Technical data

There is no difference in how the two types of filter programs are written,
and the supervisor does not verify that they are used properly. Both
modification and translation filtering can be applied to a document. When
this occurs, the modification filter receives the original document data, the
output of the modification filter is piped to the translation filter, and the
output from the translation filter is sent by the supervisor to the printer.
The supervisor cannot completely control what the filter does. A filter should
not, for example, write to a file or directly to a device, but there is nothing
the supervisor can do to prevent this.
8.1.1 Filter-Related Attributes
The following attributes provide information about filters:
• filter-definition
• excluded-filter
• modification-filter
• translation-filter
• no-filtering
filter-definition Server Attributes
The server filter-definition attribute defines a program as a
filter and contains the information needed to invoke the program. The
filter-definition attribute is a complex attribute with the syntax:
filter-definition={name type input-format output-format
command}
In addition, the filter-definition attribute is multivalued. You can
define any number of named filters.
Each component field of the attribute value is described in the following
table.
Field Value Description
name
text
The name of the filter must be unique within
the server. The print system uses the name as
a search key for new filter definitions.
type
translation or
modification
Type of filter. Defines the mechanism used to
invoke the filter. The default is translation.
input-format Document
format
The document format the filter supports as input.
If omitted, the filter can take any format as input.
Used only for translation filter invocation.
8–2 Document Data Filtering