RE: Use of XML for config files

["Robert C. Leif" <rleif@rleif.com>]

From: Bob Leif
To: Volkert Barr et al.

Following standard Ada practice, one should declare all the types for
the elements and, if one uses them, attributes. The best way to do this
is to create both an XML schema and an Ada package specification. The
data types and ranges of the two documents should be identical. The
combination of validating the schema and compiling the specification is
equivalent to man whose hazard analysis leads him to wear both a belt
and suspenders (I believe braces in the UK).

The first step is to decide on the data types. For the convenience of
all this can be done in Ada. The second step is to determine if they
should be expressed as XML elements or attributes. XMLSpy or similar
tool can be employed to both create the schema and generate a
preliminary XML document.

-----Original Message-----
From: comp.lang.ada-admin@ada.eu.org
[mailto:comp.lang.ada-admin@ada.eu.org] On Behalf Of Volkert Barr
Sent: Wednesday, June 05, 2002 12:19 AM
To: comp.lang.ada@ada.eu.org
Subject: Re: Use of XML for config files

> What that means is that if we were to use XML, we should support both
> user-defined configuration item attributes and some kind of object
> nesting (configuration items defined within other configuration
> items). I haven't really heard anyone seriously arguing the usefulness
> of this stuff.
> 
> If we are to stick with simple attribute-value pairs, then XML would
> be major overkill.

I have set up a first small datamodel for hierarchical configuration 
data (nested Config_Items containing lists of (Key,Value)-Tupels) 
and defined a BNF-Grammar for text (file) representation of this
data. I hope Stephan Leake will add it to his "Config-Proposal Page"!

The grammes defines the following style:

--
-- Comment Block
--
Config_Item1.Key := Value

-- Comment
Config_Item1.Inner_Config_Item2.Key := Value


The same can be done in XML, but the next you need is
an "XML Editor" ;-) (That is one reason, why there is so
much Business (and money) around XML.) 

XML-like Configuration:

<configuration>
  <config_item name= "Config_Item1" >
    <Key> Key </Key>
    <value> Value </value>
    <config_item name = "Config_Item2" >
      <entry>
        <key> Key </key>
        <value> Value </value>
      </entry>   
  </config_item>
</configuration>


Volkert