This Morning's Road Map
System Documentation Overview
Query System Diagram Review
Query Front End Components
How the Front End Works
Query Front End UI File Types
Query Module File
Introduction to XML
Review Sample Query Module XML
Introduction to XML
What XML it is and isn't and how it compares to
HTML and Relational Databases
XML Basics (rules and a simple example)
More than basics (current related technologies
used for the IBIS User Interface like namespaces,
XSLT, Xpath, and Xinclude)
XML document validation (dtds, xsds)
Other XML Technology to be aware of
Resources
What is XML?
XML stands for eXtensible Markup Language
XML is a markup language much like HTML (data
in between tags example <tag>my data</tag>
XML is a markup meta-language. A framework for
defining other markup languages
XML was designed to describe data (not how to
present it)
XML tags are NOT predefined. You must define
your own tags
In some cases it is a replacement for EDI
What XML is Not?
Able to do anything on it's own. It is just plain text
with some sort of tag that enclose the data so it
can be differentiated from other data.
Able to define how your data is to be shown. To
show data, you need other techniques.
Able to easily deal with binary data like gifs, jpegs,
old MS-Word documents, MS-Excel documents etc.
A replacement for HTML
A replacement for relation databases
A Silver Bullet
Compared with HTML
HTML is for the formatting and presentation of
data. XML is for the storage/structuring of data.
HTML has a fixed set of elements that are defined
for a specific function. XML has a set of user
defined elements that are dependent on the
application(s) that uses the data.
HTML can be an XML document (called XHTML)
but XML is not necessarily an HTML document.
HTML is typically very difficult to parse to share it's
contained data with an application.
XML provides a standard way of sharing data
between disparate systems.
Compared with Relational Databases
Relational databases store lists of similarly
structured data. They are used to efficiently store,
quickly search/retrieve, and join together different
lists of data. Example: A user wants to see
everyone who lives in Utah with a zip code of
84108 and drives a blue car. A list of Utah citizens
could be joined with the DMV list of cars to quickly
produce such a list.
XML typically stores nested hierarchical structures.
These nested structures can completely contain all
the data for a given item. Example: The same XML
document structure can be used to store data
about a motorcycle, car, truck, tractor, or tricycle.
Summary of XML
Allows for user defined tags and structure
which includes hierarchical nesting of related
but different data elements.
Each XML language is targeted for its own
application domain that knows how to use it.
Provides a mechanism for sharable, platform
independent files.
Has free tools and libraries that allow for the
creation, usage and adoption of XML data.
Is NOT anything special – not a silver bullet.
XML Basics
Must begin with XML declaration (prolog)
Must have one unique root element
All element tags must have an opening and
matching closing end-tag
Blank/Empty elements can be coded in a single tag
syntax. Example: <MY_TAG_NAME/>
XML element tags are case sensitive
All elements must be properly nested
All attribute values must be quoted
HTML comments are supported
Example: <!-- a comment block -->
More Basics & HTML Gotchas
Empty HTML tag elements need to be updated to have a " /"
on the tag's end (the extra space is for Netscape compatibility).
Some of these are: <br />, <hr />, <img /> and
<input />.
XML only likes three characters below the space character " "
(0x20): tab, line feed, and carriage return (0x9, 0xA, 0xD).
The "<", ">", and "&" characters are NOT allowed within an
element's text. These need to be escaped as &lt;, &gt;, and
&amp;.
&nbsp; is undefined in XML but &#xA0; / &#160; will
produce a non-breaking space character.
Special CDATA section where everything is ignored by
the parser (except characters below " "). Example:
<![CDATA[anything < can go inside here]]>
Sample XML
<?xml version="1.0"?>
<note>
<to alias='Jack Trip'>Jack</to>
<from>Jill</from>
<heading>Reminder</heading>
<body>Don't forget to bring your pail. We are
going to have a good time hiking up to
the well and fetching the water for my
goldfish Ralph.
</body>
</note>
Same Sample XML Showing that
Indenturing does NOT matter
for Validity – but does for
Readability
<?xml version="1.0"?><note><to alias='Jack
Trip'>Jack</to><from>Jill</from><heading>Reminder</h
eading><body>Don't forget to bring your pail. We
are going to have a good time hiking up to the well
and fetching the water for my goldfish Ralph.
