Attributes, UDAs, and Alternate Hierarchies

I'm often asked what the best practice is regarding implementation of Attribute Dimensions, Alternate Hierarchies, and User Defined Attributes. While there are no hard and fast rules, these guidelines outline the strengths and weaknesses of each.

Attribute Dimensions
Attribute dimensions are created by tagging members in a sparse dimension with an attribute tag. Members tagged with a member from an attribute dimension must be at the same Level as all other members tagged with an attribute from the respective attribute dimension. In theory, as long as members are at the same level they may be assigned attributes. In practice I recommend avoiding utilizing attributes for members that are not level zero members. This is due to difficulties ensuring members are at the same level. While this often is apparent in ragged hierarchies (also known as unbalanced hierarchies), symmetrical hierarchies can also have members that appear to be at the same level (i.e. they are at the same generation), but are in fact at different levels due to implied sharing where a parent only has one child. Also, this can create situations where a member is at multiple levels, and the resulting data value utilized by an attribute is not what a user expects.

User Defined Attributes (UDAs)
UDAs are flags that are placed on an Essbase member. A given UDA can be placed on any dense or sparse member in the outline. In addition, unlike Attribute dimensions, UDAs are not linked to the level of the members they are tagged to. In practice, this flexibility is most often leveraged to identify member sets for use in a calculation, especially since UDAs can be tagged to Dense members. While it is possible to refer to UDAs in most reporting and analysis packages, however, I do not recommend deploying UDAs for use by end users.

Alternate Hierarchies
Alternate hierarchies are secondary rollups of members within the same dimension. The level zero members in the alternate hierarchy are called Shared Members, and point back to an identically named real member elsewhere in the dimension. It is important to note that the real members do not have to be level zero members, or at the same level. One of the key advantages of Alternate Hierarchies is the ability for upper level summary members to have a completely unique structure (as opposed to utilizing an Attribute dimension, which merely re-totals the same hierarchy with only a subset of members). While there are many uses for this functionality, this often is utilized to build Management and Legal organizational hierarchies from the same source data, as well as facilitate financial reporting with different standards (i.e. IFRS vs. US GAAP). Conversely, Alternate Hierarchies typically require more maintenance, and increase the size of database. Therefore, they should be carefully deployed only in circumstances that justify the additional expense.


In summary, Attribute Dimensions, User Defined Attributes, and Alternate Hierarchies all have advantages and disadvantages. A typical deployment will often leverage all three areas of functionality to solve specific business problems, but will pay particular attention to the negatives of each option to prevent creating an overly difficult to support and expensive database.

XOLAP - Virtual cubes against a Data Warehouse Part 2

As mentioned in my previous blog, "XOLAP - Virtual Cubes Against a Data Warehouse Part 1", I'll address the following in this installment:

• Completing the Time Hierarchy
  
• Developing the rest of the standard dimensions
  
• Developing a measures dimension
  
• Creating the cube schema
  
• Deploying the cube
  
• Querying the data
  
• Showing real time data updates with XOLAP

When we previously left off we had just finished creating new meta data elements within DimTime. The representation of the "Total Time" hierarchy is exhibited below. Create this hierarchy leveraging the steps used to create the "Total Sales Territory" in Part 1.

Leveraging the hierarchy depicted below, create the "Total Currency" hierarchy


Leveraging the hierarchy depicted below, create the "Measures" hierarchy

Leveraging the hierarchy depicted below, create the "Total Customer" hierarchy

To create the "Total Product" hierarchy, a meta data element, "EnglishProductSubcategoryName" needs to be copied from the DimProductSubCategory table to the DimProduct table.

This can be simply accomplished by right clicking on "EnglishProductSubcategoryName" element within the Metadata Navigator window within Essbase Studio and selecting "Copy".

Pasting this element is as equally simple, highlight the DimProduct table, right click and select Paste.

You are now ready to create the "Total Product" hierarchy as shown below.

Create the "Total Promotion" hierarchy as shown below

You are now ready to create the cube schema.

Access the "Cube Schema Wizard" hotlink from the Essbase Studio "Welcome Page."

The "Cube Schema Wizard" should be displayed as shown below.

Within the "Choose Measures and Hierarchies" dialog window specify a name for the cube schema and then select each of the newly created hierarchies from the left panel and move them to the appropriate panel on the right hand side.

After clicking "Next", the "Cube Schema Options" dialog box should be displayed.

Toggle on the "Create Essbase Model" radial button and provide a name for the model.

In this case I have named my model "XOLAP Adventure WorksModel."

After clicking "Next" the Cube Schema Model should be displayed as depicted below

You are now ready to deploy the cube to Essbase.

Access the "Cube Deployment Wizard" hotlink from the Essbase Studio "Welcome Page."

The "Essbase Server Information" dialog box should now be displayed.

Leverage the previously created withing Part 1 of this blog and select this connection name within the Essbase Server Connection drop down box.

Now specify and Essbase Application Name and Database name. These names are restricted to 8 characters and can not be currently used within your Essbase environment.

Ensure that only the "Build Outline" radial box is the only box toggled on at this point and then select the "Model Properties" button from the lower left of the dialog box.

