WO1994016397A2

WO1994016397A2 - Method of enterprise-wide to do list scheduling

Info

Publication number: WO1994016397A2
Application number: PCT/US1994/000303
Authority: WO
Inventors: Henry Engelman
Original assignee: Timephaser Corporation
Priority date: 1993-01-06
Filing date: 1994-01-05
Publication date: 1994-07-21
Also published as: WO1994016397A3

Abstract

An improved critical path method for directing work centers (people or other resources) regarding which tasks to do, and/or when to do such tasks, and/or the priority of such tasks. The invention provides a way for individual users to receive directives in the form of Prioritized To Do Lists on an enterprise-wide basis, and then to use the same lists to report progress. The inventive process includes a critical path method network analysis algorithm that is specially adapted to support multiple Data Dates. The process provides clear and concise directives to the various groups performing tasks across a plurality of jobs, and a simple, reasonably foolproof method of reporting progress with minimal data entry.

Description

METHOD OF ENTERPRISE-WIDE TO DO LIST SCHEDULING

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to a method of scheduling tasks, and more particularly to a method for directing work centers (people or other resources) regarding which tasks to do, and/or when to do such tasks, and/or the priority of such tasks. 2 . Description of Related Art

Enterprise-wide "To Do Lists" are used to manage complex projects or multiple simple projects or jobs. Large projects jobs generally comprise a plurality of complex interrelated tasks which can be broken down into simpler tasks spread over time. Examples include research and development, and construction. Multiple simple projects or jobs generally comprise a plurality of simple jobs which have to pass through various work centers. Examples include claim/loan approvals, sales cycles, and bureaucratic/office processes. Managing and optimizing work schedules for large projects or multiple jobs requires synchronization of the component tasks, especially when such tasks are spread out over time. A frequently used technique for management of such projects or jobs is the generation of "To Do Lists".

A single person's To Do List is typically a list of tasks that the person has to do. The tasks can be records in a data base that can be assigned a date and a priority and then sorted accordingly. When a task is completed, then the task can be removed from the list. The tasks can also be associated with various projects. A problem with dated task records is that the tasks comprising a project can be numerous, and it is very inconvenient and often impractical to assign dates to each task. More importantly, it is very inconvenient and often impractical to update task record dates when there is some logical relationship between some of the tasks. One way to overcome this problem is through the use of the prior-art method for schedule planning, termed the critical path method (CPM) , to calculate and update the dates for such tasks.

FIGURE 1 is a graphical representation of CPM. CPM analyzes a complex project by dividing the project into individual tasks 10 with serial and parallel time- precedence relationships. Serial relationships refer to interdependent tasks, where a first task must be completed prior to commencing a second task (task A before task B in FIGURE 1) . Parallel relationships involve tasks that may be implemented simultaneously (tasks B and C in FIGURE 1) . The interrelationships between the tasks may be modeled as a network. Each task is represented by a point or node on the network. A Start Date is specified for the first task, and a Duration is assigned to each task. The model is generally created in a computer system for resolving networks of any significant size.

The computerized CPM scheduling process accepts data representing a coded network interactively and/or in batch mode. A forward pass and backward pass are executed through the network to establish dates and priorities for all tasks. During the forward pass, the earliest possible start and finish dates for each task are determined in a step-wise fashion. The process commences at the project starting date and the Durations of individual tasks are added to the starting date until an expected finish date is determined. The earliest start date of a task is equal to the latest starting date of the preceding tasks plus the Duration of the preceding tasks. The finish date of each task is its start date plus its Duration, minus one working day. In this manner, the finish date of the last task determines the completion date of the project. The backward pass through the network performs the aforementioned operations in reverse order to establish the latest possible completion dates. The latest possible completion date may be defined as the last date for which a task may be accomplished without missing the target project completion date. The difference between a task's earliest possible completion date and latest possible completion date is termed "slack" or "float". The path of work items through the network that has the longest cumulative duration is known as the "critical path", and usually will be equal to the project duration. Items along this path will have zero float, indicating that delay of any one of them will delay project completion. Items not on the critical path have positive total float.

The critical path method is a comparatively recent engineering development particularly adapted for use in the construction industry for the planning and scheduling of construction activities. For a detailed analysis of CPM, reference is made to the book entitled CPM IN CONSTRUCTION MANAGEMENT, Second Edition, by James J. O'Brien (McGraw-Hill Book Company, 1971) . See also co-pending U.S. Patent Application No. 07/753,826, assigned to the assignee of the present invention. As work progresses, a CPM schedule needs to be updated because work rarely progresses as planned. Some tasks take more time to complete than originally estimated, while others take less time, thereby shifting the critical path and changing priorities.

Progress is typically reported by taking a "snapshot" view of the tasks completed and in progress at a given point of reference (e.g., at the end of each week or month) . This point of reference is referred to herein as the "Data Date" (this point of reference is also known as the As-of Date, Time Now Date, Status Date, Reporting Date, Cutoff Date, or Reference Date) . A Data Date is, in effect, the dividing line between past and future.

