Re: Org schemas we talked to be non-free, was: [ELPA] New package: repology.el

[Eli Zaretskii]

> From: Richard Stallman <rms@gnu.org>
> Cc: ulm@gentoo.org, bugs@gnu.support, ulm@gentoo.org,
>       emacs-devel@gnu.org, ams@gnu.org, arthur.miller@live.com,
>       dgutov@yandex.ru
> Date: Thu, 28 Jan 2021 01:29:08 -0500
> 
> Is this extension mechanism limited to adding new fields and options?
> That may be sufficient most of the time in practice, but not enough
> to make it free.

Here's an example of redefining a type.  Suppose a schema defines a
type named yearType:

  <xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema";>

    <xsd:simpleType name="yearType">
      <xsd:restriction base="xsd:string"/>
    </xsd:simpleType>

  </xsd:schema>

Here's how you redefine yearType to force it to have 4 characters, no
more, no less:

  <xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema";>

    <xsd:redefine schemaLocation="prod1.xsd">
      <xsd:simpleType name="yearType">
        <xsd:restriction base="yearType">
          <xsd:length value="4"/>
        </xsd:restriction>
      </xsd:simpleType>
    </xsd:redefine>

    <xsd:element name="fullYear" type="yearType"/>

  </xsd:schema>

where prod1.xsd is the previous schema that defines the original
yearType.