Scaling Firefeed Followers - scale

I am in the research phase of a realtime application that I want to write and I think Firebase is the right choice but I'm currently stuck trying to figure out my data schema. My application is similar to the Firefeed example application in that it is a social inbox. My issue is the following code where the data is looped and copied to every user that "follows" the current user. Theoretically if this was Twitter and someone like Kim Kardashian posted a new Spark it'd have to loop through and save 50,000,000+ records.
Doing this on the client side, or doing this at all, seems extremely slow and error prone to me. Is this a valid concern? I realize my app has zero users right now but I'd like to plan my scaling ahead of time.
// Add spark ID to the feed of everyone following this user.
currentUser.child("followers").once("value", function(list) {
list.forEach(function(follower) {
var childRef = firebase.child("users").child(follower.name());
childRef.child("feed").child(sparkRefId).set(true);
});
});
I'd really appreciate any help and insight here!
Thanks.

tl;dr: I'd wait until you get further before coding up solutions. Avoid premature optimization.
Distant future scaling issues are very hard to optimize for because it's very difficult to predict how people will end up using your software.
But, to answer your specific question, there are ways to handle the Kim Kardashians of the social media world. It all comes down to partitioning behavior. You're going to have to treat them differently than the rest of your users. You'll have to do this regardless of the tech stack you use.
The extent to which you partition behavior depends a lot on the distribution of your users. Remember Tom from MySpace? That's an extreme example. I bet there were references to isTom peppered all over the codebase to deal with it, but we probably don't need to go that far.
In the case of the snippet of code in your question, it's already got a lot going for it in terms of scale. It distributes the data across all of the followers, and in doing so does not create any hot spots in the data. It will, however, take some time to run for 50,000,000 users.
My first attempt at optimization would be to take the same code and put it on a node worker. I'd then switch the client to register a task for that node worker for my really popular users.
If that still wasn't fast enough, I'd start looking into ways to partition the data for my super-users.

Related

Ideas to keep user stories small

There seems to competing best practices for user stories that I have not been able to come up with a way to deal with. Mainly:
Keep user stories small.
User stories should deliver customer values and therefore engineering focused item such as refactoring should not be separate user story and should be part of on-going work.
I feel like it's hard to achieve both of these at the same time.
For example, sometimes you need to refactor things. Some code is complex and just takes time. If it's done as part of the feature user story, then that user story will get bigger. But the refactor should not be a user story since it doesn't deliver customer values. You could argue that maybe we shouldn't let the code got checked-in in the first place, but requirement changes and therefore assumption changes so I don't think that's realistic expectation.
Another example could be dealing with starting a new project; we need to setup the repository, the project, the CI/CD pipelines. All of these are infrastructure work items and does not deliver any direct customer values. I guess in this case, we could use "engineer" as the customer but there are some debate out there whether that's a good practice or not.
Now I could bend the rule and have these as user stories. But I am curious if people are following the scrum rule strictly, is there tips and tricks to achieve both of these requirements?
Scrum does not prescribe any format for the Product Backlog items. So your Product Backlog can contain user stories but also any other kind of items.
As you are saying user stories should deliver value, typically meeting the INVEST acronym but your Product Backlog can contain items related to make functionality possible, such as upgrading libraries, implementing a log system or whatever help the team to potentially release the product. Taking into account that in your Product Backlog there will be bugs too, so it´s not just about new functionalities. So don´t fool yourself making up users who don´t exist.
Being saying that, usually a big refactor is a smell of a problem not tackled at the proper time (generating a high technical debt, a weak DoD and so on). That´s the reason many authors say that you should refactor at the same time your are developing new functionalities (your code should be in good form).
Finally, if you are in such a scenario that you need a big refactor, my advice is to try to decompose the refactor in small pieces and create a good harness of test to refactor with confidence.
