SAP BW Tutorial Best Practice on Project Management Forward Pass Analysis

Table of Contents

Scheduling Forward Pass Analysis Tutorial

This is a continuation of the SAP BW Best Practice Series on SAP Project Management. In this article I review the Scheduling Forward Pass Analysis technique. As a Project Manager, sooner or later, you will have to consider how you are going to schedule your project and this blog discusses one part of the overall scheduling process. 

Avoid Bad Starts With a Forward Pass Analysis

If you are in the middle of development for your next Go-Live or doing an upgrade of an existing SAP BW or Business Objects dashboard system or working on any type of greenfield or ongoing ERP project, I recommend taking a look at this Forward Pass Analysis discussion to avoid a bad start. We have worked with this method and it works fine in the field and we have discovered that what looks to be the obvious schedule in the beginning is not always the correct schedule once a proper analysis has been performed. In this Article, I present Project Forward Pass Analysis practices, a very important and necessary project management planning stage to your overall project success.—

 

1 Key Tip When Upgrading from SAP BW 3.X to BW 7.X [Checklist]

 

FORWARD PASS ANALYSIS

 

A Forward Pass Analysis is a systematic method of walking through a Work Breakdown Structure (WBS) Network Diagram in order to calculate the Early Start Times and Early Finish Times of each network diagram node element based on estimated WBS Dictionary Element or WBS Task Durations.

The Early Start time (ES) informs the Project Manager how early a task can start. The Early Finish time (EF) informs the Project Manager how early a task is expected to finish given the Task’s expected start time and estimated Duration.

WBS Activity Network Diagram Node Representation

Each WBS Activity Network diagram node can be represented using the following convenient format with the forward pass Early Start (ES), Task Duration (D) and Early Finish (EF) times listed along the top row while the WBS Element Task Name is displayed in the center row and the reverse pass Late Start (LS), Slack (S) and Late Finish (LF) times are listed along the bottom row.

First Pass Legend

 

BASIC FORWARD PASS FORMULAS

The basic forward pass Early Start and Early Finish time formulas are as follows:

  • Early Finish (task) = Early Start (task) + Duration (task)

  • Early Start (next task) = Early Finish (previous task) + 1

It is assumed that each task ends at the close of each business day. However, you can make whatever assumption you want, just make sure you adjust the math accordingly. For this reason, 1 is added to the Early Finish time of the previous task in order to advance the Early Start time of the current task to coincide with the start of the next business day.

The one complication with the forward pass analysis occurs when a task has more than one predecessor activity and we must choose the correct Early Finish time to use in the Early Start calculation. Luckily, we have a rule of thumb that gives us a way out of this conundrum.

FORWARD PASS – RULE OF THUMB

For each node with more than 1 predecessor activity, chose the largest Early Finish time of all connecting predecessor activities.

What this rule of thumb means is that a task has an AND relationship with all predecessor activities.

This AND relationship blocks this task from starting until all predecessor activities have finished. The current task can’t be started until all the dependency tasks have completed.

In order to find the Largest Early Finish time of all connecting predecessor activities, the Project Manager has two options. The first option is to perform two complete forward passes and them make time adjustments according to the rule of thumb. This results in a second forward pass analysis once the correct predecessor activity time is chosen. In the second option the project manager can simply perform a partial forward pass for all predecessor activity network paths and then apply the rule of thumb. Either method will work fine and gives the same results.

FORWARD PASS – TIME ZERO ELEMENT

The Early Start (ES) time of the first WBS Dictionary Node Element is assumed to be Zero (0) time.

When it becomes time to set up the project schedule, this time zero element will simply be overlaid onto an actual calendar as the project starting point.

FORWARD PASS – GO-HIGH METHOD

When identifying the paths in the Network Diagram, by always traversing from left to right and upward (go-high) along untraveled paths, this is an error free method to ensure that all paths have been identified and that no path has been missed.

