Related
I currently have a Web API project which currently has all the system processing in the same solution. I'm breaking this out into separate solutions so that they can be ran independently (e.g. an Azure WebJob) as I don't want to have to redploy the Web project if something in the backend has changed.
My issue with this is that even though I have separated the logic they are tied together by a single context so that if I make a change in one I will have to redeploy all as the migrations won't match up.
So that's why I've been looking at Bounded Context and DDD. I'm looking at how to break this up but having trouble understanding how relationships work.
A lot of the site is administrative (i.e. creating entities, no actual processing) so was going to split contexts around this e.g.:
A user adds and maintains currency conversion rates (this is two entities in
total).
A user adds and maintains details on how to process payments (note that is is not processing payments, it only holds information about paypal account details etc).
So I was splitting the context's up by this, does this sound reasonable to start with (there are a lot more like this such as tax bands, charge structures etc)?
If this is the way to go, how do I handle relationships between those two contexts? As an example:
A payment method requires a link to an 'active' currency conversion. I understand I can just have this as an Id, but I need to check it's state so need access to the model.
A currency conversion can only be set to 'Inactive' if there are no payment methods currently using it. Again this needs access to the other model.
So logically the models need access to each other, how would this be included in the context? Can I add navigation properties to a model in a different context? Or should I add it as a separate DbSet and possibly map using a view?
Thanks
So I was splitting the context's up by this, does this sound
reasonable to start with (there are a lot more like this such as tax
bands, charge structures etc)?
"So that they can be ran and deployed independently" may not be a sufficient heuristic to tell when you should split Bounded Contexts. This addresses one aspect of the solution space, but if you haven't looked well enough at the problem space, you'll suffer from a misalignment between BC's and subdomains that can cause a lot of friction. You might end up always deploying a cluster of seemingly unrelated "independently deployable units" together because you didn't realize they talk about the same thing.
Identifying subdomains is the product of distillating your business - separating the big functional areas and defining which parts are your core domain and which are ancillary activities. Each subdomain has its own specific semantics (Ubiquitous Language). In your case, as has been pointed out in the comments, Currency Conversion and Payment Methods might well be part of the same subdomain (Payment?). It does not automatically mean that they should also be in the same BC but it might be a good idea to keep subdomains aligned 1-to-1 with BC's, as additional BC's come at a cost.
Back to deployability, even if it can be one beneficial effect of Bounded Contexts, they are not always so easily translatable in terms of independent units of deployment. Context mapping patterns (Shared Kernel, Customer Supplier, etc.) and BC communication in general can lead to a model, and therefore a part of a codebase, being shared by multiple BC's. Code and API synchronization issues arise that can question a simplistic "deployable free electron" view.
Just because you're using the Bounded Context approach doesn't mean you have to use DDD's tactical patterns (Aggregate Root, invariants, etc.) inside each BC. Using them should be an educated decision to trade solution space complexity off for problem space manageability. If "Currency Conversion can only be set to inactive..." is the only rule pertaining to payment method and currency management in your business, it might not be worth the bother to give that Bounded Context a full-fledged rich domain model. CRUD could be better suited there.
Looking at all the examples of Operational Transformation Frameworks out there, they all seem to resolve around the transformation of changes to plain text documents. How would an OT framework be used for more complex objects?
I'm wanting to dev a real-time sticky notes style app, where people can co-create sticky notes, change their positon and text value. Would I be right in assuming that the position values wouldn't be transformed? (I mean, how would they, you can't merge them right?). However, I would want to use an OT framework to resolve conflicts with the posit-its value, correct?
I do not see any problem to use Operational Transformation to work with Complex Objects, what you need is to define what operations your OT system support and how concurrency is solved for them
For instance, if you receive two Sticky notes "coordinates move operation" from two different users from same 'client state', you need to make both states to converge, probably cancelling out second operation.