As noted, the Duration of a task is the time required to complete the task. The Original Duration of a task is the planned estimate. The Remaining

Duration of a task is the time left to complete the task as of a Data Date, and is equal to the Original Duration for work not yet started. The Remaining Duration of a task is used in calculating a new schedule in a CPM network analysis and schedule calculation, and can be entered directly, or can be approximated as a percentage of the task completed as of the Data Date, or derived from the actual start date of the task. There are two known ways of applying progress data to a CPM network analysis and schedule calculation of a partially completed or in-progress project:

(1) For all completed tasks, the Remaining Duration is set to zero. For all in-progress tasks, the Remaining Duration is set to the estimated number of remaining work days for the task as of the Data Date. The pro¬ ject start is set to the Data Date, and the CPM network analysis calculations are carried out as before.

(2) All completed tasks are dropped from the network. The uncompleted tasks that are left without predeces¬ sors are connected directly to the project start, which is set to the Data Date. In-progress tasks have their Remaining Durations reduced. The CPM network analysis calculations are carried out as before. Thus, in all prior art CPM network analysis and schedule calculation updates, in-progress projects are reduced to a network of tasks with Remaining Durations, and the calculation of the start and finish dates for each task proceeds from a single Data Date. For example, in FIGURE 2, the CPM network from FIGURE 1 has had Durations (RD is Remaining Duration) assigned to each task 10, a calendar scale 12 has been added, and the boxes representing each task have their left edge aligned with a Start Date (1 Jan) and the right edge aligned with a Completion Date (31 Jan) for a project starting on 1 January. Prior art CPM network calculations require a single Data Date to serve as the earliest start date for tasks not yet completed. This requirement has one very large drawback — it requires all progress reported to have the same Data Date. This a reasonable requirement where one person is performing all the tasks, but not so where a number of groups of people are performing the different tasks of a large project.

For this approach to work in a large project with multiple work groups, either one person has to obtain the current status of all in-progress work relative to the same date, or all people reporting the current status of each task have to submit such status relative to the same date. If one or more of the people submitting the current task status fails to submit, or if the person obtaining all current task status information misses one or more groups of tasks, then the schedule cannot be updated (i.e. , the start and finish dates cannot be recalculated) without introducing significant distortion in the schedule. The same problem occurs if people reporting progress do so with different Data Dates, for example, one group reporting on Friday with another group reporting on Monday.

For example, consider the project of FIGURE 2 to be in-progress with the following status: task A has been completed; the people doing task B reported 5 days remaining on 16 January; the people doing task C reported 15 days remaining on 6 January, but did not report status on 16 January; task D has not commenced. FIGURE 3 shows the time-phased project with a Data Date of 16 January where only one Data Date is applicable. The remaining work for task C is considered to be 15 days as of the single Data Date (16 January) , even though the true reference date for task C is 6 January. Under these assumptions, the Completion Date would be calculated as 5 February (i.e, 15 days for task C plus 5 days for task D) .

FIGURE 4 shows the time-phased project with two Data Dates (6 January and 16 January) , an impossibility under the prior art. This idealized graphical presentation reflects a better picture of the task status on 16 January, with the new estimate of the project Completion Date being 26 January instead of 5 February, as in FIGURE 3.

The problem of mismatched Data Dates is intensified where there are numerous jobs (multi-project scheduling) and where parts of each job are centralized, as is the case in enterprise-wide project management. For instance, assume a schedule for an enterprise includes all jobs in the enterprise's backlog, and purchasing and engineering are performed centrally by their respective departments. To be able to recalculate the schedule for the enterprise, the purchasing personnel and engineering personnel need to report current status using the same Data Date as the project managers of each of the individual projects. This becomes less likely to occur as the number of jobs and number of reporting entities increase.

An additional level of complication arises when using the concept of Prioritized To Do Lists for reporting progress. A Prioritized To Do List is basically a report listing tasks to be performed and when such tasks are to be performed, where the report has been filtered by person or group performing the tasks and has been sorted by Start Date for each task (i.e., chronologically) and then by priority. In the case of Prioritized To Do Lists, there is no concept of a true Data Date, since the person reporting status on the To Do List is doing so on a real-time basis (i.e., the "Data Date" is the date that the person is accessing the list) , whereas the recalculation of all task dates using CPM is performed only when requested using a fixed Data Date. While it is common practice to provide CPM reports that list tasks by the person or group responsible for doing such tasks, in the prior art it is impossible or impractical for the responsible person to update such To Do Lists on-line whenever desired and have a central processor collect the current status of all partici¬ pating To Do Lists to update the schedule. The problem is that each To Do List would have its own arbitrary "Data Date", and the lack of synchronization of these dates would distort the CPM calculations, in the manner shown in FIGURE 3.