Download a Free Project Management Forward Pass Analysis Tool


The following Sample WBS Activity Network Diagram is repeated here as a reference of our starting point. When finished I will provide the true and correct Project Network Diagram after all the times have been adjusted properly.  Notice that this diagram has five special case nodes shown in Red and Green that require special handling.

Sampel WBS

 

Sample WBS Activity Network Diagram

  

HOW TO CALCULATE EARLY START (ES) and EARLY FINISH (EF) TIMES

Now that we have explained the benefits of the Early Start Times and Early Finish Times, covered the basics of the Forward Pass Analysis and provided some useful rules of thumb to keep in mind when performing a forward pass, we will now continue our analysis of the seven project network paths in our sample project starting with Path-1.

 

PATH-1, FORWARD PASS

Given:

Path-1 = 1.1, 1.2, 1.3, 1.4, 2.2, 2.3, 2.4, 2.5, 3.1, 3.2, 3.3, 3.4, 3.6, 4.2, 4.3

Path-1 = 8 + 128 + 8 + 32 + 40 + 8 + 24 + 8 + 4 + 4 + 4 + 4 + 8 + 8 + 8                   = 296 Hours

perform the Forward Pass.

 

PATH-1, INITIAL CONDITION

First we start with Element 1.1 (moving from left to right). Since WBS Element 1.1 is the first activity and has no predecessor activity the Early Start (ES) time of element 1.1 is defined as zero or ES(1.1) = 0. This is in line with the rule of thumb Forward Pass – Time Zero Element which states The Early Start (ES) time of the first WBS Dictionary Node Element is assumed to be Zero (0) time.

Since we also know from the WBS dictionary, the estimated duration (D) of element 1.1 is 8 hours we can now calculate the Early Finish (EF) time of element 1.1 to be EF(1.1) = Early Start(1.1)+ Duration(1.1) = ES(1.1) + D(1.1)= 8 + 0 = 8 hours. The following diagram summarizes our results for WBS Element Task (1.1).

Initial Condition

 

Moving to element 1.2, we see element 1.2 cannot start until element 1.1 has finished (it has a dependent predecessor activity) and that element 1.1 is the only predecessor with a duration of 8 hours, so WBS Element (1.2) will start on hour 9.

The Early Start of Element ES(1.2) = EF(1.1) + 1 = 9 and the Early Finish of Element 1.2 = ES(1.2) + Duration (1.2) = 9 + 128 = 137.

Completing the forward pass exercise for all the other elements in Path-1, we get the following Forward Pass analysis results:

1)     Element 1.1: ES(1.1) = 0,

2)                             EF(1.1) = ES(1.1) + D(1.1) = 0 + 8 = 8

3)      

4)     Element 1.2: ES(1.2) = EF(1.1) + 1 = 8 + 1 = 9

5)                             EF(1.2) = ES(1.2) + D(1.2) = 9 + 128 = 137

6)      

7)     Element 1.3: ES(1.3) = EF(1.2) + 1 = 138

8)                             EF(1.3) = ES(1.3) + D(1.3) = 138 + 8 = 146

9)      

10)  Element 1.4: ES(1.4) = EF(1.3) + 1 = 147

11)                         EF(1.4) = ES(1.4) + D(1.4) = 147 + 32 = 179

12)   

13)  Element 2.2: ES(2.2) = EF(1.4) + 1 = 180

14)                          EF(2.2) = ES(2.2) + D(2.2) = 180 + 40 = 220

15)   

16)  Element 2.3: ES(2.3) = EF(2.2) + 1 = 221

17)                          EF(2.3) = ES(2.3) + D(2.3) = 221 + 8 = 229

18)   

19)  Element 2.4: ES(2.4) = EF(2.3) + 1 = 230

20)                          EF(2.4) = ES(2.4) + D(2.4) = 230 + 24 = 254

21)   

22)  Element 2.5: ES(2.5) = EF(2.4) + 1 = 255

23)                          EF(2.5) = ES(2.5) + D(2.5) = 255 + 8 = 263

24)   