This is exactly the same behaviour with text when two users generate two updates to delete a text range that overlaps completely, (or maybe partially), the second update processed must be transformed against the previous and the resultant operation will only effectively delete a portion of the original one, (or completely cancelled with a 'no-op')
You can take a look on this nice explanation about how Google Wave Operational Transformation works and guess from this point how it should work your own implementation
See the following paper for an approach to using OT with trees if you want to go down that route:
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.100.74
However, in your particular case, I would use a separate plain text OT document for each stickynote and use an existing library, eg: etherPad, to do the heavy lifting. The positions of the notes could then be broadcast on a last-committer-wins basis.
Operation Transformation is a general technique, it works for any data type. The point is you need to define your transformation functions. Also, there are some atomic attributes that you cannot merge automatically like (position and background color) those will be mostly "last-update wins" or the user solves them manually when there is a conflict.
there are some nice libs and frameworks that provide OT for complex data already out there:
ShareJS : library for Node which provides all operations on JSON objects
DerbyJS: framework for NodeJS, it uses ShareJS for OT stuff.
Open Coweb framework : Dojo foundation project for cooperative web applications using OT
Today I've been presented with a fun challenge and I want your input on how you would deal with this situation.
So the problem is the following (I've converted it to demo data as the real problem wouldn't make much sense without knowing the company dictionary by heart).
We have a decision table that has a minimum of 16 conditions. Because it is an impossible feat to manage all of them (2^16 possibilities) we've decided to only list the exceptions. Like this:
As an example I've only added 10 conditions but in reality there are (for now) 16. The basic idea is that we have one baseline (the default) which is valid for everyone and all the exceptions to this default.
Example:
You have a foreigner who is also a pirate.
If you go through all the exceptions one by one, and condition by condition you remove the exceptions that have at least one condition that fails. In the end you'll end up with the following two exceptions that are valid for our case. The match is on the IsPirate and the IsForeigner condition. But as you can see there are 2 results here, well 3 actually if you count the default.
Our solution
Now what we came up with on how to solve this is that in the GUI where you are adding these exceptions, there should run an algorithm which checks for such cases and force you to define the exception more specifically. This is only still a theory and hasn't been tested out but we think it could work this way.
My Question
I'm looking for alternative solutions that make the rules manageable and prevent the problem I've shown in the example.
Your problem seem to be resolution of conflicting rules. When multiple rules match your input, (your foreigner and pirate) and they end up recommending different things (your cangetjob and cangetevicted), you need a strategy for resolution of this conflict.
What you mentioned is one way of resolution -- which is to remove the conflict in the first place. However, this may not always be possible, and not always desirable because when a user adds a new rule that conflicts with a set of old rules (which he/she did not write), the user may not know how to revise it to remove the conflict.
Another possible resolution method is prioritization. Mark a priority on each rule (based on things like the user's own authority etc.), sort the matching rules according to priority, and apply in ascending sequence of priority. This usually works and is much simpler to manage (e.g. everybody knows that the top boss's rules are final!)
Prioritization may also be used to mark a certain rule as "global override". In your example, you may want to make "IsPirate" as an override rule -- which means that it overrides settings for normal people. In other words, once you're a pirate, you're treated differently. This make it very easy to design a system in which you have a bunch of normal business rules governing 90% of the cases, then a set of "exceptions" that are treated differently, automatically overriding certain things. In this case, you should also consider making "?" available in the output columns as well.
One other possible resolution method is to include attributes in each of your conditions. For example, certain conditions must have no "zeros" in order to pass (? doesn't matter). Some conditions must have at least one "one" in order to pass. In other words, mark each condition as either "AND", "OR", or "XOR". Some popular file-system security uses this model. For example, CanGetJob may be AND (you want to be stringent on rights-to-work). CanBeEvicted may be OR -- you may want to evict even a foreigner if he is also a pirate.
An enhancement on the AND/OR method is to provide a threshold that the total result must exceed before passing that condition. For example, putting CanGetJob at a threshold of 2 then it must get at least two 1's in order to return 1. This is sometimes useful on conditions that are not clearly black-and-white.
You can mix resolution methods: e.g. first prioritize, then use AND/OR to resolve rules with similar priorities.