Thus, the current state of the art for To Do List generation is either (1) generation of multi-project To Do Lists, which are suitable only for output purposes (i.e., for reading a report) but are completely unworkable for input purposes (i.e., for updating progress) because of the multiple Data Date problem, or (2) single-person CPM To Do Lists (usable for both input and output purposes) which are not integrated with the To Do Lists of other personnel because of the multiple Data Date problem. Some efforts have been made to overcome these short-comings in the CPM. These efforts are based on separating the tasks of an overall schedule into subnets (individual projects or sub- projects) or into smaller files. Then each subnet or smaller file can have its own Data Date and the CPM calculations are performed on each subnet or file individually and the results consolidated thereafter. While this technique can work for a small number of subnets or files, it requires too much effort and attention to detail to be practical when a significant number of subnets or files are involved, as is the case in most work situations. Another problem of the prior art is that many prior CPM network analysis methods do not allow out-of- sequence work. For example, if a precedence relationship requires task A to be completed before starting task B, then a user is not permitted to report progress on task B until task A has been completed. This is a very awkward limitation for enterprise-wide To Do Lists, where some tasks can in fact be performed out of sequence if necessary or desired. There are also prior art implementations of To Do Lists and CPM network analysis that do not provide for roll-over or slipping of non-completed tasks that should have been completed by the current Data Date. Consequently, what is needed is a practical method for applying the critical path method accommodating a plurality of Data Dates to Enterprise-Wide To Do Lists for reporting progress. The method should impose minimal requirements on the personnel reporting progress, and should maintain the integrity and synchronization of the entire schedule even under adverse conditions of user discipline (i.e., be fool¬ proof) . In addition, such a method should cause automatic roll-over for slipped tasks in enterprise- wide To Do Lists and permit out-of-sequence work. The present invention provides such a method. SUMMARY OF THE INVENTION

The invention provides a computerized method for workers and managers to receive enterprise-wide directives in the form of prioritized To Do Lists and then use the same lists to report progress. The invention accommodates the arbitrary updating practices that are utilized by the various casual users found in enterprise-wide systems. The inventive process includes a critical path method (CPM) network analysis algorithm that is specially adapted to support (1) multiple Data Dates, (2) out-of-sequence work, and (3) slipped tasks. The process provides clear and concise directives to the various groups performing tasks across a plurality of jobs, and a simple, reasonably foolproof method of reporting progress with minimal data entry. The inventive process commences with a user entering conventional CPM task data for one or more projects into a data processing system. This data includes the code or name, description, original duration, priority, and preceding tasks for each task, as well as a code or name for the person or group responsible for reporting progress. An initial Data Date (usually the start of the first project) is as¬ signed to the tasks, a CPM network is generated in conventional manner by the data processing system, and an initial schedule is calculated by data processing system using the standard CPM method.

The data processing system initially produces one or more Prioritized To Do Lists, each of which is a list of tasks to be performed by a person or group. Each Prioritized To Do List is filtered by person or group assigned to perform the tasks and sorted by start date (chronologically) and then by priority of the tasks. Each list can be printed out (hard-copy) or displayed on-line on a computer terminal. In the preferred embodiment, an on-line Prioritized

To Do List allows a user to interactively modify data displayed in the report. An updating cycle starts when a person or group identified as being responsible for reporting progress on a subset of tasks does so. Progress is reported either on-line on a data processing system, or by marking up a hard-copy report for later entry into a data processing system.

In the on-line process, a user calls up their own (personal or group) To Do List, updates the Data Date (usually by setting it to the current date) , and reviews the list for tasks (which are sorted by priority) on which work has been performed. In the preferred embodiment, when a task has been completed, the user updates the Remaining Duration for that task to zero, indicating no more remaining work. If a task has been partially completed, the user updates the Remaining Duration for that task to the time required to complete the remainder of the task. (If a task has not been started, there is no need to enter anything) . When a hard-copy list is used, a user marks up the hard-copy with the same changes as in the on-line process. A data entry person enters the changes interactively at a computer terminal using the on-line version of the same report. Progress reporting is repeated as often as people make changes to the To Do Lists for which they are responsible. Schedule recalculation occurs periodically and usually at pre-determined intervals, such as at the end of each week or month. In this step, the progress report changes that have been made since the last CPM schedule calculation are extracted from the on-line To Do Lists. The CPM schedule database is updated with the extracted transactions from the To Do Lists.

A new CPM schedule is then calculated from the updated CPM network using a modified form of the CPM which includes a forward pass that properly takes into account a plurality of Data Dates. The inventive method maintains the integrity of the Early Start date CPM calculations with respect to the various types of task precedence relationships and also with respect to various special restraints on task scheduling. The relevant task data files are updated with the newly calculated CPM schedule information (i.e., early and late start and finish dates, floats, and priorities) . New Prioritized To Do Lists are generated from the calculated CPM schedule and printed or displayed. The progress updating cycle can then be repeated. The details of the preferred embodiment of the present invention are set forth in the accompanying drawings and the description below. Once the details of the invention are known, numerous additional innovations and changes will become obvious to one skilled in the art. BRIEF DESCRIPTION OF THE DRAWINGS

FIGURE 1 is a prior art graphical representation of the Critical Path Method. FIGURE 2 is a time-phased diagram of the CPM network for a project planned to start on 1 January, in accordance with the prior art.

FIGURE 3 is a time-phased diagram of the CPM network of the in-progress project of FIGURE 2, using one Data Date in accordance with the prior art.

FIGURE 4 is a time-phased diagram of the CPM network of the in-progress project of FIGURE 2, showing a desired CPM schedule determination using two Data Dates. FIGURE 5 is a flowchart illustrating the enterprise-wide prioritized To Do Lists method using multiple Data Dates in accordance with the present invention.

FIGURE 6 is a graphical example of an on-line (computer terminal) Prioritized To Do List.

