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The Business Intelligence Semantic Model (BISM)

I’m a happy chap. Why? Because I read a blog post yesterday by T.K. Anand (SSAS Principal Group Program Manager) about the vision and roadmap of Analysis Services.

There were slightly concerning questions last November (following the PASS conference) surounding the future of Analysis Services, or more specifically the UDM, the dimensional model that we all know and love in SSAS 2005 & 2008. The arrival of PowerPivot into the Microsoft BI arsenal has without a doubt moved the goalposts and added significant power, flexibility and usability to the BI stack. My concern, along with others (most notibly Chris Webb, who sparked somewhat of a stampede on the issue), was for the future of the UDM and the multitude of existing dimensional systems out in the field. Is the dimensional approach being phased out? Will it be supported in future editions? Will it be enhanced? Will the future BISM support the complexity and power we currently have with the UDM?

There’s no doubt that the overall approach to business intelligence is evolving. And this isn’t just in the cube space, it obviously has a direct effect on all other aspects of the BI strategy; the data warehouse, reporting layer, ETL etc.

From a BI consultant’s point of view, I don’t want to be recommending tools to my clients which have a restricted life span and don’t provide them a future proof upgrade path.

From a technology perspective, I’m a hardened supporter of the dimensional model. I recently designed a complex cube system for a banking client which had over 150 dimensions and facts, with thousands of lines of MDX to create a very sophisticated calculation framework for their liquidity modelling and loan profiling. I wouldn’t dream of doing that in a tabular approach like PowerPivot (in their current form).

From a personal point of view, where do I focus my attention in terms of training, research, blogging, user groups, conference sessions etc. etc.

I should point out that I’m very excited by, and fully committed to the tabular/PowerPivot route (along with VertiPaq, Crescent, DAX, etc.) for systems that it is suited to. In fact I’m using it right now to prototype a global BI solution for a very large client. There are however some solutions that do not fit well with the tabular approach and are best suited to a dimensional approach. I’m in favour of a hybrid framework which allows the right tool to be used for the right system. And it looks like that’s what we’re going to get.

The guys at Microsoft have now evolved and clarified the roadmap, and have confirmed that the BISM (business intelligence semantic model, i.e. The core of Analysis Services in SQL Server Denali) will contain two parallel approaches that can both be used for whichever situations they are best suited to. More importantly, they are both here to stay, will both be developed further, and there will be a cross-availability of functionality and tools between them.

Multi Dimensional Model

Essentially the same as the existing UDM, the multi-dimensional data model will support MDX and ROLAP/MOLAP data access. Existing OLAP cubes in SQL 2008 will easily upgrade to this.

Tabular Model

Think of this as hosted PowerPivot. A tabular approach with a column based data store, DAX as the expression language and either VertiPaq or Direct Query for data access.

The two will co-exist side by side within a singluar BISM, albeit initially with a degree of seperation. In the upcoming CTP2 release (July 2011?) there will not be any cross-availability of functionality, i.e. VertiPaq, Crescent and DAX will not be available to the dimensional model. However TK makes it clear that this is a short term restriction in the CTP, and that Microsoft are commited to getting this cross availability in place in the finished product.

If you’re involed in BI in any way, I really do encourage you to go and read TK’s post in detail. The Business Intelligence world is changing. I now have total confidence that it’s for the better.


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The Frog Blog

I'm Alex Whittles.

I specialise in designing and implementing SQL Server business intelligence solutions, and this is my blog! Just a collection of thoughts, techniques and ramblings on SQL Server, Cubes, Data Warehouses, MDX, DAX and whatever else comes to mind.

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