One strategy:
- Consider the SRS ID as just a number, and don't imply any strong notion of consecutive order (The social security number is a reasonable example.)
- Don't recycle numbers. When an ID in a sequence is deleted, mark it "Deleted", "Deprecated", etc. I prefer to keep the requirement text in the deleted item so that I have a running record of the requirement evolution. If you choose to do this, mark the deleted text obviously, for example a strike-out font.
- #2 implies that new requirement additions will never occur "in place"; rather, they are always appended to the document.
- This strategy can become difficult to organize or cluster hierarchically as changes accumulate, so tag each SRS ID with a meaningful label for searching, i.e. [GUI], [DB], etc.
There are other strategies, such as using dotted decimals to cluster requirements, for example:
- 1.0 GUI
- 2.0 DB
- 3.0 Processing
As you might guess, the respective requirements should be ordered under the top-level number accordingly: 1.1, 1.2...for GUI, 2.1, 2.3, 2.4 for DB, etc. Note that this strategy will need some form of controlled method for managing deletions and additions.
The key thing to enforce in a requirements document: once an ID has been used for a requirement, it cannot be used again different requirement. In other words, if SRS 1234 was used and then deleted, it cannot resurface later. (Allowing it to do so wreaks absolute havoc on requirements traceability over the course of an evolving project.)
Note that virtually any SRS organization/structure will have deficiencies. Pick the one that suits your development environment and your application needs. (For example, the strategies above work reasonably well in highly-controlled development environments, such as those monitored by the FDA or other governmental bodies.)
Finally, consider using a requirements management tool. There are good ones out there (open source to $$$$$) that will take care of all of this for you.
I'm going to rely upon the SWEBOK (Software Engineering Book Of Knowledge) to guide my answer.
In the Software Requirements* chapter, we're provided with more formal definitions of the terms needed for your question.
Functional requirements describe the functions that the software is to execute; for example, formatting some text or modulating a signal. They are sometimes known as capabilities.
Nonfunctional requirements are the ones that act to constrain the solution. Nonfunctional requirements are sometimes known as constraints or quality requirements.
I point those out because there appears to be some overlap in the way you have been requested to generate your document. You stated: A SRS should only have functional, non functional and constraints
and based upon the SWEBOK / IEEE definition you can see that non-functional requirements and constraints are one and the same.
And while some may protest of overkill, there are three main documents related to requirements work.
System Definition Document This document (sometimes known as the user requirements document or concept of operations) records the system requirements. It defines the high-level system requirements from the domain perspective.
System Requirements Specification In this view, system requirements are specified, the software requirements are derived from the system requirements, and then the requirements for the software components are specified.
Software Requirements Specification establishes the basis for agreement between customers and contractors or suppliers (in market-driven projects, these roles may be played by the marketing and development divisions) on what the software product is to do as well as what it is not expected to do.
So the problem with all of that is it appears clear cut when explained, but it ends up being muddy when implemented. To help focus my answer, I'm going to ignore the System Reqs Spec as it's a huge topic and not quite necessary for your question.
The primary challenge you're encountering is that you are mixing your SDD and your SoftRS (software) documents. Since the two documents are communication bridges between three camps, it's natural and unavoidable that you'll see some overlap between the two. The SDD is a bridge between the client and the analysts, whereas the SRS is a bridge between the analysts and the developers.
So how do you draw the line between the SDD and the SRS? Let's go back to the System's Engineering trinity:
And they really should go in that order because when we look at the V-model, we use those three in order to work our way through the layers. You start with the what
& why
at the system layer. As you capture those, you start generating ideas for the how
, which goes into the next layer below in the V-Model. "Eventually" you finish up with a particular layer and you start revising the layer below in the same manner. The difference on the lower layers is that the upper layer's how
becomes this layer's what
.
Blah, blah, wall of text, let's tackle your questions.
FR 1.1 : Have I incorporated a design idea here, would " the system shall have a registration form" be a better functional requirement?
I'm going to start off with "meh" for an answer. "shall display" vs "shall have" on a form that requires user interaction is kind of pointless. If an argument erupted on a real project over the semantics between those two forms, I'd consider that a huge red flag and try to bail on the project. Seriously.
"Shall display" implies "have" whereas "shall have" implies "display" in this case. To be fully pedantic, you would need at least "shall have and display" to make it clear. Any of those three variants is fine though.
F1.2 ,2.3 : Is this not singular? Would the conditions be better written for each its own separate requirement
They are certainly related, and it gets tricky on how you want to express those. I rely upon team norms in this case as I have seen it go either way with equivalent results. The important part is to be consistent in how you handle compound requirements like this.
FR 1.4: Is this a design idea? Is this a correct functional requirement or have I incorporated non functional(performance) in it? Would it be better if I written it like this:
FR1 The system shall display an error message when check is unsuccessful.
NFR: The system will respond to unsuccesful registration form checks within 1 seconds. Same question with FR 2.8 and 2.9.
I would probably break these out, yes. Here's why: The first is providing function (display error message) while the second provides the constraints (specific amount of time) in providing that function. Constraints often change, but the functionality doesn't. By moving the constraint to its own requirement, we can get up front agreement on the functionality and then deal with the constraints (how fast was the message delivered) when we get into implementation.
FR2.3: The system shall check for "completeness", is completeness here used ambigiously? Should I rephrase it?
Your close to explaining completeness with the list of items you provide. However, you could be more clear in specifying what determines completeness or not in each of the items you listed.
FR1.2: I added that the system shall require a "Captcha code" is this a functional requirement or does it belong to the "security aspect" of a non functional requirement.
Depends upon what level of your design you are talking about. At a high level, it's a non-functional requirement because it's a constraint. At a low level, it's a functional requirement because it's specifying a function to be provided.
* SWEBOK is currently in a review state for the next release. Except for the main link, some of the additional links may go stale.
Best Answer
If you are producing a software requirements specification (SRS), I would expect that both GUI requirements and design constraints would be captured in that document.
In ISO/IEC/IEEE 29148-2011, the outline of the sample SRS says that the section for design constraints is used to "specify constraints on the system design imposed by external standards, regulatory requirements, or project limitations." The section on user interfaces is designed to contain "the logical characteristics of each interface between the software product and its users" and includes "required screen formats" and "page or window layouts" among other things as well as "all the aspects of optimizing the interface with the person who uses, maintains, or provides other support to the system".
If you look at previous iterations of the SRS standards, like IEEE 830-1998, you'll find multiple ways to structure the document. On top of that, many organizations may not produce a software requirements specification document, but keep their requirements in another format.
I wouldn't consider your examples to be examples of good software requirements. Both the statement that "requires" a three-layer design and the one that "requires" a tree object are design decisions.
In my experience, examples of design constraints include the use of a particular programming language or framework (or versions thereof), a specific operating system, or references to a standard reference architecture (and this reference architecture may, for example, levy requirements of three-layer architecture on the application). Examples of user interface requirements tend to require compliance to user interface style guides (for example, requiring a mobile app to conform to either the mobile OS style guide or the company's style guide).
At the end of the day, the requirements should be characteristics that the software must adhere to or it will fail to accomplish the stakeholder needs in the current environment.