CULTURAL DOCUMENTATION: THE CLIO SYSTEM

Cultural documentation, i.e. the recording and management of a body of knowledge about ensembles of cultural goods, presents special requirements of a computer-based information system, not met by ordinary documentation systems and cultural information bases. The CLIO system aims at covering these needs, while it can also cooperate with an administrative documentation system. Information is organized in CLIO as a knowledge base according to a specifically designed semantic model. The construction of CLIO allows extremely dense linking of information, access by unlimited chained references, expression of abstract properties and various ways of joint temporal and spatial assignment. It also allows the extension and modification of the data schema by the users, thus supporting the easy adaptation of the system to the field of work and the evolution of knowledge. 1. The documentation of cultural goods and the CLIO system. The documentation requirements of cultural goods range from keeping a simple log of objects to the management and conservation of collections and even to the recording of a variety of cultural information. We distinguish documentation into administrative, using a fixed set of data mainly to support administrative functions and to provide basic information, and cultural, aiming at organizing an evolving body of knowledge about objects, to be used in scientific study and research. The existence and interconnection of both is ideally desired. Most computer-based systems support administrative documentation and we shall call them administrative documentation systems even if they are mere log systems. They usually employ relational data base management systems, ideally suited for organizing information in table format, value-based search and report generation. On the other hand, the relatively recent multimedia information systems are mostly "closed" systems for providing multimedia information addressed to the public, featuring fixed sets of information and navigation paths through it. Cultural documentation requires a system capable of recording the entire variety of information, which constitutes the current knowledge about a set of objects. This includes formatted data and other, multimedia data (images, audio and video recordings, text.) and are characterized by a high degree of linking, large variety of references and classifications, broad usage of abstract relations and the need for multiple, mainly referential access. Moreover, this information is in general enriched but rarely modified. Ordinary administrative documentation systems and hypermedia information bases do not meet all these requirements. The CLIO system was developed at the Institute of Computer Science, Foundation of Research and Technology Hellas to fulfill the requirements of cultural documentation. Information is organized in CLIO as a knowledge base according to a specifically designed semantic model. The functional kernel of CLIO is the Semantic Index System (SIS, see [1]), built at the Institute of Computer Science. The construction of CLIO allows extremely dense linking of information, access by unlimited chained references, expression of historical and cultural context as well as of abstract properties, joint temporal and spatial assignment in absolute or relative terms, and recording alternative, possibly conflicting information along with the respective sources. Information is presented in graphical or textual form. An extensible list of predefined queries is offered. A particularly important feature is the uniform treatment of schema and data, enabling the immediate extension and modification of the schema by the users themselves. CLIO can be characterized as "open" system, in the sense that it involves a variable system of knowledge chiefly addressed to the museum curator or the researcher, and from which closed information bases for the public can be generated. Finally, it offers an interface to an administrative documentation system. The analysis of requirements for the CLIO system has been performed in close cooperation with the Benaki Museum and the Historical Museum of Crete. The development of the system was partly funded by the STRIDE and ESPRIT programmes. 2. Recording knowledge in the CLIO system. The formatted documentation data are structured according to a model which renders an appropriate ontology and is expressed in a particular knowledge representation language. 2.1. Knowledge representation. The structural part of the Telos knowledge representation language [2] is used for representing knowledge in CLIO. This offers the general mechanisms of attribution, classification and generalization, common in all the so called semantic, conceptual or object-oriented representation methods, and, in addition, it supports unbounded classification hierarchies and equal treatment of relations and entities, resulting in great expressiveness and flexibility. Attribution is a general mechanism for representing the properties of an object as relations between the object and the value ranges of the properties, also considered as objects. Classification defines classes of objects on the basis of common properties. An atomic object is declared as instance (member) of one or more classes. Classes are themselves considered as objects (sets), instances of meta-classes (sets of sets), and so on. Thus, levels of classification are distinguished: tokens, classes, meta-classes, etc. Generalization defines a subclass-superclass relation between classes at the same level of classification, characterized by the inheritance of properties: when class A is subclass of B, it inherits all the properties of B and is differentiated from it either by having additional properties of its own, or by restricting the value ranges of the inherited ones. Finally, every object (entity or relation) has a unique identifier. 2.2. Ontology of CLIO. The knowledge representation model of CLIO expresses a rather general ontology which can be complemented by derived concepts, thus specialized to particular fields. This ontology includes concepts of matter, location, occurrence, quantity, mankind, spiritual creation and naming, as well as relations between them, and is presented in detail in [3]. Here, we are restricted to a very brief review. The concepts of matter account for the kinds and the structure of physical objects, the elements of their appearance, the distinction into natural and artificial, composition or construction materials, special information concerning fine art objects and museum objects, descriptions of style and ornamentation, and kinds of tools. The concepts of location define absolute and relative location, orientation and various topological relations. The concepts of occurrence introduce certain fundamental notions, such as event, as a point in time and space, and existence, as a set of events delimited by a beginning and an end, and include categories of events of particular significance and such concepts as activity, use, creation, technique, etc. The concepts of quantity distinguish between physical, arithmetic and numismatic quantities, elaborate their kinds, and define ways of measurement. The latter are distinguished on one hand into absolute, defined with respect to conventional coordinate systems (e.g., chronology, location), and relative, expressing magnitudes in given measurement systems (e.g., time, distance, area, volume, weight), and on the other into exact, yielding a single value, and approximate, yielding a range of values. The concepts of mankind concern the description of human persons and of manifestations of activity and organization, such as subject, group, membership, institution. The concepts of spiritual creation essentially differentiate the product of spiritual creation from its physical embodiments. Finally, a system for naming and identification is defined. The CLIO knowldge representation model subsumes the CIDOC/ICOM fine arts documentation standard. 2.3. Using the abstraction mechanisms. The chief abstraction mechanisms, classification and generalization are extensively used in CLIO for reasons of economy and, mainly, expressive power. Classification, most notably multiple, is recommended for expressing intrinsic properties. The usage of higher levels of classification enables the expression of abstract or general properties which are of interest as such even when instantiated differently in particular cases (e.g., partition, overlapping, creation, measurement interval). The usage of multiple generalization enables the creation of entangled hierarchies, suitable for representing complex terminological systems and faceted classification schemes, in addition to great economy of expression. 3. Structure and function of the CLIO system. The structure of the CLIO system together with its functional incorporation in an integrated museum information system are shown in figure 1. Such an integrated system offers combined administrative and cultural documentation functionality by interfacing respective autonomous systems. Administrative and multimedia data are acquired and managed by the administrative documentation system, using a relational data base management system to store them. Part of the administrative data is also transferred to the cultural documentation system for purposes of object identification and matching certain basic information. Furthermore, multimedia data are retrieved from the common store for presentation by the cultural documentation system. Details about the architecture of the integrated museum information system, designed at the Institute of Computer Science, FORTH, and of CLIO, as part of it, can be found in [4]. In the sequel the structure and function of CLIO are briefly presented. CLIO consists of three subsystems: the semantic index (knowledge base), the user interface and the communication interface. The semantic index stores and manages information organized according to t