three generations of particles in the Standard Model? Is the Standard Model reality, a good approximation to reality, or fatally flawed? Photons, which mediate the electromagnetic interaction. "

" The controller accesses the model, possibly updating it in a way appropriate to the user's action (e. g. , controller updates user's shopping cart) A view uses the model to generate an appropriate user interface (e. g. , view produces a screen listing the shopping cart contents). The view gets its own data from the model (or direct from the data access layer - sometimes there is no domain logic to do). The model should have no direct knowledge of the view. Hot Model Wallpaper However, the observer pattern can be used to provide some indirection between model and view, allowing the model to notify interested parties of a change. A view object can register itself with the model and listen for changes but the model itself remains view-agnostic. "