dolfin team mailing list archive

[Johan Jansson <johanjan@xxxxxxxxxxxxxxxx>]

On Mon, Feb 13, 2006 at 07:39:31PM -0600, Anders Logg wrote:
...
> Maybe we can just move the writing of the header to the constructor
> and the writing of the footer to the destructor of XMLFile?

Hm, can we differentiate between reading and writing at that point?

> 
> > We can assume the incoming file is a valid DOLFIN XML file (by Schema
> > validation). The schema doesn't exist yet, but it will eventually..
> 
> I have never bothered to learn how to write a schema, but we do have
> 
>    <dolfin xmlns:dolfin="http://www.fenics.org/dolfin/";>
> 
> in the header and I suspect that is a reference to a schema? I don't
> remember why I added this line but I vaguely remember I looked at the
> XML format for an early version of Ko.
> 
> /Anders

The xmlns:dolfin="http://www.fenics.org/dolfin/"; attribute is the
namespace. A schema is defined with an attribute:
xsi:schemaLocation="http://mydatatypes.edu/ex2.xsd";. I'm still a bit
unclear about XML namespaces though (and why they are usually URLs), I
need to read up on it.

A schema (ex2.xsd is the filename of the schema above) is just an XML
file describing the data types in the file and their allowed semantics
(allowed value ranges etc.).

You define elements:

<xs:element name="pointmass" type ="pointmassType"/>
<xs:element name="radius" type="realType"/>
<xs:element name="position" type="vectorType"/>
<xs:element name="name" type="xs:string"/>

and data types:

<xs:complexType name="pointmassType">
 <xs:sequence>
  <xs:element ref="name" minOccurs="1" maxOccurs="1"/>
  <xs:element ref="position" minOccurs="0" maxOccurs="1"/>
  <xs:element ref="radius" minOccurs="0" maxOccurs="1"/>
 </xs:sequence>
</xs:complexType>

It's just a simple information description language. It would be nice
to be able to generate source code from a schema (the data types will
exist as source code as well, normally with the same semantics), but I
don't think this is possible right now.

  Johan