Re: namespace?

"cj" <cj@xxxxxxxxxxxxx> wrote in message
news:eaqL%23H7VIHA.4440@xxxxxxxxxxxxxxxxxxxxxxx
Yes, that helps. Making a namespace look like a web address is just
asking for confusion IMHO but that's life.

What you need to understand is that using what looks like a URL for a
namespace name is not directly related to .NET at all and is also not done
just for web service use.

It is an XML standard per the World Wide Web Consortium (the W3C). The
reason for needing namespaces in XML is because the very nature of XML
allows you to make up tag and attribute names yourself based on the data you
will be passing. If 2 departments within a single company were to be using
XML to represent employee data (for just their department), they each might
inadvertently use the same tag names and/or attribute names. Now, if those
two lists of XML were to get mixed up, it would be very hard to separate
who's data is who's - - namespaces are needed to prevent this from occuring
(because although the tag names might be the same, the xmlns="" value would
be different).

Now, you may ask "Ok, that makes sense, buy why use URL's and not some other
identifier?". Well, what if the two departments were "Human Resources" and
"Accounts Payable", couldn't they just use "HR" and "AP" as the namespace
names? Perhaps, but what happens if this company were to merge with another
company who is also using XML for just the same purpose and that company is
most likely going to have Human Resources and Accounts Payable departments
as well. If the two companies had been using "HR" and "AP" as their
namespace qualifiers, there would be no way to tell who's data was who's.

This is why namespaces are generally specified using URL's, because each
company/organization on the planet is guaranteed to have a unique URL and so
in the first senario above, the namespaces could be:

http://www.ACME.com/employees/HR
http://www.ACME.com/employees/AP

And, those namespaces would keep, not only those two departments XML data
separate, but when the new company gets merged with ACME, we still can keep
it all straight because the new company's namespaces would look like this:

http://www.OtherCompany.com/employees/HR
http://www.OtherCompany.com/employees/AP

So what I'm still wondering is why would it matter if you and I both use
the same namespace--or would it? It's not actually telling the client
where to send the request is it?

No. Again, namespaces are not actually resolved by any software, they just
serve as names to group related XML data. As in my example above, it could
be very confusing if your data and my data got mixed up. Namespaces are not
required in all uses of XML because sometimes making "groups" of XML isn't
really necessary, but with web services, they are because there are many
services out there and different services can still result in similar XML,
so we need to keep each service's XML separate from another's.

Does the client know the namespace before it calls the service?

Yes. The proxy classes that are built by Visual Studio (usually hidden
files in the Solution Explorer) will have knowledge of the service
namespace.

Perhaps it does and then it waits for a response to come that says it's
from that web service.

No. Again, namespaces are just strings that identify a group of XML. They
aren't used in web services in this way.

In which case it wouldn't matter if both of us used the same namespace as
long as a client wasn't requesting data from both of us in which case it
would get confused on responses.

True, but your missing the bigger point. Although it *may* not cause a
problem if two entities use the same namespace, the fact is that it *could*
and to eliminate the possibility, we make sure that different services use
different namespaces. It's more of a programming standard than a
programming issue.

-Scott



Scott M. wrote:
A "namespace" looks like a URL, but it is not. In this case "tempuri"
stands for "temporary URI", meaning that it is dummy data that you are
supposed to change.

Namespaces are used in XML (which is the format that your web service
sends/receives data) to organize/group XML tags and attributes. This is
conceptually the same as how namespaces are used in .NET - - to
organize/group classes. The difference being that in .NET, the syntax
uses dot notation (i.e. System.Web.UI) and in XML, namespaces use URI
(uniform resource indicators), such as "http://www.something.com";.
Although they look like URL's, they are not and they are not meant to be
resolved - - they are just names that you make up to keep your XML tags
and attributes used by your web service organized and marked as belonging
to you.

Generally, an XML namespace should start with the ACTUAL URL of your
company/organization, but again, not so that they can be browsed to, but
because it is highly unlikely that anyone else on the planet would start
their XML namespaces with your company/organization URL. After the
beginning of the URL, you generally add something else that defines what
your web serivice is. For example, my company is Technical Training
Solutions and my URL is http://TechTrainSolutions.com. If I were making
a web service that retrieves course ID's from a database, I might use the
following to indicate that all the xml coming back from the service be
"grouped" in the same namespace.

<System.Web.Services.WebService(Namespace:="http://www.TechTrainSolutions.com/services/courseID";)>

After adding such a namespace, you'll be able to actually see it used
when you examine the results of your web service call. You'd see
something like this:

<string
xmlns="http://www.TechTrainSolutions.com/services/courseID";>012-4A</string>

Hope this helps.

-Scott

"cj" <cj@xxxxxxxxxxxxx> wrote in message
news:usFByT5VIHA.1184@xxxxxxxxxxxxxxxxxxxxxxx
I'm still not getting this. Namespace:="http://tempuri.org/"; looks like
a web address and I've opend it but don't understand what it's saying.
Can you try again to explain what a namespace does and why my web
service needs to refer to one?

Also I think this has something to do with the WebMethodAttribute that
we are discussing in my other post. Am I correct?



Steven Cheng[MSFT] wrote:
Hi Cj,

As for the following attribute:

<System.Web.Services.WebService(Namespace:="http://tempuri.org/";)> It
is used to describe and decorate your webservice service class(applied
on class level). Certainly, you can use the same one for C# code,
they're the same. Also you can find more properites(that you can set on
this attribute for your service class): #WebServiceAttribute Class
http://msdn2.microsoft.com/en-us/library/system.web.services.webserviceattri
bute.aspx

In addition, to better understand its usage, you can visit the
service's WSDL document (view through yourservice.asmx?WSDL url).
Change the attribute setting and refresh the WSDL document to see the
changes.

Sincerely,

Steven Cheng

Microsoft MSDN Online Support Lead

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--------------------
Date: Fri, 11 Jan 2008 15:07:05 -0500
From: cj <cj@xxxxxxxxxxxxx>
User-Agent: Thunderbird 2.0.0.6 (Windows/20070728)
Subject: namespace?
Newsgroups: microsoft.public.dotnet.framework.webservices


What does the line
<System.Web.Services.WebService(Namespace:="http://tempuri.org/";)> _
do in the example below?

Imports System.Web.Services
Imports System.Web.Services.Protocols
Imports System.ComponentModel

' To allow this Web Service to be called from script, using ASP.NET
AJAX, uncomment the following line.
' <System.Web.Script.Services.ScriptService()> _
<System.Web.Services.WebService(Namespace:="http://tempuri.org/";)> _
<System.Web.Services.WebServiceBinding(ConformsTo:=WsiProfiles.BasicProfile1
_1)> _
<ToolboxItem(False)> _
Public Class Service1
Inherits System.Web.Services.WebService

<WebMethod()> _
Public Function HelloWorld() As String
Return "Hello World"
End Function

End Class

And why don't I see a similar line in the C# example at
http://dotnetjunkies.com/Tutorial/4D13CEFA-D0FD-44BE-8749-8D17B5757564.dcik
?



.

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