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Why do we need to worry about representation
You really need to do this class if you become a rocket scientist (or at least a programmer of rocket control systems):
see YouTube page for this
read about why this happened
This is a problem of PHYSICAL REPRESENTATION and was caused by forgetting to think about the way different numbers are represented on computer (64 bit real vs 16 bit integers).
See more about roundoff errors
and more here!
Representing real world things gets complicated and.... relational
Okay, we've figured out that something like representing a number can get complicated. But what about this?
Abba - Waterloo
Apart from identifying me as a child of the 70's, it:
Is a video
Is a digitized version of an analog tape recording from 1974
Is sequence of images
Is stored on a Youtube server
Is streamed live over the internet
Is snippet of a TV program called StarParade
Demonstrates that in the 70's people had fantastic outfits but couldn't dance to save their lives
Contains song called "Waterloo" written by Abba which won the 1974 Eurovision Song Contest
Contains speech in the German language
Contains a blooper
... etc ... etc ...etc
We need to constantly remember.... representation on computer is not "the thing itself"; it is an abstraction or translation into a form that the computer can understand and work with. Often we not only need to represent "the thing itself" but also relational information about how it relates to other items (in the real world or on the computer), and a context for the representation. Sometimes the "thing" is meaningless without the context.
What it represents. What are some other representations of this?
What is this?....
We figured out it's
something that helps your headaches
. But what actually do we have here? The real chemical compound is something that exists in a test tube (and sometimes in peoples' brains!) but we can't put that on a computer. The thing above is actually an image: very useful for humans who are good at pattern recognition, but not so good for computers. Here are some other ways we can represent or characterise it
0, 0, 0, 1, 0, 0, 0, 5, 1, 0, 0, 0, 3, 4, 0, 0, 6, 4, 2, 0, 0, 0, 0, 0,
chemical structure descriptors
the compund and which ones
it? Which ones tell us something about the compound? But remember it's not the real thing...
So representation is all about mapping REAL WORLD THINGS onto COMPUTERS for PARTICULAR APPLICATIONS
What representation you use makes a difference:
64-bit vs 32-bit integers - limits -
JPEG vs TIFF for pictures: quality/size tradeoff
Audio quality -
16-bit vs 24-bit
, compression: information loss
Compatibility (current and future) -
Efficiency (especially in databases)
It's a hot topic in the web world
Representation is at the heart of the
HTML - representation of text and formatting
XML and folksonomies - representation of meaning of text
OWL - representation of dictionaries and taxonomies
RDF - representation of relationships
WSDL - representation of services
What will I be able to do after taking this class?
Understand the way computers represent familiar things to us, and some of the "gotchas" ... you will be able to "translate" between human and computer ways of thinking
Understand the process of tackling a complex problem and determining the best computer representations to use
Have a basic working knowledge about storing information in relational databases and semantic triple stores
See how representations are used in a variety of domain case studies
Understand better what people are saying on Downton Abbey and Dr Who
We will take a very "informatics" approach to the subject rather than a "computer science" approach... i.e. practical, and dealing with the complexities of the world we live in
help on how to format text
Turn off "Getting Started"