FIGURE 7 is a graphical example of the on-line (computer terminal) Prioritized To Do List of FIGURE 6 with status changes shown.

FIGURE 8 is a graphical example of a marked-up hard-copy report showing changes corresponding to the changes made on the on-line (computer terminal) Prioritized To Do List of FIGURE 7.

FIGURES 9A and 9B show examples of record layouts for transactions used as input for the modified CPM network of the present invention. FIGURE 10 is a flowchart illustrating the modified CPM network calculation for multiple Data Dates in accordance with the present invention.

Like reference numbers and designations in the various drawings refer to like elements.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Throughout this description, the preferred embodiments and examples should be considered as examples, rather than as limitations on the present invention.

Overview of the Inventive Process

FIGURE 5 illustrates the scheduling method of the present invention, which applies multiple Data Dates to the critical path method (CPM) . In Step 1, a user follows conventional CPM practice in entering task data for one or more projects into a computer. Such data includes the code or name, description, original duration, priority, and preceding tasks for each task. In addition, the data for each task preferably includes the code or name of the work center (e.g., worker, manager, group, or resource) with respect to which a person is responsible for reporting progress or current status for the task. An initial Data Date is assigned; this date is usually the starting date of the first project being scheduled. In Step 2, an initial CPM schedule is calculated from the input data by any conventional CPM method, using a forward and backward pass to produce early and late start and finish dates for each task. Such computations are well-known in the art.

In Step 3 , the computer produces one or more Prioritized To Do Lists. Each Prioritized To Do List sets forth tasks to be performed, where each list has been filtered by person or group performing the tasks, and has been sorted by start date (i.e., chrono¬ logically) and then by priority. The Prioritized To Do List is also filtered to exclude completed tasks (i.e., tasks with remaining duration = 0) . The priority of a task is a value calculated from a user-defined weighted function of urgency (float) , importance (user-assigned priority) , and profitability. In the absence of such a urgency or importance information, priority is equal to the float for a task.

A Prioritized To Do List can be printed out (hard- copy) or displayed on-line on a computer terminal. In the preferred embodiment, an on-line Prioritized To Do List allows a user to interactively modify data displayed in the report.

FIGURE 6 is a graphical example of an on-line (computer terminal) Prioritized To Do List 60. In the illustrated embodiment, a Work Item column 62 identifies each task with a unique numeric code. A Description column 64 provides a human-readable description of each task. Original Duration 66, Remaining Duration 68, and Early Start 70 columns provide scheduling information. The relevant Data Date 72 (e.g., 30 November 1992) is also shown; other identifying or explanatory text may be provided, as desired. Of course, other formats for displaying task data in a To Do List form could be adopted, as desired. Referring again to FIGURE 5, in Step 4, each person or group identified as being responsible for reporting progress on a subset of the tasks does so. In the preferred embodiment of the invention, such progress reporting is accomplished either directly on-line with the computer system, or indirectly, first using hard- copy to note changes, then entering such changes into the computer system at a later time.

In the on-line progress reporting process, a user calls up their own (personal or group) To Do List, changes the Data Date (usually by setting it to the current date) , and reviews the list for tasks (which are sorted by priority) that can be or have been completed. In the preferred embodiment, when a task has been completed, the user updates the Remaining Duration for that task to zero, indicating no more remaining work. (Alternatively, a code or space is entered that can be interpreted as "zero remaining duration") . If a task has been partially completed, the user updates the Remaining Duration for that task to the time required to complete the remainder of the task. (If a task has not been started, there is no need to enter anything) . FIGURE 7 shows the on-line version of the

Prioritized To Do List of FIGURE 6 with changes reflecting the status on 1 December 1992 of tasks identified in the list. For example, the first two tasks 74, 75 have respective Remaining Durations of 12 and 14 days, down from an Original Duration of 15 days. Two other tasks 76, 77 have blanks in the Remaining Duration column 68, indicating that these tasks 76, 77 have been completed. A fifth task 78 has a Remaining Duration of 1 day, down from an Original Duration of 5 days.

Where a hard-copy Prioritized To Do List is used to indicate progress, a user marks up the hard-copy with the same changes as in the on-line process. At some later time, a data entry person enters the changes interactively at a computer terminal using the on-line version of the same report. For example, FIGURE 8 shows a marked-up hard-copy report showing changes corresponding to the changes made on the on-line (computer terminal) Prioritized To Do List shown in FIGURE 7. Put another way, inputting the changes shown in FIGURE 8 will produce an on-line display screen that looks like FIGURE 7.

The use of a Prioritized To Do List display or listing of the types shown in FIGURES 7 and 8 greatly simplifies the use of the invention, since users in the field as well as personnel with direct access to a computer terminal have a simple, clear way of reporting progress for a project. Further, the special cases of slipped tasks and out-of-order work are accommodated simply by changing the remaining duration value of the particular tasks involved for out-of-order work, and leaving the remaining duration value unchanged for slipped tasks..

