Languages for E-Business/E-commerceect7010/Materials/Lecture/Lec5.pdfSlide 5 ECT 7010 Fundamentals...

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merce Technologies Edited by Christopher C. Yang

Languages for

E-Business/E-commerce

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Aspects of content delivery

• Languages for formatting and aesthetics (HTML, DHTML, Style Sheets)

• Structure and semantics of the content (XML)

• Scripting languages for processing of data and interface with external applications (CGI, Java Server Pages, JavaScript, VBScript, Coldfusion, PHP)

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History of Web• Originally availability and dissemination of

information• Adopted SGML – Standard Generalized

Markup Language• Maintain the idea mark-up language, with

hyper links, removing complex features• HTML- HyperText Markup Language• DHTML – Dynamic HTML, more flexible• Not standardized, no common standards

adopted by the leading browsers.

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XML – eXtensible Markup Language

• Supported by major players like Microsoft and IBM.

• Projected to be the most relevant web standard of the future.

• Best suited for E-Commerce (as front-end and back end sub-systems can be conveniently integrated).

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PDF – Portable Document File

• Proprietary format from Adobe• Best suited for distributing complex

documents• Preservation of original style, format etc.• Freely available Reader (Adobe Reader),

– no charge for viewing the documents.

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SGML – Standard Generalized Markup Language

• Born out of generic coding and mark-up languages in early 1970’s.

• SGML as a formal standard under ISO• First edition in 1986• Amended in 1988.

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SGML (contd.)

• Specifies a standard method for describing the structure of a document.

• Open-ended definitions• Does not directly specify any type of content

data, no restrictions on any type of data.• Flexible, able to describe any logically structured

set of information (e.g. form, memo, book, dictionary, spreadsheets, databases).

• Sophisticated, used by a loyal group of developers,

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SGML - Not a markup scheme.

• But a means for describing any markup scheme.

• SGML can be used for developing markup schemes for different document classes.

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Uses of SGML

• Publishing• Multi-media• Save and store information for long

term – e.g. Association of American Publishers (AAP),

• Manuscript preparation and markup for publishers, authors, and editors – Air Transport Association (ATA),– Computer-aided Acquisition and Logistic Support (CALS) created

by U.S. Department of Defense• Supporting and maintaining military equipments

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HTML – Hyper Text Markup Language

• Most prevalent form of web pages is HTML.• Born out of rejection of SGML’s complexity, is

easy to use.• Both Microsoft I.E. and Netscape Communicator

support it. • HTML content can be formatted with the addition

of a few tags.• Can be created using dynamic code generators

or templates• Word processor files, even MS-Excel, Access and

PowerPoint files can be exported to HTML.

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Advantages and disadvantages of HTML

• HTML has pre-defined tags, both a strength and a weakness, depending on the user’s experience.

• Elements of HTML include title, body, background, paragraphs, lists, tables, forms, formatting (bold, italics, underline)

• Can add Java applets and ActiveX controls within HTML pages.

• HTML can be developed using editors ranging in complexity from MS Notepad to WYSIWYG.

• Limitation – tags cannot be created for new un-defined structure, format.

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Insertion of pictures and graphics in HTML

• One of the main reasons for the success of the WWW.

• Inline images, hyper-linked images (stored on a different page).

• Types of raster graphics: GIF, JPEG, PNG, no need for plug-ins.

Syntax for inserting a picture<html><head><title> Picture of a dog </title></head><body><IMG SRC = “dog.jpg” border = 0></body></html>

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Other features• Align – takes values bottom, top, left, middle and right.• Alt- an alternative message• Border – defines border width• Height- height of the image and allows resizing• HSpace- horizontal space• SRC- URL of the image• VSpace- vertical space• Width – width of the image and allows resizing• Background color

– <body bgcolor = “#99CCFF”>– Here, 99 denotes red, CC denotes green and FF denotes blue in hexadecimal notation.– or – <body background = “lightgreen.jpg”>

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Most common HTML tags<html> </html> Marks the beginning of the document and end<head> </head> Specifies the beginning and end of header<title> </title> Indicate the title ; not displayed on web page<body> </body> Indicates the main part of web page<hn> </hn> Specifies the size of heading from 1 (large) to 6<p> </p> Delimits a paragraph with a blank line<li> </li> Delimits the beginning and end of unordered list<hr> Inserts a horizontal line<br> Indicates a cut in the flow going to next line<b> </b> Indicates that the text within is emphasized<i> </i> Indicates that the text within is italicized<u> </u> Indicates that the text is underlined<table> </table> Inserts a table in the document<form> </form> Inserts a form in the document

