A decision network is a Baysian Network which is used to make decisions based on optimizing utility.

To solve a problem, we iterate through all possible decision parameters to find the one that maximizes utility.

Nodes

1. chance nodes: random variables — some inputs we can observe, some are latent variables we can’t observe — circles
2. action nodes: what we have control over — squares
3. utility nodes: output, what the results would be; we typically sum utilities together if you have multiple of them — diamonds

Edges

1. conditional edge - arrows to chance nodes: conditional probability edges
2. informational edge - arrows to action nodes: this information is used to inform choice of action
3. functional edge - arrows to utility nodes: computes how the action affects the world

Example

For \(U\), for instance, you can have a factor that loks ilke:

a student approach to learning where learning outcomes are driven by student’s own experience to deeply drive educational results independenlty

Facts

1. Everybody writes bugs
2. Debugging sucks

Defensive Programming Tools + Techniques

• Use language features
• Specs, documentations, Test-Driven Development, unit testing
• Fail fast and loudly
• Systematic debugging
• Investing in tools

Use Language Features

• Descriptors: static, final, pub./priv.
• Type checking: prevent type errors
• Automatic array bounds checking
• Memory management
• Compiler optimization

Key idea: know what language features are available, why/when to use them. don’t work against the language in circumventing them

Specs, Docs., TDD, Unit Tests

• How should it work: specs
• How does it work: docs
• How will I know it works: TDD
• How do I know it still works: unit tests

These all force you to think about your code before!! you write it so then you can correct them as soon as possible.

degrees of belief help us quantify how much we believe some event \(A\) is more/less plausible than some event \(B\).

Let us take two statements:

• \(A\) Taylor gets Nobel Prize in Literature
• \(B\) Han shot first

For instance, if we want to express “I think its more likely that Taylor gets the prize than Han shot first”:

\begin{equation} A \succ B \end{equation}

axioms of degrees of belief

universal comparability

for two statements \(A, B\), only three states can exist: