Course Outline

Adopting XML: Tomorrow's Web

1 Day Tutorial Format

Course Description

A one day workshop which gives an overview of the present state of development and future prospects for XML, (eXtensible Markup Language), the proposed new open standard for Web documents. The workshop includes some technical material and hands-on elements. Participants should have a working knowledge of HTML.

NOTE This course has not been updated since 1998 and is now woefully out of date. The successor course is here.

Who should attend

• Web developers,
• Web development managers.

Course Objectives

The course is intended to help you:

• Understand the underlying technology of XML
• Understand the benefits offered by XML, and their costs.
• Be aware of the current state of the standardisation of XML
• Be aware of commercial implementations and market committments to XML
• Be aware of available tools for generating XML documents
• Understand the issues required in switching to XML from other technologies
• Decide whether, and when, to switch your Web development to XML

Course Outcomes

The delegate will understand how XML fits into the architecture of the Web, and will have the resources to develop a strategy for incorporating XML into their organistions' Web presence, or for converting an existing Web presence entirely to XML.

• Course Notes
• Set of Online and Published references
• XML Strategy Workbook

Working Method

• Presentation of Information
• Worked case-study
• Hands-on investigation
• Personal plan workbook

But first, an apology...

This course was written by and was scheduled to be presented by me, Simon Brooke. However, what I did this summer was very carelessly roll an open car and break my back, so it will instead be presented by my friend and colleague, Gordon Howell. I'm sure he'll keep you entertained and informed for the duration...

Presenting this course

Tutors notes in the text are marked up like this - just as reminders of where you are at and any special things to mention.

There are many hypertext links in the body of the document. Except where mentioned in tutor's notes, they are not part of the course and you need not follow them. If you do follow them, please come back to the body of the course!

Please ensure that you have downloaded local copies of both the SMIL demo and the JUMBO demo in advance.

If you don't want these notes to appear while you are giving the presentation, edit slideshow.css and remove the commenting around the line 'display: none' at the end of the file

Course Outline: What we're going to do today

• What is XML
• Status of XML
• Benefits of XML
• Document Type Definitions and dialects of XML
• Anatomy of an XML system
• XML in your context
• Review of XML Tools and Technologies

What is XML

• Key features
• Differences from HTML
• Differences from SGML
• Reality check

Key Features

• A markup language
• Describes the structure of a document
• Not the visual appearance (CSS1, CSS2, XSL)
• Written in simple ASCII

Visual Appearance and Style Sheets [1]

• The visual appearance of a document should be controlled by style sheets.
• The appearance of this one is.
• In XML as in HTML you don't have to use style sheets.
• If you don't, you will get a plain, simple appearance.

If people are interested, you can open the style sheet for this presentation, slideshow.css, in a text editor.

Visual Appearance and Style Sheets [2]

• A special style sheet language, XSL, has been written to support the new features of XML.
• You can continue to use existing CSS1 and CSS2 stylesheets.
  • Probably.
  • Depending on what individual browser vendors decide to support...
• This presentation is not about style sheets.

Differences from HTML

• In a word, extensible.
• Also, strictly parsed.

Extensible: what does this mean for you?

• Allows you to define new markup.
• Describing structure, not appearance.
• Makes it easier for programs to extract information from your documents.

Extensible: a simple example [1]

     <customer-details id="AcPharm39156">
     <name>Acme Pharmaceuticals Co.</name>
     <address country="US">
         <street>7301 Smokey Boulevard</street>
         <city>Smallville</city>
         <state>Indiana</state>
         <postal>94571</postal>
     </address>
     </customer-details>
   

Extensible: a simple example [2]

• What does this do?
• For the user directly, very little.
• For the user's program, it allows it to isolate items of structured information and handle them in intelligent ways to help the user.
• But only if the user's program understands the special markup you have defined.

Strictly parsed: what does this mean for you? [1]

Documents which do not conform to the standard will not be rendered by an XML browser.

At all.

• Tags and attributes are case-sensitive;
• End tags cannot be omitted - every <p> must have a </p>.
• Tags must be correctly nested:
  <b><i>This won't work</b></i>
• Et cetera, et cetera...

Strictly parsed: what does this mean for you? [2]

• Most Web designers are sloppy.
• More than ninety percent of all commercially authored Web pages do not conform to any standard and are not valid HTML.
• Few if any of the commercially available WYSIWYG tools generate valid HTML.
• Web authors switching to XML will need to adopt much more rigorous technical discipline.

