Hierarchies About

Question

Hi,
  Can some one let me know
1. When should we use hierarchies, pls. explain with a scenario ?
2. What is the concept behind hierarchies ?
3. How to create a hierarchy - step by step ?
4. Are there any varieties in hierarchy ?
5. what are the components of hierarchy ?
KINDLY NOTE: Pls. dont give me any links to any forums or any std. docs.
Answers will be appreciated by suitable points.
Thanks,
bwlearner

Answer 1

Hi,
Hierarchies in general are essential structures for
navigation. Having characteristics and attributes in the
dimension and master data tables that are related in a
sequence of parent-child relationships, obviously
involves hierarchies. But as the real world is sometimes
irregular, so are hierarchies. In BW there are essentially three possibilities for modeling hierarchies:
•     as a hierarchy of characteristics within a dimension table
•     as a hierarchy of attributes attached to a characteristic
•     as an external hierarchy
<b>Hierarchies within a Dimension</b>
A typical example of a hierarchy of this type is a time
hierarchy with levels such as millenium – century –
decade – year – month – day – hour etc. Another typical
example is a geographic hierarchy with levels such as
continent – country – state – region – city etc.
<b>Hierarchies within a master data table of a characteristic</b>
This case is very similar to the one discussed in section
before. The difference is the increased flexibility (i.e.
realignment facilities) that comes with navigational
attributes. The hierarchy should still have a fixed
number of levels. However, changes to that hierarchy
(i.e. changes to attribute values) can be easily applied
to facts that are already loaded into a cube.
A typical example is the hierarchy of sales office –
sales group – sales person. This hierarchy has a fixed
number of levels but is frequently reorganized.
In terms of performance, this is the least attractive of the hierarchy modeling techniques.
<b>External Hierarchies</b>
This is the ideal type if a hierarchy
•     frequently changes
•     has no fixed number of levels (sometimes referred to as a "ragged" or “unbalanced” hierarchy).
A typical example is a cost center hierarchy in which
several (sub-) cost centers belong to one cost center
which itself belong to another cost center and so on.
Such a hierarchy has no fixed number of levels as cost
centers usually correspond to departments or groups
within a company, which might be reorganized into new
subgroups. Thus new levels might be introduced, old ones
disappear. The hierarchy might be deeper at one end (due
to a deeper hierarchical organization) and shallower at
the other.
Another major advantage of external hierarchies in
comparison to their alternatives is that an InfoObject
can have several such hierarchies and all these can be
used within the same cube. With the alternative
approaches the same effect could only be achieved through
difficult work-arounds.
<b>3. Creating a hierarchy</b>
http://help.sap.com/saphelp_nw04/helpdata/en/80/1a6736e07211d2acb80000e829fbfe/content.htm
<b>
How to download a hierarchy to a flat file</b>
https://www.sdn.sap.com/irj/servlet/prt/portal/prtroot/docs/library/uuid/0403a990-0201-0010-38b3-e1fc442848cb
<b>4.Varieties in hierarchy</b>
         Time dependent Hierarchies
         Time independent Hierarchies
         Version dependent Hierarchies
hope this helps
sham'm