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Lecture Note 10

Describing Process Specifications

and Structured Decisions

Systems Analysis and Design

Kendall & Kendall

Sixth Edition

Part III: The Analysis Process


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Major Topics

Process Specifications

Business Rules

Structured English

Decision Tables

Decision Trees

Horizontal Balancing


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Process Specifications

What occurs within a process? How are the input data converted to

the output information? Since DFD are not really designed toshow the detailed logic of process.

Process specifications () are created for

processes and some higher level processes on a

DFD. They are also called minispecs. Explain :

the Decision-Making Logic,

Business Logic and

Formulas that will transform process input

data into output.

Each derived () element must have process

logic to show how it is produced from the base

elements.

1

?


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Goal of Creating Process Specifications

1. To reduce the ambiguity () of the process. Compels () the SA to learn details about how the

process works.

Any vague () areas should be noted, writtendown, and consolidated () for all process

specifications.2. To obtain a precise () description of what is

accomplished ().

3. To validate () the system design, including data

flow diagrams and the data dictionary. Ensures () that a process has all the input data flow

necessary for producing the output.

All input and output must be represented on the DFD.


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Process specifications are not created for:

Processes that represent physical input or

output, e.g. read, write. (Require only simplelogic).

Processes that represent simple data validation

(easy to accomplish). The edit criteria () areincluded in the data dictionary and

incorporated () into the computer source

code.

Processes that use prewritten () code(included in a system as subprograms and functions).

E.g. validating a date or a check digit.


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Data Flow Diagram and Process Specifications

The system analyst

approaching processspecifications and

structured decisions

has many options for

documenting andanalyzing them. The

methods available for

documenting and

analyzing the logical of

decisions include

Structured English,

Decision Tables and

Decision Tree.


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Process Specification Format

Process specifications link the process to the DFD and thedata dictionary. Each process specification should beentered on a separate form. (or into a case tool screen such as theone used for Visible Analyst)

The following information should be entered:

The process number, which must match the process IDon the DFD. This specification allows SA to work on orreview any process and easily locate the DFDcontaining the process.

Process name, the same as the name displayed withinthe process symbol on the DFD.

A briefdescription of what the process accomplishes.


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A list of input and output data flow, using the namesfound on the DFD. Data names used in the formula orlogic should match those in the data dictionary to

ensure consistency and good communication. The Output data flows, using DFD and data dictionary

names.

An indication if the type of process: Batch (), On-line or Manual. All on-line processes require screen

designs, and all manual processes should have well-defined procedures for employees performing () the

process tasks.

If the process uses prewritten code, include the name of

the subprogram or function containing that code. Data names used in the formulae or logic should matchthe data dictionary, for consistency and goodcommunication.


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A description of the process logic that states policy andbusiness rules, not computer language pseudocode.Common business rule formats include the following:

Definitions of business terms Business conditions and actions

Data integrity constraints

Mathematical and functional derivations

Logical inferences

Processing sequences

Relationships among facts about the business

If there is not enough room on the form for a completestructured English description or if there is a DecisionTable or Decision Tree depicting () the logic, includethe corresponding table or tree name.

List any unresolved issues(), incomplete portions oflogic or other concerns. These issues form the basis ()of the questions used for follow-up interviews.


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Process Specification

Example 1


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Structured English

It is special form of spoken English analyst use to illustrate

the logic of processes depicted in DFD. It is based on structured logic, or instructions organized into

nested and grouped procedures, sequence, conditionalstatement, repetition, and simple English statements.

It is primarily a communication technique for analysts and

user. It is an appropriate technique for analyzing the system when

structured decisions are not complex.

Sequence Structure Selection StructureIteration Structure


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Steps to Use Structured English The following steps are needed:

Express all logic in terms of sequential structures,decision structures, case structures, or iterations.

Use and capitalize accepted keywords such as IF,THEN, ELSE, DO, and PERFORM.

Indent() blocks of statements to show theirhierarchy () (nesting) clearly.

Underline words or phrases used have been defined ina data dictionary to signify that they have a specialized,reserved meaning.

Be careful when using AND" and OR ".

Avoid confusion() when using logical comparisonssuch as "greater than" and "greater than or equal toand Like relationships. So clarify the logicalstatements now rather than waiting until the programcoding stage.


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A Structured English Example 1:

The VERIFY ORDER process

description includes logical rulesand a structured English version

of the policy. Notice the

alignment and indentation of the

logic statements.

Structured

English

Statements


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A Structured English Example 2:We process all of our claims () in thismanner().

1. First we determine () whether the

claimant () has ever sent in a claim

before; if not, we set up a new record. The

claim totals for the year are then updated.

