Unit 7 assignment

One of my last jobs was maintaining and adding to machine status in the form of an xml file. That made me pretty familiar with the assignment of creating xml. I picked some pictures from my iPhoto collection to use as the objects for my examples. So if we ever do anything with the xml file, I will have real photos behind it.

The code that I had to maintain was kind of sloppy as far as how it would look at the xml. A C++ xml parser (Xerces?) was used to parse the xml and then C code was written to read and manipulate the linked objects created by the parser. Then a final call to the parser was made to write it back out. There was also an xsd file to describe the structure of what the elements of the xml would be and also their attributes. I ended up re-writing a major part of the C code to be recursive because the values of status were hierarchical for the tape server. Bad status would cascade up the hierarchical structure and change the status of the object at the next level. Where there was more than a single point of failure, the status going up would be just degraded. Where there were single points of failure, like if the operating system crashed(think O-rings and tiles on the space shuttle), the state of the machine would go to 'failed', which shouldn't happen very often.

By the way, there were 70 single points of failure on the space shuttle and there was a statistical certainty (I have an article from 1990 somewhere) that we would loose another one before the space station was done. Why did we do it anyway? And why wasn't anyone ever held accountable for either shuttle disaster?

The quiz this week is what has really got me. I must have fell asleep while I was reading the parts I am struggling with. Good thing I have more opportunities. Or maybe its the METS baseball team that is trowing me off :)