</body></note>
Please use the [Tab] key and keep your code
and be consistently indented.
Overview of Other XML Stuff
Used for the IBIS User Interface
Namespaces
Xpath
XSLT
Xinclude
XML Namespaces
XML Namespaces provide a method to avoid
element name conflicts. Most XML extension
stuff utilizes a namespace to ensure that their
elements do not conflict with contained elements.
The XML Namespace Attribute is "xmlns:". Note
the "xi:" prefix which is part of the tag.
Example of syntax and usage:
<?xml version="1.0"?>
<xi:include href="../answers/yearAll.xml"
xmlns:xi="http://www.w3.org/2001/XInclude"/>
Xpath
XPath is a declarative language for:
Addressing XML elements (used in XLink/XPointer and
in XSLT)
Accessing XML Elements (pattern matching used in
XSLT and in XQuery)
Location paths are evaluated left-to-right and
resemble operating system directory paths
Each node resulting from evaluation of one step
is used as context for evaluation of the next
Example of selecting a module's count measure
element (selects the all the measure's elements):
/QUERY/MODULE/MEASURES/MEASURE[NAME='count']
XSL
XSL stands for eXtensible Stylesheet Language
XSL has nothing to do with HTML's CSS
XSL consists of three parts:
XSLT - language for transforming XML documents
XPath - mechanism to access XML document elements
XSL-FO - language for formatting XML documents for
printing (how XML if turned into PDF files).
Think of XSL as set of languages that can
transform XML into other XML structures, HTML,
XHTML, filter and sort XML data, format XML data
based on the data value, and output XML data to
different media, like web pages, paper, or voice.
XSLT
XSLT is the mechanism that is used to merge the
IBISQ User Interface XML data into HTML web
pages.
XSLT works by using XPath that defines parts of
the source document (nodes) that match one or
more predefined templates. When a match is
found, XSLT will transform the matching node(s)
of the source document into the result document
based on how the template rules are coded.
XSLT has XSL namespace functions that allow for
basic string, element node, and node set data
manipulation/operations.
XSLT Example –Module Overview
Section Element Template
<xsl:template match="OVERVIEW/SECTION">
<xsl:if test="string-length(TITLE) &gt; 0">
<div class="contentBlockTitle">
<xsl:value-of select="TITLE"/>
</div>
</xsl:if>
<xsl:copy-of select="TEXT/* | TEXT/text() | @*"/>
<xsl:if test="position() !=$overviewSectionsCount">
<br/>
</xsl:if>
<br/>
</xsl:template>
Xinclude
Xinclude is a mechanism that enables XML elements
to be split out into separate XML data files and
merged in at the time the file is parsed. This allows
the XML to be more modularized by having common
XML elements stored in one file and shared among
many module files instead of being replicated.
Currently, xinclude is not well supported in the open
source Java XML parsers. This feature has been
implemented as an extra XSLT step in the IBISQ
system and is only setup to work for query modules.
Note that recursive xincludes are supported.
Usage Example:
<xi:include href="sub_filename.xml"
xmlns:xi="http://www.w3.org/2003/XInclude">
XML Document Validation
A "Well Formed" XML document is a document
that conforms to the XML syntax rules outlines in
the XML Basics slide.
A "Valid" XML document is a "Well Formed" XML
document and also one which conforms to the
rules of a Document Type Definition (DTD) or a
XML Schema (XSD).
IBISQ User Interface XML Modules have XSDs but
are not used because the way xinclude has to be
implemented precludes it's usage.
XML Buzzwords
The technologies listed below have been a
standard for a few years now but they are not yet
completely implemented in most parsers/
products or are not ready for prime time.
XLink
generalization of the HTML link concept but with
higher abstraction level
more expressive power (multiple destinations, special
behaviors, linkbases, ...)
Xpointer - an extension of XPath
Xquery - SQL-like database queries
XQL - XML Query Language
XML Resources
W3Schools is a good all around website that
provides tutorials, examples, and reference
material for most web related technologies
http://www.w3schools.com/
Microsoft's MSDN
http://msdn.microsoft.com/library/
default.asp?url=/library/enus/adschema/adschema/c_group.asp
Good XML Technologies Overview can be found
at "The XML Revolution Technologies for the
future Web"
http://www.brics.dk/~amoeller/XML/