The possibilities are limitless and really depends on what your actual needs are.
To me this problem reminds business rules engine where there is no known algorithm to define outputs from inputs (e.g. using boolean logic) but the user (typically some sort of administrator) has to define all or some the logic itself.
This might sound a bit of an overkill but OTOH this provides virtually limit-less extension capabilities: you don't have to code any new business logic, just define a new rule set.
As I understand your problem, you are looking for a nice way to visualise the editing for these rules. But this all depends on your programming language and the tool you select for this. Java, for example, has JBoss Drools. Quoting their page:
Drools Guvnor provides a (logically
centralized) repository to store you
business knowledge, and a web-based
environment that allows business users
to view and (within certain
constraints) possibly update the
business logic directly.
You could possibly use this generic tool or write your own.
Everything depends on what your actual rules will look like. Rules like 'IF has an even number of these properties THEN' would be painful to represent in this format, whereas rules like 'IF pirate and not geek THEN' are easy.
You can 'avoid the ambiguity' by stating that you'll always be taking the first actual match, in other words your rules have a priority. You'd then want to flag rules which have no effect because they are 'shadowed' by rules higher up. They're not hard to find, so it's something your program should do.
Your interface could also indicate groups of rules where rules within the group can be in any order without changing the outcomes. This will add clarity to what the rules are really saying.
If some of your outputs are relatively independent of the others, you will also get a more compact and much clearer table by allowing question marks in the output. In that design the scan for first matching rule is done once for each output. Consider for example if 'HasChildren' is the only factor relevant to 'Can Be Evicted'. With question marks in the outputs (= no effect) you could be halving the number of exception rules.
My background for this is circuit logic design, not business logic. What you're designing is similar to, but not the same as, a PLA. As long as your actual rules are close to sum of products then it can work well. If your rules aren't, for example the 'even number of these properties' rule, then the grid like presentation will break down in a combinatorial explosion of cases. Your best hope if your rules are arbitrary is to get a clearer more compact presentation with either equations or with diagrams like a circuit diagram. To be avoided, if you can.
If you are looking for a Decision Engine with a GUI, than you can try this one: http://gandalf.nebo15.com/
We just released it, it's open source and production ready.
You probably need some kind of inference engine. Think about doing it in prolog.
An initial draft of requirements specification has been completed and now it is time to take stock of requirements, review the specification. Part of this process is to make sure that there are no sizeable gaps in the specification. Needless to say that the gaps lead to highly inaccurate estimates, inevitable scope creep later in the project and ultimately to a death march.
What are the good, efficient techniques for pinpointing missing and implicit requirements?
This question is about practical techiniques, not general advice, principles or guidelines.
Missing requirements is anything crucial for completeness of the product or service but not thought of or forgotten about,
Implicit requirements are something that users or customers naturally assume is going to be a standard part of the software without having to be explicitly asked for.
I am happy to re-visit accepted answer, as long as someone submits better, more comprehensive solution.
Continued, frequent, frank, and two-way communication with the customer strikes me as the main 'technique' as far as I'm concerned.
It depends.
It depends on whether you're being paid to deliver what you said you'd deliver or to deliver high quality software to the client.
If the former, simply eliminate ambiguity from the specifications and then build what you agreed to. Try to stay away from anything not measurable (like "fast", "cool", "snappy", etc...).
If the latter, what Galwegian said + time or simply cut everything not absolutely drop-dead critical and build that as quickly as you can. Production has a remarkable way of illuminating what you missed in Analysis.
evaluate the lifecycle of the elements of the model with respect to a generic/overall model such as
acquisition --> stewardship --> disposal
do you know where every entity comes from and how you're going to get it into your system?
do you know where every entity, once acquired, will reside, and for how long?
do you know what to do with each entity when it is no longer needed?
for a more fine-grained analysis of the lifecycle of the entities in the spec, make a CRUDE matrix for the major entities in the requirements; this is a matrix with the operations/applications as the rows and the entities as the columns. In each cell, put a C if the application Creates the entity, R for Reads, U for Updates, D for Deletes, or E for "Edits"; 'E' encompasses C,R,U, and D (most 'master table maintenance' apps will be Es). Then check each column for C,R,U, and D (or E); if one is missing (except E), figure out if it is needed. The rows and columns of the matrix can be rearranged (manually or using affinity analysis) to form cohesive groups of entities and applications which generally correspond to subsystems; this may assist with physical system distribution later.