I can think of several ways you can cut stories. However, keep in mind that these are ideas that can work but can also make no sense depending on the work. I only want to share my experience.
think about the three basic areas: User Interface, Data Calculation, Data Retrieval, try to cut the story along these lines
if you have to do repetitions, create a story for each iteration
try to do the first implementation as basic as possible, then create more stories for upgrading and fine tuning
even if a story seems to be straightforward, try to cut it; it is amazing how much better you can discuss as a team about smaller items and how much better you can refine it, and you it forces you to think about the details and this really can make a difference

Scrum, Possibly done wrong [closed]

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I'm not against Scrum. I love it, it's right on my second preference right after RAD, however in my current team they made me hate it. We're possibly doing it in the worst possible way.
We have the usual Sprint planning which takes roughly 30 minutes while writing user stories ourselves and that's all. Right in that 30 minute we answer questions like the following:
What should the user do?
What is needed for this (Subtasks).
How much time will it take?
Okay we're done, see you tomorrow morning in the daily stand-up meeting.
This really frustrates me and they won't listen to me. There is no planning, like at all. At the point of (2) all 4 developers talking about different ways of solving a particular problem. It would be fine, but we also don't have any clarified vision and thus everyone has different understanding of where is the whole project headed. Thus our ideas completely differs. This usually ends up in chaos. For example the most recent story in our newest shiny project's first sprint:
Vision: We need an application to perform unit testing on X application.
User stories:
User logs in
Create DB table (No schema has been clarified)
Create Login View
Authenticate user to Y server.
User sees the available unit tests
Create a view to display unit tests
Read DB table
Implement CRUD operations
User executes unit tests.
Implement selection to the upper view
Add an execute operation
Display the result in a new page
What my worries were:
Vision doesn't say anything about where this whole project is headed thus we will end up re-implementing the majority of our functions when going to the next spring, or after that, or after that... (Checked - this happened right away; I can't help it I just hate to work on something that will be erased right at the start of the next spring. I don't think Scrum is about it, it would be really useless)
No actual planning. We haven't clarified anything what the DB should look like so how to create it? I can create a DB for such a system with 1 to N tables depending on what the project should achieve in the future but this is not so serious as a DB can easily be extended.
Based on (2) we started working on different parts. I created the DB while others created views and again others created operation implementations. All of us had different understanding and even in just a day we ended up with non-compatible models that just couldn't be integrated.
What have we done wrong:
No planning. My team just hates planning, they're like act first and ask later. I'm like: I.DO.NOT.DO.SOMETHING.TWICE.BECASE.YOU.ARE.LAZY.TO.DO.PROPER.PLANNING.
No communication between team members, but even I didn't expect that just under one day we will end up like that.
What is going wrong in here? Is it just me with the wrong understanding of scrum or my worries are true? This is giving me so much stress at work I barely can handle it anymore.
I'm intrigued as to who "they" are in this line : "This really frustrates me and they won't listen to me." ?
It reads as if you're referring to the rest of the scrum team. If so, I suggest you need to get to a "we" footing as soon as possible and work on communication.
With regard to some of the items in your post, a few things come to mind immediately:
If you don't have one, you need a product owner to own the product, it's vision and it's backlog. If you do have one, they may benefit from good training or coaching
You are absolutely right about needing a Product Vision. You seem to have one but, you infer that it describes some functionality rather than a complete product vision. If so, have you tried to discuss this within your team?
If you don't have one, you need a scrum master to help the product owner and development team to play by the rules of scrum and, in your case, encourage communication within the team. If you do have one, they may benefit from good training or coaching
Concerning your worries, I would add:
I think you mean 'sprint' where you write 'spring'
It is common in scrum that product backlog items are changed to reflect better understanding
You shouldn't need to describe the database in depth when you start a project. Scrum works best with emergent architecture based on implemented functionality
If multiple developers work in the same area without communicating, it's highly likely that you will step on each other's toes and get the outcomes you describe

Calculating ratings/points in a community driven site

To learn ASP.NET MVC, I am thinking of creating a community forum like SO where people can rate posts, users etc. and the user can thereby gain points. I just can't figure out if the points should be added to the user profile whenever an action is done (post rated up/down, user created new post etc.) or if it should be calculated from the different activities the user has done.
