Ajaib - A Case Study Of An SGML/Intranet Development   Table of contents   Indexes   SGML and the On-line Legislature
  Mäkelä  Riku 
  Sundquist  Risto 
  Vendelin  Timo 
 

Keep it simple - Interactive electronic applications with SGML

 

Abstract:

  TheSGML (Standard Generalized Markup Language) world has concentrated on solving the problems of textual documentation. SGML and other information standards are rather complex to take into wide use.SGML alone is not enough to implement working solutions. There are a large number of methods, models and naming conventions developed for different application areas: microdocuments, components that contain bigger element hierarchy, etc.
  This paper describes a keep-it-simple model as a base for interactive electronic applications. The model keeps the data in life-cycle safe format (SGML ), but still gives the end-user any possible view to the data and interaction with it. One design goal of the model was to separate information, functionality and user interface from each other.
  Information is managed inSGML ,HyTime (Hypermedia-Time-based Structuring Language, ISO 10744) andDSSSL (Document Style Semantics and Specification Language) formats. The information packages, that travel between client and server (and between applications), are modeled with information standards. Functionality is achieved with engines on client and/or server side. The user interface language isHTML (HyperText Markup Language) and Java applets.
  XML (Extensible Markup Language) brings lightness and data format independence when HTML provides a common user interface description language. Java applets are a modular solution for interface functionality and platform independence.HyTime is the way to link the information chunks together in a standard way. Data is stored in databases that are part of the application or part of the information infrastructure.
  This presentation contains models for puttingSGML and other information standards to work for wide range of interactive electronic multimedia applications.
 

Uses ofSGML

  SGML and other information standards are not just for documenting. They can be used as a base for almost any kind of applications that deal with information in electronic format. The key to successful implementations is simplicity.
 

Keep it simple

  Don't re-invent the wheel. There are already lots of existing solutions that might fit to your needs. Use what exists when possible, or have good reasons for why not.
  SGML Way of Thinking is a thinking model for information structures, separation of the information and its style, an implementation model, existing (and promised) tools and features, possibilities, etc.
  Start from the strategic areas : the ones that give the biggest return on investment, the ones seen as the most important by top people, the ones required for testing the risks of the whole implementation, etc.
  Use information model levels : A logical model is the stable way to think about the information. A physical model is how the logical model is written into a digital format. A user's model is the way the user understands the information.
  Take one right size step at a time. One project phase must provide real and usable results. Many times, the best practice is to create first a fast and narrow solution through the whole problem area.
  KISS (Keep It Simple, use SGML) , try to minimize everything, but include just enough. You can later add more information content, features and user interface functions if you take it into account from the beginning.
 

Stand-alone Structured Intranet Application model

  Model is based on information chunks that are divided into distributed microdocuments and multimedia objects. Distributed approach is created with the usage ofWWW (World Wide Web) technology, especially http protocol andWWW servers that are called here as net servers. Distributed Microdocuments Server provides services for locating the right information chunks from the information space accessed by the system. Net server can be connected to a network. The end user browses the information with aWWW browser that contains added functionality as plug-ins and applets.
 
 
Structured Intranet Application model separates the information, information services and user interface.
 

Distributed Microdocuments

  KISS : Information chunking simplifies the information piece because the information itself contains small amount of consistent information.
  Create blocks of information and applications that are capable of handling the information blocks. Distributed microdocuments are microdocuments that are distributed across the network. They may be stored in the client computer or anywhere in the network. Microdocuments, information blocks, information chunks, etc., are all pieces of information as one object. Chunking of information and documents is nothing new. There exists several methodologies for how to create documents divided into information chunks and collections of them.
 
 

WWW infrastructure

  KISS : Use the delivery channel that already exists. TheWWW world contains many existing solutions that can be benefited from.
  The most inexpensive way for effective electronic information delivery is to use theWWW technology. By combining theWWW andSGML world, some real benefits can be achieved.XML is a proof of this.
 
 

Stand-alone Intranet

  KISS : Use already existing word-wide infrastructure at a stand-alone system. Minimize the work, if and when you put your application into the net.
  Intranet is traditionally (with rather short tradition) a closed network of computers. TheWWW technology can be used also in stand-alone applications. A stand-alone Intranet is an application or applications in a single computer using Intranet services provided by server applications in the same single computer.
  WWW technology is commonly used for creating client-server systems with thin clients. Stand-alone Intranet is an example of a fat client created with a WWW technology, or better, an example of a thin client in the same computer with the server.
 
 

Message broker technique

  KISS : Applications and application modules can communicate with each other. Message brokers support modular system architecture.
  Distributed microdocuments need a message brokerage service that can direct the right microdocument to right address.WWW technology is an existing and fast developing way to create messaging services also for distributed microdocuments. In most cases, it is enough to deliver only the data objects. TheDCOM (Distributed Common Object Model) ,CORBA (Common Object Request Broker Architecture) and other more complex distributed object models start from a delivery of objects containing both the data and functionality.
 
