UNIT-1 Web services

WHAT IS WEB SERVICES
 W3C: “The World Wide Web is more and more
used for application to application communication.
The programmatic interfaces made available are
referred to as Web services”
A Web service is a software system designed to
support interoperable machine-to-machine
interaction over a network.
It has an interface described in a machine- format
processble (specifically WSDL).
Other systems interact with the Web service in a
manner prescribed by its description using SOAP
messages, typically conveyed using HTTP with an
XML serialization in conjunction with other Web-
related standards.”

INTRODUCATION
Contemporary Service-Oriented Architectures (SOA)
represents an architecture that promotes service-
orientation through the use of Web services.
All functions, or services, are defined using a
description language and have invokable interface that
are called to perform business processes.
• Client
• Third party system
• Legacy
• Resources
• Modern Moves

Web service example
A stock quote service.
An application requires the current value of a stock, the
web service returns it.
A route finder for delivery of goods.
Given an initial and a final location, find the most cost-
effective delivery route.
A weather service, a map service, a web search service…
any composition of Web services.

Dickson Chiu 2006 Web Service-5
UDDI
Registry WSDL
Web
Service
SOAP
Service
Consumer
Points to description
Describes
ServiceFinds
Service
Communicates with
XML Messages
SOA Technologies

Why web services for important
From business standpoint
– Integration
• Within an organization
• Between companies
• Allows time/cost efficiencies
– Purchase orders
– Answering inquiries
– Processing shipment requests
• Do this without locking in to a single partner.

Issues distributed computing
platform
Platform Dependency
Management and Optimization
What do 99,99% availability mean?
How can I guarantee 3 seconds response
time?
Who owns the Log? Who owns the context?
Load Balancing, Caching, Replication?
Change a Process: All or Nothing
Whole system fails when a component is
upgraded
Versioning, Schema Evolution while process
runs

How do we send a Java double value to a web service
using XML?
Is scientific notation allowed?
 How large can the value be?
Etc.
What if we want to send an object?
And what if the object contains references to other
objects?

Web services enterprises
The emergence of Web services is transforming traditional
enterprises. However, the industry hype surrounding these
technologies obscures the understanding of their impact and
implications to enterprises.
Here the authors take the "big picture" perspective, offering a
thorough understanding of the concepts behind Web service
technologies: the challenges and opportunities they present,
how they fit into the enterprise stack, how they relate to the
business and IT layers of the enterprise, as well as the existing
and emerging standards and their relevance.

XML fundamentals XML
XML Fundamentals. In this first of
three chapters in Part One, we start with a discussion of
the fundamentals of the extensible Markup Language
(XML), the basic technology on which Web services are
based. From network protocols up the stack to back-end
databases, XML in all its forms has had a commoditizing
effect on enterprise computing systems and being both
platform and language independent is a natural choice for
the level of interoperability required of Web services.

XML fundamentals XML
What is XML?
XML stands for Extensible Markup Language.
XML is a markup language like HTML and not a
programming language.
It uses tags, just like HTML.
XML is not a replacement for HTML.
XML was created to transport or store data.
XML is very easy to learn compared to learn any
programming language.

Some XML History
XML is an application profile of an ISO standard SGML,
and most of XML comes from SGML unchanged.
XML version 1.0 was defined in 1998. It had many minor
revisions since then XML 1.0 is the recommended
version.
XML version 1.1 was published in February of 2004, the
same day as version 1.0’s third edition. 1.0 is generally
suggested over 1.1 unless the project needs specific
features of 1.1.
There have been discussions of an XML 2.0, although no
organization has announced plans for work on such a
project.

