Weblog van Spruit
Goal in life: Create order, think lateral.
Saturday, February 13, 2010
Specification of IT solutions
 Some work is done so routinely that you hardly think about how it is done. Here is one example.
As depicted in the model above the specification of an IT system or parts thereof can be viewed conceptually as an interplay between three components that all influence each other.
Requirements
As usual there need to be requirements. These correspond to what the demands on the IT system are in the broadest sense. Functional and non functional. Normally the intended end users or representing business party will supply these and they tell WHAT the system should do.
Model
Next there needs to be some kind of model or architecture. It is not smart to start building "ins Blaue hinein". We need rules to the game, but I am not getting into the "why do we need architecture" discussion here. More on the model part in a next blog, I have a picture of that as well. The model tells HOW the system does it.
Application
Finally both of the above lead to an IT application or parts thereof: programming. The REAL THING.
For example we may need to set up authorization for a document management system. There will be requirements like, there exist these groups of documents that are defined by these criteria and group A needs to be visible by these users defined by another set of criteria. These demands will need to be mapped on the authorization model of the document management system. For example, use security groups to group the documents vs use accounts to group the documents. Finally this will lead to actual authorization set up by populating the model according to the requirements, create security groups A, B and C, link them to roles X, Y and Z, appoint roles to users and modify programming so that documents of criteria 1, 2 and 3 end up in the correct security group.
In this interplay the three parts influence each other. For example, some requirements may not be met by the current authorization model, so we need to change one of the two. Requirements and the model dictate what the application will look like.Labels: IT solution, specification
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