# Cross-Walking WDJ and WDA: sine = opposite/hypoteneuse or sin = y/r ?

The WDA component/app WDT_QUIZ available in NW2004s is functionally parallel to the WDJ component/app which can be built by following WDJ Tutorial #2 (“Creating an Extended WebDynpro Application”). Therefore, these two parallel components provide an excellent way to really learn some things about WDA and WDJ that one might not pay complete attention to if one was looking only at the WDA or WDJ component in isolation. If you don’t agree with this, ask yourself who knows the most about the trigonometric sine function: a) the person who understands sine = opp/hyp b) the person who understands sin = y/r c) the person who understands the relation between these two definitions. Or who knows most about the hyperbolic paraboloid: d) the person who understands it is the surface swept out by a parabola moving along a parabola; e) the person who understands it is the surface defined by an equation like x**2/a**2 – y**2/b**2 = 2z; f) the person who understands the relation between these two definitions So, assuming that learning two good ways to do the same thing is always better than learning one good way, how can we speed up the time we must spend learning WDA and WDJ – really learning them? Well, let’s start with the two trees defining the Quiz Application in WDA and WDJ: Imagine a WDA or WDJ application “

**wdaj_xwalk**” with the following properties: g)**wdaj_xwalk**knows the metadata behind these two trees; h)**wdaj_xwalk**is built so that when you highlight a node in the left-hand tree, then one of two things happens: –h1) the corresponding node in the right-hand tree is highlighted (assuming there IS a corresponding node) — h2) or, a message is displayed saying there is no corresponding node AND WHY THERE ISN’T; i) same as (g-h) but starting with the right-hand tree instead of the left If there were such an application, couldn’t someone learn some important similarities and differences between WDA and WDJ very quickly – perhaps even more quickly than reading the intro chapters in a book on WDA and a book on WDJ? (No slam intended here on you-know-who: I’ve bought both books with my own money.) Going one step further, suppose the application**wdaj_xwalk**let you drill-down on the Welcome View in the left-hand tree to see the methods associated with this view: And even further, suppose that if you clicked on the method**WDDOINIT**in this display, then the application**wdaj_xwalk**popped you this display: Couldn’t someone simultaneously learn a whole lot about WDA and WDJ real fast this way? Well, I’ve done the best I could here at making a point which should now be obvious to everyone. The not-so-obvious question is why the application**wdaj_xwalk**doesn’t already exist …
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