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The IBM® SPSS® Data Collection Data Model has two ways of representing the case data:
• Using a hierarchical view (sometimes called HDATA).
• Using a flat view (sometimes called VDATA).
In most cases, IBM® SPSS® Data Collection Survey Reporter displays a hierarchical view of the data. This means that:
• The Variables pane displays hierarchical variables (such as grids and loops) as expandable items.
• You can create grid tables.
• You can use variables that are nested inside a loop or grid in your tables.
• You can choose the generation level for your tables.
• You can include slices of expanded loops and grids in your tables.
• When you create a filter, you need to specify a level.
It is generally preferable to use the hierarchical view whenever possible, because it enables you to create grid tables and provides better support for tabulating data collected using loops. Moreover, some hierarchical data cannot be represented in the flat view. For example, data collected using an unbounded loop cannot be flattened, because the maximum number of iterations is unknown. A lower level in a IBM® SPSS® Quanvert™ levels project is a typical example of an unbounded loop. The flat view is therefore unsuitable for this type of data.
In some cases, Survey Reporter displays a flat view of the data. This means that grids and loops are shown as expandable items in the Variables pane, but you cannot create a grid table, or place on a table a variable that is inside a loop or grid. However, you can use a slice of a grid or loop in a table. Moreover, because the data is flat, you do not need to worry about levels when you are generating tables or creating filters.