Traditional Systems Analysis Oracle Database Tips by Donald Burleson

There are three commonly accepted traditional methods for systems analysis:  the Gane & Sarson method, the Yourdon method, and the DeMarco systems analysis method.  All three of these models share a common goal.  Before any physical construction of the system may begin, the new systems must be completely analyzed to determine the "functional primitive" processes and the data flows between the processes.  This logical specification is used as the input to the systems design.  But how does the systems analysis change when an object-oriented database system is being developed?

It is very important to remember that the purpose of systems analysis is to logically identify the processes, the data moving between the processes, and to describe the processing rules and data items.  Only after these are defined can design begin, regardless of the physical implementation of the system.  While the design strategy for an object-oriented system may be very different from other systems, object-oriented analysis should begin with the creation of a structured specification. 

A structured specification is a document which describes all of the data, data storage, external entities and processes for the system.  This document is then used in the design phase for the creation of the behaviors, entity/relation model and class hierarchy.  The Structured Specification of a tradition systems analysis consists of the following deliverables:

1.  Data Flow Diagrams - A set of top-down diagrams which depict all processes within the system, the data flows between the processes and the data stores.  The data flow diagrams (DFDs) begin at a very general level and become progressively more detailed.  The lowest level of processing is called the "functional primitive" level, and this primitive level has been traditionally used as the starting point for systems design.

As shown in the DFD from Figure 3.2 there are four symbols that are used to represent entities.  The first is a rectangle which represents external entities, such as a vendor, another system, a customer, and so on.  These external entities are called "sources" if they provide data to the DFD and "sinks" if the receive data from the DFD.  The circle symbol represents a process which shows how data flows are changed.  The third symbol is the arrow, which represents a data flow, and the direction of the data flow is indicated by the arrowhead.  Finally we see the double line which represents a data store, which will eventually become the databases, the core of our object system.

2. Data Dictionary - The data dictionary contains a description of all of the logical data items, including all data flows, data types, data structures and data stores (Files) that appear on the DFD.

3. Process logic specifications (Minispecs) - A minispec is a description of all of the functional primitive processes that appear on the DFD.  A process is defined as an operation which modifies a data flow.  The tools used to describe processes include pseudo-code, procedure flowcharts, decision trees, and decision tables.

We should now have a general understanding of the fundamental concepts of a traditional systems analysis, and we are now ready to take a look at how analysis for object-oriented systems differs from traditional analysis.

 

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