I have a few pro's and con's for both ways of doing it:
Add rating:
Pro:
Easier to implement, and much faster and less resource intensive.
Con:
If the value of the different activities change, you can't do anything about it.
No way of showing a history on how you have gotten your points.
Calculating rating:
Pro:
Much easier to have a point-history for both the user and people viewing the account.
Possibility to change the amount of points for a given activity.
Con:
A little more difficult to implement.
More resource extensive (can be prevented by caching the data, or creating a job which calculates the points).
I think you've pretty much thought of everything. I can just offer some engineering tips. All things equal, always start of with what's easier to implement.
Now there are some cons with that as you say, so they're not equal, they don't offer the same functionality. So can you live without the history? If not, implement calculating first. Your model will be tight and well defined, which is always nice.
IF you determine later on that this is too cpu intensive, only then do you go about fixing it with a cache or a job. Good ideas, both, btw. 90% of the time, unless you really measure it, you'll be laboring on optimizations that are not necessary. Unnecessary optimizations are wrong.
It looks like you are trying to build something like stackoverflow, and Stackoverflow does have a history where your points came from. When you will use linq, the calculation method could be done purely in SQL, without a lot of effort on programming skills. (although it'd be a bit more advanced than the normal linq querys)
I'd go for the second option, merely because it's more interesting, you'll learn more about linq, caching, and MVC overall.
You can use ActionFilter classs to catch every action that adds/deletes user points. Like AuditActionFilter class. This can be done just by putting action filter attribute on top of corresponding methods. In the audit action filter class, you can figure out which method is executed easility using filterContext object and track the progress of points for each user in a flat file or xml, which you can show/parse when he wants to see his history.

Developing a online exam application, how do I prevent cheaters?

I have the task of developing an online examination software for a small university, I need to implement measures to prevent cheating...
What are your ideas on how to do this?
I would like to possibly disable all IE / firefox tabs, or some how log internet activity so I know if they are googling anwsers...is there any realistic way to do such things from a flex / web application?
Simply put, no there is no realistic way to accomplish this if it is an online exam (assuming they are using their own computers to take the exam).
Is opening the browser window full screen an option? You could possibly also check for the window losing focus and start a timer that stops the test after some small period of time.
#Chuck - a good idea.
If the test was created in Flash/Flex, you could force the user to make the application fullscreen in order to start the test (fullscreen mode has to be user-initiated). Then, you can listen for the Flash events dispatched when flash exits fullscreen mode and take whatever appropriate action you want (end the test, penalize the user, etc.).
Flash/Flex fullscreen event info.
blog.flexexamples.com has an example fo creating a fullscreen-capable app.
Random questions and large banks of questions help. Randomizing even the same question (say changing the numbers, and calculating the result) helps too. None of these will prevent cheating though.
In the first case, if the pool is large enough, so that no two students get the same question, all that means is that students will compile a list of questions over the course of several semesters. (It is also a ton of work for the professors to come up with so many questions, I've had to do it as a TA it is not fun.)
In the second case, all you need is one smart student to solve the general case, and all the rest just take that answer and plug in the values.
Online review systems work well with either of these strategies (no benefit in cheating.) Online tests? They won't work.
Finally, as for preventing googling... good luck. Even if your application could completely lock down the machine. The user could always run a VM or a second machine and do whatever they want.
My school has always had a download link for the Lockdown browser, but I've never taken a course that required it. You can probably force the student to use it with a user agent check, but it could probably be spoofed with some effort.
