Business Intelligence or Data Warehouse

  • "Handling the metadata was the really big challenge for our DW. 250 trials, each with 30-40 distinct tables, adding a new trial a week, I had to develop a dynamic ETL tool that was fed by a metadata repository. Finally, the metadata of an individual trial could and would sometimes change in the middle of a trial."

    Steven, I think you are correct that the first versions of the data warehouse model ignored metadata almost completely. In his article, "Information Management: DW 2.0 - Architecture for the Next Generation of Data Warehousing" Bill Inmon addresses this problem in the his latest version of data warehousing, what he calls "DW 2.0". In it he states: "Metadata is the glue that holds the data together over its different states. Amazingly, the first generation of data warehousing omitted metadata as part of the infrastructure."

    I have to agree that without sufficient (and automated) metadata together with proper release mechanisms, schema maintenance can and will become a full time occupation.


  • Unfortunately, one of the realizations I came to when creating the dynamic ETL tool was that there is a real limit to how much you can automate metadata maintenance. If you have a DW with a lot of heterogeneous metadata, and that metadata is not "slowly changing", then yes, management should either realize that schema maintenance is indeed a full-time job and pay for someone to do that, or just don't warehouse your data.

    Sometimes, the right answer is "forget it".

  • OLAP Cubes:

    I have a cube that is giving incorrect data. If i do a sum and group by query in enterprize manager, i get the correct results, but in the cube via excel it is wrong. The relation ships are setup correctly in the cube editor.

    Can anyone please give me some ideas?

  • Hi Danie, possible causes if the relational query is different from the cube are:

    1. Named Query in the Data Source View

    2. Measure properties such as AggregateFunction and MeasureExpression

    3. Dimension perperties such as IsAggregatable, CustomRollup, RootMemberIf



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