Specifications

[PJW]

Hi Peter,
Here is a question I was loking at in the module 7 2008 paper:-

Question 7
Provide an outline functional performance specification for procuring train detection equipment for use as the basis of a block signalling system.
[15 marks]
What are the main advantages and disadvantages of providing a functional performance specification rather than a detailed design specification?
[5 marks]

I will look into the information links you have provided and maybe attempt it.

Thanks
Aditi

I think that looking at those links etc should give you plenty for those last 5 marks.

The first 15 will need you to use your knowledge of train detection criteria but also get you to think about "all the categories of things" that are important for a particular railway and its application. I don't want to lead you too much because I want you to think, but perhaps a few hints are appropriate to get you started as you still seem hesitant.

Earlier I suggested you try to relate to decision to purchase various items in your personal life. You need to think what you really NEED and what you'd LIKE and for this you need to know what you are going to USE the object for and in what ENVIRONMENT.

Writing a specification is basically telling the supplier what is important to you- this may be entirely different to what is important to me. It may also be entirely different from what you wanted last time, because even if it is in some ways similar you may need it for a different role.

So to take one of those examples- buying footwear. I guess you take a different size to me, but each of us are likely to take the same size on each occasion we go into the shop. However on one day you may wish to buy some high heels, on another occasion some training shoes and on another a pair of safety boots. I guess the colour may be an important factor in your choice for the first two, but probably of very little relevance for the latter. Perhaps you wish to avoid wearing any leather objects; in which case that would be an important criteria to you in every case. The anti-slip nature of the sole may be a relevant consideration every time, but more important in the case of the safety boots than the others. Similarly you may try to assess for likely durability, but again that would be relevant more for some purchases than others. So you probably go into the shop with some form of idea of what you are looking to purchase and soome perhaps subjective criteria to judge potential candidate items against.

Writing a specification is just a more formal means of doing this and having some more objective criteria that a "third party" could assess against (so that they could say "yes the object complies" or "no the object does not comply in these respects to this extent"). It isn't as easy as you might think and this is where clients and contractors often get into disagreements. You ask me to supply you with a pair of brown boots (envisaging wearing them at an office party that you think that I know you are attending); I supply a perfectly good pair of brown walking boots (because you did mention that you were soon going on holiday to the Lake District). End result is that you are far from happy and criticise me as incompetent; I think you are acting totally unreasonably and demand payment for what I provided in good faith and is in accordance with what was actually specified as your requirement.

So have a goand see what you come up with. You won't come close to giving a water-tight specification in 20 minutes; however remember that you want as WIDE a consideration as possible- better to have some examples spread over the whole range of possible considerations than to concentrate in too much detail on a few very specific items, thoug a hint that you can do detail in perhaps one key area is also important. Think about the analogy above; over to you.