Martin Bryan, The SGML Centre, 29 Oldbury Orchard, Churchdown, Glos. GL3 2PU, U.K., Phone/Fax: +44 1452 714029
As part of a general re-engineering exercise in October, ISO formally disbanded its SC18 subcommittee, which had been responsible for a diverse set of standards, including those for X.400 message handling systems (MHS), office documents (ODA) and user interfaces, as well as SGML and all of its related standards. ISO/IEC Joint Technical Committee 1 (JTC1) decided that, for 1998 at least, the work relating to SGML previously carried out by Working Group 8 of SC18 should be undertaken by a working group reporting directly to the management of JTC1. As a result what was formerly referred to as SC18/WG8 is now known as JTC1/WG4, which is tasked with the preparation of standards that define Document Description Languages.
The first meeting of JTC1/WG4 was held in Alexandria, Washington, at the headquarters of the Graphic Communications Association (GCA) between 1st-5th December. Given that SGML developed as a result of the GENCODE project started by GCA back in the 1960's, the location of this meeting served as a timely reminder of the roots of SGML, XML and HTML, which were initially designed to meet the needs of the printing and publishing industries.
The main business of the meeting was the approval of a technical corrigendum (ISO speak for correction) to ISO 8879:1986 to allow SGML to be used more efficiently in Internet, intranet and extranet environments. After much, at times heated, debate as to what the minimal set of changes that should be made to the current standard was, a text was finally approved for publication on the Friday evening, six hours after the scheduled close of the meeting!
The changes made in the technical corrigendum are defined in the form of an additional annex to ISO 8879 defining facilities which can be implemented by SGML tool developers wishing to 'Internet enable' their products. The text for this Web SGML Adaptations annex, which can be reviewed at http://www.ornl.gov/sgml/wg4/document/1955.htm, is expressed as a set of revised productions to ISO 8879:1986.
As well as allowing Internet addresses to be used to reference component parts of SGML file sets, the annex provides fallback options when external entites cannot be obtained over the network. To make it easier to control this process a number of extra option switches have been added to the SGML declaration.
To allow for the use of implied declarations when part or all of a document type definition is not accessible over the network, the Web SGML Adaptations allows for multiple attribute definition list declarations to be associated with an element. It also allows for attribute definitions that are to be applied to all elements (using #ALL in place of an element name) or to elements for which no formal declaration has been obtained (using #IMPLICIT in place of an element name).
A further extension to attribute definitions is provided by the addition of a new declared value type keyword, DATA, which can be used to identify attributes whose values have been explicitly typed. The keyword is followed by the name of an appropriate notation processor, which can optionally be qualified by a data attribute specification that defines additional data processing properties. For example, using the extensions you can declare an attribute as:
<!ATTLIST order date DATA ISO8601 [type="dateonly"] #REQUIRED >
to indicate that a processor identified by the name ISO8601 in its notation declaration should be used to check the value of the date attribute of an order to ensure that the date only contains the date part of an ISO 8601 date/time specification.
Another important extension concerns the use of #IMPLIED as the name of a document type declaration to indicate that the name of the base element for the document is to be determined from the name assigned to the first element in the document instance. This change will make it possible to create document type declarations that can be used without change during the editing of documents that are generated in sections, rather than starting from a fixed point.
To make it simpler to send complete SGML documents, including SGML declarations, over the Web the adaptations allow users to reference SGML declarations stored outside of the file containing the document instance. For example, you can now define all of your document processing rules in just two simple declarations:
<SGML XML SYSTEM "http://www.w3c.org/xml/xml.sgd">
<DOCTYPE order SYSTEM "http://www.business.org/dtds/order.dtd">
The annex also contains rules that ensure that XML documents will remain valid when submitted to SGML tools that conform to the extensions.
Note: A more detailed explanation of the effect of the changes, and those of the earlier extension to the SGML declaration for the use of Extended Naming Rules, can be found on the WWW in Web SGML and HTML 4.0 Explained, http://www.sgml.u-net.com/book/sgml-4.htm#Extensions.
A standardized subset of the document markup tags defined as part of Version 4.0 of the HyperText Markup Language (HTML), which has been designed to ensure that such documents will be widely interchangeable, was reviewed by JTC1/WG4 prior to publication as an international standard. Instructions were issued to the standard's editors on how to simplify the draft definitions to align them more closely with the new specification for Version 4.0 once it has been formally approved as a W3C recommendation.
The US national standard body, ANSI, proposed that JTC1/WG4 undertake a new work item for the development of an Interchange Standard for Modifiable Interactive Documents (ISMID) http://www.ornl.gov/sgml/wg4/document/1949.htm. The standard will be an application of HyTime that will provide a standard set of:
in response to a given stimulus.
The stimuli recognized by ISMID include Activate, Change, Click, CloseMedia, Deactivate, DoubleClick, DragDestDrop, DragDestEnter, DragDestLeave, DragSourceDrop, DragSourceEnter, DragSourceLeave, ExternClick, GotFocus, KeyDown, KeyPress, KeyUp, Load, LostFocus, MouseDown, MouseEnter, MouseLeave, MouseMove, MouseUp, Event-Move, OpenMedia, Paint, QueryUnload, Resize and Unload.
ISMID responses include the creation or modification of containers (Windows, Frames, Panels, ...), panes (Image, Video, Audio, Animation, Text, ...) or controls (Button, ScrollBar, ListBox, CheckBox, ...), assigning values to or destroying objects and executing response chains. Control of responses can be done using if, loop, switch and return controls.
ISMID will use the expression language developed for the Document Style Semantics and Specification Language (DSSSL) defined in ISO 10179.
The development of a Lightweight Document Printing Specification (LDPS) was proposed as a new work item by the Japanese Industrial Standards Committee (JISC). The proposal aims to provide a small set of printer calls that can be used to print 'ordinary documents' of the type exchanged over the Internet. The proposed language would be designed to be processable by printers that do not have an in-built interpreters, and would also be applicable for preparing files for screen display.
JTC/1 WG4 prepared a call for a conference on the development of a set of Guidelines for accessing data and metadata represented in SGML from databases, knowledge bases and search tools. The aim of the conference is to bring together groups currently developing proposals for storing SGML and XML documents in databases and repositories, including those working on metadata, product data (e.g. STEP) and SQL/MM. The conference will be held in Paris on 22nd May 1998. The venue is scheduled to immediately follow SGML/XML Europe 98, and immediately precede a set of W3C meetings, both of which are to be held in Paris.
The DSSSL expert group reviewed the recently published CSS2 specification http://www.w3.org/TR/WD-CSS2/css.txt to ensure that it will be possible to generate CSS2 output from XSL. They expressed concern over a language bias when handling multilingual text with different writing directions in CSS2. Due to the use of writing direction independent left and right margins by CSS2, rather than start and end-of-line margins used by XSL and DSSSL, different style sheets are required to deal with text with different writing directions in CSS2. Other inconsistencies in describing the placing of characters on lines were also noted.
Japanese and French translations of DSSSL were prepared for publication during November 1997.
The editors of the Topic Navigation Map standard (ISO 13250) reviewed a revised draft based on the recently published 2nd Edition of HyTime (ISO 10744). After reviewing the proposed changes with one of the HyTime editors some useful extensions were identified, including one relating to the addition of a generalized filtering mechanism to facilitate the selection of user-defined submaps of a topic naviation map.
Note: A new website http://www.hytime.org/ has been set up by the HyTime Users' Group special interest group of the International SGML Users' to provide information on HyTime and its implementations.
Contact Robin Cover with corrections and updates, or to submit contributions to the ISUG online document database.
