By their very nature, inflation expectations are not directly observable. However, there exist two main ways to construct measures of inflation expectations. A direct way consists in asking people about their expectations of future inflation. A more indirect way is to extract the information revealed by observable financial data. The ECB makes constant use of both measures.
7  Lawrence Christiano and Massimo Rostagno (2001) present a theoretical framework that highlights the role of money in anchoring long-term inflation expectations in “Money Growth Monitoring and the Taylor Rule”, NBER Working Paper No 8539.