Software Reengineering is a Delicate Process

Question

Successfully reengineering a software application is often a challenging and fulfilling endeavor. The current program, written in COBOL, is an important component of an existing application. Our main objective is to reengineer the program with a object-oriented implementation that executes faster and improves maintainability. The existing implementation satisfies a subset of business requirements that form the basis of the batch processing applications and related Web applications.
The program is a data processing program. In order to reengineer the application, we need to identify what the data requirements are. These are the business requirements. At a high-level, the application must create ASCII text files in a certain format. What else is there? What data is easily extracted and what data needs to be derived from data-oriented business logic? Attempting to store all of this in human memory and immediately start writing code is a difficult process, and typically results in a longer development time and brittle software.
In my opinion, the most efficient way to design software is start with the business (aka domain) requirements gathering process. This includes identifying the high-level requirements, but also includes detailed requirements such as those mentioned above. This process is a critical step that is often overlooked. This is a mistake. I foster using the Java EE Reference Architecture as a baseline for building applications using its three-tier programming model. A data processing application is not a three-tier application, but we can use parts of the model for our purposes.
Once the business requirements are identified, a domain object model is designed. The purpose of this design is outline what business objects will exist and includes a rough outline of how they will work together to satisfy the business requirements. At this point, if we were building an enterprise application, we would use the business requirements and the domain object model to design a system architecture using the JEE Reference Architecture as a guide. We will skip this step as it does not apply.
The next step is to create a technical design that implements the business requirements. Take note that at this point, details of algorithms and data manipulation routines are not specified/coded yet. UML is the industry standard modeling language for creating object-oriented software. A free UML design tool is available at: http://jude.change-vision.com/jude-web/product/community.html
No coding yet? At this point, we have Use-case narratives that specify the business requirements (WHAT) and a series of UML Class and Sequence diagrams (HOW). The fun starts here. With this material, we can start implementing the classes and begin developing an executable prototype. Writing code and designing (HOW) is fun, but in reality, it is the WHAT that really matters.
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Answer 1

duffymo wrote:
Who said such a discussion wouldn't be useful? That's how I interpreted your directive to take the topic somewhere else, that this forum was for questions. Do I read that wrong? Do you think this is the appropriate medium for publishing articles? Because that's what this reads like. I have a ton of opinions that I could just start randomly posting new threads. Do you think that would be good if I just start spamming the forums with my unorthodox beliefs like "JavaBeans are (mostly) worthless" or "ORM is oversold"? A blog would be a much more appropriate place for such things, IMO.
It's perfectly valid to ask "How should I go about rebuilding an existing app in a different language?" I would be happy to contribute to such a discussion. So if the OP added a question mark you'd be okay with it? Then it would just not make sense. An extra sentence at the end saying something like: "Does anyone have any experience with rewritting applications and does this seem like a sound approach?" If the OP is not looking for such advice, what is the point of posting this? Is he or she going to come back later and tell us how it went?
What I see here is a post intended to bestow the great wisdom of the author on the Java Forums. The one response received was deflected with "doesn't apply" as if jschell or anyone else could know that. Sorry, I still disagree. You're being too sensitive. I don't know if you have some beef with BlueSmurf from another thread, but I'm still okay with the topic. I don't know BlueSmurf from Papa Smurf or Gargamel. I don't think the OP is looking for discussion. That's my beef.