After you perform fact-finding, you begin to work on the model. What diagrams will you create, and why? Will you use DFDs, object models, or both? Will you create an entity-relationship diagram? Explain your answers.

Question

What will be an ideal response?

Answer 1

Answers should mentionall the diagrams described in Chapters 5 and 6. It is interesting to note that multi-purpose CASE tools such as Visible Analyst provide traditional data and processing modeling tools, as well as object-oriented diagrams. Unless there is a compelling reason to restrict the modeling to one type or the other, the analyst is better off to use both approaches, because each has unique strengths. For example, using Visible Analyst, you can mix and match data flow diagrams, functional decomposition diagrams, structure charts, entity-relationship diagrams, activity diagrams, use case diagrams, state-transition diagram, unstructured diagrams, and more.

The Visible Analyst help section offers the following explanation of diagram types:
• Data Flow diagrams (DFDs) represent the functional tasks of your project analysis. For example, a data flow diagram might represent a particular functional area of a department within your company. That data flow diagram might also be an integral part of a project that consists of multiple data flow diagrams that represent multiple levels of department functions and tasks.
• Functional Decomposition Diagrams (FDDs) give you the ability to do high-level planning of business functions diagrammatically while concurrently populating the repository. You can enter business functions onto diagrams and break them down into successively finer gradations. At some point, one that is entirely up to you, you can decompose business functions (hereinafter called simply functions) into processes semantically equal to those that appear on DFDs. The processes can themselves be decomposed into smaller parts (still lower-level processes) on FDDs.
• Use case diagrams show the relationship between a user and a computer system. A use case captures some user-visible function.
• Sequence diagrams are a type of iteration diagram that describe how objects collaborate in some behavior. It is drawn in a grid-like fashion where the vertical axis represents time, while the horizontal axis represents the participating objects.
• A collaboration diagram is a second form of iteration diagram. A collaboration diagram shows an interaction organized around the objects in the interaction and their links to each other. Unlike a sequence diagram, a collaboration diagram shows the relationships among the object roles. On the other hand, a collaboration diagram does not show time as a separate dimension, so the sequence of messages must be specified using sequence numbers.
• An activity diagram is a special form of a state diagram in which the states represent the performance of actions or subactivities and the transitions are triggered by the completion of the actions or subactivities.
• Structure Charts are a graphical representation of the top-down design of a project, showing the program modules that carry out the system functions defined in a data flow diagram. They also show the hierarchical relationship between these modules and how they invoke one another.
• Entity Relationship diagrams (ERDs) graphically describe the data and the relationships among data items in your project. You can draw entities (or, more properly, entity types) and the relationships between them, including relationship names in both directions. Later, the data elements (also called attributes) composing these entities can be added to the repository and, with the Analyze function, key information can be generated for relationships. Later, if you choose, you can balance your data model against your process model to further enrich the information stored in your project.
• Unstructured diagrams are not linked to the repository. They are simply free-standing diagrams. They can be put to any use you desire. Also, cluster diagrams and views, generated from ERDs, and process decomposition diagrams, generated from DFDs, are unstructured diagrams.
• Class diagrams allow you to express the object model of your project diagrammatically. You can describe the classes in the data you are modeling and the relationships between them.
• State transition diagrams give you the ability to show the dynamic characteristics of your classes while still allowing some degree of flexibility in modeling style.