Planning Initiative Shared Planning and Activity Representation - SPAR |
Part of the DARPA/Air Force Research
Laboratory Planning Initiative (ARPI)
This is an overview of the SPAR Model.
"Getting as far as we can is the best that we can do"
(Edward Witten, Princeton University, investigator of
superstring theory as an explanation of everything)
Version: 0.2 Date: 29-Mar-99 Status: Released Request for Comments by: 31-Dec-99 |
E-mail: spar-core@isi.edu WWW: http://www.aiai.ed.ac.uk/project/arpi/spar/ |
Editors:
Steve Polyak (Steve_Polyak@ed.ac.uk), Institute of Representation and Reasoning (IRR),
University of Edinburgh
Austin Tate (a.tate@ed.ac.uk), Artificial Intelligence Applications Institute (AIAI),
University of Edinburgh
With Contributions by
Todd Carrico, DARPA;
Denise Draper, Rockwell;
Tom Garvey, SRI Internatonal;
Yolanda Gil, USC/ISI;
Karen Myers, SRI International;
Adam Pease, Teknowledge;
Bill Swartout, USC/ISI;
and members of the SPAR Review Groups.
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This work is based on the assumption that it is important that information about processes, plans and activities is able to be shared within and across organisations. Cooperation and coordination of the planning, monitoring and workflows of the organisations can be assisted by having a clear shared model of what comprises plans, processes and activities. The Shared Planning and Activity Representation is intended to contribute to a range of purposes including domain modelling, plan generation, plan analysis, plan case capture, plan communication and behaviour modelling. By having a shared model of what constitutes a plan, process or activity, organisational knowledge can be harnessed and used effectively.
This version 0.2 of the SPAR documentation is intended as a summary of some of the key contributions of this effort to date and conveys information on the lessons learned. An earlier SPAR document version (0.1a) [Spar Core Group, 1998a] will continue to be available in order to provide access to the past work on various aspects of SPAR and to the listing of issues which were encountered. For access to this earlier version see
History
As we stated, work on SPAR began back in Aug-97. An initial diagram of
SPAR concepts was created at a SPAR steering group meeting held in
Washington D.C. on (24-25)-Sep-97 [SPAR Core Group,
1997a]. This led to the first release of the SPAR document,
version 0.1 [SPAR Core Group, 1997b], on
30-Oct-97 along with a request for comments (RFC). Version 0.1a of the
SPAR document was released on 17-Dec-97 along with a new RFC. This
0.1a version reflected some of the changes incorporated and issues
recorded based on the responses from the first RFC. During this time,
a description of the SPAR effort, and in particular information on the
"roots" of SPAR giving the resources used during SPAR development, was
published [Tate, 1998]. The work on version 0.2
has mainly focused on establishing agreements at the knowledge level
on the central concepts supported by SPAR. This is reflected in the
content of this document. In subsequent sections we will present the
SPAR concepts as a sentence level presentation.
Requirements
An initial set of representational and functional requirements had
been assembled for the SPAR development process. These requirements
reflect a wide-ranging set of sources. The idea was that this set
could be used to: help determine the scope and priorities of the
project; elicit concepts and constructs; and gauge the adequacy of the
SPAR representation.
The sources for these requirements ranged from various enterprise process interchange projects and tools to individual comments on concepts and constructs from ARPI-sponsored researchers and program managers. Once the set had been pulled together from these sources, the elements were partitioned into representational and functional categories. Requirements in each category were then clustered into various groupings. The representational requirements define the elements that are needed to express information centred around plan representations, either explicitly or implicitly. The representational groupings included:
For more information on these requirements, consult the version 0.1a
SPAR document or see [Polyak, 1997].
SPAR Model
Scope
The principal scope of SPAR is to represent past, present and possible
future activity and the command, planning and control processes that
create and execute plans meant to guide or constrain future activity.
