Alternatives to XML?

[Frank Millman]

"Chris Angelico"  wrote in message 
news:CAPTjJmof_sXqax0Ury5LsBEj7cdFv92WiWKbfvAC+bM=HwtHXA at mail.gmail.com...

> Sounds to me like you have two very different concerns, then. My 
> understanding of "GUI" is that it's a desktop app running on the user's 
> computer, as opposed to some sort of client/server system - am I right?

Not exactly, but the difference in not important, as you have got the 
essentials below spot on.

For the record, the server runs an HTTP server, and anyone on the LAN/WAN 
can access the system using a browser. Because the tables that define the 
database are stored in the database itself, there is no difference between a 
form that allows a user to capture an invoice, and a form that allows a user 
to modify a column definition. It is all controlled through permissions, but 
technically they are identical.

> 1) Malicious users, as I describe above, can simply mess with your code 
> directly, or bypass it and talk to the database, or anything. So you can 
> ignore them.

Absolutely. If an organisation running my system wants to be secure, they 
should keep the server in a locked room only accessible by a trusted system 
administrator.

> 2) Non-programmer users, without any sort of malice, want to be able to 
> edit these scripts but not be caught out by a tiny syntactic problem.

Now we are getting to the nitty-gritty.

[snip some good comments]

> Here's a very simple format, borrowing from RFC822 with a bit of Python 
> added:

if: _param.auto_party_id != None
    if: on_insert
        value: =auto_gen(_param.auto_party_id)
    elif: not_exists
        value: <new>

Getting close, but it is not *quite* that simple.

For example, having isolated the LHS of the if clause, I process it 
something like this -

if source.startswith("'"):
    source_value = source[1:-1]
elif '.' in source:
    source_objname, source_colname = source.split('.', 1)
    source_record = caller.data_objects[source_objname]
    source_value = source_record.getval(source_colname)
elif source == '$None':
    source_value = None
elif source == '$True':
    source_value = True
elif source == '$False':
    source_value = False
elif source.startswith('int('):
    source_value = int(source[4:-1])

Anyway, you have isolated the essential issue. I need a DSL which is easy 
for a non-technical user to read/write, and easy to verify that it is 
achieving the desired result.

I suspect that this is quite challenging whatever format I use. Up to now I 
have been using XML, and it works for me. As Rob pointed out, I have become 
too comfortable with it to be objective, but no-one has yet convinced me 
that the alternatives are any better. I may eventually end up with an 
additional layer that prompts the user through their requirement in 'wizard' 
style, and generates the underlying XML (or whatever) automatically.

Frank