Proctored tests are the only way to prevent someone from cheating. All the other methods might make it hard enough to not be worth the effort for most, but don't discount the fact that certain types of people will work twice as hard to cheat than it would have taken them to study honestly.
Since you can't block them from using google, you've got to make sure they don't have time to google. Put the questions in images so they can't copy and paste (randomize the image names each time they are displayed).
Make the question longer (100 words or more) and you will find that people would rather answer the question than retype the whole thing in google.
Give them a very short time. like 30-45 seconds. Time to read the question, think for a moment, and click either A, B, C, D, E,
(having just graduated from CSUN I can tell you scantron tests work.)
For essay questions? do a reverse google lookup (meaning put their answer into google as soon as they click submit) and see if you get exact matches. If so, you know what to do.
Will they always take the test on test machines, or will they be able to take the test from any machine on the network? If it will be specific machines, just use the hosts file to prevent them from getting out to the web.
If it is any machine, then I would look at having the testing backend change the firewall rules for the machine the test is running on so the machine cannot get out to the interwebs.
I'd probably implement a simple winforms (or WPF) app that hosts a browser control in it -- which is locked in to your site. Then you can remove links to browsers and lock down the workstations so that all they can open is your app.
This assumes you have control over the workstations on which the students are taking the tests, of course.
As a teacher, I can tell you the single best way would be to have human review of the answers. A person can sense copy/paste or an answer that doesn't make sense given the context of the course, expected knowledge level of the students, content of the textbook, etc, etc, etc.
A computer can do things like check for statistical similarity of answers, but you really need a person for final review (or, alternatively, build a massive statistical-processing, AI stack that will cost 10x the cost of human review and won't be as good ;-))
No, browsers are designed to limit the amount of damage a website or application can do to the system. You might be able to accomplish your goals through Java, an activex control, or a custom plugin, but other than that you aren't going to be able to 'watch' what they're doing on their system, much less control it. (Think if you could! I could put a spy on this webpage, and if you have it open I get to see what other websites you have open?)
Even if you could do this, using a browser inside a VM would give them the ability to use one computer to browse during the test, and if you could fix that they could simply use a library computer with their laptop next to it, or read things from a book.
The reality is that such unmonitored tests either have to be considered "open book" or "honor" tests. You must design the test questions in such a manner that references won't help solve the problems, which also means that each student needs to get a slightly different test so there is no way for them to collude and generate a key.
You have to develop an application that runs on their computer, but even then you can't solve the VM problem easily, and cannot solve the side by side computers or book problem at all.
-Adam
Randomize questions, ask a random set of questions from a large bank... time the answers...
Unless you mean hacking your site, which is a different question.
Short of having the application run completely on the user's machine, I do not believe there is a way to make sure they are not google-ing the answers. Even then it would be difficult to check for all possible loop-holes.
I have taken classes that used web based quiz software and used to work for a small college as well. For basic cheating prevention I would say randomize the questions.
Try adding SMS messages into the mix.
I agree with Adam, that even with the limitations that I suggested, it would still be trivial to cheat. Those were just "best effort" suggestions.
Your only hopes are a strong school honor code and human proctoring of the room where the test is being given.
As many other posters have said, you can't control the student's computer, and you certainly can't keep them from using a second computer or an iPhone along side the one being used for the test -- note that an iPhone (or other cellular device) can bypass any DNS or firewall on the network, since it uses the cellular provider's network, not the college's.
Good luck; you're going to need it.
Ban them from using any wireless device or laptop and keylog the machines?
You could enforce a small time window during which the test is available. This could reduce the chance that a student who knows the answers will be free to help one who doesn't (since they both need to be taking the test at the same time).
If it's math-related, use different numbers for different students. In general, try to have different questions for different copies of the test.
If you get to design the entire course: try to have some online homeworks as well, so that you can build a profile for each student, such as a statistical analysis of how often they use certain common words and punctuations. Some students use semi-colons often; others never, for example. When they take the test you get a good idea of whether or not it's really them typing.