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For additional functionalities, we might want to add Java applets

<APPLETCODEBASE=“..”CODE=“hm30.class”NAME=“HotMedia”WIDTH=“239”HEIGHT=“50”><PARAM NAME=“mvrfile”VALUE=“data/preview.mvr”></APPLET>

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Links to other pages

• Hyper-links- most attractive feature in Hypertext media.

• Makes navigation through the pages very convenient.

• Useful for e-commerce also, as it can be used to balance and distribute the load among various servers. Delegate time consuming operations to the service providers.

• <A HREF=“second.htm”> second page </A>• Here <A> and </A> act as anchors for the link.

HREF indicates the URL of the target page.

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Web publishing

• A web server should be running on the computer where the document to be published is located.

• FTP (File Transfer Protocol) allows remote insertion of pages on a web server.

• HTML editors– Many editors available, range of attributes

starting from simple Windows Notepad

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Features of HTML editors• Collaboration and site management

– Version control, navigate and control• Database features

– Integrate with database through JDBC or ODBC– Send from data to email address or save from data to file

• Deployment features– Multilingual editing, ftp to Web server

• Design features – JavaScript & VBScript support, – easy integration with CSS1 and CSS2, – DHTML with cross-browser tuning– Visual wizard for forms, tables and frames – Support for image composition and mapping, Pixel-precise positioning– Drag and drop support– HTML syntax checking, spell checker, site navigation overview

• HTML editing features– Customizable templates– HTML validation and cross XML compliance tool.– Search, replace, replace all features– Supports Java applets, ActiveX, CGI– Syntax coloring– In-built DHTML scripts or wizard– Import, view, play multi-media files (GIF, JPEG, BMP, WAV and MIDI)

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Advanced HTML and DHTML• Dynamic behavior of a web page can be created using many

technologies, e.g. JavaScript, VBScript, Document Object Model (DOM), and Cascading Style Sheets (CSS).

• The display of the web page can be changed after the page loads.

• Use of CSS for a uniform look and feel of the whole website.• Event-driven animation can be interactive and interesting.• Additional HTML tags

– Tags <div> and <span>– Advisable to use <div> as a generic container.

• Create a box and placed anywhere in the page and filled with whatever content

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<!DOCTYPE HTML PUBLIC “-//W3C//DTD HTML 4.0 Transitional //EN”><HTML><STYLE type = “text/css”><!--#pic1{POSITION: absolute;Z-INDEX: 1;LEFT: 30px;TOP: 30px;Visibility: visible}-- ></STYLE><BODY><div id= pic1><img src= “http://mis.mgmt.umb.edu/euni.gif” width= 100height=50 alt= “ ” border = “0”></div></BODY></HTML>• Both absolute positioning and relative positioning are possible.• With DHTML, less data has to be downloaded, as there are no

large bitmap files.

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Elements that DHTML can control• Ability to hide and unhide portions of pages.• Display attributes of style sheets (text, background,

form field, images, frames, tables and paragraphs).• Animation effects, make them more interactive and

engaging• Scroll bars, ticker objects• Events

– OnBlur, OnFocus, OnLoad, OnAbort, OnChange, OnClick, OnError, OnKeyDown

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Portable Document Format (PDF)

• PDF writer and distiller• On any computer platform

– (DOS, Mac, Unix, Windows)• Preserves the format and looks• Can’t be modified, tampered with if protected• PDF Reader available free of cost to any user.• FrameMaker and Illustrator are able to write PDF

format.• Corel with WordPerfect can export to the original

PDF format but cannot modify existing documents.• Can be setup as an add-in to MS Word

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Cascading Style Sheets (CSS)• More powerful• More flexible• Useful for designing consistent looking web pages, like

templates• Designers will create style sheets and apply them to any web

page.• Developers can define their own classes, and new HTML

elements.• CSS Fundamentals

– Style sheets have a defined order of precedence– Formatting rules are applied in a hierarchical manner– CSS1 – by W3C, a set of style sheets or statements that may

determine how a given element is presented in a web page format,using Netscape and I.E. browsers.

