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PMP is a registered trademark of the Project Management Institute, Inc.

Precedence Diagramming Method

(PDM)

Four Types of

Logical Relationships – PMP®

Prep Topic

Saket Bansal

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Dependencies

Type of logical relationship

between two activities

defines how the depended

activity is constrained by

independent activity

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Dependent Watching Independent

Independent

Activity start or

finish does not

get impacted

because of the

relation

Dependent

Activity Start or

Finish is

influenced by the

relation

Activity A Activity B

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Predecessor and Successor

A predecessor activity is an activity that logically comes

before a dependent activity in a schedule. A successor

activity is a dependent activity that logically comes after

another activity on a schedule

Independent /

Predecessor

Dependent /

Successor

Activity A Activity B

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Four Types of logical Relationships

• Finish-to-start (FS)

• Finish-to-finish (FF)

• Start-to-start (SS)

• Start-to-finish (SF)

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Two Digits / Four Types

State of Independent

(Activity A) Activity on

which activity B is

dependent on

Constraint on

Dependent

activity (Activity B)

applied on

Finish (F)

Start (S)

Finish (F)

Start (S)

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Four types of logical relationships

S

F/S

Someone

watching my

finish

F

F/S

S

I can not finish

until my

predecessor

condition is met

I can not start

until my

predecessor

condition is met

Someone

watching my

start

F

FS

SS

FF

SF

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Finish to Start (FS)

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Finish to start (FS)

“A logical relationship in which a successor activity

cannot start until a predecessor activity has

finished.”

Activity A Activity B FS

Activity B is

watching my

finish date /

time I can not start

unit A

Finishes

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Finish to start (FS)

“A logical relationship in which a successor activity

cannot start until a predecessor activity has

finished.”

Activity A Activity B FS

Activity B is

watching my

finish date /

time I can not start

until A

Finishes

F S

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Example: Finish to Start

Development Activity can not be started until design is

finished. The design activity is expected to take 4 days

and development will take 10 days

Design : 4

(Independent)

Development :10

(Dependent)

Early Finish 4 Early Start 1

Early Start 5 Early Finish 14

FS

ES: Development

= Early Finish Design + 1

= 4+1

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Example: Finish to Start + Lag

Development Activity can not be started until one day

after design is finished. The design activity is expected to

take 4 days and development will take 10 days

Design : 4

(Independent)

Development:10

(Dependent)

Early Finish 4 Early Start 1

Early Start 6 Early Finish 15

FS + 1

ES: Development

= Early Finish Design + 1 + Lag

= 4+1 + 1

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Example: Finish to Start - Lead

Development Activity can not be started until one day

before design is finishing. The design activity is expected

to take 4 days and development will take 10 days

Design : 4

(Independent)

Development: 10

(Dependent)

Finish 4 Start 1

Start 4 Finish 13

FS - 1

ES: Development

= Early Finish Design + 1 - Lead

= 4+1 - 1

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Start-to-start (SS)

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Start-to-start (SS)

“A logical relationship in which a successor activity

cannot start until a predecessor activity has started.”

Activity A

Activity B

SS Activity B is

watching my

Start date /

time

I can not start

until A Starts

S

S

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Example: Start-to-start (SS)

The activity of marketing brochure preparation can not start

until user documentation activity has started. The

marketing brochure preparation activity is expected to take

4 days and user manual preparation will take 10 days

User Docs:10

Brochure:

4

Early Start 1 Early Finish 10

Early

Start 1

Early

Finish 4

ES Brochure =

ES: User Doc +/- Lag/Lead

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Finish-to-finish (FF)

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Finish-to-finish (FF)

“A logical relationship in which a successor activity

cannot finish until a predecessor activity has

finished.”

Activity A

Activity B

FF Activity B is

watching my

Finish date /

time

I can not

Finish until A

Finishes

F

F

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Example: Finish-to-finish (FF)

User Documentation activity can not finish

until development is finished. User

Documentation will take 10 days where

development will take 30 days.

Development: 30

User

Documentation

: 10

Early Start 1 Early Finish 30

Early

Finish 30

EF User Doc =

EF: Development +/- Lag/Lead

Early

Start 21

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Start-to-finish (SF)

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Start-to-finish (SF)

“A logical relationship in which a successor activity

cannot finish until a predecessor activity has

started.”

Activity A

Activity B

SF

Activity B is

watching my

Start date /

time I can not

Finish until A

Starts

S

F

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Example Start-to-finish (SF)

Support activity from development team can

not finish until production support Activity is

started . Production support is expected to

start on day 15.

Production Support

Development

Support: 10

Early Start 15

Early

Finish 14

EF Development Support =

ES: Production Support -1 +/- Lag/Lead

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Four Types of Logical Relationships

• Finish-to-start (FS)

• Finish-to-finish (FF)

• Start-to-start (SS)

• Start-to-finish (SF)

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