Re: [DFDL-WG] How to specify type/subtype combos?

20 Jun 2013

      This is most easily done by computing two physical fields that just grab
the strings, then two logical fields, which standardize those strings to
lower case (or upper if you prefer), then an assert with a big case
analysis that passes for valid pairings, and fails for invalid pairings.
Because DFDL expressions are based on XPath, there is only nested
if-then-else available to do this, but that said, at least it is
straightforward what you need to create:

<dfdl:assert message="Illegal type and subtype pair.">
                      {
                       if (../Type eq 'text') then
                            if (../Subtype eq 'html') then true
                            else if (../Subtype eq 'plain') then true
                            else false
                       else if (../Type eq 'application') then
                            if (../Subtype eq 'pdf') then true
                            else false
                       else false
                        }
</dfdl:assert>

I believe we need the fn:error function (not currently in DFDL spec, but
has been discussed), so that you can get a reasonable diagnostic message
from this rather than just "Assertion failed: illegal type and subtype
pair.", but something that actually mentions what the type and subtype
values were.

On Thu, Jun 20, 2013 at 11:33 AM, Garriss Jr., James P.
<jgarriss@mitre.org>wrote:
...
Content types come in pairs.  So while the type can be “text” and the
subtype can be “pdf”, the complete content type cannot be “text/pdf”.  It
can, however, be “text/html” or “application/pdf”.****
** **
So in my DFDL it’s not sufficient to specify enumerated lists for types
and subtypes (as I have done below), I must also specify which types are
allowed to go with which subtypes.****
** **
How would I do that, given this complexType?  TIA!****
** **
<xsd:complexType name="MimeTypeType">
        <xsd:sequence dfdl:separator="/">
            <xsd:element name="Type" dfdl:initiator="">
                <xsd:annotation>
                    <xsd:appinfo source="http://www.ogf.org/dfdl/dfdl-1.0/
">
                        <dfdl:assert test="{ dfdl:checkConstraints(.) }"message
="The type must match one of the values on the enumerated list."/>
                    </xsd:appinfo>
                </xsd:annotation>
                <xsd:simpleType>
                    <xsd:restriction base="xsd:string">
                        <xsd:pattern
                            value=
"([a|A][p|P][p|P][l|L][i|I][c|C][a|A][t|T][i|I][o|O][n|N])|
([m|M][u|U][l|L][t|T][i|I][p|P][a|A][r|R][t|T])|
                            ([m|M][e|E][s|S][s|S][a|A][g|G][e|E])|
                            ([t|T][e|E][x|X][t|T])"
                        />
                    </xsd:restriction>
                </xsd:simpleType>
            </xsd:element>
            <xsd:element name="Subtype" dfdl:terminator="">
                <xsd:annotation>
                    <xsd:appinfo source="http://www.ogf.org/dfdl/dfdl-1.0/
">
                        <dfdl:assert test="{ dfdl:checkConstraints(.) }"message
="The subtype must match one of the values on the enumerated list."/>
                    </xsd:appinfo>
                </xsd:annotation>
                <xsd:simpleType>
                    <xsd:restriction base="xsd:string">
                        <xsd:pattern
                            value="([p|P][d|D][f|F])|
([a|A][l|L][t|T][e|E][r|R][n|N][a|A][t|T][i|I][v|V][e|E])|
                            ([m|M][i|I][x|X][e|E][d|D])|
                            ([r|R][f|F][c|C]822)|
                            ([p|P][l|L][a|A][i|I][n|N])|
                            ([h|H][t|T][m|M][l|L])"
                        />
                    </xsd:restriction>
                </xsd:simpleType>
            </xsd:element>
        </xsd:sequence>
    </xsd:complexType>****
** **
** **
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Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology |
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