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a) Explain the following tools for documenting and modelling user requirements i) Entity-relationship diagrams (ERDs) ...

      

a) Explain the following tools for documenting and modelling user requirements
i) Entity-relationship diagrams (ERDs) ii) Entity Life Histories
b) What are the desirable characteristics of a user-friendly system
c) Common computer outputs include printed reports and on screen reports. Explain the main classifications of reports.

  

Answers


Gregory
a)
i) Entity-relationship diagrams (ERDs)
? An ERD is a graphical model that shows relationships among system entities
? Each entity is a rectangle, labelled with a noun
? Each relationship is a diamond, labelled with a verb

Types of relationships
? One-to-one (1:1)
? One-to-many (1:M)
? Many-to-many (M:N)

A full ERD shows all system relationships

ii) Entity Life Histories
Each entity identified on the ERM contains a specific set of attributes. During the existence of each entity-occurrence these attributes are given a value that may be updated many times until eventually the whole entity-occurrence is deemed not to be of any more interest to the system and is „killed off? or archived. Thus, each entity-occurrence has a life of its own that follows a set pattern common to every occurrence of the entity it belongs to and which has to be „discovered? by the analysts. The Entity Life History (ELH) is a diagram where the possible life of each occurrence within an entity, from its creation to its deletion, is recorded.

b) Desirable characteristics of a user-friendly system
? Ease of data entry;
? Intuitiveness;
? Consistent design;
? On-screen help;
? On-screen prompts and dialog boxes;
? Ability to back-track; and ? Convenience.

c) Common computer outputs include printed reports and on screen reports.
Explain the main classifications of reports.
Reports can be classified by content
? Detail reports
? Exception reports

Summary reports

Detail reports
? Provide the most information
? At least one line of output is produced for each record processed ? Detail reports can be quite lengthy

Exception reports
? Show only records that meet a specific condition
? Useful when particular information is required
? Special parameter queries can be used to select only the records that meet specified conditions

Summary reports
? Show only subtotals and totals
? Useful for upper-level managers who do not require extensive detail

Reports also can be classified by distribution
? Internal reports
? External reports

Internal reports
? Distributed within the organisation
? Usually printed on stock paper
? Blank, single ply, standard size
? Less expensive
? Can be used for many types of reports

External reports
? Distributed outside the organisation
? Might include statements, invoices, or pay cheques
? Usually printed on special forms
? More expensive than stock paper
? Paper must be changed for each report printing job
Multi-part forms must be separated or decollated
? Special forms can use pre-printed graphics and logos
? Special applications, such as checks, require special forms

Factors to consider:
? Types of printers
? Print volume calculations
? Print-time calculations

Gregorymasila1 answered the question on March 28, 2018 at 12:42


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