• Advantages of CSS– Separation of style and layout of HTML files from their informational content.– Provides relative measurement for any size of monitor screen or resolution.– Enable companies to implement a house look and feel on their site, promote branding.– Improve the printing of web documents instead of having unpredictable HTML transfer to

paper.– Enable access to the web for people with disabilities (larger fonts, variation of colors)

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CSS2• A newer standard proposed by W3C and agreed

upon by the industry for richer and more accessible web pages.

• See latest news:– http://www.w3.org/Style/CSS/#news

• New features – sidebars, navigation scrollbars• Images can be layered• Control over table layout• Useful features of CSS

– Both absolute and relative measurements can be applied– Color control– Fonts and texts can be formatted – Position, alignment properties– Spacing and areas (which includes borders, margins,

padding, width, height, float property and clear property).

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Example of a simple style<html><head><title>Style sheet</title><style type = “text/css”><!--body {background: #FFFFFF}A:link {color: #80FF00}A:visited {color: #FF00FF}H1 {font-size: 24pt; font-family: arial; color:blue}H2 {font-size: 18pt; font-family: braggadocio}H3 {font-size: 14pt; font-family: Desdemona}-- ></style></head><h1>this is heading 1 </h1><h2>heading 2</h2><h3>heading3</h3></body></html>

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SGML, XML, and HTML

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Relating XML to SGML

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SGML, HTML, XML

• Standard Generalized Markup Language (SGML) is a way of expressing data in text-processing applications. It’s been around for more than a decade;

•both XML and HTML are document formats derived from SGML. Thus they all share certain characteristics, such as a similar syntax and the use of bracketed tags. •But HTML is an application of SGML, whereas XML is a subset of SGML.

• The distinction is important. Basically HTML can’t be used to define new applications, but XML can.

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Relating XML to SGML

• SGML is a very powerful, very general standard, but with that power comes increased complexity.• XML is a subset of SGML intended to make SGML “light”enough for use on the Web in which XML is a proper subset of SGML - all XML documents are valid SGML documents, however not all SGML documents are valid XML documents:

SGML XML

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Relating XML to SGML (Cont’d)

The following shows the relationships among SGML, XML, and HTML, rectangle boxes indication applications, and ellipses indicate framework languages or meta-languages:

SGML XML

Text EncodingInitiative

ChannelDefinitiion

Format (CDF)

Open FinancialExchange

(OFX)

ChemicalMarkup

Language(CML)

DocBook

Edgar

HTML

SGML and XML Applications

WirelessMarkup

Language(WML)

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Relating XML to HTML

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Relating XML to HTMLXML documents consist of three distinct components, namely:

1. Data content - the words themselves2. Structure - the document type and the organization of its elements, i.e., memo, contract, cooking recipe. Also, what kindof elements it can contain and in what order they can occur.3. Presentation - the way the information is presented to the reader, on a piece of paper, a browser screen or via voice synthesis. Also which fonts or voice inflections are used for each element type and so on.

The central idea of XML is that significant benefits accrue to the document owner if these three aspects of a document are kept separate and made explicit in a computer system.

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Relating XML to HTML (Cont’d)

Let’s compare and contrast the treatment of the three strands of a document in traditional word processors to their treatment in XML.

Content

Structure

Presentation

Content

Structure

Presentation

TraditionalWYSIWYG

(HTML)Document

XML Document

Difference in XML andHTML documents

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Relating XML to HTML (Cont’d)• Structure

Traditional approach: As for structure - capturing what the information really is - the concept is hardly present at all. The only structural information stored relates to the creation of the final paper output - details about page margins, font sizes, and so on.XML approach: the inherent structure of documents such as procedure manuals, invoices, and tax returns is considered just as important as the content itself. Presentation information isalso important but is kept well separated from the content.

• In XML, you create document content by concentrating on what the information really is and how it is structured as shown in the next slide.

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What is XML?

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What is XML?

• XML is actually compatible with SGML - XML documents can be read by any SGML authoring or viewing tool.

• However, XML is less complex than SGML, and it’s designed to work across a limited bandwidth network such as the Internet.

• According to Tim Bray, coeditor of the XML specification, the idea behind XML was to take the benefits of SGML, remove the complicated parts, keep it light, and make it work on the Web.

