Glossary of Computer Science Terms
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- With relation to expert systems, these are givens - known truths that are written
in to a program. These are what expert systems use to help them make decisions.
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- The rule that defines the L-system and how it changes the
initiator.
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- A process that is used in computer science to obtain
good results for something based on a set of rules. In this case, we're trying to find a
good melody line. One way to do that would be to compute every possible melody line and
score it according to our rules for how well it complies. That would take forever. A
different idea that takes less time but is not likely to get the absolute best result is
a genetic algorithm. Start with a series of randomly generated melodies (say 50 or 100) and
score them according to the scale. Take the top scorers and find a spot (the same spot
in both melodies). Cut the melodies at that point and switch them. For instance, if the
two melodies were:
- A B E C F A A C
- G D G F E D A A
and we decided to break them after the third note and switch them, the result would be:
- A B E F E D A A
- G D G C F A A C
That process is called mating, and it is analogous to how DNA strands mix when an egg is
fertalized. Next, score those and put them back in the list. Hopefully, it created a melody
that took the best parts of both of the origonal two and combined them to make a better
melody. This is the basic idea. There are more variations on the algorithm, such as
randomly changing a single note in the melody every so often (a process called mutation).
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- This term is generally used in relation to artificial intelligence. A grammar is a
formal system for accepting or rejecting strings (sentences, in many cases). A grammar
may be used as the membership criterion for a language.
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- These are suggestions that ar written into the expert system program that give
it suggestions for how to act when it doesn't really know what to do or doesn't
have enough information.
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- With reference to L-systems, an initiator is the input string. That is to say,
it could be anything from rddlu to
.
The initiator is altered by the generator in an L-system.
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- This is actually a subject from math, but L-systems are used quite often
in computer science, so we don't feel bad about putting it here. L-systems are
what is called a string replacement algorithm. They take the input
of an initiator and a generator
and apply the generator to the initiator, then apply the generator to the result
of the last application, and so on. For instance, if the intiator is the first example
under the definition of initiator above, then a generator could be d -> ruul. That
means that in that example, rddlu would become rruulruullu, because the generator
replaces d with ruul every time it sees it in the initiator. If You then used that as
the initiator, You wouldn't get any change when You applied the generator, because
there isn't a d to replace. If You used
as the initiator and
as the generator, after
one iteration, You would get (roughly) 
,
because, in this case, You replace every line with the generator. This is
known as Koch's snowflake. You can iterate it out as many times as You want. If You wish,
You may read a brief history of L-systems.
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- A term used to mean that a computer has multiple
threads of execution that it switches between quickly to give the
illusion that it is executing them simultaneously. That means the computer will work on the
instructions in one thread of execution for a little while (a fraction of a second), then it
will stop and leave that thread of execution temporarily hanging while it works on another
one for a little while.
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- Any language spoken by people, with all of its hidden implications and
assumptions.
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- When a computer runs a program, it reads in instructions
from a file one at a time and executes them. If it only has one long list of instructions
that run in order, it has a single thread of execution. DOS only allows one thread of
execution. Better operating systems like OS/2, Unix, Windows 95, and Windows NT allow
multi-threading.
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- With reference to expert systems, these are if-then statements. If
this condition is true, then do this.