Using a Crosstab to Produce Gantt Charts -...

Proven Practice

Using a Crosstab to Produce Gantt Charts

Product(s): IBM Cognos 8, IBM Cognos ReportNet

Area of Interest: Report Design

Using a Crosstab to Produce Gantt Charts 2

IBM Cognos Proprietary Information

Copyright

Copyright © 2008 Cognos ULC (formerly Cognos Incorporated). Cognos ULC is an IBM Company. While every attempt has been made to ensure that the information in this document is accurate and complete, some typographical errors or technical inaccuracies may exist. Cognos does not accept responsibility for any kind of loss resulting from the use of information contained in this document. This document shows the publication date. The information contained in this document is subject to change without notice. Any improvements or changes to the information contained in this document will be documented in subsequent editions. This document contains proprietary information of Cognos. All rights are reserved. No part of this document may be copied, photocopied, reproduced, stored in a retrieval system, transmitted in any form or by any means, or translated into another language without the prior written consent of Cognos. Cognos and the Cognos logo are trademarks of Cognos ULC (formerly Cognos Incorporated) in the United States and/or other countries. IBM and the IBM logo are trademarks of International Business Machines Corporation in the United States, or other countries, or both. All other names are trademarks or registered trademarks of their respective companies. Information about Cognos products can be found at www.cognos.com

This document is maintained by the Best Practices, Product and Technology team. You can send comments, suggestions, and additions to [email protected] .



Contents

1 INTRODUCTION ............................................................................................ 4

1.1 PURPOSE ............................................................................................................4 1.2 APPLICABILITY .....................................................................................................4

2 WHAT IS A GANTT CHART?........................................................................... 4

3 DATA AND LAYOUT CONSIDERATIONS ........................................................ 4

4 STEPS TO CREATE A GANTT CHART .............................................................. 5

5 APPLYING THE CONCEPTS TO REPORTNET................................................ 12

6 SUMMARY ................................................................................................... 16

7 APPENDIX A – SAMPLE REPORT SPECIFIATION FOR COGNOS 8............... 17



1 Introduction

1.1 Purpose

IBM Cognos 8 and IBM Cognos ReportNet do not include a Gantt chart as an available option in chart dialogs. The technique below outlines the method to create a Gantt chart from other objects available within the product functionality.

1.2 Applicability

While the discussion and examples will target IBM Cognos 8, the technique is

also applicable to IBM Cognos ReportNet.

2 What is a Gantt Chart?

A Gantt chart is a tool typically used for project planning to display date ranges graphically for comparison to other items in a project plan. The following is a sample of what such Gantt charts look like

Additional complexity can be added to the chart by colouring the bars to display status such as red to denote a project phase that may be behind schedule or partially colouring a bar to show current progress towards a milestone.

3 Data and Layout Considerations

The layout of a Crosstab lends itself to the Gantt chart format where the task items would populate the rows while the date series would populate the columns of the crosstab.

There are a few considerations for the following technique. The first

consideration is how the data is to be derived for the time series in the columns.

A typical modelling approach for time data is to use an inner join to establish a direct correlation between a time dimension and the detail fact information for each project to ensure good performance for most queries. This is commonly represented as a time dimension for a project start date and/or the project end date. This will result in gaps in the time series for periods that fall within the range defined by a start date and an end date as the inner equi-join will not match to these records.



There are two approaches that can be taken within the model to resolve the all the dates required for a Gantt chart.

The first approach is to create a new date dimension that will return a range of dates based on a start date and an end date for a task. This can be accomplished with a between clause and an inner join to return the matching

date dimension records for the entire range. However, this approach will miss date periods that are not with any range defined by a set of project tasks. For example, if one project ends in September and the next project starts in

December then October and November will not be returned in the columns of the Gantt chart.

The second approach for resolving the date ranges is to use an outer join using a between clause to return all the records for the date table even if

there are no matching values in the set of task dates. Keep in mind that an outer join may have more negative performance impact than an inner join using a between clause.

