In order to use data objects in BPMN firstly, you have to understand the syntax and meaning of every object type.
There are eight elements representing data in BPMN specification:
Data Object – a Data Object represents information flowing through the process, such as business documents, e-mails, or letters
Data Input – is an external input for the entire process. A kind of input parameter.
Data Output – is the data result of the entire process. A kind of output parameter.
Collection of Data Object – represents a collection of information, e.g., a list of order items
Data Input Collection – represents a data input collection of information, e.g., a list of stock items
Data Output Collection – represents a data output collection of information, e.g., a list of stock items
Association – a data association is used to associate data elements to Activities, Processes and Global Tasks
Data Store – is a place where the process can read or write data, e.g., a database or a filing cabinet. It persists beyond the lifetime of the process instance.
Initiating Message – an initialing message represents an item that is transferred, manipulated, or stored during the process.
Non-Initiating Message – a non-initialing message represents an item that is transferred, manipulated, or stored during the process. The filled icon represents a non-initiating message (or a message which a participant has sent in response to a previous message it received)