Both, first step in creating a new IS according to your wanted actual Business Strategies. A carefully analsysing of needs and design of software has be done by appropriate specialists. Today you can find all levels - in best education levels.

In a second phase ou have to implement a good documentation of the even final-testet system and

in a third step you should establish and pay a permanent maintenence team (1 leader for overview and 2-5 programmers) on IS-side and a Business specialist at order-side. You have to provide a permanent update of your even new IS. That's serious state of the art.

You always have to remain critical: a critical Attitude about:

What am I doing?

What for am I doing this?

With what am I doing this?

Sodiq - You haven't said what type of business you're looking at, and whether it's public or private. And does the business already have an overall strategic planning framework? The answer to your question will very much depend on:

1) how much the business relies on information systems for its success (and how 'success' is measured);

2) whether the business has a resource constraint (ie public) or is able to fund SISP from the benefits of a successful implementation; and

3) Whether there are other strategic planning systems in the organisation (in which case IS planning should integrate with that)

Franz is right - SISP is not a one-shot exercise. There will be two phases of work: the first to set it up, and the second to maintain it long term. If you can't fund or support the second phase, you're probably wasting time and money undertaking the first phase. And in any case the entire exercise will need strong high-level executive support.

But if the organisation is REALLY intent on wasting money, they should hire external SISP consultants.