" The mass of such aggregates exceeds that of the components due to their binding energy. Tests and predictions The Standard Model predicted the existence of W and Z bosons, the gluon, the top quark and the charm quark before these particles had been observed . Their predicted properties were experimentally confirmed with good precision. The Large Electron-Positron collider at CERN tested various predictions about the decay of Z bosons, and found them confirmed. To get an idea of the success of the Standard Model a comparison between the measured and the predicted values of some quantities are shown in the following table: Quality Measured (GeV) SM prediction (GeV) Mass of W boson 80,4120±0,0420 80,3900±0,0180 Mass of Z boson 91,1874±0,0021 91,1874±0,0021 Challenges to the Standard Model Although the Standard Model has had great success in explaining experimental results, it has never been accepted as a complete theory of fundamental physics. This is because it has two important defects: The model contains 19 free parameters, such as particle masses, which must be determined experimentally (plus another 10 for neutrino masses). These parameters cannot be independently calculated. Boat Egyptian Model The model does not describe the gravitational interaction. Since the completion of the Standard Model, many efforts have been made to address these problems. "

" We discuss some of those here. View instability vs. model stability If constructed correctly, models can enjoy a fair degree of stability (owing to the stability of the domain model), whereas user interface code usually undergoes frequent and sometimes dramatic change (typically because of usability problems, the need to support growing classes of users, or simply the need to keep the application looking "fresh"). Separating the view from the model makes the model more robust, because the developer is less likely to "break" the model while reworking the view. Attempting to stitch these two worlds together in a hand coded method without architecture is very common, and results in the model object being polluted with knowledge of the interface, and vice-versa. This makes the code very inflexible and difficult to maintain. For this reason (among others), many programming shops develop the user interface design early in the process of design, and freeze the interface early. Boat Engine Model Steam The unfortunate side effect of this is that the domain of the problem often isn't clearly understood by the programmers until late in the implementation process. Thus, just at the time that the developers are finally competent to create a good interface, they are kept from changing it. "