The Business Component data type provides one property per each transaction attribute.

I.e. Transaction "Customer" has the following structure:

  CustomerId*
  CustomerName

the Customer Business Component will have the properties CustormerId and CustomerName. Example: if a variable (&Customer) is based on this data type, the properties are available in the intellitip while coding:
 

In case of multi-level transactions, besides the Business Component data type a data type per each level are created.
The Business Component data type is implemented through an SDT , the same way the level data type is implemented through a collection SDT, with all the method and properties it provides.

Example: in a typical Invoice transacion, with the following structure:
 

The Invoice and Invoice.InvoiceLevelItem data type are created.
Note that the second data type name is given by the transaction structure "description level" value (the value of the "Type" column into transaction structure for the description level).

If a variable (&Invoice) is based on the Invoice data type, the properties are available in the intellitip while coding:
 

Count

It returns the number of lines in a two level transaction. I.e. with the following code :

 &count = Invoice.InvoiceLevel1.Count