Differences from SGML

• Like HTML, much simpler!
• Like HTML, optimised for delivery over restricted-bandwidth links.
• Unlike HTML, a true subset of SGML.
• All valid XML documents are valid SGML documents.
• SGML tools (conforming to ISO 8879) will work with XML.
• Organisations with an existing committment to SGML will find the transition to XML much simpler.

Reality check

• Where is this process at?
• Will this really happen?
• Will I have to change what I do?

Where is this process at?

• A draft standard has been published.
• Software tools are emerging.
• No mainstream browser is available yet.
• About where HTML was in 1994.
• Prediction: commercially important in two years, dominant in four.

Will this really happen?

• All the major players are involved.
• Many emerging standards depend on XML.
• XML has many advantages over HTML.
• Prediction: it will really happen.

Will you have to change what you do?

• HTML documents will continue to work with XML browsers.
• May need to be more correct than at present.
• Correct HTML documents (i.e. ones which validate) are very easy to convert to XML. Automatic conversion will be possible.
• Increasingly, search engines will depend on XML-based metadata.
• Increasingly, mainstream browsers will exploit XML-based metadata.
• Conclusion: no, but...
• Prediction: commercial Web authors who don't change won't stay in business.

Status of XML

• the World Wide Web Consortium
• Netscape Communications Corporation
• Microsoft Inc
• Other significant players

The World Wide Web Consortium ('W3C') [1]

• The standards body for the Web.
• An open organisation, anyone can join.
• Not for profit.
• All major players are members.
• Should your organisation be?

The World Wide Web Consortium ('W3C') [2]

• Driving the standardisation process for XML.
• Issued the XML 1.0 Recommendation in February 1998.
• Using XML as the basis for emerging standards in privacy, multimedia, etc.

Emerging XML based standards

SMIL: Synchronised Multimedia Integration Language A set of XML extensions to handle embedded multimedia.

PICS: Platform for Internet Content Selection A means of labelling the content of documents based on criteria of taste - mainly motivated by people who want to protect children from sexually explicit material.

RDF: Resource Description Framework A standard for structuring embedded metadata - making it easier for programs to understand documents.

Some other proposed XML-based standards

This slide is included simply to give some feel of the scale of the XML project...