 

Minimize

 KISS : Minimize the information and application functions. This helps in achieving the sub-goals on a way to the goal of the whole project.
  A lot of information can often be left away from the storage after minimization. Most of the information is presented only in purpose specific applications. This can be achieved by capability of an application to ask for another application to show a particular distributed microdocument or multimedia object.
 
 

Java software

  KISS : Java is a language designed forWWW applications and it provides support for creating multi platform applications.
  Java is already really usable. The programming tools have matured and existing classes cover almost all requirements stated by interactive electronic applications.
 

CASE: information kiosk

 Information kiosk is one way to deliver information in multimedia format. Information kiosk is usually a stand-alone application that is used for browsing information with marketing and sales purpose. Data presented in information kiosks has always other possible uses. For example, digital photos in a marketing information kiosk application may be used also in an operations and maintenance guide of the product. The following solutions are different possible implementation methods for an information kiosk.
 
 

Solution 1: write it

  KISS : It is hard to followKISS without base model. You have to create everything.
 Create an information kiosk with a multimedia authoring tool. The application is rather fast to create and the creators can enjoy real artistic and technical freedom. On the other hand, the content is hard to maintain and it is too easy to create applications that are hard to use.
 
 

Solution 2: relational database

 KISS : Use already existing data management solution, relational databases, for storing different types of information.
 Store information content and some layout information into a relational database. The user interface is a collection of windows that show to the user information coming from the database. The database contains:
 
  • Screen information contents as small microdocuments in format X
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  • Multimedia objects linked to microdocuments with a coding system
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  • Relations between microdocuments
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  • Lay-out definitions
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  • Link targets managed separately from link anchors
    •  The information is maybe maintainable but the database may become really complex.
     
     

    Solution 3: do it the structural way

     KISS : Simplify information handling and management with distributed information modules and use a Stand-alone Intranet as a base for implementation.
      Use the structural methods,SGML ,XML ,HyTime ,DSSSL , distributed microdocuments and distributed multimedia objects and implement the system as simple as possible using existing components. The Solution 2 with a relational database that stores the information seems to be like re-inventing the wheel.SGML approach provides the same model with more elegant existing tools:
     
  • Screen information contents as small microdocuments inSGML /XML format
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  • Multimedia objects linked to microdocuments.
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  • Microdocuments combined to a master SGML document, although stored in pieces in a database
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  • Lay-out definitions inDSSSL format
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  • Linking managed withHyTime
    •  The information kiosk's physical information model is based on microdocuments' structure definitions, distributed microdocuments and hierarchies of distributed microdocuments:
     
  • Screen types in the kiosk are each based on a microdocumentDTD (Document Type Definition) and its accompanying lay-out definitions.
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  • Producer of information can concentrate better on writing into guiding templates with the help of existing information model.
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  • End user sees consistent screens and can also change pre-defined structures and lay-outs to others.
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  • One screen is one distributed microdocument that contains the textual information and links distributed multimedia objects to the screen.
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  • Producer creates information easier into a small and well-defined block than to a big screen jungle.
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  • End user understands the screens better because of the relatively small amount of information in one screen and consistency of the context model and content.
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  • Whole kiosk is actually one bigSGML document that is stored in pieces.
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  • Producer can create information in other applications and import it to the kiosk's information content. The producer can also create different views for the user by changing the structures, lay-outs and context definitions.
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  • End user can export information in pieces and also as a whole information collection inSGML format. Browsing can also be done in book-like linear fashion besides of a normal one screen at a time view
    •   Information in the kiosk application can be managed with existingSGML information management tools. The browser can be built by using commercialSGML browser application programming libraries. A thin client approach is aWWW browser with Java applets. Information production can be done with configured commercialSGML editors or simpler, forms based editor applications.
     The system is based on a Stand-alone Intranet approach, and this supports well the future linkage into a corporate Intranet and distributed microdocuments stored in servers in the network.
     
     

    Conclusions

     
  • Combination ofWWW andSGML /XML opens new space for information usage.
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  • Existing tools are not really ready, yet, for combiningWWW and structural information (SGML /XML ).
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  • The development speed of tools is quick and long implementation projects may have difficulties with that.
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  • Structured information is still a new thing. Authors for the material must be trained.
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  • Information management is easier for chunks of information that follow pre-defined structures.
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  • Pre-defined structures for information chunks are enough for many types of applications.
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  • Microdocuments and multimedia files can exist in the client and in network. Hybrid model is often a good solution when, e.g., the speed of the network is slow for transfer of some multimedia files.
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  • WWW technology can be used and will be used in greater extent as a base for stand-alone interactive electronic information applications with gateways to networks.
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