You could also ask a couple questions you know they don't know. For example, list 10 questions and say they must answer any 6 out of the 10. But make 3 of the questions based on materials not taught in class. If they choose 2 or 3 of these, you have good reason to be suspicious.
Finally, use an algorithm to compare for similar answers. Do a simple hash to get rid of small changes. For example, hash an answer to a list of lower-cased 3-grams (3 words in a row), alphabetize it, and then look for many collisions between different users. This may sound like an obvious technique, but as a teacher I can assure you this will catch a surprising number of cheaters.
Sadly, the real trouble is to actually enforce punishment against cheaters. At the colleges where I have taught, if a student objects to your punishment (such as flunking them on the test in question), the administration will usually give the student something back, such as a positive grade change. I guess this is because the student('s parents) have paid the university a lot of money, but it is still very frustrating as a teacher.
The full screen suggestions are quite limited in their effectiveness as the user can always use a second computer or w/ multi monitor a second screen to perform their lookups. In the end it is probably better to just assume the students are going to cheat and then not count online tests for anything important.
If the tests are helpful for the students they will then do better on the final / mid term exams that are proctored in a controlled setting. Otherwise, why have them in the first place...
Make the questions and answers jpeg images so that you cannot copy and paste blocks of text into a search engine or IDE (if it is a coding test). This combined with a tight time limit to answer each question, say three minutes, makes it much harder to cheat.
I second what Guy said. We also created a Flex based examination system which was hosted in a custom browser built in .NET. The custom browser launched fullscreen, all toolbars were hidden and shortcuts were disabled.
Here is tutorial on how to create a custom browser with C# and VB.NET.
This will solve your problem. http://www.neuber.com/usermonitor/index.html
This will allow you to view the student's browser history during and after the test as well as look in on their screen during the test. Any urls visited during test time will be logged, so you can show them the log when you put a big F on their report card. :)
No one can stop people from cheating, but everyone can receive different questions altogether.
I prefer you buy available online scripts in market as starting point for it. This will save you time, cost and testing efforts.
Below is one of the fine scripts that I worked with and it worked like charm. Using this as base I developed a online testing portal of over 1000 users using computer adaptive test.
http://codecanyon.net/item/online-skills-assessment/9379895
It is a good starting point for people looking to develop Online Exam System.
I customized the script with the help of their support.

Requirements Gathering

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How do you go about the requirements gathering phase? Does anyone have a good set of guidelines or tips to follow? What are some good questions to ask the stakeholders?
I am currently working on a new project and there are a lot of unknowns. I am in the process of coming up with a list of questions to ask the stakeholders. However I cant help but to feel that I am missing something or forgetting to ask a critical question.
You're almost certainly missing something. A lot of things, probably. Don't worry, it's ok. Even if you remembered everything and covered all the bases stakeholders aren't going to be able to give you very good, clear requirements without any point of reference. The best way to do this sort of thing is to get what you can from them now, then take that and give them something to react to. It can be a paper prototype, a mockup, version 0.1 of the software, whatever. Then they can start telling you what they really want.
See obligatory comic below...
In general, I try and get a feel for the business model my customer/client is trying to emulate with the application they want built. Are we building a glorified forms processor? Are we retrieving data from multiple sources in a single application to save time? Are we performing some kind of integration?
Once the general businesss model is established, I then move to the "must" and "must nots" for the application to dictate what data I can retrieve, who can perform what functions, etc.
Usually if you can get the customer to explain their model or workflow, you can move from there and find additional key questions.
The one question I always make sure to ask in some form or another is "What is the trickiest/most annoying thing you have to do when doing X. Typically the answer to that reveals the craziest business/data rule you'll have to implement.
Hope this helps!
Steve Yegge talks fun but there is money to be made in working out what other people's requirements are so i'd take his article with a pinch of salt.
