This paper presents an approach to representing and manipulating plans based on a model of plans as a set of constraints. The !i-n-ova? 1 (Issues -- Nodes -- Orderings/Variables/Auxiliary) model is used to characterise the plan representation used within O-Plan and to relate this work to emerging formal analyses of plans and planning. This synergy of practical and formal approaches can stretch the formal methods to cover realistic plan representations, as needed for real problem solving, and can improve the analysis that is possible for production planning systems. !I-n-ova? is intended to act as a bridge to improve dialogue between a number of communities working on formal planning theories, practical planning systems and systems engineering process management methodologies. It is intended to support new work on automatic manipulation of plans, human communication about plans, principled and reliable acquisition of plan information, and formal reasoning about plans. Motivation T...

Resource reasoning has been at the heart of many of the successful ai based scheduling systems -- yet no attempt has been made to integrate the best techniques from scheduling with the best techniques from ai activity based planning. This paper presents a set of incremental algorithms which create two separate profiles to represent the optimistic and pessimistic use of resources within an activity plan. These allow the planner to ensure that there is a feasible assignment of resources available within any plan state being considered. The paper demonstrates how these profiles can be used to track the usage of a variety of different resource types and how they can be used to provide detailed and relevant information when a resource constraint conflict is detected. 1 Introduction Resource reasoning has been at the heart of many of the successful ai based scheduling systems -- yet no attempt has been made to integrate the best techniques from scheduling with the best techniques from ai ...

The Enterprise Project is collaborative work between AIAI at the University of Edinburgh, IBM UK, Lloyd's Register of Shipping, Logica and Unilever. The project is establishing a generic framework within which enterprise tools can be used to assist users in their tasks. It is based on an Enterprise ontology which establishes shared terminology for communication between users and tools. The paper begins with an overview of the Enterprise Project and its current status. The main aim of the paper is to describe the open systems integration architecture which underlies the design of the Enterprise Tool Set. This draws on earlier work in Open Agent-based Planning and Scheduling Architectures (e.g., O-Plan [2],[8] and TOSCA [1]). A means to more easily integrate new capabilities into the toolkit is provided through the architecture which acts as a mediator between the various components. This draws on earlier work on mediators which act to help users of data base systems (e.g., PEXES/SDBA [4...

O-Plan is a command, planning and control architecture with an open modular structure intended to allow experimentation on, or replacement of, various components. The research is seeking to determine which functions are generally required in a number of application areas and across a number of different command, planning, scheduling and control systems. O-Plan aims to demonstrate how a planner, situated in a task assignment and plan execution (command and control) environment, and using extensive domain knowledge, can allow for flexible, distributed, collaborative, and mixedinitiative planning. The research is seeking to verify this total systems approach by studying a simplified three-level model with separable task assignment, plan generation and plan execution agents. O-Plan has been applied to logistics tasks that require flexible response in changing situations. Summary The O-Plan research and development project is seeking to identify re-usable modules and interfaces within plan...

realistic plan representations as needed for real problem solving, and can improve the analysis that is possible for production planning systems. 2 Representing Plans as a Set of Constraints A plan is represented as a set of constraints which together limit the behaviour that is desired when the plan is executed. Work on O-Plan [8],[34] and other practical planners has identified different entities in the plan which are conveniently grouped into three types of constraint. The set of constraints describe the possible plan elaborations that can be reached or generated as shown in figure 2. Implied Constraints Plan Level Constraints Detailed Constraints Plan State Plan Agenda Plan Entities Plan Constraints<F NaN> \Gamma<F NaN> \Gamma\Psi<F NaN> @<F NaN> @R Space of Legitimate Plan Elaborations Figure 2: Plan Constraints Define Plan Space The three types of constraint in a plan are: 1. Implied Constraints or "Issues" 1 -- represe

Condition satisfaction in planning has received a great deal of experimental and formal attention. A "Truth Criterion" lies at the heart of many planners and is critical to their capabilities and performance. However, there has been little study of ways in which the search space of a planner incorporating such a Truth Criterion can be guided. The aim of this document is to give a description of the use of condition "type" information to inform the search of an AI planner and to guide the production of answers by a planner's truth criterion algorithm. The authors aim to promote discussion on the merits or otherwise of using such domain-dependent condition type restrictions as a means to communicate valuable information from the domain writer to a general purpose domain-independent planner 1 . Introduction to Condition Typing Research in AI planning has introduced a range of progressively more powerful techniques to address increasingly more realistic applications (Allen, Hendler & Ta...

This paper describes the need to view a planner as situated in an environment dealing with the whole "planning" problem. While a planning agent deals with plan generation aspects, other agents are concerned with aspects such as task elicitation, plan analysis, reactive execution, plan repair, etc. Each of these systems has its own perspective on the planning problem and each of the systems must be capable of communicating in a way which allows other systems to assimilate new information into their perspective of the problem. Within such a collection of agents a situated planner takes task assignments from a superior agent and creates a plan or further elaborates it before passing it to the execution support agents for further processing or enactment. The paper describes the O-Plan system which has been developed as an architecture within which situated agents, such as planning agents, can be created. The paper provides a summary of work to date on the planning and execution agents. The paper then goes on to describe current research involving O-Plan which aims to address the communication between a task assignment agent and a planning agent. It concentrates on three key issues in this area: communication of plans, assessment of the quality of plans and the role of authority in the planning process.

. A generic planning system is introduced which allows for custom building of planners able to generate plans for different plan consumers in the context of intelligent assistance systems. All planners are adapted to the pecularities of different plan consumers, to their domain knowledge, their typical behavior, their preferences, and their utilization of plans. The necessary knowledge sources of the generic planner are fixed in order to enable it to produce plans of a certain specificity. Its control strategy is described in a formal specification language containing constructs which allow for the configuration of characteristic parts of the control strategy. The customized planners are defined by executable specifications. An application of the approach to deductive planning based on a modal temporal logic is shown. It is shown in an example how needs of different plan consumers in an intelligent help system can be met by a deductive planner. 1 Introduction As the complexity of int...

A planning tool box is a set of software modules implementing different planning algorithms, techniques, and representation languages. A planning system designer can use these modules---and possibly additional own ones--- for building a whole family of generic or application planners. The paper explains the concept and outlines work on developing such a tool box. In particular, it identifies descriptions of planning domain characteristics as a topic in planning theory from which results are needed for building a tool box, yet are missing. Overture: The tool box idea, and the paper Writing effective programs for difficult problem classes, like planning, would normally require to narrow down the range of the program's applicability: The more generality is admitted, the more overhead results. In consequence, it makes sense to tailor a planning system such that it fits closely the intended application domain or class of applications. In research, concentration on a single planning paradi...

The user interface to the O-Plan planning system seeks to differentiate the various roles played by users in systems which support command, planning and control functions. Appropriate support is offered to the Task Assigner, the planning specialist and the operational execution staff. The planning role is supported by a user interface that provides different views of the plan structure. These can be technical or plan structure oriented views, or they may be more visualisation or world oriented views. We provide support to either view via an interface that supports the "plugging-in" of appropriate PlanWorld viewers which conform to a specified interface. 1 O-Plan -- a Modular, Open Planning Architecture The O-Plan Project at the Artificial Intelligence Applications Institute of the University of Edinburgh is exploring a practical computer based environment to provide for specification, generation, interaction with, and execution of activity plans. O-Plan is intended to be a domain-ind...