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What is XML? (Cont’d)• HTML, SGML, and XML will continue to be used where

appropriate; none of them will render the others obsolete. • HTML will remain the simplest way to publish data

quickly on the Web, mostly short-term data such as meeting agendas or advertising brochure.

• If the data has a longer-term use and needs a bit more structure, Web builders will want to move to XML.

• Unlike HTML and XML, SGML will probably never gain widespread acceptance on the Internet, simply because it was never designed or optimized for the demands of a network protocol. For high-end, highly structured publishing applications, SGML will continue to fit the bill.

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What is XML? (Cont’d)

• XML is an acronym which stands for eXtensible Markup Language.

• XML is not a software program, and like HTML, it provides a standard approach for describing, capturing, processing, and publishing information which has significant benefits over HTML.

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• XML Vs. HTML

HTML XML  <h1>Invoice </h1> <p>From: Joe Bloggs <p>To : A. Another <p>Date : 1 Feb 1999 <p>Amount : $100.00 <p>Tax : 21 % <p>Total Due : $121.00

 <Invoice> <From>Joe Bloggs</From> <To>A. Another</To> <Date year = ‘1999’ month = ‘2’ day = ‘1’ /> <Amount currency = ‘Dollars’>100.00</Amount> <TaxRate>21</TaxRate> <TotalDue currency = ‘Dollars’>121.00</TotalDue> </Invoice>

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– XML is a markup language, unlike other markup languages, e.g. HTML, are fixed markup languages that provide a certain feature set in its markup which is fixed in the design of the language. It has a fixed set of tags with which you craft your documents - <H1>, <P>, <TABLE>, etc.

– XML, on the other hand, does not define any particular set of tags, rather, it provides a standardized framework with which to define your own, or to use those defined by others that best fit your needs.

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<Main><Name>Curry</Name><CountryOfOrigin Country = “India”/><Description>Distinctive. Excellent with slow

cooked, earthy dishes.</Description><Example>Curry Chicken</Example></Main>

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• The majority of people simply use the XML-based markup languages created by others that best fit their purpose rather than creating his/her own markup language. For instance there is already a number of industry standard XML-based languages exist in fields such as Push Technology (CDF -Channel Definition Format), Electronic Commerce (IOTP –Internet Open Trading Protocol) and WAP (WML –Wireless Markup Language).

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An Example: Use of XML

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An Example: Use of XMLThe main advantage of being able to define your own markup language is that it gives you the freedom to capture and publish useful information about what your data is and how it is structured, instead of having to stick to the defined format.For instance, a company running an e-Business selling PCs on the Internet has the following sort of information that needs topublish:

Maker: Acme PC IncModel : Blaster 555Storage:

RAM: 72 MBHard Disk : 2GB

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An Example: Use of XML (Cont’d)

<h1>Personal Computers For Sale</h1><h2>Maker : Acme PC Inc</h2><h3>Model : Blaster 555</h3><table border = 1><tr> <td>Storage</td> </tr><tr> <td>RAM</td> <td>72MB</td></tr><tr> <td>Hard Disk</td> <td>2 GB</td> </tr>

</table>

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The original data has been transformed into HTML for publishing purpose. The original data has been transformed, useful information about what the information really is has been lost. The HTML version of the data knows nothing about PCs or hard disk sizes. All it knows about are heading levels, tables, italic text, etc. As a consequence, when this document is let loose on the WWW, search engines and users alike see only a collection of levels, tables, italic text, etc as in the figure in the next slide.

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HTML document linked to the WWW:

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Instead, the XML document looks like this:

<PcForSale><Maker>Acme PC Inc</Maker><Model>Blaster 555</Model><Storage><Ram Units = “MB”>72</Ram><HardDisk Units = “GB”>2</HardDisk>

</Storage></PcForSale>

This document can have a much richer interface to the Web, an interface that presents all sorts of possibilities about how it might be put to use, as in the figure in the next slide.

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XML document linked to the WWW:

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By keeping information about what the pieces of data really are, i.e. a hard disk capacity, a PC model name, etc - you can contemplate:1. Letting the browser do the work to format the data on the user’s screen. Perhaps allowing users to choose between a variety of “looks” or presentation formats for the same data.2. Letting the user’s browser perform calculations on the data, and manipulate and display the results in a variety of ways.3. Allowing intelligent searching of the information, .e.g., “find all PCs for sale on the Web with disk drive capacity greater than 2GB.”