Requirements gathering is incredibly tough because of the manner in which communication works. Its a four step process that is lossy in each step.
I have an idea in my head
I transform this into words and pictures
You interpret the pictures and words
You paint an image in your own mind of what my original idea was like
And humans fail miserably at this with worrying frequency through their adorable imperfections.
Agile does right in promoting iterative development. Getting early versions out to the client is important in identifying what features are most important (what ships in 0.1 - 0.5 ish), helps to keep you both on the right track in terms of how the application will work and quickly identifies the hidden features that you will miss.
The two main problem scenarios are the two ends of the scales:
Not having a freaking clue about what you are doing - get some domain experts
Having too many requirements - feature pit. - Question, cull (prioritise ;) ) features and use iterative development
Yegge does well in pointing out that domain experts are essential to produce good requirements because they know the business and have worked in it. They can help identify the core desire of the client and will help explain how their staff will use the system and what is important to the staff.
Alternatives and additions include trying to do the job yourself to get into the mindset or having a client staff member occasionally on-site, although the latter is unlikely to happen.
The feature pit is the other side, mostly full of failed government IT projects. Too much, too soon, not enough thought or application of realism (but what do you expect they have only about four years to make themselves feel important?). The aim here is to work out what the customer really wants.
As long as you work on getting the core components correct, efficient and bug-free clients usually remain tolerant of missing features that arrive in later shipments, as long as they eventually arrive. This is where iterative development really helps.
Remember to separate the client's ideas of what the program will be like and what they want the program to achieve.
Some clients can create confusion by communicating their requirements in the form of application features which may be poorly thought out or made redundant by much simpler functionality then they think they require. While I'm not advocating calling the client an idiot or not listening to them I feel that it is worth forever asking why they want a particular feature to get to its underlying purpose.
Remember that in either scenario it is of imperative importantance to root out the quickest path to fulfilling the customers core need and put you in a scenario where you are both profiting from the relationship.
Wow, where to start?
First, there is a set of knowledge someone should have to do analysis on some projects, but it really depends on what you are building for who. In other words, it makes a big difference if you are modifying an enterprise application for a Fortune 100 corporation, building an iPhone app, or adding functionality to a personal webpage.
Second, there are different kinds of requirements.
Objectives: What does the user want to accomplish?
Functional: What does the user need to do in order to reach their objective? (think steps to reach the objective/s)
Non-functional: What are the constraints your program needs to perform within? (think 10 vs 10k simultaneous users, growth, back-up, etc.)
Business rules: What dynamic constraints do you have to meet? (think calculations, definitions, legal concerns, etc.)
Third, the way to gather requirements most effectively, and then get feedback on them (which you will do, right?) is to use models. User cases and user stories are a model of what the user needs to do. Process models are another version of what needs to happen. System diagrams are just another model of how different parts of the program(s) interact. Good data modeling will define business concepts and show you the inputs, outputs, and changes that happen within your program. Models (and there are more than I listed) are really the key to the concern you list. A few good models will capture the needs and from models you can determine your requirements.
Fourth, get feedback. I know I mentioned this already, but you will not get everything right the first time, so get responses to what your customer wants.
As much as I appreciate requirements, and the models that drive them, users typically do not understand the ramifications of of all their requests. Constant communication with chances for review and feedback will give users a better understanding of what you are delivering. Further, they will refine their understanding based on what they see. Unless you're working for the government, iterations and / or prototypes are helpful.
First of all gather the requirements before you start coding. You can begin the design while you are gathering them depending on your project life cicle but you shouldn't ever start coding without them.
Requirements are a set of well written documents that protect both the client and yourself. Never forget that. If no requirement is present then it was not paid for (and thus it requires a formal change request), if it's present then it must be implemented and must work correctly.
Requirements must be testable. If a requirement cannot be tested then it isn't a requirement. That means something like, "The system "
Requirements must be concrete. That means stating "The system user interface shall be easy to use" is not a correct requirment.
