tier.html

this gives an introduction to microsoft dna.

The Tier Solutions - The Holy Grail
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<P>

The Microsoft implementation of the collaborative approach 
was dubbed DNA and was realized using the following
set of technologies:

<P>

<UL>
<LI>A thin presentation client that understands 
    standard information sent to it. (Web Browser)
<LI>Encapsulation of the business logic in a manner 
    that remains flexible. (COM)
<LI>Data stored in a consistent and hopefully interchangeable 
    solution. (XML)
</UL>

<P>

We can see how the model and the 
technologies could now work together. 

<P>

First, a lightweight front-end could perform the presentation 
and client interaction in a familiar and robust environment. 
The HTML browser solves this. Information is displayed and 
submitted in a standardized fashion and governed by an 
independent and open community.

<P>

Secondly,  business rules could be captured in a middle 
tier where they could change but remain scalable. To 
capture logic, one must build an encapsulated function 
that can be accessed via the presentation layer and talk 
to the data layer. COM, which will discuss in greater 
detail in just a bit, was designed with such ideas in 
mind; code re-use, maintenance and encapsulation. 

<P>

Finally, we could store the data within it's own layer to 
protect the other layers from proprietary databases and 
Meta stores.

<P>

While this may initially seem like a utopian list of 
features, the technology had provided the solutions. 

<P>

A number of technologies are needed to make the 
collaborative or "tiered" approach work. In fact, 
DNA, and the DNA technologies hoped to
provide an 'n' tier solution (this 
will become apparent soon).

<P>
<CENTER>
<TABLE BORDER = "1">
<TR>
<TH>Technologies Needed</TH>
<TH>Microsoft Products</TH>
<TH>Other Products</TH>
</TR>

<TR>
<TD>Lightweight Presentation</TD>
<TD>Internet Explorer, HTML, XML</TD>
<TD>Others include Netscape</TD>
</TR>

<TR>
<TD>Rendering Engine</TD>
<TD>Internet Information Server (Web Engine)</TD>
<TD>For large solutions see other variants of IIS by MS.</TD>
</TR>

<TR>
<TD>Fast Implementation (between Rendering and Business Components)</TD>
<TD>Active Server Pages, Scripting (VBScript, Jscript and even PerlScript) (COM)</TD>
<TD>Enables IIS to produce flexible HTML driven by Business Components.</TD>
</TR>

<TR>
<TD>Component Communication</TD>
<TD>COM (Common Object Model), MSMQ, COM+</TD>
<TD>Competitors include Corba and RMI, PerlRPC</TD>
</TR>

<TR>
<TD>Business Components</TD>
<TD>COM Objects (with/without MTS support)</TD>
<TD></TD>
</TR>

<TR>
<TD>Fast Implementation (Business Layer to Data</TD>
<TD>ActiveX Data Objects (More COM), ODBC</TD>
<TD>Using lightweight wrappers to access a generic data abstract layer.</TD>
</TR>

<TR>
<TD>Data Access and Translation</TD>
<TD>OLEDB, Universal Data Access and ADSI</TD>
<TD>ODBC</TD>
</TR>

<TR>
<TD>Data Storage</TD>
<TD>SQL Server, Exchange, Active Directory and NTFS</TD>
<TD>Obviously other databases are included like Oracle and Informix.</TD>
</TR>
</TABLE>
</CENTER>
<P>

This table by no means provides the complete or 
definitive list of the technologies involved, or 
the boundaries of their scope. However, it does 
give some indication of where and when the 
technologies mentioned later in this tutorial are used. 

<P>

There are many other technologies used in other areas,
for example, that include access to legacy systems, third 
party integrations, and even exchangeable data format. However, 
we are primarily focused on what DNA is and where ASP sits.

<P>

By now, you will have realized that COM, the Component 
Object Model, plays a large part in the Microsoft 
implementation of the multi-tiered solutions. 

<P>

This is no co-incidence, as COM was designed to solve 
the problems of communication, implementation and open 
access within the layers. The COM approach centers on a 
language independent framework to build components and 
services. It's obviously successful - if we look at our 
table we can see that a large number of the technologies 
either use or are built from COM. Also note, that nearly 
all of the technologies presented here for DNA are mainly 
based on the Windows NT technology.

<P>

So what are the Microsoft technologies and what functions 
do they perform that we should know about? Well, almost all 
of those specified go to make up the majority of DNA based 
applications in one form or another. With this in mind a 
quick tour of the technologies is required.

<P>

For further information on Microsoft DNA, the architecture, 
the technologies and where DNA is headed you can access the 
<A HREF = "javascript:if(confirm('http://msdn.microsoft.com./  \n\nThis file was not retrieved by Teleport Pro, because it is addressed on a domain or path outside the boundaries set for its Starting Address.  \n\nDo you want to open it from the server?'))window.location='http://msdn.microsoft.com./'" tppabs="http://msdn.microsoft.com./">Microsoft Developer Network site</A>.  
For more information on COM, you can point your browser to 
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<P>

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