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4. Intelligently checking that all the pieces of information required for a proper entry on the PC selling Web page are actually there, e.g., “all PCs must have a RAM size element and can optionally have a hard disk size element.”5. Performing complex queries on the data either for your own management purposes or as a service to customers, e.g., “how many laptop PCs with built-in CD-ROM drives were sold last month in Arkansas?”6. Building rich links between different types of information, e.g., linking a sales invoice (itself perhaps an XML document!) with the particular makes/models of PCs it references.

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7. Standardizing a set of XML element types for an entire industry, such as PC vendors. Users and vendors alike would benefit from the standardization. Software “robots” could crawl the Web to find the perfect PC for you, based on criteria you specify. Vendors would be able to easily contrast their offerings with those of the competition via “tick sheets” and so forth.8. Avoiding the need to “dumb down” data into HTML prior to publishing. This activity often involves complex software and is frequently error prone. With XML, the data can be stored and published in the same format. You don’t need either batch or on-the-fly translation into HTML.

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Why’s XML important

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Why’s XML important

• Problem: A disclaimer saying “Best viewed at 800-by-600-pixel resolution”.– XML will help to solve that problem because,

rather than specifying where to display something, Web builders will be able to specify the structure of the document. For example, you can specify the document’s title, its author, a list of related links, and so on. Then any device with an XML browser -a palm-top computer, a set-top box, or a high-powered workstation, for example - will be able to render a version of the document specifically tailored to that device.

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Why’s XML important (Cont’d)

• Perhaps XML’s best feature, though, is its inherent extensibility. Companies and organizations will be able to extend XML to meet new challenges and applications. One XML-based language is already in use -Microsoft’s Channel Definition Format (CDF) - and more are on the way, including the Resource Definition Format (RDF) and the Open Software Description (OSD).

• XML holds the promise of becoming a standardized mechanism for the exchange of data as well as documents. For example, XML may become a way for databases from different vendors to exchange information across the Internet.

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Document Type Definition (DTD)

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• A Document Type Definition (DTD) is a set of syntax rules for tags. It tells you what tags you can use in a document, what order they should appear in, which tags can appear inside other ones, which tags have attributes, and so on. A DTD can be part of an XML document, but it’s usually a separate document or series of documents.

• Because XML is not a language itself, but rather than a system for defining languages, it doesn’t have a universal DTD the way HTML does. Instead, each industry or organization that wants to use XML for data exchange can define its own DTDs.

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Document Type Definition (DTD) (Cont’d)

In a DTD, the XML documents can be arranged to be automatically checked in various ways, for instance:

1. A person’s name consists of an optional title, a given name, and a surname.2. A TV timetable contains one or more channels. Each channel contains one or more time slots. Each time slot has a program title and an optional description.

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Document Type Definition (DTD) (Cont’d)

These effects can be achieved in the DTD by listing the element types you wish to use in your document and indicating the structural order in which they can occur. A utility program called an XML Parser is then able to test whether or not the document meets the prescribed rules such as the following:

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XML processor (or XML parser)

• A tool for reading XML documents is popularly called an XML parser, though the more formal name is an XML processor. XML processors pass data to an application for authoring, publishing, searching, or displaying. XML doesn't provide an application programming interface (API) to an application, it just passes data to it. No XML processor will parse data that isn’t well-formed.

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Well-formed and Valid Document

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Well-formed and Valid Document

• Two related types of XML documents– Well-formed document: A well-formed XML document

conforms to the general rules of XML syntax, which are more rigorous than those of either HTML or SGML.

– XML character data is never left hanging without an ending markup designation of some sort, either an end tag such as in the tag-pair <MYTAG></MYTAG> or a special empty element tag with a forward slash before the right-angle bracket, such as <MYTAG/>.

– XML markup always starts with a left-angle bracket or an ampersand; element types and attribute names are case-sensitive; attributes require quotation marks; and so on.

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Well-formed and Valid Document (Cont’d)

– Valid document: Valid XML documents are ones that conform to a specific DTD. Confirming the validity of XML documents is largely the work of authoring and publishing tools, whereas XML-capable browsers need only check for well -formedness in order to read XML documents.