It is also useful to add a "User" entity column to the CRUDE matrix and specify for each application (or feature or functional area or whatever you want to call the processing/behavioral aspects of the requirements) whether it takes Input from the user, produces Output for the user, or Interacts with the user (I use I, O, and N for this, and always make the User the first column). This helps identify where user-interfaces for data-entry and reports will be required.
the goal is to check the completeness of the specification; the techniques above are useful to check to see if the life-cycle of the entities are 'closed' with respect to the entities and applications identified
Here's how you find the missing requirements.
Break the requirements down into tiny little increments. Really small. Something that can be built in two weeks or less. You'll find a lot of gaps.
Prioritize those into what would be best to have first, what's next down to what doesn't really matter very much. You'll find that some of the gap-fillers didn't matter. You'll also find that some of the original "requirements" are merely desirable.
Debate the differences of opinion as to what's most important to the end users and why. Two users will have three opinions. You'll find that some users have no clue, and none of their "requirements" are required. You'll find that some people have no spine, and things they aren't brave enough to say out loud are "required".
Get a consensus on the top two or three only. Don't argue out every nuance. It isn't possible to envision software. It isn't possible for anyone to envision what software will be like and how they will use it. Most people's "requirements" are descriptions of how the struggle to work around the inadequate business processes they're stuck with today.
Build the highest-priority, most important part first. Give it to users.
GOTO 1 and repeat the process.
"Wait," you say, "What about the overall budget?" What about it? You can never know the overall budget. Do the following.
Look at each increment defined in step 1. Provide a price-per-increment. In priority order. That way someone can pick as much or as little as they want. There's no large, scary "Big Budgetary Estimate With A Lot Of Zeroes". It's all negotiable.
I have been using a modeling methodology called Behavior Engineering (bE) that uses the original specification text to create the resulting model when you have the model it is easier to identify missing or incomplete sections of the requirements.
I have used the methodolgy on about six projects so far ranging from less than a houndred requirements to over 1300 requirements. If you want to know more I would suggest going to www.behaviorengineering.org there some really good papers regarding the methodology.
The company I work for has created a tool to perform the modeling. The work rate to actually create the model is about 5 requirements for a novice and an expert about 13 requirements an hour. The cool thing about the methodolgy is you don't need to know really anything about the domain the specification is written for. Using just the user text such as nouns and verbs the modeller will find gaps in the model in a very short period of time.
I hope this helps
Michael Larsen
How about building a prototype?
While reading tons of literature about software requirements, I found these two interesting books:
Problem Frames: Analysing & Structuring Software Development Problems by Michael Jackson (not a singer! :-).
Practical Software Requirements: A Manual of Content and Style by Bendjamen Kovitz.
These two authors really stand out from the crowd because, in my humble opinion, they are making a really good attempt to turn development of requirements into a very systematic process - more like engineering than art or black magic. In particular, Michael Jackson's definition of what requirements really are - I think it is the cleanest and most precise that I've ever seen.
I wouldn't do a good service to these authors trying to describe their aproach in a short posting here. So I am not going to do that. But I will try to explain, why their approach seems to be extremely relevant to your question: it allows you to boil down most (not all, but most!) of you requirements development work to processing a bunch of check-lists* telling you what requirements you have to define to cover all important aspects of the entire customer's problem. In other words, this approach is supposed to minimize the risk of missing important requirements (including those that often remain implicit).