25)  Element 3.1: ES(3.1) = EF(2.5) + 1 = 264

26)                          EF(3.1) = ES(3.1) + D(3.1) = 264 + 4 = 268

27)   

28)  Element 3.2: ES(3.2) = EF(3.1) + 1 = 269

29)                          EF(3.2) = ES(3.2) + D(3.2) = 269 + 4 = 273

30)   

31)  Element 3.3: ES(3.3) = EF(3.2) + 1 = 274

32)                          EF(3.3) = ES(3.3) + D(3.3) = 274 + 4 = 278

33)   

34)  Element 3.4: ES(3.4) = EF(3.3) + 1 = 279

35)                          EF(3.4) = ES(3.4) + D(3.4) = 279 + 4 = 283

36)   

37)  Element 3.6: ES(3.6) = EF(3.4) + 1 = 284

38)                          EF(3.6) = ES(3.6) + D(3.6) = 284 + 8 = 292

39)   

40)  Element 4.2: ES(4.2) = EF(3.6) + 1 = 293

41)                          EF(4.2) = ES(4.2) + D(4.2) = 293 + 8 = 301

42)   

43)  Element 4.3: ES(4.3) = EF(4.2) + 1 = 302

44)                          EF(4.3) = ES(4.3) + D(4.3) = 302 + 8 = 310

This is the results of the initial forward pass for Path-1. We can see from the sequence diagram that WBS Element (2.4) and WBS Element (3.6) have more than 1 predecessor activity. For this reason, we cannot completely analyze Path-1 until we have completed the forward pass for all predecessor activities to Elements 2.4 and 3.6. Once we have those partial forward pass results, we can then adjust the Early Start times of Elements 2.4 and 3.6 and then complete the Forward Pass Path-1 analysis. Once that is done, we can then repeat the same processes with Path-2 through Path-7.

PATH-2, FORWARD PASS

Given:

Path-2 = 1.1, 1.2, 1.3, 1.5, 2.4, 2.5, 3.1, 3.2, 3.3, 3.4, 3.6, 4.2, 4.3

Path-2 Durations = 8 + 128 + 8 + 32 + 24 + 8 + 4 + 4 + 4 + 4 + 8 + 8 + 8                               = 248 Hours

Perform the Forward Pass.

We get the following Forward Pass analysis results for Path-2:

1)     Element 1.1: ES(1.1) = 0

2)                             EF(1.1) = ES(1.1) + D(1.1) = 0 + 8 = 8

3)      

4)     Element 1.2: ES(1.2) = EF(1.1) + 1 = 8 + 1=9

5)                             EF(1.2) = ES(1.2) + D(1.2) = 9 + 128 = 137

6)      

7)     Element 1.3: ES(1.3) = EF(1.2) + 1 = 138

8)                             EF(1.3) = ES(1.3) + D(1.3) = 138 + 8 = 146

9)      

10)  Element 1.5: ES(1.5) = EF(1.3) + 1 = 147

11)                          EF(1.5) = ES(1.5) + D(1.5) = 147 + 32 = 179

12)   

13)  Element 2.4: ES(2.4) = EF(1.5) + 1 = 180

14)                          EF(2.4) = ES(2.4) + D(2.4) = 180 + 24 = 204

15)   

16)  Element 2.5: ES(2.5) = EF(2.4) + 1 = 205

17)                          EF(2.5) = ES(2.5) + D(2.5) = 205 + 8 = 213

18)   

19)  Element 3.1: ES(3.1) = EF(2.5) + 1 = 214

20)                          EF(3.1) = ES(3.1) + D(3.1) = 214 + 4 = 218

21)   

22)  Element 3.2: ES(3.2) = EF(3.1) + 1 = 219

23)                          EF(3.2) = ES(3.2) + D(3.2) = 219 + 4 = 223

24)   

25)  Element 3.3: ES(3.3) = EF(3.2) + 1 = 224

26)                          EF(3.3) = ES(3.3) + D(3.3) = 224 + 4 = 228

27)   