Step 4 is repeated as often as users refer to and change their Prioritized To Do Lists to indicate progress on listed tasks. The data entered in Step 4 can be stored in the computer system in any desired format, so long as all pertinent information can be extracted at a later time to update the separate CPM network data files from which the Prioritized To Do Lists are generated. FIGURES 9A and 9B show examples of record layouts for transactions used as input for the modified CPM network of the present invention. FIGURE 9A is one format for a "B-record", used in the preferred embodiment to record information about the entering user ("entity") , the user's subnetwork and group, and to specify a new data date. FIGURE 9B is one format for a "G-record", used in the preferred embodiment to add, modify, or delete information about work items in the CPM network. In each record type, a Field Type column 90 indicates whether a record is alphabetic

("A") , numeric ("N") , or alphanumeric ("AN") . A Value column 92 indicates allowed values ("ud" means "User Defined"; "ue" means "User defined, but limited to a restricted set of Entries") . A Required/Optional column 94 indicates whether the field value is required to be entered or present, or is optional. A Function column 96 indicates the function of each field in the illustrated embodiment. Of course, other formats for storing task data relating to a To Do List could be adopted, as desired.

Again referring to FIGURE 5, in Step 5, the progress report changes that have been made since the last CPM schedule calculation are extracted from the data records generated by changes to the on-line To Do Lists. These extracted changes can be in the form of change records listing the latest Data Date for each Group and the updated Remaining Duration for each task whose Remaining Duration has changed.

In Step 6, the extracted change records are applied to the CPM network database to update the network to reflect tasks wholly completed, tasks partially completed, slipped tasks, out-of-order tasks, and multiple data dates. This step simply alters the database created in Step 1 to reflect progress made on tasks within one or more projects. A new CPM schedule is then calculated from the updated CPM network using a modified form of the CPM which includes a forward pass that properly takes into account a plurality of Data Dates. The inventive method maintains the integrity of the Early Start date CPM calculations with respect to the various types of task precedence relationships and also with respect to various special restraints on task scheduling. (This modified CPM algorithm is described below in more detail in the next subsection) .

In Step 7, the relevant task data files are updated with the newly calculated CPM schedule information (i.e., early and late start and finish dates, floats, and priorities) .

Steps 5 through 7 occur periodically and usually at pre-determined intervals, such as at the end of each week or month. The cycle repeats itself. That is, new Prioritized To Do Lists are generated from the calculated CPM schedule and printed or displayed (Step 3) , or, when new projects are added, the process begins again from step l. The updating cycle (Step 4 to Step 7) is then repeated.

Flowchart of the Modified CPM for Multiple Data Dates In further explanation of the preferred embodiment of the present invention, the details of the sub-steps described above with respect to the modified CPM network analysis in Step 6 are set forth below. FIGURE 10 is a flowchart illustrating the data flow and processing of the modified CPM forward pass algorithm of the present invention. The invention provides a method for calculating a CPM schedule in a way that takes into account a plurality of Data Dates while maintaining the integrity of the Early Start date calculations with respect to the various types of task precedence relationships and also with respect to various special restraints on task scheduling.

In FIGURE 10, "WI" refers to Work Items (also known as tasks or activities) . "PWI" refers to the Preceding Work Item of a particular WI where a precedence relationship exists (i.e., a WI must be preceded by a PWI, in the simple case, when the PWI must finish before the WI can start) . "WI-PWI relationship" refers to the logical precedence requirement between a WI and a PWI. "Group" refers to a person or group that has responsibility for reporting progress or status of a subset of Work Items (WI's) . "WI-ES" refers to the Early Start date of a Work Item. "PWI-ES" refers to the Early Start date of a Preceding Work Item.

"WI-ES"' (note the prime notation) refers to a tentative Early Start date of a Work Item. "Latest" means the furthest date into the future.

The flowchart shown in FIGURE 10 is preferably implemented as a computer program on a general purpose computer. The program performs a topological sort on the WI's in the CPM network database (Block 1010) . Such a sort orders the WI's so that each WI appears after all of its PWI's. Topological sorts are well known in the prior art.

An ascending rank is then assigned to each WI based on its position in the topological sort (Block 1020) . For example, in FIGURE 1, task A is in the first topological rank; tasks B and C are in the second topological rank; and task D is in the third topological rank. For processing efficiency, the Data Date associated with each person or Group which has reported progress is retrieved and loaded as a table into memory (RAM) in the computer system (Block 1030) . (If desired, Data Dates may be associated with other attributes, such as subnets, customers, etc.) . In addition, the ES value of each Work Item is initially set to zero (Block 1035) . The first WI-PWI precedence relationship (i.e., where the WI has the lowest rank of all WI's having a WI-PWI relationship) is then retrieved (Block 1040) . The main loop of the modified forward pass step of the inventive CPM network analysis algorithm starts with Block 1050. If the current WI is the same as the WI of the previous WI-PWI relationship (Block 1050), then program control jumps to Block 1090. If the current WI is a new WI, then the current value of the

WI-ES of the WI is stored in the record for the current WI in the CPM network database (Block 1055) . The program then checks to see whether the Group to which the current WI has been assigned is the same Group as that of the previous WI (Block 1060) . If the Groups are the same, then program control jumps to Block 1080. If the current WI belongs to a new Group, then the program looks up the Data Date of that Group in the table stored in memory in Block 1030 (Block 1070) . If there is more than one type of Group that have Data

Dates associated with them, the Latest Data Date of the respective Groups of the current WI for each type of Group is retrieved. The WI-ES of the current WI is set to the Data Date retrieved for the relevant Group (Block 1080) .