The same techniques can be approached with a report instead of within the model. In Cognos ReportNet a child tabular model can be used to return a

series of dates and these can be related to the parent tabular model using a filter object to create the join options discussed above. In Cognos 8 this is much more straight-forward and can be accomplished using a join object between two queries.

4 Steps to Create a Gantt Chart

The steps below will discuss creating the outer join using a between clause in Report Studio to satisfy the Gantt chart. The IBM Cognos 8 sample GO Data Warehouse model will be used to create the report.

1. Create a new crosstab report using the GO Data Warehouse sample model.

2. Expand the “Sales” namespace to display the “Sales order” dimension. Expand the “Sales order” dimension until the “Order number” level is

shown and then drag “Order number” into the rows of the crosstab layout.

Since the sample data does not include project details the “Order number” will play the role of a project task. The ship date and the close

date will serve as the start and end dates of each project for the Gantt chart. You may rename the data items to reflect their roles in this report if you wish.

3. In the “Sales” namespace expand the “Time (ship date)” dimension and from the properties of the lowest level, “Day (ship date)”, drag the “Ship date” property into the crosstab and nest it in the rows beneath the “Order number”.



4. In the “Sales” namespace expand the “Time (close date)” dimension and from the properties of the lowest level, “Day key (close date)”, drag the “Close date” property into the crosstab and nest it in the rows beneath

the “Ship date”.

5. To get meaningful results we must filter the sample data to return records where the ship date and the close date are not the same. As we are synthesizing project type data the “projects” with a zero length duration

will not be of use to us here. So, select the crosstab and click the filter button on the toolbar to create a new detail filter. Enter or create the following expression and click OK twice to return to the report layout.

[Ship date]<>[Close date]

6. The report should now look like the following image. This is the basis for one of the queries we will need for this report.

7. The second query will be created manually. Expand the query explorer and click Queries.

8. Drag a new query object into the query explorer pane. Double click the

new query object to access the query properties.

9. Expand the “Sales” namespace and insert the “Date” property from the

lowest level of the “Time” dimension. This is the second query that will serve our Gantt chart and should look like the following image.



10. Return to the query explorer pane and drag a new query object into the workspace. Drag a “Join” object beneath this new query and in the two

placeholders for the join drag in Query2 (the date query) to the first placeholder and Query1 (the order number query) to the second

placeholder. The result should look like the following image.



11. Select the join object in the query explorer and click the ellipses in the “Join Relationships” property to edit the join definition. Create the join with the following links (notice the operator used for each link to define a

between clause and the cardinality to define the outer join)



Note that if no gaps between project tasks are expected then the join cardinality can be set to define an inner join instead of an outer join.

12. Access the properties of the last query “Query3” and drag in all the data items from both Query1 and Query2. to get the following query definition

13. Add a new data item from the toolbox to “Query3”. Since the outer join

returns more records than are defined for the given ranges this new calculation will assist in identifying which cells of the crosstab report should be highlighted for the Gantt chart. Enter the following expression for the new data item. Name the data item “Plot Range”

if ([Query2].[Date] between [Query1].[Ship date] and

[Query1].[Close date]) then (1) else (0)

The resulting query should look like the following image.



Note that if no date gaps are expected between project tasks and an inner join was defined in step 12 then this expression could be changed to use a constant value of 1.

14. Return to the page layout and select the crosstab object on the page. In the properties of the crosstab change the Query to use “Query3” (the result of the union of “Query1” and “Query2”).

15. Drag the “Date” data item from “Query3” into the columns of the crosstab and drag “Plot Range” into the measures of the crosstab. Select the

“Date” column and set it to sort in ascending order.

16. Select the “Plot Range” measure and set the aggregate properties to use Total for both the Aggregate Function and the Rollup Aggregate Function. The resulting layout should look as follows.



17. Unlock the layout and select the text item for the Plot Range in the crosstab fact cells. Set the “Visible” property for the text item to “No” to hide the number from view.

18. Select the Crosstab Fact Cells object in the crosstab. Click the ellipses in the “Style Variable” property to bring up the “Style Variable” dialog. Select

“<new boolean variable>” in the drop-down box and in the resulting expression editor define the following condition.

