CSE1204 - Information Systems 1 Detailed Process Definitions; The Data Dictionary.

CSE1204 - Information CSE1204 - Information Systems 1Systems 1

Detailed Process Definitions;Detailed Process Definitions;

The Data DictionaryThe Data Dictionary

Monash University, SIMS, Semester One, 2005Monash University, SIMS, Semester One, 2005 22

the data dictionary is a database or repository of the data dictionary is a database or repository of information about objects identified during information about objects identified during systems developmentsystems development

every object (and each of its components) must every object (and each of its components) must have a definition in the data dictionary have a definition in the data dictionary

the data dictionary is a major source of the data dictionary is a major source of documentation about the information systemdocumentation about the information system

Data Dictionary Data Dictionary


Data Dictionary Entries for Data Dictionary Entries for Components of DFDsComponents of DFDs

the data dictionary must contain precise definitions of all the data dictionary must contain precise definitions of all components of all data flow diagrams:components of all data flow diagrams: to fully explain the meaning of the DFDsto fully explain the meaning of the DFDs to describe the contents of all data flows and data to describe the contents of all data flows and data

storesstores to describe the processing that occurs in primitive to describe the processing that occurs in primitive

processesprocesses to ensure that names and meanings of components to ensure that names and meanings of components

are used consistently (a common vocabulary)are used consistently (a common vocabulary)


Data Dictionary EntriesData Dictionary Entries

a data dictionary entry must be included a data dictionary entry must be included for each for each data flow data flow data storedata storehigher level process higher level process primitive process primitive process external agent (source/sink)external agent (source/sink)


each data flow consists of a series of each data flow consists of a series of data data elementselementsa data element is a unit of data that cannot be a data element is a unit of data that cannot be

further broken down into meaningful units of further broken down into meaningful units of datadata

each data element should also have an entry each data element should also have an entry in the data dictionaryin the data dictionary

data flows and data stores are made up of data flows and data stores are made up of data elementsdata elements

Data elementsData elements


Data Dictionary -data element Data Dictionary -data element entryentry

ACADEMIC CONSULTANCY

DATA ELEMENT: Product code

•Alias: Inventory number, product number•Description: Number to identify and differentiate each product held in warehouse•Values: Must be a positive integer•Range: 00001 to 99999

AUTHOR: David Ross

DATE: 14 Oct 2002


Data FlowsData Flows a data dictionary entry for a data flow describes the a data dictionary entry for a data flow describes the

sequence of data elements and data structures in the sequence of data elements and data structures in the data flow using the following connectors:data flow using the following connectors: == is equivalent tois equivalent to ++ andand [ ][ ] select one ofselect one of { }{ } iterations ofiterations of ( )( ) optionaloptional ** commentscomments


Data Dictionary -data flow Data Dictionary -data flow entryentry

•ACADEMIC CONSULTANCY

DATA FLOW: Sales order

•Alias: Customer order•Description: Request for product from customer•Composition: sales order =sales order no. +

sales order date +

customer number +

[account customer

cash customer] +

customer name +

customer address +

(customer telephone no) +

{item no + item desc + item price + item qty} +

sales order total amount

AUTHOR: David Ross

DATE: 03 July 2002


Data StoresData Stores a data store is made up of data flows and data a data store is made up of data flows and data

elementselements where a data store consists of a collection of data where a data store consists of a collection of data

flows it is described as repetitions of that data flowflows it is described as repetitions of that data flow e.g.e.g. Data Store:Data Store: {customer invoice}{customer invoice}

data stores may also be described by listing their data stores may also be described by listing their data elementsdata elements

e.ge.g customer deposit customer deposit == account no +account no +deposit date +deposit date +deposit amount +deposit amount +account balanceaccount balance


Data Dictionary -data store Data Dictionary -data store entryentry


DATA STORE: Sales

•Description: Store of all pertinent data about product sales made to customers•Composition: sales = date+