28)  Element 3.4: ES(3.4) = EF(3.3) + 1 = 229

29)                          EF(3.4) = ES(3.4) + D(3.4) = 229 + 4 = 233

30)   

31)  Element 3.6: ES(3.6) = EF(3.4) + 1 = 234

32)                          EF(3.6) = ES(3.6) + D(3.6) = 234 + 8 = 242

33)   

34)  Element 4.2: ES(4.2) = EF(3.6) + 1 = 243

35)                          EF(4.2) = ES(4.2) + D(4.2) = 243 + 8 = 251

36)   

37)  Element 4.3: ES(4.3) = EF(4.2) + 1 = 252

38)                          EF(4.3) = ES(4.3) + D(4.3) = 252 + 8 = 260

39)   

 

PATH-3, FORWARD PASS

Given:

Path-3 = 1.1, 1.2, 1.3, 1.6, 2.4, 2.5, 3.1, 3.2, 3.3, 3.4, 3.6, 4.2, 4.3

Path-3 Durations = 8 + 128 + 8 + 4 + 24 + 8 + 4 + 4 + 4 + 4 + 8 + 8 + 8                                  = 220 Hours

perform the Forward Pass.

We get the following Forward Pass analysis results for Path-3:

1)     Element 1.1: ES(1.1) = 0,

2)                             EF(1.1) = ES(1.1) + D(1.1) = 0 + 8 = 8

3)      

4)     Element 1.2: ES(1.2) = EF(1.1) + 1 = 8 + 1=9

5)                             EF(1.2) = ES(1.2) + D(1.2) = 9 + 128 = 137

6)      

7)     Element 1.3: ES(1.3) = EF(1.2) + 1 = 138

8)                             EF(1.3) = ES(1.3) + D(1.3) = 138 + 8 = 146

9)      

10)  Element 1.6: ES(1.6) = EF(1.3) + 1 = 147

11)                          EF(1.6) = ES(1.6) + D(1.6) = 147 + 4 = 151

12)   

13)  Element 2.4: ES(2.4) = EF(1.6) + 1 = 152

14)                          EF(2.4) = ES(2.4) + D(2.4) = 152 + 24 = 176

15)   

16)  Element 2.5: ES(2.5) = EF(2.4) + 1 = 177

17)                          EF(2.5) = ES(2.5) + D(2.5) = 177 + 8 = 185

18)   

19)  Element 3.1: ES(3.1) = EF(2.5) + 1 = 186

20)                          EF(3.1) = ES(3.1) + D(3.1) = 186 + 4 = 190

21)   

22)  Element 3.2: ES(3.2) = EF(3.1) + 1 = 191

23)                          EF(3.2) = ES(3.2) + D(3.2) = 191 + 4 = 195

24)   

25)  Element 3.3: ES(3.3) = EF(3.2) + 1 = 196

26)                          EF(3.3) = ES(3.3) + D(3.3) = 196 + 4 = 200

27)   

28)  Element 3.4: ES(3.4) = EF(3.3) + 1 = 201

29)                          EF(3.4) = ES(3.4) + D(3.4) = 201 + 4 = 205

30)   

31)  Element 3.6: ES(3.6) = EF(3.4) + 1 = 206

32)                          EF(3.6) = ES(3.6) + D(3.6) = 206 + 8 = 214

33)   

34)  Element 4.2: ES(4.2) = EF(3.6) + 1 = 215

35)                          EF(4.2) = ES(4.2) + D(4.2) = 215 + 8 = 223

36)   

37)  Element 4.3: ES(4.3) = EF(4.2) + 1 = 224

38)                          EF(4.3) = ES(4.3) + D(4.3) = 224 + 8 = 232

39)   

 

PATH-4, FORWARD PASS

Given:

Path-4 = 1.1, 1.2, 1.3, 2.1, 2.4, 2.5, 3.1, 3.2, 3.3, 3.4, 3.6, 4.2, 4.3

Path-4 Durations = 8 + 128 + 8 + 4 + 24 + 8 + 4 + 4 + 4 + 4 + 8 + 8 + 8                                  = 220 Hours

Perform the Forward Pass.

