9.FAQ(Frequently Asked Questions)

1.Disintegration of Goals

When disintegrating a goal into subgoals using a strategy node there are a several possible outcomes.For example, when discussing the dependability of a system, there are two possible outcomes.(1)We could first discuss the functions of a system and then discuss how each function could avert a risk.(2)Or we could first discuss the risks and then discuss which function of the system could be used to avert a certain risk.Furthermore, there are a vast number of documents generated throught the lifecycle of a system and each discussion varies paramountly depending on the document which we focus on.For example, when describing a D-Case on a web server we could first focus on the architecture design document, and then divide into seperate topics such as web server, application server, database server and discuss accordingly.Or we could fould on the SLA document and discuss related topics respectively.The research on dependability cases upto now has not clearly defined how to disintegrate a goal into subgoals.We would like to present the basic criterion that has hitherto been used to disintegrate a goal.

Consider the contents and structure of a discussion from the point of view of a D-case presenter
When explaining to a stakeholder using a D-Case, there is no point in using a meaningless incomprehensible explanation.For example, it is useless to explain in detail the technology behind a system to a top management personnel from a client company.When dealing with top management personnel it is best to omit a detailed explanations and explain system`s dependability requirements (SLA documents etc.) according to a finely constructed subgoal structure.In contrast, when explaining to an engineer from a client company it is best to use a detailed D-case showing the technical particulars of a system and discuss dependability requirements, goals achieved by appropriate tests and benchmarks.Ultimately it is ideal to create a D-case with a finely constructed structure and technical particulars.

Start the discussion from a topic that is vital to the dependability of a system
The dependability of a system is closely related to all the documents created in the lifecycle of a system.It is possible that a D-Case would become enormous if we used all the documents created in the lifecycle of a system to describe a D-case.Therefore it is recommended to consider the following when creating a D-case.Firstly, establish vital factors and point of views (point of view from the operation work flow etc.) that affect the dependability of a system.Secondly, discuss according to the vital point of views and choose the necessary documents to create a D-case.

2.The difference between D-Case and existing documents

This is a frequently asked question.D-Case is not a document that replaces the position of existing documents such as risk analysis/solution documents and specification document etc.D-case is a document that is used to guarantee dependability by referencing to or expanding existing documents(Fig.1).

3.The difference between D-Case and other goal oriented requirements analysis techniques

D-Case can be classified as a goal oriented requirements analysis technique.The difference between D-case and similar techniques can be simply summarized as follows.

  • Goal
    • D-Case : Confirmation and guarantee of the system`s dependability
    • Other techniques : Analysis of means used to achieve a required goal

  • How to disintegrate a goal
    • D-Case : Several possible methods exists but places emphasis on vital point of views of disintegrating a goal
    • Other techniques:Almost always only one point of view is used to disintegrate a goal

However D-case and other techniques both use a tree structure and thus in reality, it is difficult to differentiate between the two.We frequently get feed back on D-case from clients and they all say that they have never used a similar document before.D-case is a document that is thought out with respect to the point of view of a system`s dependability, using various documents, all the while being a easily comprehensible document aimed at stakeholders.

The disintegration of a goal, structure of a discussion etc. can not be easily determined.We have considerably rounded up the methods to construct a discussion, how to disintegrate a goal into appropriate subgoals via description experiments.We plan to summarize and publish the results in the near future.Our goal is to develop the D-case technique and make it more compatible with other similar techniques and also identify the differences between the applications of D-case and other techniques.