• The XML parser in an authoring tool will have to worry about the checking for well-formedness and validity, but browsers will have to worry only about looking for well-formed XML.

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• Well-form– Minimum set of requirements– logically coherent in the manner defined by

the XML specification• Valid

– well-form– conforms to a document type definition

containing declarations that specify structure of a document

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Well-formed

• Well-formed– Elements

• contain one or more elements• contain a uniquely name element (root

element), no part of which appears in the content of other elements

• all other elements within the root element must be correctly nested

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<customer><customer-id id=“aa0001”>

<customer-name><first-name>Peter</first-name><last-name>Taylor</last-name>

</customer-name><customer-address>123, High Street</customer-address><customer-phone>21234567</customer-phone>

</customer-id><customer-id id=“aa0002”>

…</customer-id>

</customer>

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– Attributes• values pass to the application by the XML

parser• do not constitute part of the content of the

element• should not contain <, &, or single ‘ or “

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– Entities• a mechanism to associate a name with a long

piece of text• general entities

– <!ENTITY entityname “some lengthy text …. ”>– <!ENTITY entityname SYSTEM

“http://www.server.com/file.html”>

• parameter entities– <!ENTITY % entityname “some lengthy text … ”>

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HTML Vs. Well-formed XML

• HTML<TITLE>Reasonable HTML</title>Some text, and I <I>really</I> don’t want a line break between “line” and “break.”<P>Here’s a picture: <IMG src=madonna.jpg>

• Well-formed XML<HTML><TITLE>Well-formed XML</TITLE>Some text, and I <I>really</I> don’t want a line&#Xa0; break between “line” and “break.”<P>Here’s a picture: <IMG src=“madonna.jpg”/></P></HTML>

Unicode non-breaking space

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XML Applications

• Push TechnologiesCDF - Channel Definition Format

• Electronic Commerce transactions IOTP – Internet Open Trading Protocol

• MathematicsMathML - Mathematical Markup Language

• Wireless Application ProtocolWML – Wireless Markup Language

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DTD

• Content Models: XML allows element types to be declared that can contain other elements, the order and occurrence of these elements can be constrained in various ways.

• Element type declarations<!ELEMENT …>e.g.,

<!ELEMENT foo EMPTY>foo element to be empty element

<!ELEMENT foo ANY>foo element contains any mixture of character data and other

elements as long as those element type have been declared in the DTD

<!ELEMENT foo (apple|orange|banana)>foo can contain exactly one apple, one orange, or one banana

element

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DTD• A sequence of elements, one after another

<!ELEMENT person (name, address, telephone)>A person element consists of a name element, an address element, and a telephone element, in exactly that order.

E.g., (VALID)<person>

<name>…<address>…<telephone>…

</person>E.g., (INVALID)

<person><name>…<address>…

</person>

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DTD

• A selection from a list of elements, only one allowed<!ELEMENT fruit (apple|orange|banana)>

A fruit element consists of an apple element, or an orange element, or a banana element.

E.g., (VALID)<fruit>

<apple>…</fruit>

E.g., (INVALID)<fruit>

<apple>…<orange>…<banana>...

</fruit>

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DTD• An element occurring once or not at all

<!ELEMENT person (name, address, telephone?)>A person element consists of a name element, followed by an address element, optionally followed by a telephone element.

E.g., (VALID) or<person> <person>

<name>… <name>…<address>… <address>…<telephone>… </person>


<person><name>…<address>…<telephone>…<telephone>…

</person>

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DTD• An element occurring zero or more times

<!ELEMENT person (name, address, telephone*)>A person element consists of a name element, followed by an address element, optionally followed by zero or more telephone elements.

E.g., (VALID) or<person> <person>

<name>… <name>…<address>… <address>…

</person> <telephone>…<telephone>…

</person>or

<person><name>…<address>…<telephone>…

</person>

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DTD• An element occurring one or more times

<!ELEMENT person (name, address, telephone+)>A person element consists of a name element, followed by an address element, optionally followed by one or more telephone elements.

E.g., (VALID) or<person> <person><name>… <name>…<address>… <address>…<telephone>… <telephone>…</person> <telephone>…


<person><name>…<address>…</person>

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, Strict ordering| Selection+ Repetition with minimum 1* Repetition with minimum 0? Optional() Grouping

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DTD• An element containing any other element(s) in any order

<!ELEMENT person ANY>A person element consists of any combination of element in any order.

