what are xml schemas

Thread view:

Enable EMail Alerts

Start New Thread

Thread rating:

Madhur - 23 Jul 2006 07:43 GMT

Hello

I am a .net developer and normally see the entries like
<webparts xmlns="schemas.microsoft.com/webparts/v2>

I get confused here about what does xmlns refers to and how does the program
locates this schema.

Since this schema refers to internet location, but a normal program doesnt
require an Internet location?

Where is this schema stored and how can I view them?

--
Madhur Ahuja

http://madhurahuja.blogspot.com

Reply to this Message

Barry Kelly - 23 Jul 2006 11:07 GMT

> I am a .net developer and normally see the entries like
> <webparts xmlns="schemas.microsoft.com/webparts/v2>
>
> I get confused here about what does xmlns refers to and how does the program
> locates this schema.

'xmlns' means an XML namespace, and it is not a schema. The URI referred
to by the 'xmlns' attribute doesn't need to be a valid location from
which stuff can be downloaded. What it does is scope attributes and
elements by the given namespace. It's a little like namespaces in .NET &
C# - it permits the same identifier (an element or attribute in XML) to
be used in different namespaces without conflicting with one another.

> Since this schema refers to internet location, but a normal program doesnt
> require an Internet location?

Even for schemas, XML documents are typically not validated against the
schema unless you use a validating reader. Using a validating reader can
slow things down, so they aren't always used.

> Where is this schema stored and how can I view them?

Schemas are generally in a DTD (document type definition) header at the
start of the document, or in an 'xsd' (XML schema definition) attribute.
There are other schema definition formats too.

-- Barry

Signature

http://barrkel.blogspot.com/

Reply to this Message

Madhur - 23 Jul 2006 17:19 GMT

>> I am a .net developer and normally see the entries like
>> <webparts xmlns="schemas.microsoft.com/webparts/v2>
[quoted text clipped - 24 lines]
>
> -- Barry

I got your point! But as you said they are just namespaces, If I change
one of them, .NET compilation throws error that this namespace is not a
valid one. I want to know how it determines validity and where this info
is stored.
For ex .dwp file use namespace
schemas.microsoft.com/webparts/v2
while the v3 of .dwp file use
schemas.microsoft.com/webparts/v3

I dont see this info documented anywhere, and how can I see the difference
between two.

--
Madhur Ahuja

http://madhurahuja.blogspot.com

Reply to this Message

Barry Kelly - 23 Jul 2006 21:22 GMT

> >> I am a .net developer and normally see the entries like
> >> <webparts xmlns="schemas.microsoft.com/webparts/v2>

> I got your point! But as you said they are just namespaces, If I change
> one of them, .NET compilation throws error that this namespace is not a
> valid one. I want to know how it determines validity and where this info
> is stored.

If you change the namespace, it's as if you changed the element name -
if the program is XML namespace aware, it won't recognize the element at
all.

No schema needs to be anywhere for this to occur - the program may be
reading hard-coded namespace-element name pairs from the XML.

> For ex .dwp file use namespace
> schemas.microsoft.com/webparts/v2
[quoted text clipped - 3 lines]
> I dont see this info documented anywhere, and how can I see the difference
> between two.

The difference between the two is that one ends in '2' and the other in
'3', it seems to me.

-- Barry

Signature

http://barrkel.blogspot.com/

Reply to this Message

Chris Mullins - 23 Jul 2006 19:19 GMT

http://www.google.com/search?complete=1&hl=en&q=xml+schema

--
Chris Mullins

Reply to this Message

what are xml schemas

Free Magazines