DARPA Rome Lab. 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.

Introduction | History | Requirements | Model | Issues | Conclusions | Acknowledgements | References

Introduction

In August 1997, DARPA and the Air Force Research Laboratory (Rome) Planning Initiative (ARPI) Program Managers proposed an effort to build on the accumulated expertise from past DARPA and ARPI sponsored research in order to create a shared plan representation suitable for use in ARPI and on applied research programmes in their communities. This effort was named the Shared Planning and Activity Representation (SPAR). In addition to the past ARPI research efforts and experiences related to building shared plan representations (e.g. KRSL, KRSL-Plans, PIF, OMWG CPR) this work also intended to draw on relevant pre-standards research including work on representing and interchanging process knowledge within and across enterprises.

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

SPAR's impact has mainly been at the conceptual or model overview level and this is what is reported on in this version and for which the request for comments (RFC) for version 0.2 is based. For example, SPAR has been a contributing source towards the development of the Core Plan Representation (CPR) [Pease & Carrico, 1997]. In fact, the core of CPR can be viewed as an object-oriented presentation of SPAR. The work on SPAR has been conducted alongside the development of the National Institute of Standards and Technology Process Specification Language (NIST PSL) [Schlenoff et. al., 1996] and work on the Process Interchange Format (PIF) [Lee et. al., 1998] with considerable exchange of ideas and compatibility between these three activities. SPAR has also been utilised in the design of a set of Java classes for the for the C2MUVE (Command and Control Multi-User Virtual Environment) program [Jones et al., 1998]. In the following section we provide a brief synopsis of the SPAR project history. We then discuss some of the categories of requirements which we considered at the outset of this work. Next, we look at the SPAR model, focusing on a sentence level presentation and a model of some of the core concepts. Finally we present a listing of selected issues as well as conclusions drawn from this report.

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:

The functional requirements defined some of the intended uses of a rich, shared plan representation. These uses have been clustered into various categories. Many of these categories overlap in their functionalities but they have been listed separately in order to provide a more balanced presentation of the requirements. These categories are:

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.


SPAR Core Sentences

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.
[Index]


SPAR Extension 1 - Additional Terminology

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.
[Index]


SPAR Extension 2 - World State

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).
[Index]


SPAR Extension 3 - Timelines

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.
[Index]


SPAR Extension 4 - Values, Uncertainty and Imprecision

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.
[Index]


SPAR Extension 5 - Conditions and Effects

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.
[Index]


SPAR Extension 6 - Evaluations Details

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.
[Index]


SPAR Extension 7 - Libraries

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.
[Index]


Ontology

In order to provide a more integrated view of the relationship between some of the core SPAR concepts, we have created a UML class diagram presentation [Booch et al., 1998]. The relationships expressed in this figure mainly corresponds to the statements expressed in the SPAR core sentences.

SPAR Model

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

Booch, G., Rumbaugh, J., and Jacobson, I., 1998. "Unified Modeling Language User Guide", Addison-Wesley, ISBN 0-201-57168-4. http://www.rational.com

Jones, P.M., Jacobs, J.L., and Dorneich, M., 1998. "Activity Representation and Management for Crisis Action Planning", In Proceedings of the 1998 IEEE International Conference on Systems, Man, and Cybernetics.

Lee, J., Gruninger, M., Jin, Y., Malone, T., Tate, A., Yost. G., 1998. "Process Interchange Format and Framework", The Knowledge Engineering Review, Vol 13(1), Special Issue on Ontologies (eds. M. Uschold and A. Tate), Cambridge University Press. http://ccs.mit.edu/pif

Pease, R.A. and Carrico, T.M., 1997. "Object Model Working Group (OMWG) Core Plan Representation - Request for Comment", version 2, 24 January 1997, Defense Advanced Research Projects Agency. http://www.teknowledge.com/CPR2/

Polyak, S., 1997. "Requirements for a Rich, Shared Plan Representation", Institute of Representation and Reasoning (IRR), University of Edinburgh, DP 187, Presented at: ARPI's Shared Planning and Activity Representation (SPAR), Steering Group Meeting, Washington D.C., Sepetember 24, 1997.

Schlenoff, C. (ed.), Knutilla, A., and Ray, S., 1996. "Unified Process Specification Language: Functional Requirements for Modeling Processes", National Institute of Standards and Technology, Technical Report, NISTIR 5910, Gaithersburg, Maryland. http://www.nist.gov/psl/

SPAR Core Group, 1997a. "Initial SPAR Diagram 0.0", Artificial Intelligence Applications Institute (AIAI), University of Edinburgh, Scotland. http://www.aiai.ed.ac.uk/project/arpi/spar/IMG/spar-0.0-25sep97.gif

SPAR Core Group, 1997b. "Planning Initiative Shared Planning and Activity Representation - SPAR, version 0.1", Artificial Intelligence Applications Institute (AIAI), University of Edinburgh, Scotland. http://www.aiai.ed.ac.uk/project/arpi/spar/spar-doc-01.html

SPAR Core Group, 1998a. "Planning Initiative Shared Planning and Activity Representation - SPAR, version 0.1a", Artificial Intelligence Applications Institute (AIAI), University of Edinburgh, Scotland. http://www.aiai.ed.ac.uk/project/arpi/spar/spar-doc-01a.html

SPAR Core Group, 1998b. "SPAR Sentence-Level Discussion Notes for version 0.2", Artificial Intelligence Applications Institute (AIAI), University of Edinburgh, Scotland. http://www.aiai.ed.ac.uk/project/arpi/spar/spar-doc-02-discussion.html

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.ps

Tate, A., 1998. "Roots of SPAR - Shared Planning and Activity Representation", The Knowledge Engineering Review, Vol 13(1), pp. 121-128, Special Issue on Ontologies (eds. M. Uschold and A. Tate), Cambridge University Press. http://www.aiai.ed.ac.uk/project/arpi/spar/DOCS/spar-roots.html

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