eXtreme Programming (XP) is an agile development methodology developed by Kent Beck et al. It emphasises the human aspect of software development and how issues such as respect, trust and communication are key issues along with purely technical aspects of software development.
The agile manifesto is a set of 12 principles for developing software in an agile manner, somewhat similar to eXtreme Programming.
A deductive reasoning agent is one that contains an explicitily represented, symbolic model of the world. It then makes decisions via symbolic reasoning.