I-X: Technology for Intelligent Agents & Tools
Systems Architecture Overview

Introduction | I-Arch | <I-N-CA> | Shared Models | Development Areas | Issues

Work in Intelligent Planning and Activity Management at the University of Edinburgh (See http://www.aiai.ed.ac.uk/project/plan/) has led to a number of significant assets that are re-used on a number of projects. These assets include: Nonlin, O-Plan, <I-N-OVA>, Enterprise Ontology, Enterprise Architecture, Task Manager, O-P3 Process Panels, Common Process Editor, etc. A new generation of the work will drawn on this work, generalise it, and significantly extend the application of the core concepts and assets, leading to new re-usable components, and create opportunities for applications and further research.

This new programme is called I-X and the core components are a shared model representation called <I-N-CA> and a systems integration architecture called I-Arch. A variety of re-usable components and systems will be build on the new architecture and these will be collectively referred to as I-Technology and I-Tools.

I-Arch is pronounced "Eye Arch". "Arch" stands for "architecture". The "I" in I-X, I-Technology and I-Arch reflects the following:
I-Arch is a new systems integration architecture. Its design is based on the O-Plan agent architecture. I-Arch incorporates components and interface specifications which account for simplifications, abstractions and clarifications in the O-Plan work. I-Arch provides an issue-handling workflow style of architecture, with reasoning and functional capabilities provided as plug-ins. Also via plug-ins it allows for sophisticated management and use of the internal model representations to reflect the application domain of the system being buit in I-Arch. I-Arch agents may be recursively or fractally composed, and may interwork with other processing cells or architectures. This is a systems integration approach now being advocated by a number of groups concerned with large scale, long-lived, evolving and diverse systems integration issues.

The I-Technology programme has 5 aspects:

  1. Systems Integration - A broad vision of an open architecture for the creation of intelligent systems for the synthesis of a result or "product" which is based on a "two cycle" approach which uses plug-in components to "handle issues" and to "manage and respect the domain model".
  2. Representation - a core notion of the representation of a product as a set of nodes making up the components of the product model, along with constraints on the relationship between those nodes and a set of outstanding issues - <I-N-CA> - Issues, Nodes, Critical Constraints and Auxiliary Constraints.
  3. Reasoning - the provision of reusable reasoning and model management capabilities.
  4. Viewers & User Interfaces - to understand user roles in performing activities and to provide generic modules which present the state of the process they are engaged in, their relationships to others and the status of the artifacts/products they are working with.
  5. Applications - work in various application sectors which will seek to create generic approaches (I-Tools) for the various types of Task in which users may engage.


We propose to bring together a number of threads of previous research and development, and use state-of-the-art understanding of the conceptual basis for flexible, incremental, mixed-initiative planning and activity management systems. We will incorporate these into an open, flexible, lightweight and embeddable system. This will be written in Java for portability and to maximise reuse potential. The core of the system will be an agenda-based issue handling system based on workflow principles. It will be specialised to any particular task by incorporating suitable issue-handling capabilities which could be supplied by human or system components. It will be designed to allow for very significant extension via an open capability plug-in interface and via an interface to allow for the use of constraint management methods, feasibility estimators, simulators, etc. The system will be able to inter-work with other workflow and cooperative working support systems, and will not make assumptions about the internal architecture of those other systems.

The components of I-Arch are as follows:

A number of different types of "sockets" are available within the framework to reflect the protocols or interfaces into which the various components can fit. The necessity for specific sockets and the types of components vary across projects to some extent, but the separation into viewers, processing assets, constraint managers and information assets has been found to be useful in a number of AIAI projects. This also puts the I-X work on a convergent path with other Model/Viewer/Controller styles of systems framework.

<I-N-CA> Ontology

The <I-N-CA> (Issues - Nodes - Critical/Auxiliary) Model is a means to represent plans and other synthesised or designed artifacts or products as a set of constraints. By having a clear description of the different components within a synthesised artifact, the model allows for them to be manipulated and used separately from the environments in which they are generated.

The positive node constraints (these are in the form ``include node'') in the <I-N-CA> model set the space within which the description of the artifact may be further constrained. The I (issues) and CA constraints restrict the artifacts within that space which are valid. If the product or artifact is an activity plan, some types of ordering (temporal) and variable (object) constraints are distinguished from all other auxiliary constraints since these act as critical constraints or cross constraints, usually being involved in describing the others -- such as in a resource constraint which will often refer to objects/variables and to time points or intervals.

Addition needed here about "yes, no, maybe (in terms of critical constraints)" responses from constraint managers.

Issues can be categorised as to whether they will, may or will never add a "node". The I constraints which can lead to the inclusion of new nodes are of a different nature in the planning process to those which cannot.

