The most important yet most ambiguous, most amorphous component of the Corporate Information Factory (CIF) is the metadata. From the standpoint of cohesiveness and continuity of structure across the many different components of the CIF, metadata is easily the most important component.
What Is Metadata?
A very common way of thinking about metadata is that it is data about data. An alternate way of describing metadata is that it is everything about data needed to promote its administration and use. These two widely accepted definitions of metadata, however, do not do justice to what metadata really is. A more practical approach to describing metadata by citing some examples:
- Date layout. The customer-record layout contains the list of attributes,
and their relative position and format of data on the storage media.
- Cust-id char (15)
- Cust-name varchar (45)
- Cust-address varchar (45)
- Cust-balance dec fixed (15, 2)
- Content. There are 150,000 occurrences of transaction X in table PLK.
- Indexes. Table XYZ has indexes on the following columns:
- Column HYT
- Column BFD
- Column MJI
- Refreshment scheduling. Table ABC is refreshed every Tuesday at 2:00 P.M.
- Usage. Only 2 of the 10 columns in table ABC have been used over the past
six months.
- Referential integrity. Table XYZ is related to table ABC by means of the
key QWE.
- General documentation. “Table ABC was designed in 1975 as part of the
new accounts payable system. Table ABC contains accounts overdue data
as calculated by . . . ”
These examples of metadata only begin to scratch the surface of the possibilities. The final form will only be limited by your imagination and those needs that govern the use and administration of the CIF.
The reason why metadata is so important to the corporate information factory, and its different components, is that metadata is the glue that holds the architecture together. Figure 12.1 illustrates this role of metadata.>/p>
Without metadata, the different components of the CIF are merely standalone structures with no relationship to any other structure. It is metadata that gives the different structures—components of the architecture—an overall cohesiveness. Through metadata, one component of the architecture is able to interpret and make sense of what another component is trying to communicate.
The Conflict within Metadata
Despite all the benefits of metadata, a conflict exists: Metadata has a need to be shared, and a propensity to be managed and used, in an autonomous manner. Unfortunately, these propensities are in direct conflict with each other. Equally unfortunate is that the pull of metadata is very, very strong in both directions at the same time. Because of this conflict, metadata can be thought of as polarized, as shown in Figure 12.2.
Because the pull is so strong and so diametrically opposite, metadata is sometimes said to be schizophrenic. This leads to some fairly extreme conflicts within the CIF. As an example of the propensity of metadata to be shared, consider an architect who is building an operational database. If the operational database is to be integrated, the basic integrated, modeled design of the data
Figure 12.1 Metadata is the glue that holds the different components of the CIF together. Without metadata, there would be no cohesiveness across the CIF.
Figure 12.2 Metadata is stretched by two opposing forces.
needs to be shared from the data modeling environment. As the data ages and is pushed off to the data warehouse, the structure of the data needs to be shared within the data warehouse. As the data is moved into a data mart, the data once again needs to be shared. If there is to be any consistency across the corporate information factory, then metadata must be shared.
|