({product}

product quantity)+

sales total

{customer}

AUTHOR: David Ross

DATE: 10 Oct 2002


Describing ProcessesDescribing Processes

each process in higher level DFDs is defined by the DFD each process in higher level DFDs is defined by the DFD that decomposes the process at the next level down: that decomposes the process at the next level down:

these are these are parentparent processes processes

each such process should have a data dictionary entry each such process should have a data dictionary entry which includes a brief description of the overall nature which includes a brief description of the overall nature and purpose of the processand purpose of the process


Describing ProcessesDescribing Processes

example data dictionary entry for a processexample data dictionary entry for a process

Treat patients:Treat patients: Patient consultations are carried out to Patient consultations are carried out to determine the causes of patients’ illnesses/ determine the causes of patients’ illnesses/ medical medical problems. Further treatment/ problems. Further treatment/ follow up is follow up is recommended if appropriate. recommended if appropriate. Details of Details of consultations are recorded.consultations are recorded.

specific process description (minispecs)specific process description (minispecs)




DATA PROCESS Treat patient

•Description: Patient consultations are carried out to determine the causes of patients’ illnesses/ medical problems. Further treatment/ follow up is recommended if appropriate. Details of consultations are recorded, and fees charged to the patient on the basis of these sessions.•Data required: {Patient}+

Fee schedule

AUTHOR: David Ross

DATE: 10 Oct 2002


Describing External AgentsDescribing External Agents

each external agent (source or sink) should have a data each external agent (source or sink) should have a data dictionary entry which describes its relationship with the dictionary entry which describes its relationship with the systemsystem

e.g.e.g.

Referring Doctors:Referring Doctors:

These are doctors who refer their patients to a specialist These are doctors who refer their patients to a specialist medical practitioner for treatment. They are usually general medical practitioner for treatment. They are usually general practitioners.practitioners.


Data Dictionary –external Data Dictionary –external agent entryagent entry


DATA AGENT: Referring

doctor

•Alias: Inventory number, product number•Description: Doctors who refer their patients for treatment.

•Values: Must be a positive integer•Range: 00001 to 99999

AUTHOR: David Ross

DATE: 14 June 2002



doctor

•Alias: Inventory number, product number•Description: Doctors who refer their patients for treatment.

•Values: Must be a positive integer•Range: 00001 to 99999

AUTHOR: David Ross

DATE: 14 June 2002



doctor

•Alias: Referrer, GP•Description: Doctors who refer their patients for treatment.

AUTHOR: David Ross

DATE: 14 June 2002


Building and Maintaining Building and Maintaining the Data Dictionarythe Data Dictionary

determine standard formats and information content for determine standard formats and information content for all types of data dictionary entriesall types of data dictionary entries

have a standard means of organising and storing the have a standard means of organising and storing the entries in the data dictionaryentries in the data dictionary

ensure that all components of the DFDs have entries in ensure that all components of the DFDs have entries in the data dictionary and that they are kept up-to-datethe data dictionary and that they are kept up-to-date

cross-referencing of entries in the data dictionary can cross-referencing of entries in the data dictionary can help to check the completeness and consistency of the help to check the completeness and consistency of the DFDs and other types of modelsDFDs and other types of models


Detailed Process DefinitionsDetailed Process Definitions

the processing that occurs within the bottom level the processing that occurs within the bottom level (primitive) processes in DFDs needs to be defined(primitive) processes in DFDs needs to be defined

detailed process descriptions are also known as detailed process descriptions are also known as minispecsminispecs

detailed process descriptions form part of the data detailed process descriptions form part of the data dictionary: they define the contents of primitive dictionary: they define the contents of primitive processesprocesses



many techniques can be used to define the many techniques can be used to define the details of processing: details of processing:

e.g.e.g. narrative textnarrative text

Structured EnglishStructured English

decision tablesdecision tables

decision treesdecision trees

flow chartsflow charts



detailed process descriptions should:detailed process descriptions should:

express express whatwhat the process does (i.e. policy), not the process does (i.e. policy), not howhow the the process is carried out (i.e. procedure)process is carried out (i.e. procedure)

be in a form that can be easily understood and verified be in a form that can be easily understood and verified by both users and systems analystsby both users and systems analysts

be in a form that can be easily communicated to all be in a form that can be easily communicated to all potential stakeholders:potential stakeholders:

e.g. e.g. end-users, systems analysts, managers, system end-users, systems analysts, managers, system designers, project leaders, programmersdesigners, project leaders, programmers