The choice of which constraints are considered critical is itself a decision for an application of I-X and I-Arch. It is not pre-determined for all applications. A temporal activity-based planner would normally have objects/variable constraints (equality and inequality of objects) and some temporal constraints (maybe just the simple before(time-point1, time-point-2) constraint) as the critical constraints. But, in a 3D design or a configuration application object/variable and some other critical constraints (possibly spatial constraints) might be chosen. It depends on the nature of what is communicated between constraint managers in the application of the architecture.

Shared Models

The I-X approach involves the use of shared models for task directed communication between human and computer agents who are jointly exploring a range of alternative options for the synthesis of an artifact such as a design or a plan.

A number of concepts are being used as the basis for exploring task orientated multi-agent and mixed-initiative work involving users and systems. Together these provide for a shared model of what each agent can and is authorised to do and what those agents can act upon. The concepts are:

  1. Shared Object/Product Model -- a structured representation of the object being modelled or produced using a common constraint model of the object or product (<I-N-CA>).
  2. Shared Planning and Activity Model -- a rich plan and activity representation using a common constraint model of activity (<I-N-OVA>, itself a specialisation of <I-N-CA>).
  3. Shared Task Model -- Mixed initiative model of "mutually constraining the space of objects/products" - also using <I-N-OVA>.
  4. Shared Space of Options -- explicit option management.
  5. Shared Model of Agent Processing -- handlers for issues (functional capabilities) and constraint managers - described using <I-N-OVA>.
  6. Shared Understanding of Authority -- management of the authority to do work (to handle issues) and which may take into account options and levels of abstraction of the model of the object or product.

In particular, this work will carry forward the development of a strong systematic ontology to underpin the models of processes and activity - including continuing to engage in and promote its use as a basis for standards. The work will draw on the initial efforts to create an ontology suitable for the conceptual description of all apsects of an organisation - the Enterprise Ontology and on the development of a constraint model of activity <I-N-OVA>. The work will promote the aim that PIF, NIST PSL, OMWG CPR and SPAR all converge on a single core model of activity based on <I-N-CA>.

Development Areas

The initial areas of development under the I-X research programme include:
  1. Characterisation of the separate components of a single I-X agent to establish what features each has and how they should differ. Establish whether the a priori view on the separate com pone ts is desirable.
  2. Initial Java encoding experiments to establish that the envisaged plug-in framework is feasible and to experiment with different approaches.
  3. Consideration of how to describe plug-in components. This is envisaged as being in the <I-N-CA> ontology, reified in Sorted First Order Logic and storable in XML/RDF.
  4. The provision of an ontology for issues and issue handler descriptions for some sample applications of I-X: (e.g. I-Plan, I-Config).
  5. Consideration of how to describe the design, architecture and implementation. Possible use of UML models.


Some issues to consider while refining the I-X and I-Arch design are listed here: Other areas of study include:

Motivation for I-X

Some factors which motivate the I-X work are:

Standards Efforts related to Plan Representations

A number of members of the AI plan representation research community have been engaged over the last 4 years with colleagues interested in process and plan representations fro manufacturing, e-commerce, military, engineering, construction, aerospace and other uses. Some of this work has led to shared interlinguas, ontologies and models that have been used in practical work.

The DARPA sponsored Process Interchange Format (PIF) group, an Object Model Working Group (OMWG) Core Plan Representation effort, the Shared Planning and Activity Representation (SPAR) work and other efforts have led to a high degree of commonality in the models adopted. The National Institute for Standards and Technology (NIST) in the US brought some of these threads of separate work together and created a collaboration which has led to the Process Specification Language (NIST PSL) [See http://www.nist.gov/psl/ for more details of NIST PSL]. For references to this work, some of the history and relationships between earlier work in AI on plan representations and the standards bodies, and the part that \inova played in this see Tate (1998).}. NIST PSL uses the PIF core model at its heart and has a formally specified core semantics. <I-N-OVA> and <I-N-CA> are compatible with the approach taken in the PIF Core and therefore NIST PSL.

[This paragraph is a report provided in a personal communication from Craig Schlenoff who led the NIST PSL program from its inception through to February 2000.] In late 1999, at an International Standards Organization (ISO), Technical Committee (TC) 184, Subcommittee (SC) 4 standards meeting in Lillehammer, Norway, a resolution proposing the Process Specification Language (PSL) work as a Preliminary Work Item (PWI) was approved. The PWI is the first stage of the standardization process, in which countries who are interested in the work come together to further pursue the work. TC184 focuses on industrial automation systems and integration while SC4 specifically focuses on standardization of information which is shared or exchanged in the area of industrial and manufacturing applications.

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