XML vs. HTML
There is no comparison between HTML and XML.
They are completely different and are used in different
situations.
XML is a Data Interchange Format; it’s a way to
structure and store data and also to transport data.
XML was created to transport and store data and is
more behind the scenes.XML has no pre-defined tags.
HTML is used to display data in a browser and focus
on physical presentation. HTML has pre-defined tags.
Now let’s s

Document structure
In the XML file structure, the first line is
the declaration that contains the document
information like version information, character set,
etc.
Declaration must come first in the document.
Every opening tag should have a closing tag.
Each XML document has a root element.
Root element contains the child elements which can
in turn have sub-child elements.
All the sub-child elements in a child element are
called the siblings of each other.
Attributes like gender=”male” can also be given to
the tags.

THE LINGUA FRANCA OF WEB
SERVICES
XML is a standard for data mark-up backed by the
World Wide Web Consortium, which has been branded
"the universal format for structured documents and data
on the Web.“
The entire XML suite of standards, models, and
processing technologies have been under development
since 1998 with the initial XML specification, and has
since been augmented by several additional supporting
standards and notes that have brought XML to its current
rich state.
In fact, though XML is undeniably a richly specified
technology, it has retained its simplicity and the entire

XML is for Structuring Data:
Structured data includes things like spreadsheets, address
books, configuration parameters, financial transactions, and
technical drawings. XML is a set of rules for designing text
formats that support the developer in creating structured data.
Though it vaguely resembles source code, XML is not a
programming language, but it does make it easy for a
computer to generate data, read data, and ensure that the data
structure is unambiguous. XML avoids common pitfalls in
language design. It is extensible, platform-independent,
supports internationalization and localization, and is fully
Unicode-compliant.
XML platform can be profiled as follows

XML Resembles HTML:
Like HTML, XML makes use of
tags (words surrounded by angle brackets, "<" and
">") and attributes (of the form name="value"). While
HTML specifies what each tag and attribute means
and often how the text between them will render in a
browser, XML uses the tags only to delimit pieces of
data and leaves the interpretation of the data
completely to the application that reads it.

XML is Human Readable, but Humans Shouldn't Read It:
Programs that produce structured data often store that data on
disk, using either a binary or text format. An advantage of a textual
format is that it allows people, if necessary, to look at the data without
the program that produced it, using tools like text editors. XML files
are text files that people shouldn't have to read, but may read as and
when the need arises. Care must be taken when manually editing XML
since its rules are strict. A forgotten tag or an attribute without quotes
makes an XML document unusable. The official XML specification
forbids applications from trying to second-guess the creator of a broken
XML file; if the file is broken, an application has to stop and report an
error.

XML is Verbose:
Since XML is a textual format and uses tags to
delimit the data, XML files are nearly always larger than
comparable binary formats. That was a conscious decision
by the designers of XML. The advantages of a text format
are evident, and the disadvantages can usually be
compensated at a different level by compression
applications.
XML is a Suite of Technologies:
XML 1.0 is the specification that defines
what "tags" and "attributes" are. Beyond that specification,
the XML family is a growing set of modules that offer
useful services to accomplish important and frequently
demanded tasks.

XML is Modular:
XML allows you to define a new document format by
combining and reusing other formats. Since two formats
developed independently may have elements or attributes
with the same name, care must be taken when combining
those formats. To eliminate name confusion when
combining formats, XML provides a namespace mechanism
that is supported in all XML-based technologies.
XML is License-Free, Platform-Independent,
and Well-Supported:
Basing Web services on XML is similar to basing a
database strategy on SQL you still have to build your own
database, programs, and procedures that manipulate it, but
there are many tools and commodity components available
to help. Furthermore, since XML is license-free, Web
services can be built without incurring royalty payments.

What is namespaces:
As an example, let's assume we have an RDB with a table
of the following structure (employee Table, section
Table). What kind of SQL statement would you create to
obtain a list of Employee ID, Employee Department
Name, and Employee Name? If we merged employee
Table and section Table with the sec ID column, then we
would be able to obtain a list of employee IDs, employee
departments and employee names. However, since the
name column and sec ID column exist in both tables, we
would have to designate the table name before the name
and sec ID columns, or designate the alias of the table in
order to clarify the table of the name and sec ID columns
in question.

