Data modeling: Difference between revisions

Revision as of 22:27, 3 March 2024

Revision as of 12:46, 28 April 2024

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{{main|Data model}}

[[File:3-4 Data model roles.svg|thumb|320px|How data models deliver benefit.<ref name="MW99"/>]]

Data models provide a framework for [[data]] to be used within [[information system]]s by providing specific definitiondefinitions and formatformats. If a data model is used consistently across systems then compatibility of data can be achieved. If the same data structures are used to store and access data then different applications can share data seamlessly. The results of this are indicated in the diagram. However, systems and interfaces are often expensive to build, operate, and maintain. They may also constrain the business rather than support it. This may occur when the quality of the data models implemented in systems and interfaces is poor.<ref name="MW99">Matthew West and Julian Fowler (1999). [https://sites.google.com/site/drmatthewwest/publications/princ03.pdf Developing High Quality Data Models] {{Webarchive|url=https://web.archive.org/web/20200909121755/https://d2024367-a-62cb3a1a-s-sites.googlegroups.com/site/drmatthewwest/publications/princ03.pdf?attachauth=ANoY7crjITgBSUdEyb3UlEOS2OxXk3r-iJk0-S4EfbK3PtqCZvEgcZwvpBiF3VGC7M0IMhTWLZoERz8Otd2Tu5Bquzo4NmuOxyeAzvQa0DZlSIea0KlbnoKFHPK9zM3Pg1p7f2b_OcaIv3_J8mkFK8rMoR_UABqsAM_Pa9wd6qHK1by_hBvYNRPKQZpTM4-rqh1D4x68mcRDzADCED8sFixAn4Nezq0zd_hunEOcJ8m7FSTyRa2xnOA%3D&attredirects=0 |date=September 9, 2020 }}. The European Process Industries STEP Technical Liaison Executive (EPISTLE).</ref>

Some common problems found in data models are:

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* Entity types are often not identified, or are identified incorrectly. This can lead to replication of data, data structure and functionality, together with the attendant costs of that duplication in development and maintenance. Therefore, data definitions should be made as explicit and easy to understand as possible to minimize misinterpretation and duplication.

* Data models for different systems are arbitrarily different. The result of this is that complex interfaces are required between systems that share data. These interfaces can account for between 25 and 70% of the cost of current systems. Required interfaces should be considered inherently while designing a data model, as a data model on its own would not be usable without interfaces within different systems.

* Data cannot be shared electronically with customers and suppliers, because the structure and meaning of data hashave not been standardised. To obtain optimal value from an implemented data model, it is very important to define standards that will ensure that data models will both meet business needs and be consistent.<ref name="MW99"/>

=== Conceptual, logical and physical schemas ===

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In the context of [[Business process modeling#Business process integration|business process integration]] (see figure), data modeling complements [[business process modeling]], and ultimately results in database generation.<ref name="SS93"/>

The process of designing a database involves producing the previously described three types of schemas - conceptual, logical, and physical. The database design documented in these schemas areis converted through a [[Data Definition Language]], which can then be used to generate a database. A fully attributed data model contains detailed attributes (descriptions) for every entity within it. The term "database design" can describe many different parts of the design of an overall [[database system]]. Principally, and most correctly, it can be thought of as the logical design of the base data structures used to store the data. In the [[relational model]] these are the [[table (database)|tables]] and [[view (database)|views]]. In an [[object database]] the entities and relationships map directly to object classes and named relationships. However, the term "database design" could also be used to apply to the overall process of designing, not just the base data structures, but also the forms and queries used as part of the overall database application within the [[Database management system|Database Management System]] or DBMS.

In the process, system [[Interface (computer science)|interface]]s account for 25% to 70% of the development and support costs of current systems. The primary reason for this cost is that these systems do not share a [[common data model]]. If data models are developed on a system by system basis, then not only is the same analysis repeated in overlapping areas, but further analysis must be performed to create the interfaces between them. Most systems within an organization contain the same basic data, redeveloped for a specific purpose. Therefore, an efficiently designed basic data model can minimize rework with minimal modifications for the purposes of different systems within the organization<ref name="MW99"/>