• W3C Specifications Documentation
• Text Encoding Initiative (TEI)
• Channel Definition Format, CDF (Based on XML)
• W3C Document Object Model (DOM), Level 1 Specification
• Web Collections using XML
• Meta Content Framework Using XML (MCF)
• XML-Data
• Namespaces in XML
• Resource Description Framework (RDF)
• The Australia New Zealand Land Information Council (ANZLIC) - Metadata
• XML Metadata Interchange Format (XMI) - Object Management Group (OMG)
• Educom Instructional Management Systems Project (IMS)
• Structured Graph Format (SGF)
• Legal XML Working Group
• Web Standards Project (WSP)
• HTML Threading - Use of HTML in Email
• Open Software Description Format (OSD)
• XLF (Extensible Log Format) Initiative
• WAP Wireless Markup Language Specification
• HTTP Distribution and Replication Protocol (DRP)
• Chemical Markup Language
• Bioinformatic Sequence Markup Language (BSML)
• Virtual Hyperglossary (VHG)
• Weather Observation Definition Format (OMF)
• Open Financial Exchange
• Open Trading Protocol (OTP)
• FIXML - A Markup Language for the FIX Application Message Layer
• Signed Document Markup Language (SDML)
• Bank Internet Payment System (BIPS)
• OpenMLS - Real Estate DTD Design
• Customer Support Consortium
• XML for the Automotive Industry - SAE J2008
• X-ACT - XML Active Content Technologies Council
• Mathematical Markup Language
• OpenTag Markup
• Metadata - PICS
• CDIF XML-Based Transfer Format
• Synchronized Multimedia Integration Language (SMIL)
• Precision Graphics Markup Language (PGML)
• Vector Markup Language (VML)
• WebBroker: Distributed Object Communication on the Web
• Web Interface Definition Language (WIDL)
• XML/EDI - Electronic Data Interchange
• XML/EDI Repository Working Group
• European XML/EDI Pilot Project
• EEMA EDI/EC Work Group - XML/EDI
• DISA, ANSI ASC X12/XML
• Information and Content Exchange (ICE)
• CommerceNet Industry Initiative
• eCo Framework Project and Working Group
• vCard Electronic Business Card
• Telecommunications Interchange Markup (TIM, TCIF/IPI)
• Encoded Archival Description (EAD)
• UML eXchange Format (UXF)
• Translation Memory eXchange (TMX)
• P3P Syntax Specification
• Scripting News in XML
• InterX.org Initiative
• NuDoc Technology
• Coins: Tightly Coupled JavaBeans and XML Elements
• DMTF Common Information Model (CIM)
• Process Interchange Format XML (PIF-XML)
• Ontology and Conceptual Knowledge Markup Languages
• LACITO Projet Archivage de données linguistiques sonores et textuelles [Linguistic Data Archiving Project]
• Astronomical Markup Language
• GedML: [GEDCOM] Genealogical Data in XML
• Newspaper Association of America (NAA) - Classified Ads Format
• Notes Flat File Format (NFF)
• Java Help API
• Cold Fusion Markup Language (CFML)
• Document Content Description for XML (DCD)
• XSchema
• WEBDAV (IETF 'Extensions for Distributed Authoring and Versioning on the World Wide Web')
• Tutorial Markup Language (TML)
• Development Markup Language (DML)
• Java Speech Markup Language (JSML)
• XML and VRML (Virtual Reality Modeling Language)
• XML for Workflow Management [NIST]
• SWAP - Simple Workflow Access Protocol
• Theological Markup Language (ThML)
• XML-F ('XML for FAX')
• Extensible Forms Description Language (XFDL)
• Broadcast Hypertext Markup Language (BHTML)
• IEEE LTSC XML Ad Hoc Group
• Open Settlement Protocol (OSP) - ETSI/TIPHON
• WDDX - Web Distributed Data Exchange
• Common Business Library (CBL)
• Open Applications Group - OAGIS 6
• Schema for Object-oriented XML (SOX)
• VoxML Markup Language
• XMLTP.Org - XML Transfer Protocol
• The XML Bookmark Exchange Language (XBEL)

Netscape Communications Corporation

• Publicly committed to XML.
• Tim Bray of Netscape and Textuality is joint editor of XML standard document.
• Developing XML-based indexing protocol, MCF.
• Navigator 4 does not handle XML.
• Navigator 5 Beta

  "...includes XML support..."

• Source code is available

Microsoft Inc

• Publicly committed to XML.
• Jean Paoli of Microsoft is joint editor of XML standard document
• Developing XML-based indexing protocol, PICS
• Have an XML parser written in Java
• Have an XML authoring tool, XML Notepad
• Internet Explorer 4 partially handles XML
• Internet Explorer 5 will not fully handle XML

Benefits of XML

• SMIL: Glitz and eye-candy
• Meta information frameworks: benefits for searching and indexing
• Benefits for dynamic content
• Benefits for precise layout and visual appearance
• Limitations and costs

SMIL: Glitz and eye-candy

• Essentially a framework for embedding multimedia objects, so that they can intercommunicate
• Has some built-in multimedia capabilities
• Optimised for low bandwidth
• Designed to make it easy to add new handlers for new multimedia formats
• First commercial implementation: Real Networks G2

Say 'Smile'!

SMIL: An Example

Larry Bouthillier: "What I did last summer..."

• The presentation direct from Harvard
• The presentation: local copy
• The source

NB: You should ensure you have the G2 beta of RealPlayer to view this. As of November 1998, bugs in the server prevented the presentation from completely working over the Internet, but what does work on a 28k modem is still worth showing. To demonstrate the complete presentation, download the source and media in advance from here .

Document Type Definitions and dialects of XML

• What is a DTD?
• Do I have to use a DTD
• What DTDs are available?
• Who will write DTDs?

What is a Document Type Definition [1]?

• Every Web author has heard of one
• Every good Web author has seen one
  • typically http://www.w3.org/TR/REC-html40/loose.dtd
• Very few Web authors have written one

Do I have to use a DTD

• As with HTML, you don't have to specify a DTD.
• Even if you define new markup...
• ... but client programs won't know how to interpret your new markup unless you also define a DTD.
• As with HTML, you should specify a DTD...
• ... and we all do, don't we, children?

What DTDs are available?

• All the XML extensions discussed in this presentation are defined as DTDs.
• Thousands of SGML DTDs are available which can relatively easily be converted.
• Relatively few XML DTDs yet available.

