Technical data

8
Document Data Filtering
Often, document data needs to be modified before it can be printed. For
example, simple text documents need to be translated into PostScript
before they can be printed on a PostScript printer. Or, documents using the
EBCDIC character set might need to be converted to the ASCII character set
before they can be printed on common desktop printers.
Because the need for document data modification varies by customer
and country, the supervisor includes a mechanism for user-written or
platform-supplied programs to modify document data before it is sent to a
printer. These programs are known as filters or data type translators and
can be applied to documents printed as part of a job.
Filters are executed by the supervisor in a child process. The document
data is piped to the filter, and the supervisor reads the data back before
it is sent to the printer. The supervisor controls the communication and
control of the printer.
The information in this chapter applies only to physical printers supported
by the supervisor, pdspvr. The Outbound Gateway Supervisor does not
perform data filtering. It relies on a remote host or printer to perform
filtering tasks.
8.1 Types of Filters
Advanced Printing Software supports translation filters and modification
filters. Translation filters perform the following functions:
• Translate the document format (PDL) of the document to a document
format supported directly by the printer (a document format included on
the printer native-document-formats-ready attribute).
• Perform the required document format translation when a supervisor
invokes it.
Modification filters perform the following functions:
• Perform document data modifications that do not change document
format, such as character set translation or simple text formatting.
• Perform data modifications only when invoked by a user for a specific
document.
Document Data Filtering 8–1