Frames(ID:6540/fra002)Minsky's pioneering FRLMinsky's concept of frame/slot for representing knowledge, based on the Quilian semantic network and the foundation for all frame languages Related languages
References: External link: Online copy Extract: The concept of frames A frame is a data-structure for representing a stereotyped situation, like being in a certain kind of living room, or going to a child"s birthday party. Attached to each frame are several kinds of information. Some of this information is about how to use the frame. Some is about what one can expect to happen next. Some is about what to do if these expectations are not confirmed. We can think of a frame as a network of nodes and relations. The "top levels" of a frame are fixed, and represent things that are always true about the supposed situation. The lower levels have many terminals?"slots" that must be filled by specific instances or data. Each terminal can specify conditions its assignments must meet. (The assignments themselves are usually smaller "sub-frames.") Simple conditions are specified by markers that might require a terminal assignment to be a person, an object of sufficient value, or a pointer to a sub-frame of a certain type. More complex conditions can specify relations among the things assigned to several terminals. Collections of related frames are linked together into frame-systems . The effects of important actions are mirrored by transformations between the frames of a system. These are used to make certain kinds of calculations economical, to represent changes of emphasis and attention, and to account for the effectiveness of "imagery." For visual scene analysis, the different frames of a system describe the scene from different viewpoints, and the transformations between one frame and another represent the effects of moving from place to place. For non-visual kinds of frames, the differences between the frames of a system can represent actions, cause-effect relations, or changes in conceptual viewpoint. Different frames of a system share the same terminals; this is the critical point that makes it possible to coordinate information gathered from different viewpoints. Much of the phenomenological power of the theory hinges on the inclusion of expectations and other kinds of presumptions. A frame"s terminals are normally already filled with "default" assignments. Thus, a frame may contain a great many details whose supposition is not specifically warranted by the situation. These have many uses in representing general information, most likely cases, techniques for bypassing "logic," and ways to make useful generalizations. The default assignments are attached loosely to their terminals, so that they can be easily displaced by new items that fit better the current situation. They thus can serve also as "variables" or as special cases for "reasoning by example," or as "textbook cases," and often make the use of logical quantifiers unnecessary. The frame-systems are linked, in turn, by an information retrieval network. When a proposed frame cannot be made to fit reality?when we cannot find terminal assignments that suitably match its terminal marker conditions?this network provides a replacement frame. These inter-frame structures make possible other ways to represent knowledge about facts, analogies, and other information useful in understanding. Once a frame is proposed to represent a situation, a matching process tries to assign values to each frame"s terminals, consistent with the markers at each place. The matching process is partly controlled by information associated with the frame (which includes information about how to deal with surprises) and partly by knowledge about the system"s current goals. There are important uses for the information, obtained when a matching process fails. I will discuss how it can be used to select an alternative frame that better suits the situation. A frame is a data-structure for representing a stereotyped situation, like being in a certain kind of living room, or going to a child's birthday party. Attached to each frame are several kinds of information. Some of this information is about how to use the frame. Some is about what one can expect to happen next. Some is about what to do if these expectations are not confirmed. We can think of a frame as a network of nodes and relations. The "top levels" of a frame are fixed, and represent things that are always true about the supposed situation. The lower levels have many terminals?"slots" that must be filled by specific instances or data. Each terminal can specify conditions its assignments must meet. (The assignments themselves are usually smaller "sub-frames.") Simple conditions are specified by markers that might require a terminal assignment to be a person, an object of sufficient value, or a pointer to a sub-frame of a certain type. More complex conditions can specify relations among the things assigned to several terminals. Collections of related frames are linked together into frame-systems . The effects of important actions are mirrored by transformations between the frames of a system. These are used to make certain kinds of calculations economical, to represent changes of emphasis and attention, and to account for the effectiveness of "imagery." For visual scene analysis, the different frames of a system describe the scene from different viewpoints, and the transformations between one frame and another represent the effects of moving from place to place. For non-visual kinds of frames, the differences between the frames of a system can represent actions, cause-effect relations, or changes in conceptual viewpoint. Different frames of a system share the same terminals; this is the critical point that makes it possible to coordinate information gathered from different viewpoints. Much of the phenomenological power of the theory hinges on the inclusion of expectations and other kinds of presumptions. A frame's terminals are normally already filled with "default" assignments. Thus, a frame may contain a great many details whose supposition is not specifically warranted by the situation. These have many uses in representing general information, most likely cases, techniques for bypassing "logic," and ways to make useful generalizations. The default assignments are attached loosely to their terminals, so that they can be easily displaced by new items that fit better the current situation. They thus can serve also as "variables" or as special cases for "reasoning by example," or as "textbook cases," and often make the use of logical quantifiers unnecessary. The frame-systems are linked, in turn, by an information retrieval network. When a proposed frame cannot be made to fit reality?when we cannot find terminal assignments that suitably match its terminal marker conditions?this network provides a replacement frame. These inter-frame structures make possible other ways to represent knowledge about facts, analogies, and other information useful in understanding. Once a frame is proposed to represent a situation, a matching process tries to assign values to each frame's terminals, consistent with the markers at each place. The matching process is partly controlled by information associated with the frame (which includes information about how to deal with surprises) and partly by knowledge about the system's current goals. There are important uses for the information, obtained when a matching process fails. I will discuss how it can be used to select an alternative frame that better suits the situation. 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 |