Who will write DTDs

• Very specialised documents, technically demanding to write.
• For most purposes, suitable DTDs will quickly become available.
• Most Web authors will never write a DTD.
• Large organisations with special documentation requirements may write DTDs.
• Corporations which sell word-processors will probably write DTDs.
• Corporations which sell WYSIWYG Web authoring tools will certainly write DTDs.
  • In future, there will be much less distinction between a word processor and a Web authoring tool.
• Communities of interest with special technical needs will certainly write DTDs.

Anatomy of an XML system

• CML: Chemical Markup Language
• The JUMBO XML browser and CML

Chemical Markup Language

• An application of XML
• Specified by a special-purpose DTD
• Allows chemists to interchange information

The Jumbo XML Browser: Introduction

• Peter Murray-Rust, University of Nottingham, England.
• Prototype software.
• Developed for displaying and editing CML, but claimed to be general-purpose XML browser.
• Architecturally interesting.
• Almost unusable and certainly nowhere near user-ready!

The Jumbo Browser: Illustration

I'm including this because in my experience the browser is so hard to use you may not be able to make it do anything the course will see as interesting.

• Scalable, interactive diagrams linked into text.
• Links from objects in the diagrams into the text.
• Complex special notation.

Using Jumbo [1]

The XML source code for this demo

• This is an old version; I couldn't make the latest version do anything interesting to show you!
• Ignore the window called 'SGMLTree'.
• When the 'TableOfContents window opens, it's too small and you have to resize it.
• I think there should be some way of rendering the document as a readable document, but I can't work out how!
• Open the folder marked 'Assignments'
• Click on any of the little circles by the assignments.
  • A window opens with a picture of the molecule.
  • A window opens with predicted spectroscopy of the molecule.
  • You'll probably have to resize these.
• Rotate the molecule.
• Click on the highlighted atom and note how a highlight appears on the graph.
• Click on the little circles against other assignments and note how the graph and molecule change.
• Finally, look at the XML source for this demo.

Using Jumbo [2]

• No, I don't really understand it either - I'm not a chemist!.
• Notice how simple the XML source is.
• Notice how small the XML source is.
• XML is used to display complex technical information to a specialist audience in a form that audience will understand.

XML in your context

• Applications which will benefit greatly from XML
• Applications which will benefit little from XML
• Early adoption: arguments for
• Organisations which should aim to be early adopters
• Wait and see: arguments for
• Organisations which should aim to wait and see
• Hybrid strategy: arguments for
• Organisations which should adopt a hybrid strategy

Applications which will benefit greatly from XML

• Multimedia applications.
• Technical documentation applications, or applications involving special notation (e.g., mathematics, music).
• Applications incorporating client-end software agents.
• Applications requiring highly detailed illustrations.

At present, only where the audience is controlled

Applications which will benefit little from XML

• Simple publishing of text, with or without simple graphics.
  • What I did last summer..!

But even here the advantages of XML will gradually take over.

Early adoption: arguments for

• Better representation of technical information.
• Improved multimedia capabilities.
• Improved indexing capabilities.
• Development of new skills which will very rapidly become important.

Organisations which should aim to be early adopters

• Technical information
• Specialist search
• Gaining Experience

Early Adopters: Technical information [1]

Organisations which distribute large quantities of technical information to a targetted audience should adopt early.

• Improved indexing and searching allows better navigation of the documents.
• Special markup can be used to help document users and maintainers understand document structure.
• Technical notation can be easily incorporated where required.
• Vector graphics allow 'zoomable' detail.

Early Adopters: Technical information [2]

• Engineering companies distributing technical manuals.
• Companies exchanging technical specifications.
• Science and research establishments publishing technical information.

Early Adopters: Specialist search [1]

Organisations which publish volumes of reference information which users typically search should adopt early.

• Improved indexing and searching allows better navigation of the documents.
• Special markup allows client-side user agents to understand document structure and select 'interesting' information.

Early Adopters: Specialist search [2]

• News providers, especially upstream news providers such as PA and Reuters.
• Market information providers.
• Online libraries.
• Search engines.

Early Adopters: Gaining experience [1]

Organisations which view the Web as core to their business should adopt early.

• XML is radically different from HTML:
  • Much richer, more powerful;
  • Technically much more demanding.
• New skillsets and tools will be needed to publish effectively in XML.
• The learning curve is steep.