[Query3].[Plot Range]>0

Click OK twice to return to the page layout.

19. From the Condition Explorer select the “Yes” condition for the new Boolean variable.

20. The Crosstab Fact Cells should still be selected. From the properties of the Crosstab Fact Cells define a Navy Background colour.

21. Run the report and view the results. Note that the execution time with an outer join will be slower than the inner join approach due to the extra processing required at the database. If you apply an ascending sort to the Order number rows then the results should look similar to the following although the crosstab has been truncated below to show the portion of the time series that has the given project ranges highlighted.



5 Applying the concepts to ReportNet

The steps below will discuss creating the outer join using tabular models and filter expressions in Report Studio to satisfy the Gantt chart. The IBM Cognos ReportNet sample GO Sales and Retailers model will be used to create the

report.

1. Create a new crosstab report using the GO Sales and Retailers sample

model.

2. Expand the “Orders” query subject and drag “Order number” into the rows of the crosstab layout.

Since the sample data does not include project details the “Order number” will play the role of a project task. The order date and the return

date will serve as the start and end dates of each project for the Gantt chart. You may rename the data items to reflect their roles in this report if you wish.

3. From the “Orders” query subject drag “Order date” and nest it in the rows beneath “Order number”.

4. Expand the “Returned items” folder in the “Orders” query subject and

drag “Return date” to the crosstab rows and nest it beneath “Order date”.

5. To get meaningful results we must filter the sample data to return records where the order date and the return date both exist and are not the same. As we are synthesizing project type data the “projects” with a zero length duration will not be of use to us here. So, select the crosstab and click the filter button on the toolbar to create a new detail filter. Enter or create the following expression and click OK twice to return to the report layout.

[Order date]<>[Return date] AND [Return date] is not null

6. The report should now look like the following image. This is the basis for one of the queries we will need for this report.



7. The second query will be created manually. Expand the query explorer and click on the Tabular model for Query1.

8. Drag a new Tabular model object from the Toolbox into the Children area

of the existing tabular model for Query1.

9. Double click the new tabular model to access the properties and, in the

properties pane, set the name of the tabular model to “Date Sequence”

10. Drag the Order date query item from the Orders query subject into the Data Items area of the new Tabular model. Note that the sample data we are working with is transactional and is sparse. This means that the entire

date sequence will not be represented and there may be gaps in the resulting Gantt chart. Normally a time series from a full date dimension would be the appropriate choice instead of a date derived from

transactional records.



11. Since we are working with transactional data we will modify the date values to remove the timestamp portion of the dates. Double-click on the “Order date” data item to modify the expression as follows1:

convert({datetime}, convert({varchar}, [gosales_goretailers].[Orders].[Order date], 104), 104)

12. Return to the query explorer pane and select the “Query1” object.

13. In the properties of the query object set the “Cross Product Allowed”

property to Allow.

14. Return to the query explorer pane and select the original "Tabular model"

object.

15. Drag a new filter object into the Filters area of the Tabular model. Set the filter expression to:

[Date Sequence].[Order date] between [Order date] and [Return date]

This will populate the date columns between the start and end date to fill in the length of the bars for the Gantt chart without having to perform a

full cross product of all the dates in the data warehouse.

16. From the Query Items tab of the Insertable Objects pane, drag “Order

date” into the original Tabular model Data Items pane.

17. From the Toolbox of the Insertable Objects pane, drag a new Data Item into the Data Items pane and set the expression to2

if ([Order date1] between [Order date] and [Return date]) then (1) else (0)

18. Select the new Data Item and set the Aggregate Function property to Total.

19. For the sake of illustration and to lower the data volume being processed,

drag a new filter from the Toolbox into the Filters area of the Tabular model and set the expression to:

[Order number] between 1000 and 1500

The resulting query should look like the following image.

1 Note that the convert function is native to SQL Server and is used here to strip the time

portion from a datetime type. Refer to your database vendor documentation for appropriate function calls to accomplish this if you are using the samples databases in a different

environment. 2 Note that due to the filter condition above not including a full cross join of the two data sets

it is also possible to use a constant numeric value for the data item expression.



