How to know if we're dealing with Star Schema or SnowFlake ?

[sanchoniathon]

Gents,

I usually don't play with FrameWork Manager as for i usually develop reports when working with Cognos Products but i do remember once or twice beeing
asked to modify certain calculated columns in an existing FrameWorkManager Model (in another job and years ago) and then to publish a package. So sorry if my question seems novice ...

My question is the following:

1- I need to know wether the cognos package i will be reporting on is based on a Star Schema Model or wether it is based on a Snow Flake model ?

2- A hint, when i launch Report Studio (v10) from Cognos Connection, and decide to create a blank report against the only available cognos package, i see:
- Different dimensions (Client, Time, Company, etc ...)
- 3 Fact tables

3- The thing is that i will need to add a new fact table to contain a new metric but i don't seem to need to add new dimensions as for all the dimensions needed
seems to already be existing. So my other question would actually be: IN A STAR SCHEMA MODEL, can we add new fact tables like we want ?


Thanks !

[Lynn]

Gents,

I usually don't play with FrameWork Manager as for i usually develop reports when working with Cognos Products but i do remember once or twice beeing
asked to modify certain calculated columns in an existing FrameWorkManager Model (in another job and years ago) and then to publish a package. So sorry if my question seems novice ...

My question is the following:

1- I need to know wether the cognos package i will be reporting on is based on a Star Schema Model or wether it is based on a Snow Flake model ?

2- A hint, when i launch Report Studio (v10) from Cognos Connection, and decide to create a blank report against the only available cognos package, i see:
- Different dimensions (Client, Time, Company, etc ...)
- 3 Fact tables

3- The thing is that i will need to add a new fact table to contain a new metric but i don't seem to need to add new dimensions as for all the dimensions needed
seems to already be existing. So my other question would actually be: IN A STAR SCHEMA MODEL, can we add new fact tables like we want ?


Thanks !

I guess I'll skip attempting to answer since I'm not a gent ;-)

[sanchoniathon]

Oups ... I'm sorry as for i also meant "ladies" or anyone having valuable information to provide.
I usually write in french so sorry for the lack of proper English word selection.

:)

[bbtresoo]

Gents,

I usually don't play with FrameWork Manager as for i usually develop reports when working with Cognos Products but i do remember once or twice beeing
asked to modify certain calculated columns in an existing FrameWorkManager Model (in another job and years ago) and then to publish a package. So sorry if my question seems novice ...

My question is the following:

1- I need to know wether the cognos package i will be reporting on is based on a Star Schema Model or wether it is based on a Snow Flake model ?

2- A hint, when i launch Report Studio (v10) from Cognos Connection, and decide to create a blank report against the only available cognos package, i see:
- Different dimensions (Client, Time, Company, etc ...)
- 3 Fact tables

3- The thing is that i will need to add a new fact table to contain a new metric but i don't seem to need to add new dimensions as for all the dimensions needed
seems to already be existing. So my other question would actually be: IN A STAR SCHEMA MODEL, can we add new fact tables like we want ?


Thanks !

hi

1) I think you need to go back to your FM to really identify the type of your model, it's not really difficult to make the difference, a snow flake is just a variation of star shema, when you notice several dimensions linked together that means it's a snow flake. in a star shema all the dimension are only related to the fact tables not between them.

2) to add your new fact, I think you need to understand the business behind, you need to think how relevant it's gonna be. Are you really sure you have to create a new fact ? maybe you can add the new metric in an existing one , for this question it's all about your business requirement

[Lynn]

Oups ... I'm sorry as for i also meant "ladies" or anyone having valuable information to provide.
I usually write in french so sorry for the lack of proper English word selection.

:)

Sorry I couldn't resist making the joke :)

I would suggest that modeling in FM requires a variety of skills and experience, so investing in some training would be really sensible if it is a role you want to fulfill.

It is certainly possible to have more than one fact table in your model. Setting the determinants properly and identifying the granularity are critical in terms of generating predictable SQL. When a user creates a report using more than one fact table there will be stitch query generated to put the metrics together appropriately.

Of course understanding the requirements is very important as bbtresoo pointed out. If there is anyone else more experienced with FM in your organization it would be helpful to have some in depth conversations about your scenario.

Good luck!

[sanchoniathon]

@bbtresoo
When you say:

1) I think you need to go back to your FM to really identify the type of your model, it's not really difficult to make the difference, a snow flake is just a variation of star shema, when you notice several dimensions linked together that means it's a snow flake. in a star shema all the dimension are only related to the fact tables not between them.

==> Thanks i looked and in deed we are dealing with a "Star Schema" model.


2) to add your new fact, I think you need to understand the business behind, you need to think how relevant it's gonna be. Are you really sure you have to create a new fact ? maybe you can add the new metric in an existing one , for this question it's all about your business requirement

==> I've informed myself and in deed i cannot include this new metric inside our existing SALES fact table as for the existing fact table's granularity goes down to the invoice ID. Which in the case of our new metric is not the case.

[sanchoniathon]

I would suggest that modeling in FM requires a variety of skills and experience, so investing in some training would be really sensible if it is a role you want to fulfill.

Lynn,

In deed i'm planning on getting some training sometime soon and discuss with the Modeling team as for i might be starting dealing with modeling issues here even though i originally was mandated to be a cognos reports developer between many other tasks of course.

:P

I might soon get back with other questions but so far you both helped me.

Thanks to all !