In expressions you can reference the value of certain pivot variables in the context of a particular scope. Some pivot variables values are not are affected by the current scope, but others - like data set field values - are.

Pivot variable references share the following common format:

[ScopePath.]CollectionName!ObjectName[.ValueDescriptor]

where:

ScopePath - is an optional path to the scope of the collection.
CollectionName - is a mandatory collection name.
ObjectName - is a mandatory object name.
ValueDescriptor - is an optional suffix to the object, that clarifies what object value must be obtained. If omitted the default object value is returned.

Currently there are two collections, that store variable values that expressions can consume:

• Fields - the fields collection is automatically populated with the data source columns and the extended [RowIndex] and [RowCount] fields. Each field has a Value and Name value descriptors (properties). The Value is the default field object value. It returns either a single value or an array of values, depending on the count of records in the current scope recordset. The returned single or multiple values are the values for a specific data source column. See Fields for more information.
  
  
• Parameters - the parameters collection holds a set of predefined parameters related to the current web part environment and can also include user defined (custom) parameters. See Parameters for more info.