Want to use the API from this site. I'm having trouble using the same parameters.

But I can do this with curl as shown on the site:

curl -F url=http://sbml.org/validator/api/sample-01.xml -F output=xml -F offcheck=u http://sbml.org/validator/

But I can't get the same with Mathematica:

t1 = URLExecute@HTTPRequest["http://sbml.org/validator/",
    <|"Method" -> "POST",
     "Headers" -> {
       "Content-Type" -> "multipart/form-data;",
       "Expect" -> ""},
     "MultipartElements" ->
      {
       {"name=\"url\";"} -> "http://sbml.org/validator/api/sample-01.xml"
       }
     |>, CharacterEncoding -> None
    ];
ImportString[StringJoin[t1], "XHTML"]

OUTPUT

File : null
Options :
Units consistency checking: on Identifier consistency checking: on \
MathML consistency checking: on SBO consistency checking: on \
Overdetermined model checking: on Modeling practices checking: on \
Overall SBML consistency checking: on Remove unrecognized packages: \
on Results: No model was given or it could not be resolved.

Want to use the API from this site. I'm having trouble using the same parameters.

But I can do this with curl as shown on the site:

curl 
  -F url=http://sbml.org/validator/api/sample-01.xml 
  -F output=xml 
  -F offcheck=u 
  http://sbml.org/validator/

But I can't get the same with Mathematica:

t1 = URLExecute @ HTTPRequest[
  "http://sbml.org/validator/"
, <|"Method" -> "POST"
  , "Headers" -> {
      "Content-Type" -> "multipart/form-data;"
    , "Expect" -> ""
    }
  , "MultipartElements" -> {
      {"name=\"url\";"} -> "http://sbml.org/validator/api/sample-01.xml"}
  |> 
, CharacterEncoding -> None
]; 

ImportString[StringJoin[t1], "XHTML"]

OUTPUT

File : null
Options :
Units consistency checking: on Identifier consistency checking: on \
MathML consistency checking: on SBO consistency checking: on \
Overdetermined model checking: on Modeling practices checking: on \
Overall SBML consistency checking: on Remove unrecognized packages: \
on Results: No model was given or it could not be resolved.