UNITS(ID:5638/uni022)

Frame language 

Frame language, part-influence (with KRL) on LOOPS

Stefik Stanford 1976

Written in and giving access to INTERLISP
Places
Related languages
Frames => UNITS   Influence
INTERLISP => UNITS   Written using
UNITS => KEE   Commercialisation
UNITS => LOOPS   Influence
UNITS => RLL   Implementation
UNITS => STROBE   Implementation
UNITS => UNIT Package   Implementation
References:
  • Martin N., Friedland P., King J., Stefik M., "Knowledge Base Management for Experiment Planning" pp. 882-887 view details
          in Proceedings of the 5th International Joint Conference on Artificial Intelligence IJCAI-77, MIT, Cambridge, Mass., August, 1977 view details
  • Stefik M.J., "Orthogonal Planning with Constraints, Report on a knowledge-based program that plans syothesis experiments in molecular genetics" PhD Computer Science Department, Stanford University (September 1979) view details
          in Proceedings of the 5th International Joint Conference on Artificial Intelligence IJCAI-77, MIT, Cambridge, Mass., August, 1977 view details
  • Stefik, M. An examination of a frame-structured representation system.Proceedings of the International Joint Conference on Artificial Intelligence, Tokyo, Japan, pp. 845-852, August 1979. view details Abstract: The Unit Package is an interactive knowledge representation system with representations for individuals, classes, indefinite individuals, and abstractions. Links between the nodes are structured with explicit definitional roles, types of inheritance, defaults, and various data formats. This paper presents the general ideas of the Unit Package and compares it with other current knowledge representation languages. The Unit Package was created for a hierarchical planning application, and is now in use by several Al projects. Extract: History
    When the MOLGEN project was started, many ideas about frame systems and semantic networks were being widely discussed, but no software was available. In collaboration with other members of the MOLGEN project, the author developed a representation system called the Unit Package which became operational in July 1977, In some cases (and usually in ignorance), this work has duplicated other representation work that was happening at about the same time. The Unit Package is now being used by several other projects including two away from Stanford. It is written in INTERLISP and runs under the TENEX and WPS2O operating systems. It is an interactive system for building knowledge-based programs. It also provides a substantial virtual memory so that knowledge bases of several thousand nodes can created without sacrificing the INTERLISP environment. Extract: Elements of the Representation
    Elements of the Representation
    Knowledge in the Unit Package is organized as a partitioned semantic network. Following KRL terminology, the nodes are alternatively called units and the links are called slots. A built-in generalization relationship provides a hierarchy with several modes of property inheritance. Conspicuous for its absence is a comprehensive inference mechanism. While the Unit Package provides some built-in inferential facilities - notably the property inheritance mechanism, the pattern matchers, and the attached procedure mechanism - most of the inference control must be provided by application-specific methods, The ideas in the Unit Package will be presented in the following order.

    1. Partitions - The boundaries in the network which divide it into (possibly overlapping) explicit sets of nodes.
    2. Units - The nodes in the network. The Unit Package has nodes for constant individuals and classes as well as for undetermined and abstract entities. For the latter it permits naming them, anchoring them to constants, adding details to them, and indicating whether they are the same or different (without necessarily anchoring them).
    3. Slots - The links between the nodes. The fine structure of links is defined by a set of "aspects" which define their inheritance and definitional roles, datatypes, defaults, and attached procedures. These aspects provide declarative meta- knowledge which indicates how a slot is to be interpreted.
    4. Attached procedures - Procedures may be attached to units, slots, or datatype units, depending on what they are used for. They are activated by messages and have explicit purposes. A small set of purposes is recognized by the Unit Package to allow automatic activation under specified circumstances. Attached procedures are the chief mechanism for making inferences in the Unit Package.
    Extract: Survey
    The Unit Package is a frame-structured representation language whose main elements are partitions, nodes, links, and attached procedures. Our goal has been to develop a concise and structured representation language in which the important kinds of relationships are explicit and uniformly represented for processing by uniform network processing routines. This has led to formalisms for kinds of nodes, links, inheritance, and attached procedures. Some of these formalisms have been inspired by and instrumental for the MOLGEN planning application. Probably the most important example of this is the idea of a hierarchical variable to which one can add information and constraints. These variables provide a notation for hierarchical planning. Some shortcomings of the Unit Package have been noted in passing. These include a need for allowing multiple generalizations, a need for explicit indication of mutual exclusion, and a more adequate use of quantification. These problems are not difficult to fix. Space does not permit discussion of more substantial representational problems beyond the current research, such as the structured representation of processes and causal relationships. The reader interested in a discussion of some unsolved problems is referred to [171. Abstract: The Unit Package is an interactive knowledge representation system with representations for individuals, classes, indefinite individuals, and abstractions. Links between the nodes are structured with explicit definitional roles, types of inheritance, defaults, and
    various data formats. This paper presents the general ideas of the Unit Package and compares it with other current knowledge representation languages. The Unit Package was created for a hierarchical planning application, and is now in use by several Al projects. pdf
          in Proceedings of the 5th International Joint Conference on Artificial Intelligence IJCAI-77, MIT, Cambridge, Mass., August, 1977 view details
  • Smith, R.G.; Friedland, P. and Stefik, M. "Unit Package user's guide" Technical Report HPP-80-28, Stanford University Knowledge Systems Laboratory, December 1980 view details
          in Proceedings of the 5th International Joint Conference on Artificial Intelligence IJCAI-77, MIT, Cambridge, Mass., August, 1977 view details
  • Stefik, M. Planning with constraints. Memo HPP-80-2 (Knowledge Systems Laboratory), January 1980. Also Stanford CS Report STAN-CS-80-784, 1980. view details
          in Proceedings of the 5th International Joint Conference on Artificial Intelligence IJCAI-77, MIT, Cambridge, Mass., August, 1977 view details
    Resources
    • HIstory page at Stanford AI

      MOLGEN (1975-84)



      The MOLGEN project has applied AI methods to research in molecular biology. Initial work focused on acquiring and representing the expert knowledge needed to design and simulate experiments in the domain. This led to the development of UNITS, described below. The second phase of research resulted in two expert systems, representing distinct approaches to the design of genetic experiments. One system used "skeletal plans," which are abstracted outlines of experiment designs that can be applied to specific experimental goals and environments. The other system was based on planning with constraints, in which planning decisions are made in the spaces of overall strategy, domain-independent decisions, and domain-dependent laboratory decisions, and the interaction of separate steps or subproblems of an experiment constitute constraints on the overall problem. These two systems were later synthesized into a third system, called SPEX. Current work, known as MOLGEN-II (see the section "The Heuristic Programming Project"), is investigating the process of theory formation in molecular biology.

      UNITS (1975-81)



      The frame-based UNITS system was developed in the MOLGEN project as a general-purpose knowledge representation, acquisition, and manipulation tool. Designed for use by domain experts with little previous knowledge of computers, it provides an interface that allows the expert to describe both factual and heuristic knowledge. It contains both domain-independent and domain-specific components, including modified English rules for describing the procedural knowledge. UNITS has been licensed by Stanford University for commercial development.external link