• Some more complex examples– <!ELEMENT invoice (from,to,item+)>

An invoice element consists of a from element followed by a toelement followed by one or more item elements.

– <!ELEMENT invoice (from,to?,item+)>An invoice element consists of a from element, optionally followed by a to element, followed by one or more itemelements.

– <!ELEMENT invoice (from,to*,item+)>An invoice element consists of a from element, followed by zero or more to element, followed by one or more item elements.

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DTD• Some more complex examples

– <!ELEMENT invoice (from,to,(item+|batch*))>An invoice element consists of a from element followed by a toelement. This is followed either by one or more item elements or zero or more batch elements.

– <!ELEMENT invoice ANY>An invoice element consists of a any combination of elements and character data, in any order.

– <!ELEMENT invoice (((from,to)|(to,from)),item?)>An invoice element consists of the elements from and to in any order, followed by an optional item element.

– <!ELEMENT invoice (from,to,(item+|batch?))>An invoice element consists of a from element followed by a toelement followed by either one or more item elements or an optional batch element.

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X (x,(y|z)?)x followed by either y or z optional<X><x> </x>

</X>

<X><x> </x><y> </y><z> </z>

</X>

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x, y, and z in any order or a

( ( (x,y,z) | (x,z,y) | (y,x,z) | (y,z,x) | (z,x,y) | (z,y,x) ) | a )

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Attributes – Example 1<?xml version="1.0"?><!DOCTYPE Attribute_test [

<!ELEMENT Attribute_test ANY><!ELEMENT fruit (#PCDATA)><!ATTLIST fruit

type (Orange|Apple|Mango) "Apple"From CDATA #IMPLIEDProvider CDATA #FIXED "ABC Company"Price CDATA #REQUIRED>

<!ELEMENT Owner (#PCDATA)><!ENTITY owner "D.J.">

]><Attribute_test>

<fruit From="USA" Provider="ABC Company" Price="1.0"/><Owner>&owner;</Owner>

</Attribute_test>

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AttributesAttribute List Declarations

– String– Enumerated– ID, IDREF, IDREFS– ENTITY, ENTITIES– NMTOKEN, NMTOKENS– NOTATION

• String Attributes<!ATTLIST foo bar CDATA … >

• Enumerated attributese.g.,

<!ATTLIST apple quality (GOOD|BAD|INDIFFERENT) … >

Valid: <apple quality = “GOOD”>Invalid: <apple quality = “good”>

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Attributes• ID/IDREF/IDREFS

ID:<!ATTLIST foo UniqueName ID … >

e.g.,<foo UniqueName = “P1234”>

IDREF: IDREF attributes are the flip side of the coin. Amy IDREF attributes assigned values in a valid XML document must match the value assigned to an ID attribute somewhere in the document.Here is an example of a bar element using its IDREF attribute to point to the foo element of the last example.<!ATTLIST bar Reference IDREF … ><bar Reference = “P1234”>

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Attributes• ENTITY/ENTITIES

ENTITY is similar to the sort of macros you would expect to find a word processing package they are short strings or characters that can be used as abbreviations for large pieces of text (or markup)

(SEE Example 1)

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Attributes

• NMTOKEN/NMTOKENSAn NMTOKEN attribute is restricted to certain characters allowed in a name: any combination of letters, digits, and some punctuation characters “.”, “_”, “-”, and “:”. Note that this list does not contain any white space characters.

E.g.,<ATTLIST product code NMTOKEN …>

Valid: <product code = “Alpha-123”><product code = “333”>

Invalid: <product code = “A 123”>

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Attributes defaults

• Required attributes

(SEE Example 1)

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Attributes defaults

• Implied attributesThese are attributes that can be left unspecified if desired. The XML processor passes the fact that the attribute was unspecified through to the XML application, which can then choose what best to do.

(SEE Example 1)

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Attributes defaults

• Fixed attributesThese are attributes that have their value fixed in

the DTD.

(SEE Example 1)

Languages for E-Business/E-commerceect7010/Materials/Lecture/Lec5.pdfSlide 5 ECT 7010 Fundamentals...

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