The Tier Solutions - The Holy Grail
June 5, 2000
The Microsoft implementation of the collaborative approach
was dubbed DNA and was realized using the following
set of technologies:
- A thin presentation client that understands
standard information sent to it. (Web Browser)
- Encapsulation of the business logic in a manner
that remains flexible. (COM)
- Data stored in a consistent and hopefully interchangeable
solution. (XML)
We can see how the model and the
technologies could now work together.
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.
Secondly, business rules could be captured in a middle
tier where they could change but remain scaleable. 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 we will discuss in greater
detail in just a bit, was designed with such ideas in
mind; code re-use, maintenance and encapsulation.
Finally, we could store the data within it's own layer to
protect the other layers from proprietary databases and
Meta stores.
While this may initially seem like a utopian list of
features, the technology had provided the solutions.
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).
| Technologies Needed |
Microsoft Products |
Other Products |
| Lightweight Presentation |
Internet Explorer, HTML, XML |
Others include Netscape |
| Rendering Engine |
Internet Information Server (Web Engine) |
For large solutions see other variants of IIS by MS. |
| Fast Implementation (between Rendering and Business
Components) |
Active Server Pages, Scripting (VBScript, Jscript and even
PerlScript) (COM) |
Enables IIS to produce flexible HTML driven by Business
Components. |
| Component Communication |
COM (Common Object Model), MSMQ, COM+ |
Competitors include Corba and RMI, PerlRPC |
| Business Components |
COM Objects (with/without MTS support) |
|
| Fast Implementation (Business Layer to Data |
ActiveX Data Objects (More COM), ODBC |
Using lightweight wrappers to access a generic data abstract
layer. |
| Data Access and Translation |
OLEDB, Universal Data Access and ADSI |
ODBC |
| Data Storage |
SQL Server, Exchange, Active Directory and NTFS |
Obviously other databases are included like Oracle and
Informix. |
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.
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.
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.
This is no coincidence, 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.
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.
For further information on Microsoft DNA, the architecture,
the technologies and where DNA is headed you can access the
Microsoft Developer Network site.
For more information on COM, you can point your browser to
Microsoft.
Collaborative Business Systems
Introduction to ASP For Web Developers | Table of Contents
COM - The Component Object Model
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