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From Xavier MACHENAUD <xavier.machen...@st.com>
Subject Re: XML based system architecture
Date Thu, 03 May 2001 08:44:54 GMT
I want tiers to be on separate servers to put them in different
subnets/DMZ for security reason.
I want to ensure that the user agent will only be able to see the
presentation layer (PL), and not the business layer (BL).
The BL should only accept incoming requests from the PL going to the
data layer (DL).
The DL should only allow incoming/outgoing requests from the BL.

Xavier

alistair@berthengron.co.uk wrote:
> 
> Why do the tiers need to be on different machines?
> 
> My app works on a very clear MVC architecture:
> 
> Request ----> Controller ----> BL ----> Controller ----> XSLT
> processor ----> Response
>         HTTP                    INTERNAL                RETURNS         PROCESSES   
           WHATEVER
>                                 WRAPPER         XML                     XML TO ...  
           [Currently HTML, XML, CSV, pdf]
>                                 ROUND
>                                 REQUEST
> 
> The request URL is therefore constructed to say what action/information is
> required AND how it is to be presented
> eg \controller\Order?order_no=1034&csv=true for a spreadsheet of order 1034.
> 
> If I need to return raw XML over http I just tell it to forget the XSLT view
> processing stage.
> 
> If I need to scale, I will load balance, as all of this happens within a
> webapp (the controller is just a servlet which loads the relevant Action
> (BL) which the URL specifies)
> 
> It's all a lot easier than other RPC, etcetera
> 
> Alistair
> 
> -----Original Message-----
> From: mx2@dais.cro.st.com [mailto:mx2@dais.cro.st.com]On Behalf Of
> Xavier MACHENAUD
> Sent: Wednesday, May 02, 2001 4:28 PM
> To: general@xml.apache.org
> Subject: Re: XML based system architecture
> 
> This is fine with a 2 tier architecture because XML servers can do SQL
> queries.
> 
> But it becomes more complicated if you want to do more generic requests
> (not just SQL) to a business logic (BL) layer.
> 
> In my case, I also like to be able to pass on the authentication
> information and to add a load-balancing mechanism later on in front of
> the BL.
> That's why I was thinking of a BL server accessible via HTTP.
> 
> That's why I was thinking of a way to do an HTTP request from the XML
> server, do get to a sort of servlet chaining.
> Am I going to a wrong way thinking that?
> If not, how can I do servlet chaining from the XML server?
> Should I implement a tag library that will allow me to do servlet
> chaining? (or to make and XML-RPC/SOAP call if my BL server is an
> XML-RPC/SOAP service)
> 
> Xavier
> 
> lyndon.samson@ssmb.com wrote:
> >
> > You could use XML-RPC ( simpler ) or SOAP ( more functionality ).
> >
> > I did something similar, but only 2-tier distributed.
> >
> > Outbound
> >  XML -> SQL - > XML -> HTML
> >
> > Inbound
> >  HTML FORM -> XML -> SQL
> >
> > ie for Outbound
> >
> > <queryset name="listCustomers">
> >   <sql>select * from customers</sql>
> > </queryset>
> >
> > select * from customers;
> >
> > <customers id="1">
> >  <name>aaa</name>
> >  <address>123 abc</address>
> > </customers>
> > <customers id="2">
> >  <name>bbb</name>
> >  <address>456 xzy</address>
> > </customers>
> > ...
> >
> > ...
> > <table>
> >  <tr><td>Name</td></td>Address</td></tr>
> >  <tr><td>aaa</td></td>123 abc</td></tr>
> >  <tr><td>bbb</td></td>456 xyz</td></tr>
> > </table>
> > ...
> >
> > -----Original Message-----
> > From: Xavier MACHENAUD [mailto:xavier.machenaud@st.com]
> > Sent: Wednesday, May 02, 2001 10:23 AM
> > To: General@xml.apache.org
> > Subject: XML based system architecture
> >
> > Hi,
> >
> > I'm in the process of designing an XML based application and I'm running
> > into a problem.
> >
> > I want to separate the Presentation layer (XML server) and the Business
> > Logic layer (servlet/cgi/...) by using XML : the presentation layer is
> > querying  the business logic layer which is returning XML data.
> > Of course, I don't want my BL layer to do any output formatting.
> >
> >         http
> > +-----+ get/post  +-----+       query         +-----+
> > |user | --------> |     | ------------------> |     |
> > |agent|           |Pres.|                     | BL  |
> > |     | <-------  |layer| <------------------ |layer|
> > +-----+  html     +-----+        XML          +-----+
> >          pdf      Xml Server                Servlet/cgi/...
> >          wml
> >
> > My problem is how can implement such an architecture?
> > More specifically, what protocol (compatible with that fact that there
> > could be a firewall between the 2 layers) can be used to query the BL
> > servlet?
> >
> >
> > Cheers,
> > Xavier
> >
>

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