week 4

In week 5 we have started the chapter 4 and learned some basic concepts of data flow diagrams in the lecture. These answers are written from my self-learning, and may not be up to the standard.

Q1: What were the most important concepts you learnt about data and process modelling this week?

A1: According to Shelly et al (2006) data process modelling involves three main tools; data flow diagram (DFD), data dictionary and process description.

(i) DFD: This shows how data moves through an information system but does not show the programming logic or processing steps. A set of DFDs provides a logical model that shows what the system does and how it does it. This is important, because focusing on implementation issues at the initial state would restrict the search, and lead to a most effective system design. Four symbols used in DFD; they are,

Process; receives input data and produce output that has a different content, form, or both.

Data Flows; a path for data to move from one part of the information system to another.

Data stores; represent the data, which is stored in the system.

Entities; external entities provide data to the system or receive output from the system.

(ii) Data Dictionary/Data Repository: This can be defined as either documented information, which is shown in DFDs’ or ‘central storehouse of information about the system data’. This is used to collect, document and organise specific facts about the system.

(iii) Process Description: Document the details of a functions primitive, and represents a specific set of processing steps and business logic is called Process Description. Typical process description tools include structured English, description tables and decision trees.

Q2: Why do you think those concepts are important?

A2: As mentioned in (A1), to have a effective system design or to identify the boundary of the system before starting the system design or coding these concepts are very useful. Since these concepts document all the external entities, inputs, outputs, data should be stored, and the data flow, this will help in any stage of the project including design, coding, and maintenance. The availability of all the external entities and the processes gives the advantage to analyse the difficulties may arise during the System Development Life Cycle as well, and this can reduce the project failure up to certain extent. So I feel these concepts are very important in any Information System implementation.

Q3: What are the data and process modelling concepts that are still causing you the greatest problems?

A3: Identify the internal processes for the low level DFD is a pretty confusing one. I feel this part is very important in a system development since both data dictionary and process description are based on DFDs and they are straight forward if the DFD is available. For me in context diagram level finding the external entities and the data flows between them and the process is still a complicated one, there is a chance to mistreat a process as an entity and vis versa on this level. This may effect the entire system design.

Q4: How might the problems you are having be solved?

A4: Only practising more DFD drawing can solve this problem, but I am planning to refer some other system design documents and books for understand more about this.