The Early Start date of the PWI of the current WI- PWI relationship is then retrieved (Block 1090) . The program then checks to see if the retrieved PWI-ES is zero, indicating that the PWI has not had an ES calculated for it, which would be the case where the PWI has no predecessors itself (i.e., the current PWI is itself a "start" WI) (Block 1100) . If the retrieved PWI-ES ≠ zero, then program control jumps to Block 1130. If the retrieved PWI-ES = zero, then the Group for the current PWI is retrieved and the Data Date for that Group is looked up in the Data Dates table (Block 1110) . The PWI-ES of the current PWI is set at the Data Date brought back for the relevant PWI Group (Block 1120) .

Thereafter, a tentative Early Start date, WI-ES', is calculated based on the current PWI-ES, the current WI and PWI Remaining Durations, and the nature of the WI-PWI relationship (Block 1130) . The purpose of computing tentative values of WI-ES' is to eventually obtain the Latest Early Start date for each Work Item. In the simple case of a standard finish-start relationship (i.e., PWI finishes before WI can start), then the WI-ES is calculated by adding the PWI- Remaining Duration to the PWI-ES. Similarly, an early start date can be derived from the precedence relationship of a task and the early start date of each preceding task of such task. For other types of WI-PWI relationships, the early start date calculations are prior art and not repeated here. Examples of such calculations are found in such software products as Microsoft Project 3.0 by Microsoft Corp., CA-SuperProject 2.0 by Computer Associates, and

Instaplan EMS 4.0 by Micro Planning International.

The tentative WI-ES' is tested against the Latest WI-ES calculated in Block 1130 for the current WI from the current WI-PWI relationship and Data Dates (Block 1140) . If the tentative WI-ES' is later than the

Latest WI-ES, then the tentative WI-ES' replaces WI-ES (Block 1150) . Otherwise, the latest WI-ES remains unchanged.

The program then checks for the existence of "special restraints" on the current WI (Block 1160) . (Programming efficiency might be improved if this check is performed elsewhere in the program, depending on database structure. However, this does not change the basic procedure of the invention.) Special restraints are scheduling conditions affecting dates and floats directly, independently of the network task precedence relationships. Examples of special restraints include Mandatory Start or Mandatory Finish dates for tasks, or "Not Earlier Than", "Not Later Than", "As Soon As Possible", or "As Late As Possible" conditions for tasks. If there are no special restraints on the current WI, program control jumps to Block 1200. Otherwise, a tentative WI-ES' is calculated based on the special restraint (Block 1070) . The calculations are prior art and not repeated here. Examples of such calculations are found in such software products as

Microsoft Project 3.0 by Microsoft Corp., CA-SuperProject 2.0 by Computer Associates, and Instaplan EMS 4.0 by Micro Planning International.

The tentative WI-ES' is tested against the Latest WI-ES for the current WI (Block 1180) . If the tentative WI-ES' is later than the Latest WI-ES, then the tentative WI-ES' replaces such WI-ES (Block 1190) . Otherwise, the latest WI-ES remains unchanged.

The next WI-PWI relationship is retrieved in the order of the ranked WI's (Block 1200) . If the next WI-PWI relationship is not the last WI-PWI relation¬ ship, then program control is transferred back to Block 1050 to repeat the main loop for the current WI-PWI pair (Block 1210) . Otherwise, after the last WI-PWI pair has been processed, program control exits the forward pass loop, and the WI-ES of the last WI is stored or recorded (Block 1220) . A completion date for each task can be computed by adding the remaining duration RD of the task to the Early Start date of the task. Thereafter, the backward pass through the CPM network is performed (Block 1230) . The backward pass is conventional, and is not repeated here.

In essence, the above-described modified CPM network analysis and schedule calculation sorts the task precedence relationships into topological order, and then determines the Latest Early Start date for each task (or at least each uncompleted task, in a variation) from the following factors: (1) the data date associated with the task; (2) each early start date derived from each precedence relationship of the task and the early start date of each corresponding preceding-task of the task; and (3) each special restraint applied to the task which sets the early start date of such task independently of the network task—preceding-task precedence relationships.

This algorithm accommodates Work Items in the CPM network having a remaining duration of zero even when preceding tasks have not been completed (i.e., out-of- sequence work progress) , and tasks which still have a remaining duration after such tasks were scheduled to be completed (i.e., slipped tasks). This provides a substantial improvement over many prior art CPM network analysis and schedule calculation methods. The effect of the modified CPM forward pass of the present invention is to calculate early start and finish dates for each uncompleted task in the CPM network in a manner that takes into account multiple Data Dates, allows tasks to slip, and allows out-of-sequence work. Example

Using FIGURE 2 as an example of a CPM network before any work has started, then FIGURE 4 would show the correct current status after the following work had been reported: Data Date Task Group Remaining Duration

6 January A X 0 B Y 15 C X 12

16 January B

Using the above information, the forward pass of the inventive modified CPM network analysis and schedule calculation would work as follows:

Block 1030 loads the Latest (most current) Data Dates for Group X (16 January) and Group Y (6 January) into a table in memory. Block 1040 retrieves the WI- PWI relationship B-A; accordingly, the new WI is B (Block 1050) , and the group is X with a Data Date of 16 January (Block 1070) . The WI-ES date for Work Item B is 16 January and remains unchanged and is recorded in the WI record for Work Item B (Block 1055) .