Solving the Name Conflict Using
a Prefix
Name conflicts in XML can easily be avoided using a name prefix.
This XML carries information about an HTML table, and a piece of
furniture:
<h:table>
<h:tr>
<h:td>Apples</h:td>
<h:td>Bananas</h:td>
</h:tr>
</h:table>
<f:table>
<f:name>African Coffee Table</f:name>
<f:width>80</f:width>
<f:length>120</f:length>
</f:table>
In the example above, there will be no conflict because the two <table>
elements have different names.

XML Namespaces - The xmlns Attribute:
When using prefixes in XML, a namespace for the prefix must be
defined.
The namespace can be defined by an xmlns attribute in the start tag of
an element.
The namespace declaration has the following syntax.
xmlns:prefix="URI".
<root>
<h:table xmlns:h="http://www.w3.org/TR/html4/">
<h:tr>
<h:td>Apples</h:td>
<h:td>Bananas</h:td>
</h:tr>
</h:table>
<f:table xmlns :f="https://www.w3schools.com/furniture">
<f:name>African Coffee Table</f:name>
<f:width>80</f:width>
<f:length>120</f:length>
</f:table>

Uniform Resource Identifier (URI):
A Uniform Resource Identifier (URI) is a string of characters
which identifies an Internet Resource.
The most common URI is the Uniform Resource
Locator (URL) which identifies an Internet domain address.
 Another, not so common type of URI is the Uniform
Resource Name (URN)

Default Namespaces:
Defining a default namespace for an element saves us from using prefixes in
all the child elements. It has the following syntax:
xmlns="namespaceURI"
This XML carries HTML table information:
<table xmlns="http://www.w3.org/TR/html4/">
<tr>
<td>Apples</td>
<td>Bananas</td>
</tr>
</table>
This XML carries information about a piece of furniture:
<table xmlns="https://www.w3schools.com/furniture">
<name>African Coffee Table</name>
<width>80</width>
<length>120</length>
</table>

Namespaces in Real Use
XSLT is a language that can be used to transform XML documents into other formats. The XML
document below, is a document used to transform XML into HTML. The namespace
"http://www.w3.org/1999/XSL/Transform" identifies XSLT elements inside an HTML document:
<html>
<body>
<h2>My CD Collection</h2>
<table border="1">
<tr>
<th style="text-align:left">Title</th>
<th style="text-align:left">Artist</th>
</tr>
<xsl:for-each select="catalog/cd">
<tr>
<td><xsl:value-of select="title"/></td>
<td><xsl:value-of select="artist"/></td>
</tr>
</xsl:for-each>
</table>
</body>
</html>
</xsl:template>

NAMESPACES AND VISUAL
INHERITANCE:
Inheritance namespaces
INTRODUCTION Namespaces:
 allow you to organize a large number of classes into a
hierarchical structure, which promotes code reuse and
inheritance among classes. Without namespaces, a project
quickly becomes cluttered with classes and other objects
that are all on the same root namespace (the project name).
Moving classes into namespaces that grow out of your
own custom root namespace allows you to keep classes
separate.
WHAT IS A NAMESPACE? A namespace is a
hierarchical structure for organizing classes. You can
create and use any namespace name that you want in your
programs

 VISUAL INHERITANCE
INTRODUCTION Visual inheritance is a new feature in
VB.NET, which allows you to reuse forms and controls
between projects. Ideally, you would compile a form or
control as a component into a.DLL file, so it could be
shared. For demonstration purposes, I’ll just show you how
to inherit one form into another, within the same project.
 CREATING A REUSABLE FORM Create a new
Windows Application called Visual Inheritance. Add four
controls to the default Form1: a Label, a Text Box, and two
Button controls. Now, double-click the first button to open
up the default event for the button and type the following
code: If TextBox1.Text.Length > 0 Then Msg Box(“Hello, “
& TextBox1.Text & “!”)