It can be used descriptively for past and present activity and
prescriptively for possible future activity.
Model Overview
A set of statements called the KRSL-Plans description (version dated
20-Sep-96) was used as a starting point for the SPAR model of planning
and activity. These were created by the Plan Ontology Construction
Group (POCG) within ARPI. These statements were a refinement of an
earlier version dated 2-Feb-95 (published in [Tate,
1996b]). The later version of these statements was also used to
provide ARPI participants input to the development of the Object Model
Working Group's Core Plan Representation (OMWG CPR) [Pease & Carrico, 1997]. In this section we
present the latest version of the SPAR sentences which can be viewed
as an evolved version of the earlier POCG KRSL-Plans sentences and the
knowledge-level sentences description in earlier versions of SPAR. For
historical reference we have also retained notes [Spar Core Group, 1998b] which outline some of the
discussion surrounding these sentences during work on the version 0.2
release.
C.1. | A PLAN relates an ACTIVITY-SPECIFICATION and an OBJECTIVE-SPECIFICATION. |
C.2. | An ACTIVITY-SPECIFICATION describes ACTIVITY. |
C.3. | ACTIVITY-SPECIFICATIONS can include ACTIVITY-CONSTRAINTS that impose restrictions over a set of ACTIVITIES and ACTIVITY-RELATABLE-OBJECTS. |
C.4. | An OBJECTIVE-SPECIFICATION describes OBJECTIVES. |
C.5. | OBJECTIVE-SPECIFICATIONS can include OBJECTIVE-CONSTRAINTS that impose restrictions over a set of WORLD-STATES or which specify required ACTIVITY. |
C.6. | An OBJECTIVE may have one or more EVALUATION-CRITERIA which may be applied to one or more WORLD-STATES to create an EVALUATION. |
C.7. | EXECUTION of an ACTIVITY can change the WORLD. |
C.8. | An AGENT is an ACTIVITY-RELATABLE-OBJECT which can PERFORM ACTIVITIES and/or HOLD OBJECTIVES. |
C.9. | An ACTIVITY takes place over a TIME-INTERVAL identified by its two TIMEPOINTS, the BEGIN-TIMEPOINT and the END-TIMEPOINT. |
E1.1. | An ACTION is a synonym for an ACTIVITY. |
E1.2. | An ACTOR is an AGENT which PERFORMS some ACTIVITY. |
E1.3. | A RESOURCE is an ACTIVITY-RELATABLE-OBJECT which is USED, MODIFIED, CONSUMED or DESTROYED during the EXECUTION of an ACTIVITY. |
E1.4. | A SUB-ACTIVITY of an ACTIVITY is an ACTIVITY included in an ACTIVITY-SPECIFICATION of the PROCESS which expands an ACTIVITY. |
E1.5. | A SUB-OBJECTIVE of an OBJECTIVE is an OBJECTIVE included in an OBJECTIVE-SPECIFICATION which expands an OBJECTIVE. |
E1.6. | A PROCESS is an ACTIVITY whose ACTIVITY-SPECIFICATION includes more than one SUB-ACTIVITY. |
E1.7. | A PRIMITIVE-ACTIVITY is an ACTIVITY which has no expansion. |
E2.1. | A PLAN is designed for and (possibly) EXECUTED within a specified WORLD. |
E2.2. | A particular snapshot of the WORLD at a given TIMEPOINT is called a WORLD-STATE. |
E2.3. | A WORLD-MODEL provides a description of the WORLD (possibly incomplete and/or inaccurate). |
E2.4. | A WORLD-STATE-DESCRIPTION describes a set of WORLD-STATEs (actual, expected, or hypothetical). |
E3.1. | Any TIMEPOINT may be associated with one or more TIMELINES. |
E3.2. | A TIMELINE has a nominated BEGIN-TIMEPOINT and a TIME-UNIT and may have a nominated END-TIMEPOINT. |
E4.1. | An ENTITY can have a set of PROPERTIES. |
E4.2. | Each PROPERTY of each ENTITY has a set of possible VALUEs. |
E4.3. | The set of VALUEs for a PROPERTY is called a DOMAIN. |
E4.4. | A PROPERTY may be ASSIGNED one or more specific VALUEs (possibly concurrently) from its associated DOMAIN. |
