Tom Kralidis asked the following question about OWS common metadata parsing, but it could be asked about almost any aspect of web GIS:
But then I thought why not just implement this in MapServer, and have the functionality exposed via mapscript?
Why write new web GIS software? Why not add to MapServer? I'm going to explain by analogy: it's like picking camping gear.
Call me soft, but I like filtered water, hot meals and drinks, shelter from the rain, and a warm bed when I go camping. For the sake of argument, let's call these the basic requirements for alpine camping equipment:
water filtration and storage;
heat source for cooking food;
shelter from rain and snow;
means of transporting the above.
There are 2 distinctly different philosophical approaches to meeting these requirements. The first involves acquiring:
a hand-pumped sub-micron water filter, and several liter bottles;
a compact single-burner kerosene stove, with pot, kettle, cup, and spoon;
a weatherproof, folding tent with light, collapsable graphite framework;
a sleeping bag and stuff-sack;
The REI approach, if you will (disclosure: I am an REI member). The second approach is to get a recreational vehicle with everything (including the kitchen sink) built in. See where I'm going with this analogy? The RV is certainly convenient, but gives you no flexibility. The configuration of its components is fixed. None of them can be removed and used away from the vehicle. The REI approach, on the other hand, provides maximum flexibility. Want to camp kilometers from a road? Pack your gear in the backpack and walk. Water sources are far from your campsite? Take your filter and bottles to the source and carry treated water back. Maybe you're just "carpet camping" at a friend's ski cabin? Bring only your sleeping bag.