 

We get the following Forward Pass analysis results for Path-4:

1)     Element 1.1: ES(1.1) = 0,

2)                             EF(1.1) = ES(1.1) + D(1.1) = 0 + 8 = 8

3)      

4)     Element 1.2: ES(1.2) = EF(1.1) + 1 = 8 + 1=9

5)                             EF(1.2) = ES(1.2) + D(1.2) = 9 + 128 = 137

6)      

7)     Element 1.3: ES(1.3) = EF(1.2) + 1 = 138

8)                             EF(1.3) = ES(1.3) + D(1.3) = 138 + 8 = 146

9)      

10)  Element 2.1: ES(2.1) = EF(1.3) + 1 = 147

11)                          EF(2.1) = ES(2.1) + D(2.1) = 147 + 4 = 151

12)   

13)  Element 2.4: ES(2.4) = EF(2.1) + 1 = 152

14)                          EF(2.4) = ES(2.4) + D(2.4) = 152 + 24 = 176

15)   

16)  Element 2.5: ES(2.5) = EF(2.4) + 1 = 177

17)                          EF(2.5) = ES(2.5) + D(2.5) = 177 + 8 = 185

18)   

19)  Element 3.1: ES(3.1) = EF(2.5) + 1 = 186

20)                          EF(3.1) = ES(3.1) + D(3.1) = 186 + 4 = 190

21)   

22)  Element 3.2: ES(3.2) = EF(3.1) + 1 = 191

23)                          EF(3.2) = ES(3.2) + D(3.2) = 191 + 4 = 195

24)   

25)  Element 3.3: ES(3.3) = EF(3.2) + 1 = 196

26)                          EF(3.3) = ES(3.3) + D(3.3) = 196 + 4 = 200

27)   

28)  Element 3.4: ES(3.4) = EF(3.3) + 1 = 201

29)                          EF(3.4) = ES(3.4) + D(3.4) = 201 + 4 = 205

30)   

31)  Element 3.6: ES(3.6) = EF(3.4) + 1 = 206

32)                          EF(3.6) = ES(3.6) + D(3.6) = 206 + 8 = 214

33)   

34)  Element 4.2: ES(4.2) = EF(3.6) + 1 = 215

35)                          EF(4.2) = ES(4.2) + D(4.2) = 215 + 8 = 223

36)   

37)  Element 4.3: ES(4.3) = EF(4.2) + 1 = 224

38)                          EF(4.3) = ES(4.3) + D(4.3) = 224 + 8 = 232

39)   

PATH-5, FORWARD PASS

Given:

Path-5 = 1.1, 1.2, 1.3, 2.6, 2.4, 2.5, 3.1, 3.2, 3.3, 3.4, 3.6, 4.2, 4.3

Path-5 Durations = 8 + 128 + 8 + 8 + 24 + 8 + 4 + 4 + 4 + 4 + 8 + 8 + 8                                  = 224 Hours

Perform the Forward Pass.

 

We get the following Forward Pass analysis results for Path-5:

1)     Element 1.1: ES(1.1) = 0,

2)                             EF(1.1) = ES(1.1) + D(1.1) = 0 + 8 = 8

3)      

4)     Element 1.2: ES(1.2) = EF(1.1) + 1 = 8 + 1=9

5)                             EF(1.2) = ES(1.2) + D(1.2) = 9 + 128 = 137

6)      

7)     Element 1.3: ES(1.3) = EF(1.2) + 1 = 138

8)                             EF(1.3) = ES(1.3) + D(1.3) = 138 + 8 = 146

9)      

10)  Element 2.6: ES(2.6) = EF(1.3) + 1 = 147

11)                          EF(2.6) = ES(2.6) + D(2.6) = 147 + 8 = 155

12)   