I know it may sound like magic, but it isn't. It still takes a substantial mental effort to come to those "magic" check-lists: you have to articulate the customer's problem first, then analyze it thoroughly, and finally dissect it into so-called "problem frames" (which come with those magic check-lists only when they closely match a few typical problem frames defined by authors). Like I said, this approach does not promise to make everything simple. But it definitely promises to make requirements development process as systematic as possible.
If requirements development in your current project is already quite far from the very beginning, it may not be feasible to try to apply the Problem Frames Approach at this point (although it greatly depends on how your current requirements are organized). Still, I highly recommend to read those two books - they contain a lot of wisdom that you may still be able to apply to the current project.
My last important notes about these books:
As far as I understand, Mr. Jackson is the original author of the idea of "problem frames". His book is quite academic and theoretical, but it is very, very readable and even entertaining.
Mr. Kovitz' book tries to demonstrate how Mr. Jackson ideas can be applied in real practice. It also contains tons of useful information on writing and organizing the actual requirements and requirements documents.
You can probably start from the Kovitz' book (and refer to Mr. Jackson's book only if you really need to dig deeper on the theoretical side). But I am sure that, at the end of the day, you should read both books, and you won't regret that. :-)
HTH...
I agree with Galwegian. The technique described is far more efficient than the "wait for customer to yell at us" approach.
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One of the items in the Joel Test is that a project/company should have a specification.
I'm wondering what makes a spec good. Some companies will write volumes of useless specification that no one ever reads, others will not write anything down because "no one will read any of it anyway". So, what do you put into your spec? What is the good balance between the two extremes? Is there something particularly important that really, really (!) should always be recorded in a specification?
The best spec is one that:
Exists
Describes WHAT, not HOW (no solutions)
Can be interpreted in as few ways as possible
Is widely-distributed
Is agreed-upon as being THE spec by all parties involved
Is concise
Is consistent
Is updated regularly as requirements change
Describes as much of the problem as is possible and practical
Is testable
What to put in a spec
You need to look at the audience of the spec and work out what they need to know. Is it just a document between you and a business sponsor? In this case it can probably be fairly lightweight. If it's a functional spec for a 100+ man-year J2EE project it will probably need a bit more detail.
The audience
The key question is: who is going to read the spec - A spec will have several potential sets of stakeholders:
The business owner who is signing
off the system.
The developer who is building the
system (which may or may not be you)
QA people who have to write test plans for it.
Maintenance staff wanting to
understand the system
Developers or analysts on other projects who
may want to integrate other systems into it.
Requirements of typical key stakeholders:
The business owner needs to have a clear idea of what the system workflows and business rules are so they can have a fighting chance of understanding what they have agreed to. If they are the only major audience of the spec, concentrate on the user interface, screen-screen workflow and business and data validation rules.
Developers need a data model, data validation rules, some or all of the user interface design and enough description of the expected system behaviour so they know what to build. If you are writing for developers concentrate on the user interface, mapping to data model and rules in the user interface. This should be more detailed than if you are doing the development yourself because you are acting as an intermediary in a communication between two third parties.
If you are specifying an interface between two systems, this has to be very precise.
QA staff need enough information to work out how to test and validate the logic, validation and expected user interface behaviour of the application. A spec intended for developers and QA staff needs to be fairly unambiguous.
Maintenance staff need much the same information as developers plus a system roadmap document describing the architecture.
Integrators need a data model and clear definitions of any interfaces.
Key components of a spec:
I'm assuming that one is writing specs for business apps, so the content below is geared to this. Specs for other types of systems will have different emphasis. In my experience the key elements of a functional spec are:
User Interface: screen mockups and a description of the interaction behaviour of the system and workflow between screens.
Data Model: Definition of the data items and mapping to the user interface. User interface mappings are normally done in the bits of the spec describing the user interface.
Data Validation and Business Rules: What checks for correctness need to be be made on the data and what computations are being made, along with definitions. Examples can be quite useful here.
Definitions of interfaces: If you have interfaces exposed that other systems can use, you need to specify those pretty tightly. The simpler internet RFC's give quite good examples of protocol designs and are quire a good start for examples of interface documents. Clearly defining interfaces isn't easy but almost certainly save you grief down the track.