20. Using the Query Explorer, select Query1.

21. Drag “Order date1” into the Dimensions pane to create a new dimension and drag “Data Item” into the Facts as shown in the following image.

22. Use the Page Explorer to return to the page layout.

23. From the Query Items tab of the Insertable Objects pane, drag “Order date1” to the crosstab columns and drag “Data Item” to the measures section of the crosstab.

24. Select the “Order date1” column and apply an ascending sort using the Sort button on the toolbar.

25. Unlock the layout and select the text item for the Data Item measure in

the crosstab fact cells. Set the “Visible” property for the text item to “No” to hide the number from view.

26. Select the Crosstab Cells object in the crosstab. Click the ellipses in the “Conditional Style” property to bring up the “Conditional Style” dialog.



27. Click the Variables button and in the new Variables dialog click the New button at the bottom left to create a new Boolean variable (leave the name as the default).

28. Set the new Boolean variable expression to:

[Data Item] > 0

29. Click the OK button three times to return to the page layout.

30. From the Condition Explorer select the “Yes” condition for the new Boolean variable.

31. The Crosstab Fact Cells should still be selected. From the properties of the Crosstab Fact Cells define a Navy Background colour.

32. Run the report and view the results. The crosstab below has been truncated to show the portion of the time series that has project ranges highlighted. The rows with multiple return dates are due to the transactional nature of the data. True project-related data will likely not encounter such a scenario where multiple project end dates have been defined.

6 Summary

The steps above should provide a starting point for developing your own Gantt charts. By filtering the result set for the time dimension it is possible to build reports that target the listed projects and provide a graphical representation for timelines and project milestones.

Note that not all data will follow the same structure as in the sample GO Data

Warehouse tables. You may need to implement your own changes and customization of the above technique to account for these differences in data

structure.



7 Appendix A – Sample Report Specifiation for IBM

Cognos 8

The following report specification can be copied to the clipboard and opened in Report Studio using the “Open Report from Clipboard” option available in the Tools menu. Note that the GO Data Warehouse samples must be deployed to execute and validate this report.

<report xmlns="http://developer.cognos.com/schemas/report/2.0/"

expressionLocale="en">

<modelPath>/content/package[@name='GO Data

Warehouse']/model[@name='model']</modelPath>

<queries>

<query name="Query1">

<source>

<model/>

</source>

<selection><dataItem name="Order number"

aggregate="none"><expression>[Sales].[Sales order].[Sales

order].[Order number]</expression></dataItem><dataItem name="Ship

date" aggregate="none"><expression>[Sales].[Time (ship date)].[Time

(ship date)].[Day (ship date)].[Ship

date]</expression></dataItem><dataItem name="Close date"

aggregate="none"><expression>[Sales].[Time (close date)].[Time (close

date)].[Day key (close date)].[Close

date]</expression></dataItem></selection>

<detailFilters><detailFilter><filterExpression>[Ship

date]<>[Close

date]</filterExpression></detailFilter></detailFilters></query>


<source>

<model/>

</source>

<selection><dataItem name="Date"

aggregate="none"><expression>[Sales].[Time].[Time].[Day].[Date]</expre

ssion></dataItem></selection>

</query>


<source>

<joinOperation>

<joinOperands>

<joinOperand cardinality="1:N"><queryRef

refQuery="Query2"/></joinOperand>

<joinOperand cardinality="0:N"><queryRef

refQuery="Query1"/></joinOperand>



</joinOperands>

<joinFilter>

<filterExpression>[Query2].[Date] >= [Query1].[Ship

date] and

[Query2].[Date] <= [Query1].[Close date]</filterExpression>

</joinFilter>

</joinOperation>

</source>

<selection><dataItem name="Order

number"><expression>[Query1].[Order

number]</expression></dataItem><dataItem name="Ship

date"><expression>[Query1].[Ship

date]</expression></dataItem><dataItem name="Close

date"><expression>[Query1].[Close

date]</expression></dataItem><dataItem

name="Date"><expression>[Query2].[Date]</expression></dataItem><dataIt

em name="Plot Range" aggregate="total"

