Scheduling techniques in the ROSE are presented in the form of the viewgraphs. The following subject areas are covered: agenda; ROSE summary and history; NCC-ROSE task goals; accomplishments; ROSE timeline manager; scheduling concerns; current and ROSE approaches; initial scheduling; BFSSE overview and example; and summary

Zoch, David R.

English

NASA Technical Reports Server

  9 -11o58
SCHEDULING TECHNIQUES IN
THE
REQUEST ORIENTED SCHEDULING ENGINE
(ROSE)
December 13, 1990
SEAS
Systems, Engineering, and Analysis Support
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David R. Zoch
Telenmll: DZOCH
Phone: 805.0457
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Agenda
• Introduction to ROSE
• NCC-ROSE (test results)
• ROSE Scheduling Approach
• Scheduling Techniques
• Summary
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GSFC Contacts for ROSE Prolects:
G. Mike Tong (Code 520) ATR for ROSE'Ada
L=nryHull(cod=s2o)
I_ncy Goodman (Code 520) ATR for NCC-ROSE
Sylvl-, Shepperd (Coda 520)
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ROSE Summary
ROSE is a prototype scheduling tool that has demonstrated viable solutions to difficult
scheduling issues such as:
- Fast, automated, conflict-free schedule creation () 4,000 request/hour @ 2,000 req's.)
- Schedule enhancement through post-processing: Best First Search for Schedule
Enhancement (BFSSE).
- Rescheduling / contingency scheduling techniques
- Operator tools for computer-assisted scheduling (graphical Interfaces, etc.)
The ROSE effort Involves the cooperation of experienced users, operators, and
Implementors of spacecraft data systems
The ROSE effort has had positive impacts far beyond its orlginal scope
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ROSE History
i 1987 (FORD) I
Telesclence Imptlcaticms
on Ground Syuems
('rIGs)
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1988 (SEAS t Loml)
NCC ScIteduJin0
Prototype
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NCC - ROSE Task Goals
• Prototype a viable generic NCC request scheduling process with predicted load levels
for the 1995 tlmeframe using:
- Existing ROSE prototype
- Different request selection and placement strategies
- Different scheduling algorithms
• Use requests that represent a realistic contention for TDRSS resources with realistic
view periods
• Prototype required user request flexibility
• Evaluate FERN language for use In the NCC environment
• Determine tradeoffs between success rates and time-to-schedule lor different
scheduling algorithms
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Accomplishments
Verified ability of FERN to represent realistic generic requests by building and
scheduling generic requests:
- 31 Genedc user requests
- 11 Missions
- Requests for 1645 activltles per week
- Realistic TDRS vlew periods
- Realistic resource contentlon
• Prototyped and compared scheduling architectures
• Results documented In Scheduling Results Analysis Report for the NCC Prototype
• Able to schedule over 94% of anticipated requests for week long schedule In 1995 In
less than 2 hours
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neroSue
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ROSE Timeline Manager
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Scheduling Concerns
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• Need to reduce time needed to get a conflict-free schedule
• Satlsf7 customers
• Respond quickly to changes (Targets of opporlunlty, shuttle slips)
• Implement NASA policy
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L.lll'illl.
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Current Approach
1 Users submit requests for services at a specific time
2 INITIAL SCHEDULING (2 hours) - An Initial schedule Is created by computer
CONFLICT RESOLUTION (3 to 5 days) - operators phone users and ask
- what Is the type of event? (orbit adjust, tape dump, etc.)
- can request be shortened?
- can request be moved?
- can request use a downgraded service (MA vs. SA)
- can request use the other TDRS?
- I1'neither conflicting user is flexible, choose the higher priority one,
4 Operators schedule PM and tests (hardware/software upgrades) around user requests
5 If there Is a conflict with a user, do the conflict resolution process
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ROSE Approach
1 Users il_LOJ_JJEtgJ1submit tlcXibJ_requests with preferences, constraints, and
alternatives
2 INITIAL SCHEDULING (1 to 2 hours). An Initial schedule is created (without conflicts),
Some requested events are not scheduled
3 CONFLICT RESOLUTION (2 to 5 hours) - Algorithms that imitate the human conflict
resolution process are executed to try to schedule the non*scheduled requests
4 (done)
5 (done)
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Initial Scheduling
ADD TO SCI,_DULE.
ALLOCATE RE_O_URCES
NOTE SUCCESS
2.1,6
__| _ START TNEI 2,tA
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BFSSE Overview
• Start with an Initial conflict-free schedule and some un-scheduled requests
• Identity one un-scheduled request that you would like to try to schedule
• The algorithm executes the following three steps repeatedly as needed until either a
solution Is found or a tlmeout occurs
-SELECT
Find places on the schedule where the request almost fits.
-MOVE
Determine what requests need to be moved to schedule the unscheduled request
- ._2LEEUJ_
Repeat the SELECT and MOVE steps tor all moved requests
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BFSSE Example
• Goal is to add request "A" to the existing schedule shown below
• Three potential times for request "A" are shown
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l Mission 1
I1-'-'-----1 Mission 2
IF'--" I Mission 3
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• it is known that "A" cannot be scheduled anywhere if the rest of the
schedule remains as Is.
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I °,,°, iBFSSE Exam e cont'
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375 _ 200
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<= Heuristics for
Picking Times
•:== Heuristics for
Selecting which
activities to move
Q Attempt to Schedule X
Schedule Y at time Z
Ic-o-Ei_,e,eC.O.andE
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Summary
• ROSE has shown to be an effective scheduler for solving the types of scheduling
problems faced by the NCC
• The ROSE approach fully supports the NCC operations scenario
• Conflict-free schedules can be created in 2 to 4 hours instead of 3 to 5 days.
• ROSE can create schedules quickly enough that alternative contingency schedules are
possible
• The ROSE conflict resolution strategy utilizes flexibilities in user requests to reduce
conflicts
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Scheduling techniques in the Request Oriented Scheduling Engine (ROSE)

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