Glue: this is where use cases, workflow diagrams and other requirements related artifacts help. Generally an exhaustive listing of these is pointless, but there will be key areas within the system where this type of documentation helps to put items in context. My experience is that selective inclusion of use cases and other requirements level descriptions does a lot to add clarity and meaning to a spec but writing up a user story for every single interaction with the system is a waste of time.
Joel (of 'on software' fame) wrote a good series of articles on this called Painless Functional Specification which I've referred people to on quite a few occasions. It's quite a good set of articles and well worth a read. In my opinion, your objective is to clearly explain what the system is supposed to do in a way that minimises ambiguity. It's quite useful to think of the spec as a reference document - what might the various stakeholders want to be able to easily look up.
Having written a glib set of bullet points about specs, the clear communication part is harder than it looks. Specs are actually non-trivial technical documents and are quite a test of one's technical writing and editorial skills. You are actually in the business of writing document that describes what someone is supposed to build. Doing good specs is a bit of an art.
The pay-off for doing specs is that no-one else wants to do them. As you've written what is probably the only document of any importance for the system, you get to call the shots. Anyone else with an agenda has to either lobby you to change the spec or somehow impose a competing spec on the project. This is a good example of the pen being mightier than the sword.
EDIT: It has been my experience that debate about the distinction between 'how' and 'what' tends to be pretty self-serving. On any non-trivial project the data model and user interface will have multiple stakeholders, not all of whom are the system's developers. Working in data warehousing will give one a taste for the chaos that ensues when an application data model is allowed to become a free-for all, and PFS should give one a feel for the potential set of stakeholders a spec has to cater to.
The fact that someone owns a data model or user interface design doesn't mean that these are just decided by fiat - there can be a discourse and negotiation process. However, as a project gets larger the value of ownership and consistency in these gets greater. It's been my observation in the past that the best way to appreciate the value of a good analyst is to see the damage done by a bad one.
In my experience a spec will have more chance of being read if it has the following:
Use diagrams where possible - pictures are worth 1000 words
Have a title page that clearly indicates what the spec is describing
Have a style that is used throughout the document. Make all headers the same font, size and style. Make the font the same all the way through, use the same bullet styles etc
DONT WAFFLE - Be clear concise and to the point, and don't add extra cruft to pad out your document. If a point can't be explained in a few lines of text, then maybe you need to break it down further
I have seen in companies where the person writing the spec doesn't understand the system. It's almost a way of learning the system by writing the spec. This usually ends in tears...
As someone who develops bespoke software for clients, the best spec is the one which the customer has signed.
It doesn't matter how refined your spec is - if the customer hasn't explicitly agreed to it in writing, they'll change it and expect you to roll with their changes seamlessly, wrecking your beautiful architecture...
Good specs should contain requirements that are measurable and verifiable. When looking at each requirement, you should be able to easily answer the question, "How can I prove I have fulfilled this requirement?".
Read Joel's series of "Painless Functional Specifications" followups to the Joel Test article. They also appear in the "Joel on Software" book.
Depends on how big the project is and (like all architecture decisions) what the constraints are. A good start is
a short description, a "one pager"
a context diagram -- where are the
boundaries, what interacts with the
system?
use cases/user stories
a GUI prototype or paper prototype,
if applicable
a description of the needed
nonfunctional requirements
(performance etc.)
Best of all is to have an acceptance test, ie, a testable statement of things that can be checked, along with an agreement that when those things are done, the project is complete.
It also helps if you start by stating the goal the user has or what the global idea of a certain function is; rather than filling in the exact implementation. This always feels to me like narrowing down the open mindedness or using less creative (more usable) solutions. So you should keep "all options open".
Example
Your writing a software to measure "X".
Instead of stating:
There has to be a start button and a save button.
Use:
The user has to be able to start a measurement and save it.
Why?
