" calculating if today is the user's birthday or the totals, taxes and shipping charges for shopping cart items. View: This renders the model into a form suitable for interaction, typically a user interface element . MVC is often seen in web apps: the view is the html page and the code which gathers dynamic data for the page. Controller: This responds to events, typically user actions, and invokes changes on the model (but *not* the view). Many applications use a persistent storage mechanism (such as a database) to store data. MVC does not specifically mention this data access layer. It's common to think of an application as having three main layers: presentation (UI), domain,and data access. 1 4 Airplane Cessna Model Scale In MVC, the presentation layer is split into controller and view. The most important separation is between presentation and domain. "

" 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. W and Z bosons, which mediate the weak nuclear force Eight species of gluons, which mediate the strong nuclear force. Six of these gluons are labelled as pairs of "colors" and "anti-colors" (for example, a gluon can carry "red" and "anti-green". ) The other two species are a more complex mix of colors and anti-colors. The Higgs bosons, which induce spontaneous symmetry breaking of the gauge groups and are responsible for the existence of inertial mass. It turns out that the gauge transformations of the gauge bosons can be exactly described using a unitary group called a "gauge group". The gauge group of the strong interaction is SU(3), and the gauge group of the electroweak interaction is SU(2)×U(1). Model Airplane Flight Simulator Therefore, the Standard Model is often referred to as SU(3)×SU(2)×U(1). The Higgs boson is the only boson in the theory which is not a gauge boson; it has a special status in the theory, and has been the subject of some controversy. "