The "View, edit, and save properties" should now be displayed.

With the "XOLAP Adventure WorksModel" highlighted, select the "General" tab and activate the "XOLAP Model" radial button.

With "Total Time" highlighted, select the "Info" tab and set the dimension type to "Time" and dimension storage to "Dense"

With "Measures" highlighted within the "Info" tab, ensures that measures is set to a dimension type to "Accounts" and dimension storage to "Dense"

Select "Close" and then "Finish"

The following image will be displayed while the cube is being deployed

When successfully completed, a notification of successful deployment will be presented.

Navigate to Oracle Essbase Administration Services and review the application and database just created. Your application should look much the image below:

Remember at this point, the outline is the only thing that has been built, no data has been loaded to the application, nor has an calculation been executed.

Leveraging the Hyperion Add-in, connect to the XOLAP database that you have just created, notice data is present and aggregated. Format your query as exhibited, focusing on the following members:

• Customer:Yang, Jon V
• Measure: Unit Price
• Sales Territory: Australia
• Time: Total Time
• Promotion: No Discount
• Currency: Australian Dollar
• Measures: Fenders, Helmets, Jerseys, Mountain Bikes, Tires and Tubes, Touring Bikes

Notice the Unit Price for the data intersection of Mountain Bikes (3399.99)

Now access the underlying relational database, I have leveraged Microsoft SQL Server Management Studio in this instance.

Open the table FactInternetSales and go to row 88, it should agree with the information depicted in the exhibit below:

Update the Unit Cost for row 88 from 3399.9900 to 999999.99 and commit this value to the database

Execute a retrieve against the spreadsheet set up just moments ago.

Notice the data has changed in the underlying relational repository and also through your ad hoc query tool.

While some restrictions do exist in structuring a XOLAP model, which were mentioned in Part 1 of this blog, the robustness of delivering an application of this nature is pretty self evident.
When asked previously by customers, "Can I do ad hoc, real time analysis against transactional data in my data warehouse?" I often struggled to provide an answer that really meet each of those criteria. Now with XOLAP a definitive approach can certainly be presented to the customer.

XOLAP - Virtual cubes against a Data Warehouse Part 1

Can it be true? Real time ad hoc analysis against a Data Warehouse using an Essbase cube that contains no data?

Well with XOLAP, these capabilities a being brought together. I have created a brief tutorial within this article to demonstrate to overall concept relating to XOLAP.

In Part 1 of this article, I'll discuss:

• Setup that needs to occur to emulate sample
  
• Background into XOLAP
  
• Current restrictions relating to XOLAP
  
• Creating Data Sources in Essbase Studio
  
• Defining a MiniSchema
  
• Defining Standard Hierarchies

Due to the number of screen shots and the size of this blog article, I have set the image properties to small. While the screens may be difficult to decipher within the article, each can be clicked on to be rendered in a much larger resolution for viewing.

Setup The Needs to Occur to Emulate Sample

The example delivered in this article involves leveraging AdventureWorksBI.msi on SQL Server 2005 as the Data Warehouse. This database can be downloaded from http://msftdbprodsamples.codeplex.com/releases/view/4004 . The installer for this download requires you to manually attach the database after installation.

Within the dbo.DimCustomer table add a new column called "ProperName" with a property of "nvarchar(100)."

Update the ProperName column within dbo.DimCustomer using a SQL statement similar to the following :

Update dbo.DimCustomer
Set ProperName = LastName + ', ' + FirstName + ' ' + MiddleName

Within the dbo.DimTime table add 3 new columns called "Month", "Day" and "Year" with each having a property of "nchar(10)."

Update the newly added columns within dbo.DimCustomer using a SQL statement similar to the following :

Update dbo.DimTime
Set Month = DatePart(Month,FullDateAlternateKey)
Set Day = DatePart(Day,FullDateAlternateKey)
Set Year = DatePart(Year,FullDateAlternateKey)

A little background into XOLAP

XOLAP (extended online analytic processing) is a variation on the role of OLAP in business intelligence. Specifically, XOLAP is an Essbase multidimensional database that stores only the outline metadata and retrieves data from a relational database at query time. XOLAP thus integrates a source relational database with an Essbase database, leveraging the scalability of the relational database with the more sophisticated analytic capabilities of a multidimensional database.

OLAP and XOLAP store the metadata outline and the underlying data in different locations:

In OLAP, the metadata and the underlying data are located in the Essbase database.

In XOLAP, the metadata is located in the Essbase database and the underlying data remains in your source relational database.

Restrictions For XOLAP

• No editing of an XOLAP cube is allowed. To modify an outline, you must create a new outline in Essbase Studio. XOLAP operations will not automatically incorporate changes in the structures and the contents of the dimension tables after an outline is created.
  
• When derived text measures are used in cube schemas to build an Essbase model, XOLAP is not available for the model.
  
• XOLAP can be used only with aggregate storage. The database is automatically duplicate-member enabled.
  
• Alternate hierarchies and attribute dimensions are supported; however, attribute hierarchies are not supported.
  
