Steve Wright needs 2 BIS reps from each Studio cohort Please select/elect from amongst yourselves...

Steve Wright needs 2 BIS repsfrom each Studio cohort

Please select/elect from amongst yourselves and contact him soon

(preference for gender equality but not mandatory)

What you need to know to keep your job

a rant about paying attention to details

IMS3000 Semester 2, 2005 3

Three things students don’t like

• IMS3000 seminars

• well meaning advice from older people

• hearing about stuff they have already passed

• Oh dear!

• …here comes Andrew with IMS1002 again!


the Requirements Spec

• First Semester’s deliverable

• why produce it?

• … to direct Second Semester’s activities

• (refer to IMS1002 notes for FRS contents)


FRS in the Real World?

• an expression of the Client’s information needs

• information needs translate to processing and reporting of business activity

• these needs are met by delivering conformant processing ~ the software artefact plus human procedures


needs

• expressed (to the Analyst by the Clients) in plain English as a wish list of desires ~ both functional and non-functional

• FRS is an expression (by the Analyst for the Designer) of what must be done

• DS is a specification (by the Designer for the Implementer) of how it will be done


What must be done

• provide the information that is necessary for decision making in the agreed operational activities of the business

• information is created from the available data and used, and stored for retrieval when required


To find out what is needed…

• inter alia, know how the business sees itself:• guardian of a set of principles for action• custodian of resources which people can use• responder to environmental requests• manufacturer of products/services to meet specific

objectives• creator of solutions to individual problems

• Indicates the business’s attitude to control


Control

• Prescribed or Discretionary

• Procedural or Event Driven

• implies (but doesn’t prescribe) the choice of representation paradigm: the language of communication

• Structured or Object Oriented


Paradigms and tools

• Structured• Event lists• DFDs• ERDs• Structured English

sequential logic controlled by conditional branches

• Object Oriented• Event lists• Use Case desc/diags• Class diagrams• Sequence diagrams• State Machines

autonomous objects reacting and communicating on demand


the Key point!!

• the FRS portrays the Client’s information needs as abstract diagrams and declarative statements (representing the essence of the business as it interacts with its environment) in sufficient detail for the system Implementer to create corresponding software artefacts


your task …

• the appropriate paradigm

• the appropriate tools

• accurate mapping of functional need to abstract representation• because some poor mug programmer has to

write appropriate code and data structures!

Think like the programmer

Does the Spec that tell me all about what to do?

(I can then figure out how to do it)


“The devil is in the detail”

• DFD Contexts• Every event has to be there• If aggregating input flows – decompose them in

the Data Dictionary

• Use case diagrams• Every use has to be there• Every <<include>>, <<extend>> must be there


Partitioning (Structured methods)

• By process type?

• By common data?

• By event type? i.e. business process

• This is more a control structure issue than a processing issue


Process descriptions/ Methods

• Obtain all required data (coupling/cohesion)• Evaluate all conditions• Define the transformations for all conditions

• Accommodate the non-functional issues here• Record locking, partial commits, txn rollback• APIs needed? TP monitor needed?• Heterogeneous environments?


Summary

• you are performing a three way cross-cultural translation• client – analyst/designer - implementer

• the cost of mistranslation is very high• incorrect software operations, giving …• incorrect information, leading to …• incorrect decision making, resulting in …• compromised business processes, causing …• business failure

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