2. Next we determine if a claimant has policy

A or policy B, which differ() in

deductibles () and co-payments (the

percentage of the claim claimants pay

themselves). For both policies, we check to

see if the deductible has been met ($100 for

plan A and $50 for plan B). If the

deductible has not been met, we apply the

claim to the deductible.

3. Another step adjusts () for the co-

payment; we subtract () the percentage the

claimant pays (40% for plan A and 60% forplan B) from the claim.

4. Then we issue () a check if there is

money coming to the claimant, print a

summary of the transaction (), and

update our accounts. We do this until all

claims for that day are processed. The example demonstrates how a spoken procedure for processingmedical claims in transformed into structured English.


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Advantages of Structured English

Clarifying the logic and relationships found in

human languages

An effective communication tool, and easy toteach and understand.

Structured English might look familiar to

programming students because it resembles

pseudo code, which is used in program design.


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Data Dictionary and Structured English

All computer programs may be coded using the threebasic constructs: sequence, selection and iteration.The data dictionary indicates which of theseconstructs must be included in the processspecification.

The data dictionary is a starting point for creatingstructured English: Sequenced data dictionary entries become simple

structured English statements.

Selection [] entries become IF..THEN...ELSE statements.

Iteration { } entries become DO WHILE, DO UNTIL, orPERFORM UNTIL structured English statements.


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Decision Tables It is graphical methods for representing process logic.

It provide a way to examine, describe, and documentdecisions using a table.

They are used to: Describe the conditions.

Identify possible decision alternatives.

Indicate actions should be performed. Describe actions.

The standard format used for presenting a decision table.


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Decision Table Example 1

Rule 3: saysIf N (the total sale is NOT under $50)

AND

If Y (the customer paid by check and had

two forms of ID )

AND

If N (the customer did not use a credit card)

THEN

DO X ( call the supervisor for approval)

conditions

Actions

Decision alternatives


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Developing Decision Tables

Determine the number of conditions that may affect ()

the decision. Combine () rows that overlap (). Determine the number of actions that can be taken.

Determine the number of condition alternatives (Y, N) foreach condition.

Calculate the maximum number of columns in the decisiontable by multiplying () the number of alternatives for eachcondition.

Condition 1: 2 alternatives

Condition 2: 2 alternativesCondition 3: 2 alternatives

Condition 4: 2 alternatives

24 =16 possibilities


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5. Fill in the condition alternatives. Start with the 1st conditionand divide the number of columns by the number ofalternatives for that condition.

6. Complete the table by inserting an X where rules suggestactions.

7. Combine rules where it is apparent () that an alternativedoes not make a difference in the outcome ().

8. Check the table for any impossible situations, contradictions (), and redundancies ().

9. Rearrange () the conditions and actions if this makes thedecision table more understandable.

Condition 1: YY

Condition 2: YNAction 1: XX

Condition 1: Y

Condition 2:

Action 1: X

Condition 1: YYYYYYYYNNNNNNNN

Condition 1: YYYYYYYYNNNNNNNN

Condition 2: YYYYNNNNYYYYNNNN

Condition 3: YYNNYYNNYYNNYYNN

Condition 4: YNYNYNYNYNYNYNYN


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Creating the Decision Table Example 1

For each ORDER

IF CUSTOMER STATUS CODE = Y and IF PRODUCT DETAIL = OKOutput ACCEPTED ORDER

ELSE

Output REJECTED ORDER

Structured English Statements

1

2 3

4

1. Place the

name of the

process in a

heading at the

top left.

2. Enter the conditions under

the heading, with one

condition per line, to

represent the customer status

and available of products.

3. Enter the potential

combinations of Y/N for the

conditions. Each column

represents a numbered

possibility called a rule.

4. Place an X in the

action entries area for

each rule to indicate

whether to accept or

reject the order.

Four columns = (2 alternatives 2 alternatives)


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Decision Table Example 2

This tables an

illustration of a decisiontable. The company is

trying to maintain a

meaningful mailing list

of customers. The

objective is to send outonly the catalogs from

which customers will

buy merchandise.

A decision table is constructed for three conditions, each having twoalternatives (Y or N). Three actions can be taken. The regular

decision table has six rows (3 conditions and 3 actions) and eight

columns (2 alternatives 2 alternatives2 alternatives).


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Rules 2,4,6 and 8 can be combined because they all have two things in common:

1. They instruct us to send out this years Christmas catalog.

2. The alternative for Condition 3 is always N


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Suppose the rule is:

IF the customer did not order more than $50

THEN do not send any catalogs


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Checking for Completeness and Accuracy

Decision tables help analysts ensurecompleteness and accuracy.

Four main problems that can occur indeveloping decision tables:

Incompleteness. Impossible situations.

Contradictions ().

Redundancy.


