Creating the Time Dimension

Create a time dimension using any of several methods. Whichever method you choose, you must define or confirm the date input format. You may discover that some of your data sources include information about their columns (sometimes called metadata), while others do not. Cognos® Transformer requires information about how dates are formatted in order to correctly interpret them.

To create a time dimension, you can use any of the following methods:

  • Use the Date Wizard.

    Cognos Transformer prompts you for information about the time dimension and then creates the dimension for you.

  • Manually create a new time dimension and then successively drag the required date columns to each level in the dimension.

    Set the appropriate date function and other date-related properties for each level.

  • Drag the time dimension source category from the Data Sources list to the Dimension Map.
    Note: The Data class of the time dimension source category must be set to Date.

    This automatically creates a time dimension with the standard levels Year, Quarter, and Month.

  • Design the dimension before you have any items in the Data Sources list.

    Insert a new dimension, setting the Dimension type to Time. Click the Time tab on the Dimension property sheet, and you are prompted to specify the source column containing the dates for your new time dimension in the Date Level Creation dialog box. Click OK twice, and from the Run menu, click Generate Date Categories.

    Note: If you manually type the name for the source column in the Date Level Creation dialog box, you are warned that the columns do not exist in the Data Sources list.

    Cognos Transformer uses standard date functions to generate categories in the levels of the time dimension without actually referring to a data source. Later, when the source file is available, you can add it to the Data Sources list and regenerate the time dimension categories by using data from the source column. The name you specify for the levels must match the source column name.

Most date formats can be automatically determined during the AutoDesign process. In the time dimension, if Cognos Transformer generates a category named Invalid Dates, it is likely that the date format is not defined, or not properly defined, for the values in the source file. For flat files such as .asc or .csv files, the date format is predefined in the source file. To change this default setting, you must open the property sheet for the column that contains your dates, click the Time tab, and use the Date input format box to specify the format you want to use.