PHI : a logic-based tool for intelligent help systems

We introduce a system which improves the performance of intelligent help systems by supplying them with plan generation and plan recognition components. Both components work in close mutual cooperation. We demonstrate two modes of cross-talk between them, one where plan recognition is done on the basis of abstract plans provided by the planner and the other where optimal plans are generated based on recognition results. The examples which are presented are taken from an operating system domain, namely from the UNIX mail domain. Our system is completely logic-based. Relying on a common logical framework--the interval-based modal temporal logic LLP which we have developed--both components are implemented as special purpose inference procedures. Plan generation from first and second principles is provided and carried out deductively, whereas plan recognition follows a new abductive approach for modal logics. The plan recognizer is additionally supplied with a probabilistic reasoner as a means to adjust the help provided for user-specific characteristics

A new logical framework for deductive planning

In this paper we present a logical framework for defining consistent axiomatizations of planning domains. A language to define basic actions and structured plans is embedded in a logic. This allows general properties of a whole planning scenario to be proved as well as plans to be formed deductively. In particular, frame assertions and domain constraints as invariants of the basic actions can be formulated and proved. Even for complex plans most frame assertions are obtained by purely syntactic analysis. In such cases the formal proof can be generated in a uniform way. The formalism we introduce is especially useful when treating recursive plans. A tactical theorem prover, the Karlsruhe Interactive Verifier KIV is used to implement this logical framework

Semantic web services for simulation component reuse and interoperability: An ontology approach

Commercial-off-the-shelf (COTS) Simulation Packages (CSPs) are widely used in industry primarily due to economic factors associated with developing proprietary software platforms. Regardless of their widespread use, CSPs have yet to operate across organizational boundaries. The limited reuse and interoperability of CSPs are affected by the same semantic issues that restrict the inter-organizational use of software components and web services. The current representations of Web components are predominantly syntactic in nature lacking the fundamental semantic underpinning required to support discovery on the emerging Semantic Web. The authors present new research that partially alleviates the problem of limited semantic reuse and interoperability of simulation components in CSPs. Semantic models, in the form of ontologies, utilized by the authors’ Web service discovery and deployment architecture provide one approach to support simulation model reuse. Semantic interoperation is achieved through a simulation component ontology that is used to identify required components at varying levels of granularity (i.e. including both abstract and specialized components). Selected simulation components are loaded into a CSP, modified according to the requirements of the new model and executed. The research presented here is based on the development of an ontology, connector software, and a Web service discovery architecture. The ontology is extracted from simulation scenarios involving airport, restaurant and kitchen service suppliers. The ontology engineering framework and discovery architecture provide a novel approach to inter-organizational simulation, by adopting a less intrusive interface between participants Although specific to CSPs this work has wider implications for the simulation community. The reason being that the community as a whole stands to benefit through from an increased awareness of the state-of-the-art in Software Engineering (for example, ontology-supported component discovery and reuse, and service-oriented computing), and it is expected that this will eventually lead to the development of a unique Software Engineering-inspired methodology to build simulations in future

Plan modifications versus plan generation : a complexity-theoretic perspective

The ability of a planner to modify a plan is considered as a valuable tool for improving efficiency of planning by avoiding the repetition of the same planning effort. From a computational complexity point of view, however, it is by no means obvious that modifying a plan is computationally as easy as planning from scratch if the modification has to follow the principle of "conservatism", i.e., to reuse as much of the old plan as possible. Indeed, considering propositional STRIPS planning, it turns out that conservative plan modification is as hard as planning and can sometimes be harder than plan generation. Furthermore, this holds even if we consider modification problems where the old and the new goal specification are similar. We put these results into perspective and discuss the relationship to existing plan modification systems. Although sometimes claimed otherwise, these systems do not address the modification problem, but use a non-conservative form of plan modification as a heuristic technique

SAGA: A project to automate the management of software production systems

The Software Automation, Generation and Administration (SAGA) project is investigating the design and construction of practical software engineering environments for developing and maintaining aerospace systems and applications software. The research includes the practical organization of the software lifecycle, configuration management, software requirements specifications, executable specifications, design methodologies, programming, verification, validation and testing, version control, maintenance, the reuse of software, software libraries, documentation, and automated management

Plan reuse versus plan generation : a theoretical and empirical analysis

The ability of a planner to reuse parts of old plans is hypothesized to be a valuable tool for improving efficiency of planning by avoiding the repetition of the same planning effort. We test this hypothesis from an analytical and empirical point of view. A comparative worst-case complexity analysis of generation and reuse under different assumptions reveals that it is not possible to achieve a provable efficiency gain of reuse over generation. Further, assuming "conservative" plan modification, plan reuse can actually be strictly more difficult than plan generation. While these results do not imply that there won\u27t be an efficiency gain in the "average case", retrieval of a good plan may present a serious bottleneck for plan reuse systems, as we will show. Finally, we present the results of an empirical study of three different plan reuse systems, which leads us to the conclusion that the utility of plan-reuse techniques is limited and that these limits have not been determined yet

Intelligent user support in graphical user interfaces

1. This paper presents a frontend to an intelligent help system based on plans called InCome (Interaction Control Manager). It visualizes user actions previously executed in a specific application as a graph structure and enables the user to navigate through this structure. A higher level of abstraction on performed user actions shows the dialog history, the interaction context and reachable goals. Finally, the user is able to act on the application via InCome by performing undo mechanisms as well as specifying user goals inferred already by the help system. 2. This paper describes the system PLUS, a plan-based help system for applications offering an object-oriented user interface. Our plan recognition process is based on a predefined static hierarchical plan base, that is modelled using a goal plan language. This language is designed to especially cope with the problems arising when plan recognition is performed in a graphical user interface environment whose interaction is based on a user-directed dialog by means of direct manipulation -- so-called Direct Manipulation User Interfaces. The plan hierarchy is entered using the interactive graphics-oriented plan editor PlanEdit+. The plan recognition module PlanRecognizer+ builds a dynamic plan base by mapping user actions to plans stored in the static plan base. The dynamic plan base contains hypotheses about tasks the user is pursuing at the moment. These plan hypotheses serve as a basis to offer various kinds of assistance to the user. A central component of our graphical help is the module InCome+. InCome+ visualizes user actions previously executed in an application as a graph structure and enables the user to navigate through this structure. A higher level of abstraction on performed actions shows the dialog history, the interaction context, and reachable goals. InCome+ offers special features like task-oriented undo und redo facilities and a context-sensitive tutor. As a substantial extension of the graphical user assistance, we integrate the presentation of animated help within PLUS. Animation sequences are generated in the context of the tasks the user is currently working on

Planning from second principles : a logic-based approach

In this paper, a logical formalization of planning from second principles is proposed, which relies on a systematic decomposition of the planning process. Deductive inference processes with clearly defined semantics formalize planning from second principles. Plan modification is based on a deductive approach which yields provably correct modified plans. Reusable plans are retrieved from a dynamically created plan library using terminological logic as a query language to the library. Apart from sequential plans, this approach enables a planner to efficiently reuse and modify plans containing control structures like conditionals and iterations