Steve Elkins Proposed OLAP Glossary Addendum

There are a lot of terms that we bandy about on this forum that aren't
included in the "official" OLAP glossary.  


Metadata
Data which describes the structure of a hypercube.  Literally: data about
data.  

MDD or MDDB: Multi-Dimensional Database Server
An OLAP server that physically stores its data in multi-dimensional array
format.  
Synonym: "Pure" OLAP Server
See:  RDBMS based OLAP Server

RDBMS Based OLAP Server
An OLAP server that physically stores its data in a set of tables in a
relational database.  
Synonym: "Virtual" OLAP Server
See: MDD or MDDB: Multi-dimensional Database, Star Schema, Snowflake
Schema.  

Star Schema Database
A database schema used in some RDBMS based OLAP servers in which all
values of measures are stored in a "fact table" along with simple numeric
keys representing the dimension members with which the values are
associated.  The descriptive member names that are associated with each
numeric key in the fact table are stored in denormalized dimension tables,
one per dimension of the hypercube.  The dimension tables also describe
the hierarchical relationships in each dimension.  
See: RDBMS Based OLAP Server, Snowflake Schema Database

Snowflake Schema Database
A variation of the star schema database in which the dimension tables are
normalized.  This will improve performance in cases where a star schema
dimension table would so large that unreasonable amounts of disk storage
would be required and query performance would be degraded  
See: RDBMS Based OLAP Server, Star Schema Database

Tuple
See: Cell

Measure
A member with a numeric value.  For example, revenue, units sold,
operating cost, etc.  
Synonyms: Variable, Key Performance Indicator (KPI)
See: Member-Dimension, Calculated Member,

Variable
See: Measure

Drill Through
See: Reach Through

Combinatorial Explosion
The tendency of hypercubes to grow very quickly in size (number of member
combinations) as dimensions, (and, to a lesser degree, members) are added
to its structure.  

Partitioning
The division of a single, ideal, logical hypercube into several smaller
logical cubes in order to address the problem of combinatorial explosion. 

See:  Combinatorial Explosion

Multicube
A logical hypercube physically composed of several smaller cubes, usually
one per measure.  

Scenario
A dimension used in many hypercubes that contains members that describe
different versions of measures.  For example, budget, actual, forecast,
etc.  

Multiple Simultaneous Hierarchies
The ability of a child to have hierarchical relationships with more than
one parent.  For example, a child, cola in 12oz cans, with two parents:
canned drinks and cola drinks.  The same detailed data is rolled-up
through two or more hierarchical aggregation paths.  
See: Hierarchical Relationships, Parent, Children

Intelligent Agent
A software object that searches a database on a set schedule, looking for
pre defined patterns in the values of measures.  When patterns that meet
these criteria are found they are automatically brought to the attention
of the end user.  For example, an intelligent agent might search a
hypercube each time it is updated with new values, looking for cities
where sales have dropped by more than 10% from the prior period to the
current period, and present this information to the sales manager when he
logs on to the system.