Essentially, an information system is comprised of three focuses. One of the first steps in a systems analysis and design
effort will be to understand the data.
After all, an information system that does not store or handle data isn’t really an information system.
Understanding the data can be an involved process in itself. Many diagram-based tools assist in this process. Certainly,
smaller projects will afford a quicker discovery process where understanding the data is concerned, and consequently less
diagramming (if any) will be needed. Regardless, during systems analysis and design, a clear understanding of the data
requirements must be developed early on (in the first couple of hours for the very small projects, or the first couple of
weeks or so for the larger ones). This understanding will shed light on the essential, or logical, characteristics of this data.
What data entities are important to the business? How do these entities relate to each other? How many occurrences of one
entity can be expected to exist with an occurrence of another (e.g., one sales order can contain one or more items)? The
Context Data Model, as shown below, is an excellent tool for answering these questions.
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