REUSING THE REUSABLE FORM
 Now, creating inherited forms is fairly easy,
because VB.NET has a menu item that does
all the work for you. And actually, you can do
it yourself because the code that VB.NET
generates is extremely short, as you’ll see.
Select Project, Add Inherited Form. The Add
New Item dialog appears, with the Inherited
Form template already selected.

Schema Overview
Elements
Cardinality
Simple Types
Complex Types
Compositors
Global Types
Attributes
mixed Content

overview
An XML schema, commonly Known as an
Xml Schema Definition (XSD), formally
describes what a given XML document can
contain, in the same way that a database
schema describes the date that can be
contain in a database. The XML schema
defines the shape, or structure, of an XML
document, along with rules for data content
and semantics such as what fields an
element an contain which sub elements it
can contain and how many item can be
present. It can also describe the type and
values that can be placed into each elements
or attributes. The XML data constrains are
called facets and include rules such as min
and max length.

XML schema abstract
this report presents a series of BT user
stories which chart our experience in using
XML Schema to describe messages
exchanged by Web services.
We explain how the value of a standard is
greatly diminished, even one as widely used
as XML Schema, when it is implemented
inconsistently and offer best practices in
conjunction with test cases targeted at
description as the best way of
communicating which aspects of schema
maybe
relied upon to interoperate.

structure of the
global cache
the global cache consists of both
WSDL documents and XML schema
documents
the global cache of WSDL
documents contains all WSDL documents
that have been imported into API Gateway
The global cache of schema
documents contains:
user defined catalog-This contains
all user defined schema documents that
have been imported into API Gateway.
System catalog-This contains all
common schemas that are preloaded during
API Gateway installation.

manage WSDL and XML schema
documents
Overview
WSDL files contain XML schemas that define the elements that
appear in SOAP messages. When you import a WSDL file to register a
web service, the imported WSDL file, and any XML schemas included
in the WSDL, are added to a global cache of WSDL and XML schema
documents. You can also add XML schemas and WSDL documents to
the cache indepently.
If you select a cached WSDL file or XML schema in a
Schema Validation filter, API Gateway can retrieve it from the cache
instead of fetching it from its original location. This improves the
runtime performance of the filter, and also ensures that an
administrator has complete control over the schemas used to validate
messages.
API Gateway can maintain multiple versions of WSDL and
XML schema documents in the global cache, and keeps an explicit
version history as they change over time. The cache is prepopulated

document object model
document object model (DOM) is a cross-
platform and language-independent
interface that treats an XML or HTML
documents as a tree structure wherein each
node is an object representing a part of the
document. The DOM represents a
document with a logical tree. each branch
of the tree ends in a node, and each node
contains objects. DOM methods allow
programmatic access to the tree; with them
one can change the structure, style or
content of a document. Nodes an have evet
handlers attached to them. Once an event is
triggered, the event handlers get exeuted
xslt (Extensible stylesheet language
transformations) is a language for
tranforming XMl documents into other XML
documents, or other formats such as HTML
for web pages, plain text or XSL formatting
objects, which may subsequency be
converted to other formats, such as PDF,

XSLT
introduction
xsl(extensible stylesheet language) is a
styling language for XML
xslt stands for XSL transformation
This tutorial will teach you how to uSe XSLt
to transform XML documents into other
formats

XPATH
XPATH(xml path language) is a
query language for selecting nodes from an
xml document in addtion path maybe used
to compute values
the global cache consists of both WSDL
documents and XML schema documents
the global cache of WSDL
documents contains all WSDL documents
that have been imported into API Gateway
The global cache of schema documents
contains:
user defined catalog-This contains all user
defined schema documents that have been
imported into API Gateway.
System catalog-This contains all common
schemas that are preloaded during API
Gateway installation.

UNIT-1 Web services

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UNIT-1 Web services