In order to actually "gather" the requirements you need to first make sure you understand the businness model. The client will tell you what they want with its own words, it is your job to understand it and interpret it in the right context.
Make meetings with the client while you're developing the requirements. Describe them to the client with your own words and make sure you and the client have the same concept in the requirements.
Requirements require concise, testable example, but keep track of every other thing that comes up in the meetings, diagrams, doubts and try to mantain a record of every meeting.
If you can use an incremental life cycle, that will give you the ability to improve some bad gathered requirements.
You can never ask too many or "stupid" questions. The more questions you ask, the more answers you receive.
According to Steve Yegge that's the wrong question to ask. If you're gathering requirement it's already too late, your project is doomed.
High-level discussions about purpose, scope, limitations of operating environment, size, etc
Audition a single paragraph description of the system, hammer it out
Mock up UI
Formalize known requirements
Now iterate between 3 and 4 with more and more functional prototypes and more specs with more details. Write tests as you go. Do this until you have functional software and a complete, objective, testable requirements spec.
That's the dream. The reality is usually after a couple iterations everybody goes head-down and codes until there's a month left to test.
Gathering Business Requirements Are Bullshit - Steve Yegge
read the agile manifesto - working software is the only measurement for the success of a software project
get familiar with agile software practices - study Scrum , lean programming , xp etc - this will save you tremendous amount of time not only for the requirements gathering but also for the entire software development lifecycle
keep regular discussions with Customers and especially the future users and key-users
make sure you talk to the Persons understanding the problem domain - e.g. specialists in the field
Take small notes during the talks
After each CONVERSATION write an official requirement list and present it for approving. Later on it would be difficult to argue against all agreed documentation
make sure your Customers know approximately what are the approximate expenses in time and money for implementing "nice to have" requirements
make sure you label the requirements as "must have" , "should have" and "nice to have" from the very beginning, ensure Customers understand the differences between those types also
integrate all documents into the latest and final requirements analysis (or the current one for the iteration or whatever agile programming cycle you are using ... )
remember that requirements do change over the software life cycle , so gathering is one thing but managing and implementing another
KISS - keep it as simple as possible
study also the environment where the future system will reside - there are more and more technological restraints from legacy or surrounding systems , since the companies do not prefer to throw to the garbage the money they have invested for decades even if in our modern minds 20 years old code is garbage ...
Like most stages of the software development process its iteration works best.
First find out who your users are -- the XYZ dept,
Then find out where they fit into the organisation -- part of Z division,
Then find out what they do in general terms -- manage cash
Then in specific terms -- collect cash from tills, and check for till fraud.
Then you can start talking to them.
Ask what problem they want you want to solve -- you will get an answer like write a bamboozling system using OCR with shark technoligies.
Ignore that answer and ask some more questions to find out what the real problem is -- they cant read the till slips to reconcile the cash.
Agree a real solution with the users -- get a better ink ribbon supplier - or connect the electronic tills to the network and upload the logs to a central server.
Then agree in detail how they will measure the success of the project.
Then and only then propose and agree a detailed set of requirements.
I would suggest you to read Roger-Pressman's Software Engineering: A Practitioner's Approach
Before you go talking to the stakeholders/users/anyone be sure you will be able to put down the gathered information in a usefull and days-lasting way.
Use a sound-recorder if it is OK with the other person and the information is bulky.
If you heard something important and you need some reasonable time to write it down, you have two choices: ask the other person to wait a second, or say goodbye to that precious information. You wont remember it right, ask any neuro-scientist.
If you detect that a point need deeper review or that you need some document you just heard of, make sure you make a commitment with the other person to send that document or schedule another meeting with a more specific purpose. Never say "I'll remember to ask for that xls file" because in most cases you wont.
Not to long after the meeting, summarize all your notes, recordings and fresh thoughts. Just summarize it rigth. Create effective reminders for the commitments.