13)  Element 2.4: ES(2.4) = EF(2.6) + 1 = 155

14)                          EF(2.4) = ES(2.4) + D(2.4) = 155 + 24 = 179

15)   

16)  Element 2.5: ES(2.5) = EF(2.4) + 1 = 180

17)                          EF(2.5) = ES(2.5) + D(2.5) = 180 + 8 = 188

18)   

19)  Element 3.1: ES(3.1) = EF(2.5) + 1 = 189

20)                          EF(3.1) = ES(3.1) + D(3.1) = 189 + 4 = 193

21)   

22)  Element 3.2: ES(3.2) = EF(3.1) + 1 = 194

23)                          EF(3.2) = ES(3.2) + D(3.2) = 194 + 4 = 198

24)   

25)  Element 3.3: ES(3.3) = EF(3.2) + 1 = 199

26)                          EF(3.3) = ES(3.3) + D(3.3) = 199 + 4 = 203

27)   

28)  Element 3.4: ES(3.4) = EF(3.3) + 1 = 204

29)                          EF(3.4) = ES(3.4) + D(3.4) = 204 + 4 = 208

30)   

31)  Element 3.6: ES(3.6) = EF(3.4) + 1 = 209

32)                          EF(3.6) = ES(3.6) + D(3.6) = 209 + 8 = 217

33)   

34)  Element 4.2: ES(4.2) = EF(3.6) + 1 = 218

35)                          EF(4.2) = ES(4.2) + D(4.2) = 218 + 8 = 226

36)   

37)  Element 4.3: ES(4.3) = EF(4.2) + 1 = 227

38)                          EF(4.3) = ES(4.3) + D(4.3) = 227 + 8 = 235

 

PATH-6, FORWARD PASS

Given:

Path-6 = 1.1, 1.2, 3.5, 3.6, 4.2, 4.3

Path-6 Durations = 8 + 128 + 4 + 8 + 8 + 8                                                                                                           = 164 Hours

Perform the Forward Pass.

 

We get the following Forward Pass analysis results for Path-6:

1)     Element 1.1: ES(1.1) = 0,

2)                             EF(1.1) = ES(1.1) + D(1.1) = 0 + 8 = 8

3)      

4)     Element 1.2: ES(1.2) = EF(1.1) + 1 = 8 + 1=9

5)                             EF(1.2) = ES(1.2) + D(1.2) = 9 + 128 = 137

6)      

7)     Element 3.5: ES(3.5) = EF(1.2) + 1 = 138

8)                             EF(3.5) = ES(3.5) + D(3.5) = 138 + 4 = 142

9)      

10)  Element 3.6: ES(3.6) = EF(3.5) + 1 = 143

11)                          EF(3.6) = ES(3.6) + D(3.6) = 143 + 8 = 151

12)   

13)  Element 4.2: ES(4.2) = EF(3.6) + 1 = 152

14)                          EF(4.2) = ES(4.2) + D(4.2) = 152 + 8 = 160

15)   

16)  Element 4.3: ES(4.3) = EF(4.2) + 1 = 161

17)                          EF(4.3) = ES(4.3) + D(4.3) = 161 + 8 = 169

18)   

Finally we reach Path-7.

PATH-7, FORWARD PASS

Given:

Path-7 = 1.1, 1.2, 4.1, 3.5, 3.6, 4.2, 4.3

Path-7 Durations = 8 + 128 + 120 + 4 + 8 + 8 + 8                                                                            = 284 Hours

Perform the Forward Pass.

