Without an understanding and ability to exploit this structure, conventional portal software loses much of the true information contained within a database. As an example, suppose that a computer system on a UNIX server provides a company with marketing contacts, accounts receivable and payables, and manages the General Ledger. Raw information in a web page does have structure. It is based upon HTML, CSS, etc. However, this structure mostly relates to the presentation of the information, not its inherent structure, or its relationship with other information.
Databases contain more complete and sophisticated organizational structures.
This schema , or model, is often described through the use of metadata , or a language of structure. The structure of a database is often more important that the data contained within, in terms of the information that can be extracted. It is also critical in ensuring that the data is in fact accurate, relevant and consistent with other data in the same database. The schema defines what data can be present, what its possible values are, how it relates to the other data elements in the database, and oftentimes, what can be done with the data. Use of the Schema to Define a Portal One way to look at a portal into a database, is to define a relationship, or mapping , between a database structure and the elements of a screen or report.