Again, just after the meeting, is the perfect time to understand why the gathering you just did was not as right as you thought at the end of the meeting. That's when you will be able to put down a lot of meaningful questions for another meeting.
I know the question was in the perspective of the pre-meeting, but please be aware that you can work on this matters before the meeting and end up with a much usefull, complete and quality gathering.
I've been using mind mapping (like a work breakdown structure) to help gather requirements and define the unknowns (the #1 project killer). Start at a high level and work your way down. You need to work with the sponsors, users and development team to ensure you get all the angles and don't miss anything. You can't be expected to know the entire scope of what they want without their involvement...you - as a project manager/BA - need to get them involved (most important part of the job).
There are some great ideas here already. Here are some requirements gathering principles that I always like to keep in mind:
Know the difference between the user and the customer.
The business owners that approve the shiny project are usually the customers. However, a devastating mistake is the tendency to confuse them as the user. The customer is usually the person that recognizes the need for your product, but the user is the person that will actually be using the solution (and will most likely complain later about a requirement your product did not meet).
Go to more than one person
Because we’re all human, and we tend to not remember every excruciating detail. You increase your likelihood of finding missed requirements as you talk to more people and cross-check.
Avoid specials
When a user asks for something very specific, be wary. Always question the biases and see if this will really make your product better.
Prototype
Don’t wait till launch to show what you have to the user. Do frequent prototypes (you can even call them beta versions) and get constant feedback throughout the development process. You’ll probably find more requirements as you do this.
I recently started using the concepts, standards and templates defined by the International Institute of Business Analysts organization (IIBA).
They have a pretty good BOK (Book of Knowledge) that can be downloaded from their website. They do also have a certificate.
Requirements Engineering is a bit of an art, there are lots of different ways to go about it, you really have to tailor it to your project and the stakeholders involved. A good place to start is with Requirements Engineering by Karl Wiegers:
http://www.amazon.com/Software-Requirements-Second-Pro-Best-Practices/dp/0735618798/ref=pd_bbs_sr_2?ie=UTF8&s=books&qid=1234910330&sr=8-2
and a requirements engineering process which may consist of a number of steps e.g.:
Elicitation - for the basis for discussion with the business
Analysis and Description - a technical description for the purpose of the developers
Elaboration, Clarification, Verification and Negotiation - further refinement of the requirements
Also, there are a number of ways of documenting the requirements (Use Cases, Prototypes, Specifications, Modelling Languages). Each have their advantages and disadvantages. For example prototypes are very good for elicitation of ideas from the business and discussion of ideas.
I generally find that writing a set of use cases and including wireframe prototypes works well to identify an initial set of requirements. From that point it's a continual process of working with technical people and business people to further clarify and elaborate on the requirements. Keeping track of what was initially agreed and tracking additional requirements are essential to avoid scope creep. Negotiation plays a bit part here also between the various parties as per the Broken Iron Triangle (http://www.ambysoft.com/essays/brokenTriangle.html).
IMO the most important first step is to set up a dictornary of domain-specific words. When your client says "order", what does he mean? Something he receives from his customers or something he sends to his suppliers? Or maybe both?
Find the keywords in the stakeholders' business, and let them explain those words until you comprehend their meaning in the process. Without that, you will have a hard time trying to understand the requirements.
i wrote a blog article about the approach i use:
http://pm4web.blogspot.com/2008/10/needs-analysis-for-business-websites.html
basically: questions to ask your client before building their website.
i should add this questionnaire sheet is only geared towards basic website builds - like a business web presence. totally different story if you are talking about web-based software. although some of it is still relavant (e.g. questions relating to look and feel).
LM
I prefer to keep my requirements gathering process as simple, direct and thorough as possible. You can download a sample document that I use as a template for my projects at this blog posting: http://allthingscs.blogspot.com/2011/03/documenting-software-architectural.html

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