 

We get the following Forward Pass analysis results for Path-7:

1)     Element 1.1: ES(1.1) = 0,

2)                             EF(1.1) = ES(1.1) + D(1.1) = 0 + 8 = 8

3)      

4)     Element 1.2: ES(1.2) = EF(1.1) + 1 = 8 + 1=9

5)                             EF(1.2) = ES(1.2) + D(1.2) = 9 + 128 = 137

6)      

7)     Element 4.1: ES(4.1) = EF(1.2) + 1 = 138

8)                             EF(4.1) = ES(4.1) + D(4.1) = 138 +120 = 258

9)      

10)  Element 3.5: ES(3.5) = EF(4.1) + 1 = 259

11)                          EF(3.5) = ES(3.5) + D(3.5) = 259 + 4 = 263

12)   

13)  Element 3.6: ES(3.6) = EF(3.5) + 1 = 264

14)                          EF(3.6) = ES(3.6) + D(3.6) = 264 + 8 = 272

15)   

16)  Element 4.2: ES(4.2) = EF(3.6) + 1 = 273

17)                          EF(4.2) = ES(4.2) + D(4.2) = 273 + 8 = 281

18)   

19)  Element 4.3: ES(4.3) = EF(4.2) + 1 = 282

20)                          EF(4.3) = ES(4.3) + D(4.3) = 282 + 8 = 290

21)   

 

Table 1 summarizes the results of the first pass through the Forward Pass.

 

 

WBS Element Code

Description of Work

WBS Element Code

Dependencies

Estimated

Time Hrs

(Duration)

Forward Pass One

Early Start (ES)

Early Finish (EF)

1.0

 

 

 

 

 

1.1

Task A

None

8

0

8

1.2

Task B

1.1

128

9

137

1.3

Task C

1.2

8

138

146

1.4

Task D

1.3

32

147

179

1.5

Task E

1.3

32

147

179

1.6

Task F

1.3

4

147

151

2.0

 

 

 

 

 

2.1

Task G

1.3

4

147

151

2.2

Task H

1.4

40

180

220

2.3

Task I

2.2

8

221

229

2.4

Task J

2.3, 1.5, 1.6, 2.1, 2.6

24

230

254

2.5

Task K

2.4

8

255

263

2.6

Task L

1.3

8

147

155

3.0

 

 

 

 

 

3.1

Task M

2.5

4

264

268

3.2

Task N

3.1

4

269

273

3.3

Task O

3.2

4

274

278

3.4

Task P

3.3

4

279

283

3.5

Task Q

1.2, 4.1

4

138

142

3.6

Task R

3.5, 3.4

8

284

292

4.0

 

 

 

 

 

4.1

Task S

1.2

120

138

258

4.2

Task T

3.6

8

293

301

4.3

Task U

4.2

8

302

310

Total

 

 

468 hours

 

 

Table 1.

Special Cases, Adjusting the Forward Pass times.

The following chart shows the unadjusted First Pass, Early Finish (EF) times for each node element.

Special Case Adjust Forward Pass Times

 

We can see that Element (2.4), Element (3.5) and Element (3.6) each have more than one predecessor activities. These three elements require a second Forward Pass to properly adjust their Early Start and Early Finish times.

Element (2.4) Special Case

Element (2.4) has five connecting predecessor activities:

  • Element (2.3) on Path-1 with an Early Finish Time of 229
  • Element (1.5) on Path-2 with an Early Finish time of 179
  • Element (1.6) on Path-3 with an Early Finish time of 151
  • Element (2.1) on Path-4 with an Early Finish time of 151
  • Element (2.6) on Path-6 with an Early Finish time of 155

SAP Project Node

 

Referring to the RULE that says : For each node with more than 1 predecessor activity, when selecting the Early Start (ES) time for that node, choose the largest Early Finish time of all connecting predecessor activities.

Since Element (2.3) has the largest Early Finish Time of 229, then 229+1 = 230 is the correct Early Start Time to use for Element(2.4).

 

Element (3.5) Special Case

Element(3.5) has two predecessor activities:

  • Element (1.2) on Path-1 with an Early Finish Time of 137
  • Element (4.1) on Path-7 with an Early Finish time of 258

SAP Project Special Case

 

Referring to the RULE that says : For each node with more than 1 predecessor activity, when selecting the Early Start (ES) time for that node, choose the largest Early Finish time of all connecting predecessor activities.