rollupAggregate="total"><expression>if ([Query2].[Date] between

[Query1].[Ship date] and [Query1].[Close date]) then (1) else

(0)</expression></dataItem></selection>

</query>

</queries>

<layouts>

<layout>

<reportPages>

<page class="pg" name="Page1">

<pageBody class="pb">

<contents>

<crosstab class="xt" refQuery="Query3">

<crosstabCorner

class="xm"><contents><textItem><dataSource><dataItemLabel

refDataItem="Plot

Range"/></dataSource></textItem></contents></crosstabCorner>

<style>

<CSS value="border-collapse:collapse"/>

</style>



<crosstabRows><crosstabNode><crosstabNestedNodes><crosstabNode><cros

stabNestedNodes><crosstabNode><crosstabNodeMembers><crosstabNodeMember

refDataItem="Close date"

class="ml"><contents><textItem><dataSource><memberCaption/></dataSourc

e></textItem></contents></crosstabNodeMember></crosstabNodeMembers></c

rosstabNode></crosstabNestedNodes><crosstabNodeMembers><crosstabNodeMe

mber refDataItem="Ship date"



rosstabNode></crosstabNestedNodes><crosstabNodeMembers><crosstabNodeMe

mber refDataItem="Order number"



rosstabNode></crosstabRows><crosstabColumns><crosstabNode><crosstabNod

eMembers><crosstabNodeMember refDataItem="Date"



rosstabNode></crosstabColumns><defaultMeasure refDataItem="Plot

Range"/><crosstabFactCell

class="mv"><contents><textItem><dataSource><cellValue/></dataSource><s

tyle><CSS

value="visibility:hidden"/></style></textItem></contents><conditionalS

tyles><conditionalStyleCases refVariable="Boolean1"><conditionalStyle

refVariableValue="1"><CSS value="background-

color:navy"/></conditionalStyle></conditionalStyleCases><conditionalSt

yleDefault/></conditionalStyles></crosstabFactCell></crosstab>

</contents>

</pageBody>

<pageHeader class="ph">

<contents>

<block class="ta">

<contents>

<textItem class="tt">

<dataSource>

<staticValue/>

</dataSource>

</textItem>

</contents>

</block>

</contents>

<style>

<CSS value="padding-bottom:10px"/>

</style>

</pageHeader>

<pageFooter class="pf">



<contents>

<table class="tb">

<tableRows>

<tableRow>

<tableCells>

<tableCell>

<contents>

<textItem>

<dataSource>

<reportExpression>AsOfDate()</reportExpression>

</dataSource>

</textItem>

</contents>

<style>

<CSS value="vertical-

align:top;text-align:left;width:25%"/>

</style>

</tableCell>

<tableCell>

<contents>

<textItem>

<dataSource>

<staticValue>- </staticValue>

</dataSource>

</textItem>

<textItem>

<dataSource>

<reportExpression>PageNumber()</reportExpression>

</dataSource>

</textItem>

<textItem>

<dataSource>

<staticValue> -</staticValue>

</dataSource>

</textItem>

</contents>

<style>




align:top;text-align:center;width:50%"/>

</style>

</tableCell>

<tableCell>

<contents>

<textItem>

<dataSource>

<reportExpression>AsOfTime()</reportExpression>

</dataSource>

</textItem>

</contents>

<style>


align:top;text-align:right;width:25%"/>

</style>

</tableCell>

</tableCells>

</tableRow>

</tableRows>

<style>

<CSS value="border-

collapse:collapse;width:100%"/>

</style>

</table>

</contents>

<style>

<CSS value="padding-top:10px"/>

</style>

</pageFooter>

</page>

</reportPages>

</layout>

</layouts>

<reportVariables><reportVariable type="boolean" name="Boolean1">

<reportExpression>[Query3].[Plot Range]>0</reportExpression>

<variableValues>

<variableValue value="1"/>

</variableValues>

</reportVariable>

</reportVariables></report>

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