Structured English is a modified form of English with Structured English is a modified form of English with some major restrictions on vocabulary and structure:some major restrictions on vocabulary and structure:

only action (imperative) verbs such as only action (imperative) verbs such as get, put, add, get, put, add, calculate, find, delete calculate, find, delete are usedare used

only nouns/noun phrases which refer to components of only nouns/noun phrases which refer to components of the DFDs should be used, i.e. data flows, data stores, the DFDs should be used, i.e. data flows, data stores, data elementsdata elements



sentences consist of action verbs and DFD sentences consist of action verbs and DFD componentscomponents

sentences are combined to form process sentences are combined to form process descriptions using the control structures of descriptions using the control structures of sequencesequence, , conditioncondition, and , and repetitionrepetition


Control StructuresControl Structures Condition uses Condition uses If... Then...Else If... Then...Else

or or

Select Case Select Case Case 1...Case 2...End CaseCase 1...Case 2...End Case

E.g. E.g.

If qty-in-stock is less than minimum-order-qtyIf qty-in-stock is less than minimum-order-qty

Then update stock-reorder indicatorThen update stock-reorder indicator

Else do nothingElse do nothing


Control StructuresControl Structures e.g.e.g.

Select CaseSelect Case

CASE 1CASE 1 qty-in-stock is less than qty-in-stock is less than minimum-order-qtyminimum-order-qty

Do update stock-reorder indicatorDo update stock-reorder indicator

CASE 2CASE 2 qty-in-stock is equal to minimum-qty-in-stock is equal to minimum-order-qtyorder-qty

Do nothingDo nothing

CASE 3CASE 3 qty-in-stock is greater than minimum-qty-in-stock is greater than minimum-order-qtyorder-qty

Do nothingDo nothing

End CaseEnd Case




DATA PROCESS Stock reorder

•Description: Current levels of stock in warehouse are matched to optimal requirements. Shortfalls are ordered immediately.•Select Case

CASE 1 qty-in-stock is less than minimum-order-qty

Do update stock-reorder indicator

CASE 2 qty-in-stock is equal to minimum- order-qty

Do nothing

CASE 3 qty-in-stock is greater than minimum- order-qty

Do nothing

End Case

AUTHOR: David Ross

DATE: 10 Oct 2002


Sequence is represented with one sentence Sequence is represented with one sentence following another in sequence:following another in sequence:

Add student to class listAdd student to class list

Decrease available-placesDecrease available-places

Calculate class-feeCalculate class-fee

Control StructuresControl Structures


Repetition uses Repetition uses Do-UntilDo-Until or or Do-WhileDo-While loops: loops:

DoDo

Accept customer-account-detailsAccept customer-account-details

Calculate daily-interest = daily balance * daily Calculate daily-interest = daily balance * daily interest rateinterest rate

Add daily-interest to monthly-interest-dueAdd daily-interest to monthly-interest-due

UntilUntil

no more customer-accountsno more customer-accounts

Control StructuresControl Structures


Example Structured Example Structured EnglishEnglish

Accept sales-orderAccept sales-order

Find customer-detailsFind customer-details

If customer-details not foundIf customer-details not found

Then reject sales-orderThen reject sales-order

ElseElse

Create sales-order-headerCreate sales-order-header

Do while more sales-order-itemsDo while more sales-order-items

find item-detailsfind item-details

calculate sales-order-item price = calculate sales-order-item price =

item price *order-qtyitem price *order-qty

EnddoEnddo

Authorise sales-orderAuthorise sales-order

Endif Endif


Guidelines for Structured Guidelines for Structured EnglishEnglish

use indentation to indicate control structures and their use indentation to indicate control structures and their scope: assists readability and understandingscope: assists readability and understanding

avoid more than three levels of nesting: complicated logic avoid more than three levels of nesting: complicated logic can be represented using other techniquescan be represented using other techniques

