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Standard Generalized Mark Up Language (SGML) SGML is the parent language from which both XML and HTML were derived. SGML is a rich Meta language that is useful for defining an almost endless supply of mark up languages. Generalized mark up language GML was developed in the1960’s.Later ISO standardized it to Standard generalized mark up language (SGML).SGML offers a system of marking up documents that is independent of any software application. It also contains an international standard that defines device independent and machine independent methods for representing electronic documents. Advantages of SGML 1) It has long term viability. 2) It is non proprietary and platform independent. 3) It supports user defined tags and architecture. 4) It is portable. Disadvantages of SGML 1) It was not well suited for quick development of web pages. 2) It is costly to set up, requiring real expertise. 3) SGML’s tools are relatively expensive when compares to html. 4) Creating document type definitions with SGML is expensive 5) SGML has a steep learning curve. 6) It is not web friendly. 7) It is complicated software. 8) Lack of supported style sheets. 9) No main stream browser support. 10) Difficult to understand since complex tags are used. Basic parts of SGML are SGML declaration Document type definition (DTD) Document instance Information in SGML is divided into 3 categories Data : supports multimedia data and hidden data Structure: it indicates the relationship among the data elements Format : indicates the appearance of objects