Early Adopters: Gaining experience [2]

• Web authors and Web production companies.
• Especially, software houses which make tools for Web authoring;
  • Still a considerable market opportunity in which new starters might succeed.

Wait and see: arguments for

'It's not ready':

No commercial quality XML browsers are yet available, and it may be some time before any emerge.

'It may never happen':

Some powerful software houses may see it as to their advantage to undermine the standardisation process.

'What we've got is good enough':

For many organisations, the present capabilities of HTML as enhanced with applets and various proprietary multimedia plug-ins will continue to fulfill their needs for some time to come.

Organisations which should aim to wait and see

• Successful on-line retailers: organisations with a big investment in existing Web technology, which is paying off for them, do not need to change now, but should track the technology.
• Organisations with simple 'brochureware' Web sites will not need to change for some time.
• Organisations for whom the Web is not a core part of their business do not need to change now.

Remember: better tools will emerge; this is still a bleeding edge.

Review of XML Tools and Technologies

• Parsers
• Editors
• Browsers

Parsers

Everyone and his dog seems to have written an XML parser in Java:

• James Clark
• DataChannel
• Chris Hubick (this one can be played with on line)
• IBM
• Megginson
• Microsoft

There are also a few parsers available in C, Python, etc...

Parsers are essential technology if you want to build user-level tools for XML, but, by themselves, don't do anything useful for the average user.

Editors

• University of Edinburgh XED,
  • Little more than a simple text editor with syntax checking.
  • In Java so platform-independent.
• Microsoft XML Notepad
  • Tree-view style editor.
  • Windows only.
• XML Pro
  • 'Tree-View' style editor similar to Jumbo's tree-view.
  • Windows only.
  • Vendor's Web site technically incompetent, which isn't encouraging...
• CLIP
  • Combines 'Tree-view' with highlighted source text, similar to early versions of HotMetal.
  • Windows and Solaris only.
• Visual XML
  • A great deal of thought has clearly gone into the user interface of this product.
  • Several user interface styles care available.
  • All are completely incomprehensible to me.
  • In Java, so platform independent.
• WebWriter
  • Based on existing SGML editor.
  • More than usually incomprehensible tree view.
  • Windows only.
• EMACS
  • Fortunately, Emacs SGML mode handles XML.
  • Text editor with syntax highlighting and well-formedness verification.
  • No WYSIWYG view.
  • Runs on all <joke>proper computers</joke>.

  (Yes, of course this presentation was written in EMACS).

A number of other SGML editing tools can be used for XML.

Browsers

• Jumbo
  • Demonstrates interesting new functionality not possible with HTML.
  • Edits as well as browses.
  • Extremely counter-intuitive and hard to use
• Fujitsu HyBrick
  • Looks like a browser!
  • Lays out simple documents straightforwardly.
  • All menu text, help text, et cetera, in Japanese.
  • Can't layout any of the documents from the Jumbo or SMIL demos
• Microsoft IE 5
  • Intended for real users to really use.
  • Renders all XML into HTML in order to lay it out, so can't do anything which couldn't be done with HTML.

SGML Browsers may also work.

Tools: The state of play

• None of the available XML browsers can even render the demos distributed with any of the other XML browsers.
• No WYSIWYG editor is yet available, and, indeed, to build one you would first have to build a working browser.
• None of the available XML editing tools appears suitable for creating large or complex document structures.
• There are good, established SGML tools, but these may be too expensive or too technically demanding (or both) for most Web production houses.
• There are still very considerable market opportunities.

Conclusions

Early days

When we planned this presentation in April 1998, we thought that by November this technology would be beginning to stabilise. It hasn't; it isn't ready for the real world yet.

Scope

XML and the family of proposals based around it could radically change the way we interact with all data and all machines: it has the potential to be far more pervasive than the Web is now.

Development could be very rapid

Given good document authoring, conversion and maintenance tools and at least one solid mass-market browser, conversion to XML could be very rapid indeed.

Thank you

Marketing Note

This course is new in second quarter 1998.

Course Author and Presenter

Simon Brooke has been a technical consultant in advanced software applications for thirteen years. He advises on the development of software architectures and systems, primarily for Internet and Intranet application.

As a consultant, Simon has advised many blue chip companies, primarily in the IT, Telecoms and Chemical industries, on the application and development of advanced software systems.