SAP Business Objects 4.0 (SP02) Information Design Tool (Universe Designer) Creating Queries (SQL Traps (CHASM and FAN trap))

1. Information Design Tool (**Universe
Design Tool)
Creating a Universe using IDT
**Here the data is stored in a MS Access DB and connection to the DB is made
using ODBC**
Our intension is to design/develop a Universe, which can be used by the webI
users to create reports as per the requirements. The process is as follows;
1: Creating a project
2: Creating Database Connections
3: Creating Data Foundation layer
4: Insert Tables and Joins to DFX layer
5: Creating Business Layer
6: Creating Folders/Classes and Objects in BLX layer
7: Creating Queries to Test Tutorial 5
8: Publish to repository
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2. INFORMATION DESIGN TOOL TUTORIAL 5
SQL Traps
A trap is a situation during the Universe design where the query returns higher
number of rows, than expected results. There are two types of SQL traps;
CHASM trap
This is a problem with join path between three tables, where a single table
has 2 one-to-many join paths between the other two tables and there is no
context to separate the converging path. The relationship between three
tables will be “many-to-one-to-many”.
In above case when a query includes object from table B and Table C and
objects from table A, the CHASM trap causes a query to return every
possible combination of one measure with other. This result gets multiplied
by number of rows in result set and output is similar like a Cartesian
product. Chasm trap is not dependent on object types.
FAN trap
This occurs when there is a one-to-many join to a table that fans out into
another one-to-many join to another table. It does not result into fan trap
unless a query includes a measure object on the middle table ('B') of the
table path and an object (of any kind) from the subsequent table ('C'). The
trap only occurs where a column in table B holds data values which are
already a sum of those values held at table C.
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SAP Business Objects 4.0 SP02

3. INFORMATION DESIGN TOOL TUTORIAL 5
If we run a query with objects Y and Z, the SQL will relate table tables B and
C which have 1: N relationship. The result will be inflated as the value for Y
object being multiplied by the number of values of the Z object related to
the Y object value. We cannot automatically detect FAN traps but needs to
visually examine the direction of the cardinalities.
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SAP Business Objects 4.0 SP02

4. INFORMATION DESIGN TOOL TUTORIAL 5
How to resolve Chasm Trap?
Analyze one –to-many join paths in the schema, Chasm trap is resolved by
executing separate SELECT statements for object Y and object Z.
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SAP Business Objects 4.0 SP02

5. INFORMATION DESIGN TOOL TUTORIAL 5
This is why the Sale and Rental revenues got doubled
Either modify the SQL parameters for the universe and generate separate SQL
queries for each measure or simply use context for each fact table.
How to resolve FAN Trap?
For resolving the FAN trap the best method will be to use a combination of Aliases
and Contexts. Create an Alias for the table which contain the aggregated value (B
table in the example) and then detect and implement contexts to separate the
query.
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SAP Business Objects 4.0 SP02

6. INFORMATION DESIGN TOOL TUTORIAL 5
Create an alias for a middle table (B). Create a join between new alias table (Ba)
and first table (A) which is at one end. Set the cardinality and set context for the
join. Change the parameter in Business layer of measure “Y” to refer to new alias
table.
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SAP Business Objects 4.0 SP02