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Fall 04 Midterm 2 Review: Tools for Space Scientists

A total guess here...

a. I would use observer as a design pattern because the information provided looks much like MVC. The model or subject would be the "Data Planning Documents" which contain the information on gathering and processing sensor data. The application specific or concrete subjects would be gathering sensor data and processing sensor data. The view or observers would be the "Data Visualization Documents". The specific UI components or concrete observers would be the 2D and 3D graph visuals.

b. O-O design keep information nessessary for one object encapsulated to help better understand what each specific object's funtionality is and also easier to mantain. O-O allows for reuseability of code through inheritance and reduces bugs by preventing dependent code.

yes i agree, but to elaborate just a bit more, i'm going to cheat and grap something from a previous semester that elaborates a bit more:

Scallability - multiple satellites or satellite pictures.
Polymorphism - 2D and 3D picturess can share some common functionality through SatellitePicture.
SensorData can be processed or received by other
devices than just satellites.
Easily Modifiable - we can easily add new devices to an OO
system. IE - a computer that gathers data
from several satellites and displays the data in one graph.

-ellie

~Quoc Tran

a) I don't agree that the Observer pattern would be good because of MVC, the Observer pattern has nothing to do with MVC, as far as my understanding goes (rather, I know MVC implements an Observer style, but the Observer design is not pigeon-holed into being MVC). However, I agree that the Observer pattern is the best for the job here, but not because of an MVC design. Rather, there is a single set of satellite data from which many must watch. This means two things to me: 1) an observer design pattern will be used for the various document types to watch the satellite data 2) since there is one set of satellite data, it should be designed as a Singleton, which would ease the accessing of data from it. However, only one can be chosen, so I'd say Observer is more important for the design than the Singleton.

i think he might have been making an analogy between the pieces of mvc and the pieces of this problem, but yes, you're right, mvc is an exemplar of the observer pattern, but observer shouldn't be pigeonholed as only mvc. also, i'm not so sure that a singleton pattern would "ease the accessing of data" - it really just guarrantees that only one instance of a class exists. -ellie

b) Fortran is cool. If you do this in Fortran: DIV(N) N = N/2 and then do DIV(2), the value of 2 will be 1 for the remaining lifetime of your program! If that's not the most useful thing ever, I'd be surprised. But, uh, yeah, it sucks here.


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