Basic BISM
Chris Webb
Crossjoin Consulting Ltd
chris@crossjoin.co.uk
Who Am I?
• Chris Webb
chris@crossjoin.co.uk
• Independent Analysis Services consultant and
trainer www.crossjoin.co.uk
• Author: “MDX Solutions” and “Expert Cube
Development with SSAS 2008”
• SQL Server MVP
• Blogger: http://cwebbbi.wordpress.com
Agenda
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What is BISM?
Tabular vs Multidimensional positioning
Building a Tabular Model
Demos, demos, demos…
What is BISM?
• BISM = BI Semantic Model
• It’s the new UDM (if you remember that)
• The product is still officially called SQL Server
Analysis Services
• SSAS now has two design experiences:
– Multidimensional models, ie cubes
– Tabular models, a ‘corporate’ version of what we
have with PowerPivot
• BISM = Multidimensional + Tabular
Tabular vs Multidimensional
• It’s an either/or choice at the moment:
– An instance can only be one or the other
– A project can only be one or the other
• Though in the future we may be able to have a
single database that can be viewed or
designed in both ways
Tabular Pros
• Represents the future
• Concepts easier to understand for those with a
relational/SSRS background
• Speed of the Vertipaq storage mode
• Support for Project Crescent
• DirectQuery = ROLAP done right (hopefully)
• Ability to import existing PowerPivot models
• No more processing-this-unprocesses-that
dependencies
Tabular Cons
• Version 1.0 product, therefore immature
– DirectQuery has a lot of limitations
– No parallel processing for partitions -> big impact on
processing times
– No display folders and other ‘nice to have’ stuff
• Vertipaq effectively limited by RAM available on
the server
– Some paging options, but performance suffers
• DAX still unable to do the same kind of complex
calculations that MDX Scripts can
Multidimensional Cons
• Regardless of the official line, unlikely ever to
get much priority for new features
– Very few new features in Denali
• No support for Crescent yet (though coming at
some point)
• No integration with PowerPivot
• Cubes are just too confusing for some
developers
• Old technology
Multidimensional Pros
• Mature technology, well understood and well
resourced in the marketplace
• MDX Scripts allow for complex calculations
• Disk-based model allows for greater scalability
at the very high-end than Vertipaq
• Allows for complex modelling, eg many-tomany relationships
Creating a New Tabular Project
• Tabular projects require Visual Studio 2010
• Projects are built in three ways:
– Start from scratch
– Import from PowerPivot
– Import from an existing Tabular model
• Projects consist of a single .bim file, plus some
hidden files and folders
Importing Data Into Tables
• All the data sources that PowerPivot supports
are present in the Tabular model
– So you get more supported datasources that with
Multidimensional, eg Odata
• Data can be imported by either
– Selecting tables and then filtering in the UI
– Writing your own SQL/MDX
• Tables can be partitioned
• You can create calculated columns with DAX
Workspace Databases
• Workspace databases are a ‘working copy’ of your
database that allow you to see your data while you
model it
– Probably hosted on a local SSAS instance, not a separate
server (even your dev server)
– Probably with a subset of your real data
• Do not confuse this with your production or even your
dev server!
• Various options relating to whether it’s retained on the
server, detached or deleted after you close BIDS
• No cube browser in BIDS – you can open Excel direct
from BIDS and browse your workspace database
Relationships
• Relationships can be added between tables just
as in PowerPivot
• New relationship designer makes life much easier
• Two tables can now have multiple relationships
between them
– eg Role-playing date dimension tables
– Only one relationship is ‘active’
– DAX has a UseRelationship() function to allow you to
choose which one to use
Hierarchies
• Values in a column can be sorted by using the
Sort By Column property
– eg for day or month names
• Hierarchies can be built with drag and drop
inside diagram view
• No true support for parent/child hierarchies
– But can be flattened using calculated columns and
several new DAX functions like Path()
Measures
• Simple measures (sums, counts etc) can be
created with a single click
• More advanced measures can be created with
DAX expressions
• Format strings have been replaced by
separate properties
• Measures are displayed in a grid under the
table in BIDS (ugh)
DAX Queries
• DAX is now a query language as well as a
calculation language
– Very different from MDX
– Tabular models can still be queried with MDX
• Much more suitable for detail-level reporting
than MDX
• Much more ‘relational’ – but not SQL
• DAX queries will often perform better than
MDX queries against the same model
DirectQuery
• DirectQuery is essentially ROLAP for Tabular
– All queries are translated to SQL
– Only works with SQL Server data sources
• Several limitations:
– Some DAX functions don’t work (eg time intelligence)
– No calculated columns
– No MDX queries, only DAX
• Vertipaq/DirectQuery mixed mode possible
– Data exists in both storage modes
– One storage mode used by default
– Clients can choose which storage they use with a
connection string property
Security
• Tabular models have something similar to
Multidimensional dimension security
– No cell security
• Allow you to use DAX expressions to filter
rows in tables for particular roles
• Basic administrative security, can either
– Read data and/or
– Refresh data
– Or be an administrator
Summary
• Tabular is very easy to get up and running
• Suitable for 70% of SSAS projects today
– Certainly good for all the small-scale or basic
projects
– Good if you never liked or understood cubes
– Outperforms Multidimensional in most cases
• Download the CTP3 demo VM!
Blogs
• Cathy Dumas
http://blogs.msdn.com/b/cathyk/
• Kasper de Jonge
http://www.powerpivotblog.nl/
• Marco Russo
http://sqlblog.com/blogs/marco_russo
• Alberto Ferrari
http://sqlblog.com/blogs/alberto_ferrari