Semantic Interoperability. 2.2.1 The main problems ▇▇▇▇▇▇▇-▇▇▇ et al. write [13]: "Some low-level service-discovery schemes are currently available such as Microsoft's Universal Plug and Play, which fo- cuses on connecting di erent types of devices, and Sun Microsystems's Jini, which aims to connect services. These initiatives, however, attack the prob- lem at a structural or syntactic level and rely heavily on standardization of a predetermined set of functionality descriptions. Standardization can only go so far, because it can not anticipate all possible future needs. The Semantic Web, in contrast, is more exible." Internet and the World Wide Web is increasing the number of information sources, the need of data exchange, the need of integration / interoperability and introducing new problems. The problems can be categorized in informa- tion sources and information exchange. Information sources in Internet introduces problems as follows [52]: the product of many individuals who have di erent domain and inter- est. Di erent domain can use di erent 'vocabulary', the main factor of the di erences of vocabulary is less of control in content and catalog. Furthermore, con icts can be occurred among the web as information sources. Increasing of autonomy will give other problem for integration. There are many kind of autonomy according to ▇▇▇▇ [80] as follows: design autonomy (own data representation, own domain), communi- cation autonomy (communicate to others), execution autonomy (local operation without in uenced by external operation), and association autonomy (share degree of sources). According to ▇▇▇▇▇ [89] there are 2 groups of heterogeneity: information and system heterogeneity. Many types of heterogeneity are due to technolog- ical di erences. Researchers and developers have been working on resolving the heterogeneity for many years. Information heterogeneity has lead to dif- ferent level in interoperability of system, syntactic, structure, and semantic. Table 2.1 present diversity of information system. Syntactic heterogeneity is concerned with di erences in the representation and encoding of data. It also referred to as format, such as: data format heterogeneity. Schemas are de nitions that specify the structure of data and are the result of a database design phase. For example: homonyms, synonyms or di erent attributes in database tables Hakimpour [49] distinguishes two types of heterogeneity: data hetero- geneity and semantic heterogeneity. Data heterogeneity refers to di erences among local de nitions, such as attribute types, format or precision. ▇▇▇▇▇- tic heterogeneity refers to di erences or similarities in the meaning of local data. Semantic is de ▇▇▇ as the meanings of terms and expressions according to their understanding of the world [102]. Hence semantic interoperability is "the ability of information systems to exchange information on the basis of shared, pre-established and negotiated meaning of terms and expression," and is needed in order to make other types of interoperability work (syntactic, cross cultural, international, etc.). Internet is to become global in the sense of re ecting all the diversity of the world. It must re ect knowledge at all levels: locally, regionally, nationally and internationally. From ▇▇▇▇▇▇▇ survey [102], English language has changed as dominant language at Internet, the data as follows: 1995 95%, 2000 50%, 2001 43% and his projection for 2005 is 25%. Table 2.2 present di erent layer of semantic interoperability from ▇▇▇▇▇▇▇. Traditional approaches for information integration or interoperability have been introduced. Some e ort focused at 2 areas; standardization and archi- tecture. Example of standardization as follows: [104]: Architecture of traditional approaches has introduced a converter pro- gram approach. Traditional architectures are not appropriate solutions for current challenges. Semantic Web is introduced by using semantic approach to solve the problems. Ontology becomes the backbone tool for semantic approach. Semantic interoperability is achieved by using terminological rela- tionships between terms across ontologies, such as synonyms, hyponyms and hypernym. Early approaches for semantic integration were mainly based on the use of thesauri to translate between speci c vocabularies. This approach will depend on domain of thesauri, the solution is used at global integrated on- tology. A crucial aspect of creating the Semantic Web is to enable users who are not logic experts to create machine readable content Some approach to solve the semantic heterogeneity problem for semantic interoperability will be discused in section 2.2.2. Table 2.1: Heterogeneity in Information System, from [89] Type of Heterogeneity Type of Interoperability Information Heterogeneity Semantic Heterogeneity Semantic Interoperability Structural, Representational/Schematic Heterogeneity Schematic Interoperability Syntactic, Format Heterogeneity Syntactic Interoperability System Heterogeneity System Interoperability Information System Heterogeneity Operational Level Digital Media Repository Management Systems Database Management Systems (hetero- geneity of DBMS, data models, system capabilities such as concurrency control, and recovery Platform Heterogeneity Low Level Operating System (heterogeneity of le system, naming le type, operation, transaction support, IPC, protocol, services) Hardware System (heterogeneity of in- struction set, data representation/ coding) Table 2.2: Di erent Layers of Semantic Interoperability, from [102] 1. ers Contain- Fields/Elements Meaning of De - nition of Fielders 2. Contents Within Containers the Fields/Elements International Terminological Meaning Domain speci c se- mantic where meaning of contents or negoti- ated world wide (ex. ISO) Dictionary Mean- ing Formal Meaning National Terminological Meaning Domain speci c se- mantic where meaning of contents or negoti- ated countrywide (ex. NIST) Dictionary Mean- ing Formal Meaning Corpus Written ized not formal- Regional Terminological Meaning Domain speci c se- mantic where meaning of contents or negoti- ated regionally Dictionary Mean- ing Formal Meaning Corpus Written ized not formal- Oral Recorded Archived not written Local Terminological Meaning Domain speci c se- mantic where meaning of contents or negoti- ated locally Dictionary Mean- ing Formal Meaning Corpus Written ized not formal- Oral Recorded Archived not written Oral Not systematically archive 2.2.2 Semantic Interoperability Approaches There are some views to classi es the semantic interoperability approach. From BUSTER[104] team (University of Bremen) makes classi cation based on ontology view (single/merge ontology, multiple/map ontology, and share/translation ontology). Uschold [101] also make classi cation based on ontology function. a. The agent ▇▇- ▇▇▇▇▇▇; b. The ontology designer; c. The agents.
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