Hi folks,
does someone has a guideline to roughly estimate how long the
development of a dwh can be (in weeks) ??
Some possible factors:
the number of inflow files, fact tables, dimension tables and the
variables in these tables..
how many olap cubes, ...

thx,
Herman

Hi Herman!


Are you looking for a closed formula, giving you the time
needed/estimated to complete a data warehousing project
given the parameters you quoted above? If yes, such a
formula doesn't and can't exist.

The only way to get an estimate, is to hire an experienced
Project Manager for data warehousing, who will analyze
your requirements and calculate/estimate the total effort.

Still, to give you an idea of the life cycle, here is a list
of some major phases for a typical DW project:

- project management (on-going)
- collecting business requirements
- defining the dimensional model
- defining architecture for the back room
- defining architecture for the front room
- defining the security model
- physical model
- ETL design and development
- client applications design and development


A Project Manager for data warehousing will decompose
each of those phases into a corresponding WBS (Work
Breakdown Structure), that is, into subtasks and estimate
effort (measured in "staff day" units) for each of those
subtasks.

Finally, he will roll up all efforts for the most detailed subtasks
and calculate the total effort for the project.


Example (ER = Effort Eemaining):


[ 10%]...Sämtliche DW Arbeit...ER: 207 staff day
[100%]...Phase 0 (Vorführung/Demo)...ER: none (completed).
[ 93%]...Phase 1 (Projekt Definition)...ER: 1 staff day
[100%]...Preliminary Scope...ER: none (completed).
[100%]...Build Business Justification...ER: none
(completed).
[100%]...Establish Project Identity...ER: none
(completed).
[100%]...Staff the Project...ER: none (completed).
[100%]...Develop initial schedule and WBS...ER: none
(completed).
[100%]...Develop communications plan...ER: none
(completed).
[ 0%]...Project team kick-off meeting...ER: 1 staff
day
[ 50%]...Phase 2: Technologie Definition...ER: 1 staff day
[100%]...Design der Arhitektur...ER: none (completed).
[ 0%]...Produktauswahl und Installation...ER: 1 staff
day
etc.

--
HTH, Sven
---
http://www.svenkolar.net

A very unscientific approach:
About 6 months as an average, depending om the complexity
of your project. Longer projects are usually problematic as the
requirements and organizational focus tends to change over time.
Project lasting for more than 1 year often go wrong.

Additionally to the various technical aspects such as number of
files/tables
complexity of roll-ups and formulas, writeback/non-writeback etc as
others here has pointed out, don't underestimate specification work.

Usually engagements of the users/project owners (your customer) might
be a problem and bottle neck - as these people usually have limited
spare time for DW projects....and often 1 to max two workshops per
week can be managed for specification and design of the DW solution -
which often end up with a month or two for specification details.

Even though the users have been doing a quite good specification job
ahead before the DW project start - expect to to a lot of
respecification of the whole solution.


RE
Bjørn T






"Sven Kolar" <devnull (AT) svenkolar (DOT) net> wrote