Block 1200 retrieves the WI-PWI relationship C-A; accordingly, the new WI is C (Block 1050) , and the group is X with a Data Date 6 of January (Block 1070) . The WI-ES date for Work Item C is 6 January and remains unchanged and is recorded in the WI record for Work

Item C (Block 1055) .

Block 1200 retrieves the WI-PWI relationship D-B; accordingly, the new WI is D (Block 1050) , and the group is Y with a Data Date of 6 January (Block 1070) . The WI-ES date for Work Item C is 6 January (Block

1080) . In Block 1130, the WI-ES' date for Work Item D is calculated as the ES date for Work Item B plus the RD for Work Item B (i.e., WI-ES' = 16 Jan + 5 = 21 Jan) , and this value replaces the Latest value of the WI-ES date (Block 1150) .

Block 1200 retrieves the WI-PWI relationship D-C. In Block 1130, the WI-ES' date for Work Item D is calculated as the WI-ES date for Work Item C plus the RD for Work Item C (i.e., WI-ES = 6 Jan + 15 = 21 Jan) . This value of the WI-ES date for Work Item D gets recorded in the WI record for Work Item D (Block

1220) .

Alternative Embodiments

The flowchart of the modified CPM for multiple Data Dates for the preferred embodiment (described above and illustrated in FIGURE 10) uses a network analysis forward pass that processes the precedence relationships in topological order. In an alternative embodiment, the Work Items are processed in topological order, thereby moving from Work Item to Work Item instead of from precedence relationship to precedence relationship. Then, for each Work Item, the Early Start of the remaining work for that Work Item would be the latest of: (1) the Early Start dates for that Work Item resulting from each Preceding Work Item for that Work Item, (2) the special restraints for that Work Item, and (3) the data dates of the different groups with which the Work Item could be associated.

The flowchart of the modified CPM for multiple Data Dates for the preferred embodiment (described above and illustrated in FIGURE 10) uses the "activity-on-the- node" form of the critical path method. An alternative embodiment could use the "activity-on-the-arrow" form of the critical path method. (See CPM IN CONSTRUCTION MANAGEMENT, Second Edition, by James J. O'Brien (McGraw-Hill Book Company, 1971) for a general discussion of the two forms) . It is well-known in the art that the two forms are essentially similar for purposes of computing CPM schedules. The computation process in accordance with the present invention would be similar to the method described in the previous paragraph, using a forward pass that processes the Work Items in topological order with early event dates replacing Work Item Early Start dates. Another alternative embodiment uses the concept of special restraints in a non-conventional manner to cope with the multiple Data Date problem. This can be done, for example, by automatically converting Data Dates to special restraints (e.g., Not Earlier Than a specified date) for all tasks or for subsets of the tasks. In this embodiment, the method sorts the task precedence relationships into topological order, and then records a special restraint record for at least each task on which progress has been made in order to link the data date associated with each such task to the task during later processing. In later processing, such special restraint records (and any others defined for other reasons) are used to set the early start date of corresponding tasks independently of the network task— preceding-task precedence relationships. Thereafter, the method determines the Latest Early Start date for each task (or at least each uncompleted task, in a variation) from the following factors: (1) each early start date derived from each precedence relationship of the task and the early start date of each corresponding preceding-task of the task; and (2) any special restraints. A drawback of this approach is that it requires creating a special restraint record for at least every task for which progress is reported. Hence, this variation is inefficient.

In the preferred embodiment, Actual Start dates, when given (and in the absence of an updated Remaining Duration) , are compared to the Data Date (in the single or multiple data date method) , and the difference subtracted from the Original Duration to give an updated Remaining Duration. It is this Remaining Duration value that is used in the inventive network analysis. An alternative embodiment could use the Actual Start date for a task as a special restraint (e.g., a Mandatory Start Date on the Actual Start date, which causes the calculated ES to be equal to the reported Actual Start date) and be an extension of the special restraints embodiment described in the previous paragraph. In Step 5 in FIGURE 5 of the preferred embodiment, changes that have been made since the previous schedule recalculation are extracted from the on-line To Do Lists and the network database is updated before schedule recalculation. In an alternative embodiment, a single CPM network database can be used, and changes to the To Do Lists can be directly applied to the network database used in the CPM schedule recalculation without the extra step of extracting and updating a separate network database.

Summary

Thus, the present invention provides a way for individual users to receive directives in the form of Prioritized To Do Lists on an enterprise-wide basis, and then to use the same lists to report progress. The invention accommodates the arbitrary updating practices that are utilized by the various casual users found in enterprise-wide systems. The inventive process includes a CPM network analysis and schedule calculation algorithm that is specially adapted to support (1) multiple Data Dates, (1) out-of-sequence work, and (3) slipped tasks. The process provides clear and concise directives to the various groups performing tasks across a plurality of jobs, and a simple, reasonably foolproof method of reporting progress with minimal data entry. Furthermore, the invention provides a way of integrating separate personal or group To Do Lists in an enterprise with the enterprise work-load in the form of CPM networks. The preferred embodiment also has the advantages of data processing efficiency, simplicity of updating procedure, and maintenance of the integrity of the CPM calculations under various combinations of data.