Because in the first situation you already determined what the solution has to be, while the second situation gives you flexibility on how to implement something. Now this may seem trivial, but I have the feeling "programmers" tend to think more in solutions rather than in problems (or situations). When you add more functionality this becomes more obvious, because then it might have been better to use a wizard or automate the process, but you already narrowed the idea's down to using buttons.
For functional requirements—or, more specifically, behavioral requirements—I like to use Cucumber and Gherkin.
Here’s an example of a simple and short specification for a new feature in a simple mapping application. The feature allows small businesses to sign up to the mapping platform and add their places of business on a Google Maps-like service.
Feature: Allow new businesses to appear on the map
Scenario Outline: Businesses should provide required data
Given a <business> at <location>
When <business> signs up to the map platform
Then it <should?> be added to the platform
And its name <should?> appear on the map at <location>
Examples: Business name and location should be required
| business | location | should? |
| UNNAMED BUSINESS | NOWHERE | shouldn't |
Examples: Allow only businesses with correct names
| business | location | should? |
| Back to Black | 8114 2nd Street, Stockton | should |
| UNNAMED BUSINESS | 8114 2nd Street, Stockton | shouldn't |
Examples: Allow businesses with two or more establishments
| business | location | should? |
| Deep Lemon | 6750 Street South, Reno | should |
| Deep Lemon | 289 Laurel Drive, Reno | should |
Examples: Allow only suitable locations
| business | location | should? |
| Anchor | 77 Chapel Road, Chicago | should |
| Anchor | Chicago River, Chicago | shouldn't |
| Anchor | NOWHERE | shouldn't |
This specification looks deceivably simple, but is in fact quite powerful.
Good specifications are clear, unambiguous and concrete. They don't need to be deciphered in order to write working code. That’s exactly what Gherkin specs are. They’re best served short and simple. Instead of writing a long ass specification document, you let the specification suite evolve along with your product by writing new specs in every iteration.
Gherkin is a business-readable language for writing specification documents based on the Given-When-Then template. The template can be automated into acceptance tests. Automating the specification ensures it stays up to date because the captured conversation is directly tied to testing code. This way, tests can be used as documentation, because Gherkin features have to change every time the code changes.
When each business rule is given an automated test, Gherkin specifications become so-called executable specifications—specifications that can be run as computer programs. The program tests whether the acceptance criteria were implemented correctly. So at the end of the day, we get a yes-or-no answer to the question of whether our product is actually doing what we expect it to do—which in itself is very valuable, as it contributes to making software of better quality.
The direct connection between Gherkin specifications and testing code often reduces the damage of waste by creating and cultivating a system of living documentation. Thanks to frequent validation of tests, as in continuous integration systems, you can know that Given-When-Thens are still up to date—and when you trust your tests, you can use the corresponding Gherkin specifications as documentation for the entire system.
In fact, there’s an entire methodology called Specification by Example that uses tools like Gherkin. Specification by Example's practices reduce possibility for misunderstandings and rework by giving you a framework for talking with business stakeholders by forcing you to use concrete, discrete, unambiguous examples in your specification documents.
If you want to read more about Cucumber, Gherkin, BDD, and Specification by Example, I wrote a book on the subject. “Writing Great Specifications” explores the art of writing great scenarios and will help you make executable specifications a core part of your development process.
If you are interested in buying “Writing Great Specifications,” you can save 39% with the promo code 39nicieja2 :)
I think writing "Use cases" should save you bunch of pages
+1 #KiwiBastard and I would add write bullet-like and make each bullet testable.
A blueprint that describes all of the critical information necessary for the implementation, but doesn't waste any effort on describing all of the trivial or obvious information that is also necessary.
It should just be enough information to insure that the implementation is "as expected", without providing too much additional noise that isn't necessary.
In practice, most people get this wrong, as they focus on the easy stuff (which is the least necessary) and shy away from the hard stuff (which is what you really really want to lock down). I've seen way too many 2 inch documents that completely and utterly miss the point, and very few 3 page ones that hit it dead on.
Specs don't have to be long, they just have to contain the right stuff!
(hint: if the programmer didn't look at that page while coding, it probably wasn't required)
Paul.