Template expressions are a way to map field values in a document. They are used to configure some Fusion pipeline stage and messaging services. When the value of a configuration parameter is a template expression, that expression is dynamically evaluated at runtime by the StringTemplate library. Fusion template expressions are delimited by angle bracket characters < and >. The expression consists of the name of a variable in the scope of that component. Since these variables are Java objects, if object foo of type Foo has a field named bar, the expression <foo.bar> will evaluate to the string representation of the contents of field bar. For example, given a PipelineDocument where a field named title has a value of Star Wars, the template expression <doc.title> evaluates to Star Wars. See the reference guide for index pipeline stage, query pipeline stage, and messaging service template expression variables.