Since Element (4.1) has the largest Early Finish Time of 258, then 258+1 = 259 is the correct Early Start Time to use for Element(3.5) resulting in a new Early Finish time of Element (3.5) = 263.

 

Element (3.6) Special Case

Element(3.6) has two predecessor activities:

  • Element (3.4) on Path-1 with an Early Finish Time of 283
  • Element (3.5) on Path-5 with an Early Finish time of 263

 

Project Element

SAP Project Special Case                                                         

 

 

 

 

 

 

 

Referring to the RULE that says : For each node with more than 1 predecessor activity, when selecting the Early Start (ES) time for that node, choose the largest Early Finish time of all connecting predecessor activities.

Since Element (3.4) has the largest Early Finish Time of 283, then 283+1 = 284 is the correct Early Start Time to use for Element(3.6) with an Early Finish time of Element(3.6) of 292.

To complete the forward pass analysis, it is necessary to go through all seven paths and to make time adjustments as we have done with Path-1. The following chart and table summarizes the final Forward Pass results for all 7 Project WBS Network Diagram Nodes.

SAP Project Planning

 

Completed WBS Network Diagram after completing the Forward Pass Analysis

 

We can also summarize and update the results of the Forward Pass Analysis in the WBS Dictionary.

 

WBS Element Code

Description of Work

WBS Element Code

Dependencies

Estimated

Time Hrs

(Duration)

Forward Pass

Reverse Pass

Early Start (ES)

Early Finish (EF)

Late Start (LS)

Late Finish (LF)

1.0

 

 

 

 

 

 

 

1.1

Task A

None

8

0

8

 

 

1.2

Task B

1.1

128

9

137

 

 

1.3

Task C

1.2

8

138

146

 

 

1.4

Task D

1.3

32

147

179

 

 

1.5

Task E

1.3

32

147

179

 

 

1.6

Task F

1.3

4

147

151

 

 

2.0

 

 

 

 

 

 

 

2.1

Task G

1.3

4

147

151

 

 

2.2

Task H

1.4

40

180

220

 

 

2.3

Task I

2.2

8

221

229

 

 

2.4

Task J

2.3, 1.5, 1.6, 2.1, 2.6

24

230

254

 

 

2.5

Task K

2.4

8

255

263

 

 

2.6

Task L

1.3

8

147

155

 

 

3.0

 

 

 

 

 

 

 

3.1

Task M

2.5

4

264

268

 

 

3.2

Task N

3.1

4

269

273

 

 

3.3

Task O

3.2

4

274

278

 

 

3.4

Task P

3.3

4

279

283

 

 

3.5

Task Q

1.2, 4.1

4

259

263

 

 

3.6

Task R

3.5, 3.4

8

284

292

 

 

4.0

 

 

 

 

 

 

 

4.1

Task S

1.2

120

138

258

 

 

4.2

Task T

3.6

8

293

301

 

 

4.3

Task U

4.2

8

302

310

 

 

Total

 

 

468 hours

 

 

 

 

 

This concludes the explanation of the forward pass. From the above table, we can see that the 2 columns for the reverse pass are blank. The reverse pass will be the topic of the next blog where we start where we have left off with the Forward Pass and then work our way backwards through the network diagram to calculate the Late Start and Late Finish times of each WBS Node Element.

 

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Thanks

 

 

Topics from this blog:
Project Scheduling Reverse Pass Analysis

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Doug Ayers

I am an MBA, B.S. in Computer Engineering and certified PMP with over 33 years working experience in software engineering and I like to go dancing after work. I program computers, solve problems, design systems, develop algorithms, crunch numbers (STEM), Manage all kinds of interesting projects, fix the occasional robot or “thing” that’s quit working, build new businesses and develop eCommerce solutions in Shopify, SAP Hybris, Amazon and Walmart. I have been an SAP Consultant for over 10 years. I am Vice-President and Co-Founder of SAP BW Consulting, Inc.

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