Uniformization and selection over ordinals and trees We will discuss the uniformization, church synthesis and selection problems in the monadic second-order theory of ordinals and trees. We recall the definitions of these problems and survey known results, including (as time permits): 1. The Shelah-Lifsches results concerning uniformization over the class of trees. 2. McNaughton's reduction of the Church synthesis problem to $\omega$-length two person games of perfect information with winning conditions definable by monadic formulas. 3. Buchi-Landweber's finite-memory determinacy result for these games. 4. Rabin's tree theorem and basis theorem (which implies selection over the full binary tree). 5. Gurevich-Shelah's proof that uniformization fails over the tree, in fact, that there is no definable choice function over the tree. We will also present some new results concerning selection and games over countable ordinals longer than $\omega$. If time permits, we will sketch the proof of some of the above. No preliminary knowledge is required (it might help a little if you know what a finite automaton is...)