Data Models

Data Models - In addition to process modeling, there is another type of modeling that may be needed on large, complex projects – data modeling.

Years ago on the mainframe, there were flat files and databases (okay, there were VSAM files too). Flat files were under the control of the programmer, and they could be created at will.

Databases, however, were too complex for mere programmers to understand and manipulate.

They required Data Analysts (DA’s) and Data Base Administrators (DBA’s).

Data Analysts would work with you to logically model the data, and then the DBA’s would implement the resulting model in a physical database.

In today’s client/server and web development environments, the databases are much more within the control of the developers. SQL*Server and Oracle databases in use at many companies do not require database specialists, and the developers do the database design work themselves.

There are two fundamental purposes for formal data modeling:

  1. First, it provides a precise language and syntax to represent the relationships between data entities. All the important data utilized by the company can be represented this way.

    As an example, think of whether it would be difficult for your company to agree on the precise definition of a customer? It may take months to define what a customer is, agree on the common attributes, and gain a common understanding of how the customer related with various other entities.

    However, from that point on, everyone could rally around the common definition.

  2. The other important aspect to data modeling is that it is used to define entities and relationships in ways that can be used to store the underlying business data.

    This leads us to be able to define files and databases in a way that will allow business applications to process the information correctly. As an example, you may discover that many customer attributes are relatively static.

    You may also realize that one customer may generate many orders. These simple facts allow you to create two database tables – one to hold the customer attributes and one to hold order information.

    Each can be keyed on a common customer number. This saves storage space, allows for faster processing and makes the data easier to maintain.

There are two components of a data model:

  1. The first is the Entity Relationship Diagram that shows the relationship of the data elements in picture form.

  2. The second is a data dictionary that shows fundamental characteristics of each data element in words. The data dictionary can include information such as a description of the element, how it is created, what applications use it, what databases and tables the field is in, synonyms for the element name, etc.

Desicion Tree

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