E4.5. | An asserted PROPERTY/VALUE ASSIGNMENT may have a PROBABILITY. |
E4.6. | An asserted PROPERTY/VALUE ASSIGNMENT may have an IMPRECISION. |
E5.1. | ACTIVITY-CONSTRAINTs may be called CONDITIONS. |
E5.2. | The EFFECTS of an ACTIVITY describe expected changes to the WORLD that would be occasioned by EXECUTION of the ACTIVITY. |
E6.1. | An EVALUATION produces an EVALUATION-RESULT. |
E6.2. | The VALUEs in the DOMAIN of an EVALUATION-RESULT may be grouped into EVALUATION-CATEGORIES. |
E6.3. | A simple case of EVALUATION-CATEGORIES may be one in which there are two categories: one where some EVALUTION-CRITERIA holds (i.e. the EVALUATION-RESULT is true); and another where the EVALUTAION-CRITERIA does not hold (i.e. the EVALUATION-RESULT is false). |
E6.4. | For comparisons, EVALUATION-CATEGORIES may be ranked (i.e. partially-ordered) according to some PREFERENCE-CRITERIA. |
E7.1. | A PLAN-LIBRARY contains PLANs which may be reused in creating new PLANs. |
E7.2. | A PLAN-LIBRARY has one or more PLAN-LIBRARY-INDEXes which can be used to catalog PLANs and aid in searching for them. |
Issues
Throughout the work on SPAR, there has been an active effort to
identify and document the issues involved in developing a shared plan
and activity representation. These issues may be of interest to future
efforts aimed at similar ontological engineering or knowledge sharing
efforts. For the complete list of issues see the SPAR document version
0.1a. In this section, we present a selection of these issues on which
progress was made in version 0.2 along with some guidance for a
solution.
Conclusions
Work on SPAR has helped to develop and refine a perspective on the
concepts and terms required for expressing knowledge of plans and
activity. This perspective is the result of shared agreements between
the SPAR core group members which range across a series of ontological
decisions. The SPAR model version 0.2 can be used as a basis for
future work seeking to define representations which may support
communication and collaboration of shared plan knowledge. The more
detailed document describing SPAR version 0.1a is to be left available
since it addresses some of the "engineering" issues of large-scale,
long-lived and changing process and activity models that can be put to
productive use.
Acknowledgements
The SPAR Project is a part of the Defense Advanced Research Projects
Agency (DARPA) and U.S. Air Force Research Laboratory (AFRL) Planning
Initiative (ARPI). The work is supported by ARPI and other
participants, and by their host organizations.
The U.S. Government is authorised to reproduce and distribute reprints for governmental purposes notwithstanding any copyright notation hereon. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of DARPA, Air Force Research Laboratory or the U.S. Government.
References
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Tate, A. (ed.), 1996. "KRSL-Plans", Appendix of Tate, A, "Towards a Plan Ontology" AI*IA Notizie (Quarterly Publication of the Associazione Italiana per l'Intelligenza Artificiale), Special Issue on "Aspects of Planning Research" 9(1), pp. 19-26. http://www.aiai.ed.ac.uk/project/oplan//documents/1996/96-aiia-plan-ontology.pdf
Tate, A., 1998. "Roots of SPAR - Shared Planning and Activity
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http://www.aiai.ed.ac.uk/project/arpi/spar/DOCS/spar-roots.html
Other World Wide Web accessible references and resources can be
accessed through the SPAR Resources Area at
http://www.aiai.ed.ac.uk/project/arpi/spar/#reso
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