add a bit on the output

lectures/user-experience/slides.qmd

@@ -445,6 +445,27 @@ Take safe_copy.py and add useful error messages and return codes.
 
 # Output
 
+## stdout and stderr
+
+* stdout is for ouput somebody else might want to process
+  `grep bash /etc/bashrc | wc `
+* stderr is for *error* messages  
+  `grep bash file_that_does_not_exist |wc`
+
+## Datasets
+* a dataset is a way to communicate information
+* clarity in the dataset structure is clear communication
+* group things together that belong together
+* follow standards
+
+## Dataset normalization
+(normal as in orthogonal, not *the usual mess*)
+
+* Idea: Only provide information that is not already contained otherwise.
+* Keeps your dataset clean
+* Balance with the effort it takes to compute information that you optimized out.
+* Provide scalars as scalars, not as 3D fields / ...
+* Aggregation levels can be worth the extra data / effort
 
 # Take-home: take a user's perspective! {.special}