• XOLAP supports dimensions that do not have a corresponding schema-mapping in the catalog; however, in such dimensions, only one member can be a stored member.
  
• A model that is designated as XOLAP-enabled must be deployed to a new Essbase database because incremental builds for XOLAP are not supported.
  

Creating a Data Source

• From the "Essbase Studio - Getting Started" page within Essbase Studio, select the hot link "Data Source Wizard", the "Define Connection" portion of the Connection Wizard is displayed.

• Enter a Connection Name.
  
• Enter an optional Description.
  
• Select the appropriate Data Source Type. For example, if you are creating a connection to a Microsoft SQL Server data source, select Microsoft SQL Server from the drop-down list.
  
• In Server Name, enter the name of server where the database resides.
  
• To use a port number other than the default, clear the Default check box next to Port and enter the correct port number in the text box.If you are using the default port number, you can skip this step.
  
• Enter the User Name and Password for this database.
  
• In Database Name, select "AdventureWorksDB"
  
• Click Test Connection. If the information you entered in the wizard is correct, a message confirms a successful connection.If you entered incorrect information in the wizard, a message is displayed explaining that invalid credentials have been provided. Correct the errors and retest until the connection is successful.
  
• Clicking Next takes you to the Select Tables page of the wizard

Select the following tables for the Select Tables dialog box and then select "Next":

• dbo.DimCurrency
• dbo.DimCustomer
• dbo.DimProduct
• dbo.DimProductSubCategory
• dbo.DimPromotion
• dbo.DimSalesTerritory
• dbo.DimTime
• dbo.FactInternetSales
  
  

The Select MiniSchema dialog is now presented.

• Select the radial button for "Create a new schema diagram"
• Enter a name for this schema, In this instance I used "XOLAP Adventure Works DWSchema"
• Leave "Skip Schema" and "Use Introspection to Detect Hierarchies" unchecked
• Select Next
  
  
• The "Populate Schema" dilog box is displayed. Each of the tables that were previosly selected should be displayed on the right hand panel.
• Select "Next"
  
  
• The "Create Metadata Element" dialog box should now be displayed.
• Toggle on the radial button next to the "XOLAP Adventure Works DW", this should toggle on all members displayed in this dialog window
• Select "Next"
  
  
• The "XOLAP Adventure Works DWSchema" should now be displayed.
  
  
• Navigate back to the "Welcome" screen
• Highlight the "DimSalesTerritory" within the Metadata Navigator. Once highlighted, select the "Hierarchies" hotlink from the "Welcome" screen.
  
  
• Above is a representation of the contents from the DimSalesTerritory table. This is provided to deliver an understanding of how the hierarchy will be developed from the underlying relational table
  
  
• The hierarchy wizard should now be displayed at this point.
• Specify the "Dimension Head Name", in this case "Total Sales Territory" and then drag the "SalesTerritoryGroup" data element from the Metadata Navigator into the Data grid.
• The grid should should now contain the "SalesTerritoryGroup" element. Highlight this element and click "Add" and select "Child"
  
  
• Within the "Select Entity" dialog box, select "SalesTerritoryCountry" and then "OK"
  
  
• Leveraging the same approach for you used for adding "SalesTerritoryCountry", now add "SalesTerritoryRegion" to deliver a hierarchy as depicted above.
  
  
• By right clicking on the "Total Sales Territory" hierarchy data element in the MetaData Navigator panel and selecting "Preview Hierarchy" the above sampling of data should be displayed
  
  
• 
  
  Next, we will create the Time hierarchy for the model. This step will be slightly different, we will leverage the newly create columns in SQL server to build out a time hierarchy.
• With the DimTime metadata element highlighted in the MetaData Navigator, right click and select "New" and "Dimension Element"
  
  
  
  
• The "Edit Properties" dialog window for the new data element should appear.
• Enter "Month Day Year" in the name window
• Paste the following syntax into the Caption Binding window:
• 'trim'( connection : \'XOLAP Adventure Works DW'::'AdventureWorksDW.dbo.DimTime'.'Month' ) "/" 'trim'( connection : \'XOLAP Adventure Works DW'::'AdventureWorksDW.dbo.DimTime'.'Day' ) "/" 'trim'( connection : \'XOLAP Adventure Works DW'::'AdventureWorksDW.dbo.DimTime'.'Year' )
  
  
• Repeat the following steps for "Month Year" and place the following syntax in the caption binding window for "Month Year":
• trim'( connection : \'XOLAP Adventure Works DW'::'AdventureWorksDW.dbo.DimTime'.'Month' ) "/" 'trim'( connection : \'XOLAP Adventure Works DW'::'AdventureWorksDW.dbo.DimTime'.'Year' )
  
  
• Repeat the following steps for "Year" and place the following syntax in the caption binding window for "Year":
• 'trim'( connection : \'XOLAP Adventure Works DW'::'AdventureWorksDW.dbo.DimTime'.'Year' )
  

In my next blog, which should be published shortly I'll address the following:

• Completing the Time Hierarchy
• Developing the rest of the standard dimensions
• Developing a measures dimension
• Creating the cube schema
• Deploying the cube
• Querying the data
• Showing real time data updates