The time attribute will be used in two ways？

[shuijian-xu]

1. As part of the selection constraint in a query

2. As an aid to joining the dimensions to higher-level groupings

[shuijian-xu]

For each event or change there is, as has been said, an associated time. Different applications have different requirements with respect to the grain of time. Some applications require only a fairly coarse grain such as day. These might include:

1. Companies selling car insurance

2. Banks analyzing balances

3. Supermarkets analyzing product-line sales

Some other applications might wish to go to a finer grain, perhaps hours. These might include:

1. Supermarkets analyzing customer behavior

2. Transport organizations monitoring traffic volumes

3. Meteorological centers studying weather patterns

[shuijian-xu]

Other applications would require a still more fine grain of time to say, seconds. An example of this is the telecommunication industry monitoring telephone calls.

[shuijian-xu]

Some applications require more than a single grain of time. Consider the examples above. The supermarket example shows a different requirement with respect to time for product analysis as distinct from customer behavior analysis. In any case, almost all organizations conducting dimensional analysis will require the ability to summarize information, from whatever the granularity of the base event, to a higher (coarser) level in order to extract trend information.