PARF uses a modified ARFF format for the datasets, which is mostly compatible with the original format used by Weka project. In short: The file starts with the relation name, which is followed by the specification of attributes, and finally comes the data block. An attribute specification gives the attribute its name, and possible values (either numeric, string, or a set of categories in curly braces). Wherever a value contains a space, it must be quoted. Example:

% this is an example parf arff file
@relation test
@attribute name string
@attribute height numeric
@attribute sex { male, female }
@attribute "marital status" { married (6) "not married" divorced widowed (1.2) }
@data
"Anne Appleby", 162, female, married
"Bob Barnes" 181.5 male "not married"
'Charlie Coombs', 175, ?, divorced
"Dan D'Angelo", ?, male, widowed
"Ellen Ellis", 167.5, "female", "widowed"
"Francis Ford", &
  165, female, married
"George Gorsky", ?, ?, ?
?, 200, male, ?
Iris, 159, female, ?

Notable differences from ARFF:

• Only numeric, string and nominal attributes are supported - date is not a valid attribute type.
• Wherever the ARFF syntax requires a comma, a whitespace works as well. Also, in each such place, an ampersand (&) can be placed to continue in the next line.
• The line continuation token above is particularly important in wide datasets, since line length is limited for technical reasons, and set to 1024 characters.
• Both single and double quotes work. If a single quotation mark is to be included in a string, use the double quotes for the string, and vice versa.
• Sparse ARFFs are not supported.
• String variables are ignored in computation. Additional ways to make an attribute ignored is to change @attribute into @ignored, and by specifying used/unused attributes on the command line (-u[u] switch)
• Nominal attributes can specify category weights in parentheses immediately following the category name. The default weight, if not specified, is 1. The weights are only used for the attribute that is selected to be the class attribute.