Update link to JSON Table Schema specification and explain variations

[Stephen-Gates]

The specification is now at https://specs.frictionlessdata.io/table-schema/ not http://dataprotocols.org/json-table-schema/ as used in the about page.

The link in the about page redirects to the new specification.

The about page says, "We currently recognise schemas that use the JSON Table Schema, with a few modifications." but doesn't explicitly say what these variations are.

Why not just support the JSON Table Schema as it is defined?

[mhGLEIF]

Or this language:

https://github.com/digital-preservation/csv-schema

?

[mhGLEIF]

@Stephen-Gates @quadrophobiac seems like the variations are substantial.

I tried to use a schema with minimum lengths of 1 for all columns, with any empty values i.e. "" indicated as missingValues but this failed spectacularly, with all the empty values failing the minLength check.

[Stephen-Gates]

@mhGLEIF if you need software libraries or apps to valid csv files against a schema, I'd look here https://frictionlessdata.io/software/ I lead the Data Curator project.

Be warned not every software listed supports v1 of the specification (see frictionlessdata/website#135) - e.g. CSVLint

The correct link for the CSVLint About page to use is now https://frictionlessdata.io/specs/table-schema/