Stuctured English descriptions should illustrate the Stuctured English descriptions should illustrate the logiclogic of of the processing, not the the processing, not the implementation implementation of the processingof the processing


Decision TablesDecision Tables

decision tables are useful for describing processes decision tables are useful for describing processes where several different conditions apply and the where several different conditions apply and the particular actions that are taken are determined by particular actions that are taken are determined by combinations of the values of the conditionscombinations of the values of the conditions

decision tables are useful where the process logic is decision tables are useful where the process logic is complexcomplex

decision tables show all the possible choices and the decision tables show all the possible choices and the conditions they depend on in a tabular formconditions they depend on in a tabular form

Monash University, SIMS, Semester One, 2005

30

Decision Tables

decision tables have three stubs (four quadrants):

conditions rules

actions

outcomesfor each setof conditionvalues

combinations of condition values


31

Example Decision Table

avg account bal > $1,000

overdraft amount < $50,000previous paid-out loan

approve

conditional approval

reject

Y Y Y Y N N N N

Y Y N N Y Y N N

Y N Y N Y N Y N

X X

X

X

X

X X X


32

wholesalecustomer

retailcustomer

local item

local item

imported item

imported itemDetermine Customer Discount

15%

10%

12%

7%

decision trees are an alternative graphical representation of a decision situation as a connected series of nodes and branches

Decision Trees


Selecting Techniques for Selecting Techniques for Process DescriptionsProcess Descriptions

Structured English is useful where a process Structured English is useful where a process has a sequence of activities and there is no has a sequence of activities and there is no more than three levels of more than three levels of nesting of nesting of decisionsdecisions

decision trees and decision tables are useful decision trees and decision tables are useful where a process involves a decision based on where a process involves a decision based on combinations of values of several conditionscombinations of values of several conditions


Selecting Techniques for Process Selecting Techniques for Process DescriptionsDescriptions

decision trees visually distinguish the decision conditions decision trees visually distinguish the decision conditions and their values from the actions: and their values from the actions:

they show the paths that decisions can follow but soon they show the paths that decisions can follow but soon become cluttered if each condition has several possible become cluttered if each condition has several possible valuesvalues

decision tables are able to show decisions involving decision tables are able to show decisions involving many conditions each with many possible valuesmany conditions each with many possible values


Overview of Process ModellingOverview of Process Modelling

several techniques are available for representing several techniques are available for representing the processing within systemsthe processing within systems

the aim of process modelling in systems analysis the aim of process modelling in systems analysis is to define the processing that occurs within a is to define the processing that occurs within a systemsystem


models representing:models representing:

an overview of the system processing an overview of the system processing

the structure of the system processing the structure of the system processing

the flow of data into and out of the processes the flow of data into and out of the processes

the detailed logic of the processesthe detailed logic of the processes

can be constructedcan be constructed

Process Modelling TechniquesProcess Modelling Techniques


ReferencesReferences

HOFFER, J.A., GEORGE, J.F. and VALACICH (2005) 4th ed., HOFFER, J.A., GEORGE, J.F. and VALACICH (2005) 4th ed., Modern Systems Analysis and DesignModern Systems Analysis and Design, Benjamin/Cummings, , Benjamin/Cummings, Massachusetts.Massachusetts.

Chapter 8 Chapter 8

CSE1204 - Information Systems 1 Detailed Process Definitions; The Data Dictionary.

Documents

data dictionary data

data elements data elements

data elements data flows

data stores

data structures

unit of data

data dictionary entry

data dictionary entries