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Rule 1 is not feasible, because a

person cannot earn greater than

$50,000 per year and less than

$2,000 per month at the sametime.

Contradictions often occur of dashes

[--] are incorrectly inserted into the

table. Redundancy occurs when

identical sets of alternatives requirethe exact same action. The analyst has

to determine what is correct and then

resolve the contradiction or

redundancy.


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More Advanced Decision Tables Decision tables can become very big because they grow rapidly

as the number of conditions and alternatives increases. In order to avoid a decision table to grow rapidly, we can use

Extended Entries orELSE rule.

C1: Did not order YNNN

C2: Ordered once NYNN

C3: Ordered twice NNYY

C4: Ordered more than twice NNNY

C1: Number of times customer ordered 0 1 2 >2

1. Extended entries: to reduce the possibility of redundancy

and contradiction.

Example:

The number of required columns and rows decreases and the

understandability increases. Instead of using four rows for the number of

timers a customer orders, only one row is needed.


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An example of a structured inventory ordering policy.


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2. ELSE Rule: to eliminate repetitive rules

requiring the exact same action.


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Decision Trees

Decision tree is a graphical representation of a

decision situation. Decision trees are used when complex

branching occurs in a structured decisionprocess.

Trees are also useful when it is essential tokeep a string of decisions in a particularsequence.

Decision tree are most often drawn with theroot of the tree on the left side and the tree

branches out to the right. This orientationallows the analyst to write on the branches todescribe conditions and actions.


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Drawing Decision Trees

First, identify all conditions and actions and the order and

timing of these (if they are critical). Second, begin building the tree from left to right while

making sure you are complete in listing all possible

alternatives before moving over to the right.

A square node indicates an action (THEN). A circle to represent a condition (IF).

Numbering the circles and squares sequentially.

D i i T E l 1


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Decision Tree Example 1

A point-of-sale example was used to determine the purchase

approval () actions for a department store. Conditions

included the amount of the sale (under $50) and whether thecustomer paid by check or credit card. The four actions possible

were to ring up the sale, look up the credit card in a book, call

the supervisor for approval, or call the bank for credit card

authorization.


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Decision Tree Advantages

Three advantages over a decision table are:

The order of checking conditions and executing

actions is immediately noticeable ().

Second, conditions and actions of decision trees are

found on some branches but not on others, which

contrasts with decision tables, in which they are all

part of the same table. Those conditions and actions

that are critical are connected directly to other

conditions and actions. The tree does not have to be

symmetrical ().

Third, compared to decision tables, decision trees are

more readily understood by others in the organization.


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Selecting a Structured Decision Analysis Technique

Guidelines are as follows:

Use structured English when there are manyrepetitious actions or when communication toend users is important.

Use decision tables when complex combinationof conditions, actions, and rules are found oryou require a method that effectively avoidsimpossible situations, redundancies, andcontradictions.

Use decision trees when the sequence ofconditions and actions is critical or when notevery condition is relevant to every action (the

branches are different).


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Using Process Specifications

All the process specifications are consolidated () for acomputer program and are included in the specificationpacket given to the computer programmer.

Process specifications may be used for generating ()computer language source code and for analyzing the

system design. Process specifications are developed on a small scale (

), one process at a time, each one may be analyzed forcomplete and correct logic. The logic is easier tounderstand.

When the SA is finished and corrections are made for allprocesses within a program, the final programspecifications should be complete and accurate.


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Horizontal () Balancing

It is used to verify that each process has the required datadictionary entries defined and the formulas and logicnecessary to produce the output.

Process specifications may be used to analyze the DFD anddata dictionary through a method called horizontal balancing.

Horizontal balancing dictates () that all output data-flow

elements must be obtained from the input elements andprocess logic.

Base elements on an output data flow must be present () onthe input flow.

Derived elements on an output flow must be either present onan input data flow or created using the process specifications.

Unresolved areas should be summarized into a series ofinterview questions.

H St t d E li h h l l t th DFD


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How Structured English can help us complete the DFD.


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Shows corresponding data

dictionary entries forproducing the Supplier Sales

Receipt.


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R i Q ti


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Review Question List the three reasons for producing process specifications.

What is the advantage of using structured English to

communicate with people in the organization? What three advantages do decision trees have over decision

tables?

In which two situations should you use structured English?(when many actions are repeated and when communicating with others isimportant)

In which two situations do decision tables work best?

(When complex combinations of conditions, actions, and rules are found or yourequire a method that effectively avoids impossible situations, redundancies, andcontradictions.)

In which two situations are decision trees preferable? (when the

sequence of conditions and actions is critical or not every condition is relevant toevery action )

What four elements must be known for the systems analyst todesign systems for structured decisions?

(Conditions, Condition Alternatives, Actions, and Action Rules)

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