A number of embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the invention is not to be limited by the specific illustrated embodiment, but only by the scope of the appended claims.

Claims

1. A computerized method of controlling performance of a plurality of tasks performed by a plurality of work centers, comprising the steps of:

(a) defining a network of tasks to be performed by the plurality of work centers, wherein at least two of the tasks have different associated data dates;

(b) applying, in a computer, a modified critical path method network analysis supporting multiple data dates to the network of tasks to determine at least one of:

(1) the identity of tasks to be performed, selected by work center;

(2) scheduling of such tasks; and (3) priority among such tasks.

2. A computerized method of controlling performance of a plurality of tasks performed by a plurality of work centers, comprising the steps of:

(b) applying a modified critical path method network analysis supporting multiple data dates to the network of tasks to determine at least one of:

(1) the identity of tasks to be performed, selected by work center;

(2) scheduling for such tasks; and (3) priority among such tasks;

(c) producing a plurality of prioritized to do lists of such tasks, selected by work center.

3. A computerized method of controlling performance of a plurality of tasks performed by a plurality of work centers, comprising the steps of:

(a) defining a network of tasks to be performed by the plurality of work centers;

(b) producing a plurality of prioritized to do lists of such tasks from the network, selected by work center;

(c) using the prioritized to do lists to update in the network the current status of the tasks, wherein at least two of the tasks have different associated data dates;

(d) applying a modified critical path method network analysis supporting multiple data dates to the network of tasks, using independent data dates for each work center, to determine at least one of:

(1) the identity of tasks to be performed, selected by work center; (2) scheduling for such tasks; and

(3) priority among such tasks.

4. The method of claim 3, further including the step of repeating steps (b) through (d) until all tasks are completed.

5. The method of claim 3, wherein at least one of the prioritized to do lists is produced in printed form, and the network is updated from input derived from at least one printed prioritized to do list.

6. The method of claim 3, wherein at least one of the prioritized to do lists is produced for display on at least one computer terminal, and the network is updated from input into one of the computer terminals using one of the displayed prioritized to do lists.

7. The method of claims 1, 2, or 3, wherein the network of tasks is defined as an activity-on-the- node network.

8. The method of claims 1, 2, or 3, wherein the network of tasks is defined as an activity-on-the- arrow network.

9. The method of claims 1, 2, or 3, wherein the tasks in the network have at least one task—preceding- task precedence relationship, and the modified critical path method network analysis supporting multiple data dates comprises the steps of:

(a) sorting the task— receding-task precedence relationships into topological order;

(b) for at least each uncompleted task, determining the latest early start date for such task from the following factors:

(1) the data date associated with the task;

(2) each early start date derived from each precedence relationship of such task and the early start date of each corresponding preceding task of such task;

(3) any special restraint applied to such task which sets the early start date of such task independently of the network task— receding-task precedence relationships.

10. The method of claims 1, 2, or 3, wherein the tasks in the network have at least one task— receding- task precedence relationship, and the modified critical path method network analysis supporting multiple data dates comprises the steps of:

(a) sorting the task—preceding-task precedence relationships into topological order;

(b) recording a special restraint for at least each task on which progress has been made to link the data date associated with each such task to the task;

(c) for at least each uncompleted task, determining the latest early start date for such task from the following factors: (1) each early start date derived from each precedence relationship of such task and the early start date of each corresponding preceding task of such task; (2) any special restraint applied to such task which sets the early start date of such task independently of the network task—preceding-task precedence relationships.

11. The method of claims 1, 2, or 3, wherein the tasks in the network have at least one task—preceding- task precedence relationship, and the modified critical path method network analysis supporting multiple data dates comprises the steps of:

(b) recording a special restraint for at least each task on which progress has been made to link the actual start date of each such task to the task;

(c) for at least each uncompleted task, determining the latest early start date for such task from the following factors: (1) each early start date derived from each precedence relationship of such task and the early start date of each corresponding preceding task of such task; (2) any special restraint applied to such task which sets the early start date of such task independently of the network task— receding-task precedence relationships.

12. The method of claims 1, 2, or 3, wherein the tasks in the network have at least one task—preceding- task precedence relationship, and the modified critical path method network analysis supporting multiple data dates comprises the steps of:

(a) sorting the tasks into topological order;

(b) for at least each uncompleted task, determining the latest early start date for such task from the following factors: (1) the data date associated with the task;

13. The method of claims 1, 2, or 3, wherein the tasks in the network have at least one task— receding- task precedence relationship, and the modified critical path method network analysis supporting multiple data dates comprises the steps of:

(a) sorting the tasks into topological order;

(c) for at least each uncompleted task, determining the latest early start date for such task from the following factors:

(1) each early start date derived from each precedence relationship of such task and the early start date of each corresponding preceding task of such task;

(2) any special restraint applied to such task which sets the early start date of such task independently of the network task—preceding-task precedence relationships.

14. The method of claims 1, 2, or 3, wherein the tasks in the network have at least one task— receding- task precedence relationship, and the modified critical path method network analysis supporting multiple data dates comprises the steps of:

(a) sorting the tasks into topological order;