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XML, Ajax, Web Services, Semantic Web
Week 13
INFM 603
Agenda• XML• Ajax• Web Services• Semantic Web
XML• XML eXtensible Markup Language• XML
• An XML document is a text-based document• XML is a language for describing data or for creating markup languages• Allows data to be structured, stored and transmitted in a hierarchical
fashion• XML tags (element type names) provide a reader an idea of what data
means• XML is human-readable
• Goals for XML• Easily adapted to specific tasks (e.g., Rendering Web pages, Encoding
metadata, Semantic Web)• Easily created/processed/read• Concise
XML• Example (Providing information about a course)
<?xml version="1.0" encoding="ISO-8859-1"?> <semester>
<course courseNum=“bio101”><name>Intro to Biology</name><instructor>Prof Cell</instructor>
</course> </semester>
XML• XML is case sensitive• XML declaration is the first statement
– <?xml version="1.0"?>• An XML document is a “tree”
– Must contain one root element– Other elements must be properly nested
• All start tags must have end tags• Attribute values must have quotation marks
– <item id=“33905”>• Certain characters are “reserved”
– For example: < is used to represent <• You can generate different types of documents from an XML document
(through a process call Transformation). You could generate HTML, CD, DVD, Video, etc.
Some XML Applications• Text Encoding Initiative
– For adding annotation to historical manuscripts– http://www.tei-c.org/
• Encoded Archival Description– To enhance automated processing of finding aids– http://www.loc.gov/ead/
• Metadata Encoding and Transmission Standard– Bundles descriptive and administrative metadata– http://www.loc.gov/standards/mets/
The XML Family Tree
SGML
XML
HTML TEI
. . .
. . .
XHTML
SMIL
MathML
VoiceXML
RDF
RSS
• Some languages based on XML• XHTML• SMIL Demo available at
http://www.umiacs.umd.edu/~oard/teaching/603/spring12/slides/13/media.html
• SVG XML application language that replaces many uses of bitmap graphics
• RSS• Rich Site Summary or Really Simple Syndication• Format for delivering changing web content
• MathML• Used to describe mathematical notations
• WAP and WML• For handheld devices
Languages Based on XML
• Used with XML documents to transform data into a particular context (e.g., HTML, word, pdf, etc.) or another XML document
• In order to define the transformation an XSLT stylesheet is defined• The stylesheet is an XML document
9
XSLT
XML Example• View “The Song of the Wandering Aengus”• http://www.umiacs.umd.edu/~oard/teaching/603/spring12/slides/13/xml.htm
XML Example<?xml version="1.0"?>
<!DOCTYPE POEM SYSTEM "poem01.dtd">
<?xml-stylesheet type="text/xsl" href="poem01.xsl"?>
<POEM>
<TITLE>The Song of Wandering Aengus</TITLE>
<AUTHOR> <FIRSTNAME>W.B.</FIRSTNAME>
<LASTNAME>Yeats</LASTNAME>
</AUTHOR>
<STANZA>
<LINE>I went on to the hazel wood,</LINE>
<LINEIN>Because a fire was in my head,</LINEIN>
<LINE>And cut and peeled a hazel wand,</LINE>
</STANZA>
</POEM>
Document Type Definition (DTD)
<!ELEMENT poem ( (title, author, stanza)* )>
<!ELEMENT title (#PCDATA) >
<!ELEMENT author (firstname, lastname) >
<!ELEMENT firstname (#PCDATA) >
<!ELEMENT lastname (#PCDATA) >
<!ELEMENT stanza (line+ | linein+) >
<!ELEMENT line (#PCDATA) >
<!ELEMENT linein (#PCDATA) >#PCDATA span of text a,b a followed by ba|b either a or ba* 0 or more a’sa+ 1 or more a’s
Specifying Appearance: XSL(T)
<xsl:template match="POEM">
<HTML>
<BODY BGCOLOR="#FFFFCC">
<xsl:apply-templates/>
</BODY>
</HTML>
</xsl:template>
<xsl:template match="TITLE">
<H1>
<FONT COLOR="Green">
<xsl:value-of/>
</FONT>
</H1>
</xsl:template>
• From:• http://www.w3.org/Style/CSS-vs-XSL
• We have two different style languages. Which one to use?• CSS when you can• XSL when you must
CSS vs XSL
• XML and HTML derive from a meta language called SGML (Standard Generalized Markup Language)
• XML Uses a subset of syntax rules allowed in SGML• XML tags are specific to applications and users know what
they mean, while HTML tags have fixed meaning and browsers know what they are
• HTML tags are used for display purposes while XML tags are used to describe data and documents
15
XML vs. HTML
Well-Formed XML Documents• An XML document that follows the XML syntax rules is said to be
well-formed• XML Parser/XML Processor allow us to detect whether a
document is well-formed• Two types of Parsers
• Non-validating XML Parser checks whether document satisfies XML syntax rules (well-formed), but does not check for any specific structure of elements/attributes
• Validating XML Parser checks whether document is well-formed and also verifies it satisfies the specific structure of elements/attributes
JSON• JavaScript Object Notation• Text-based standard for data interchange• Light-weight alternative to XML• Derived from JavaScript but it is language independent• JSON Example: http://json.org/example.html
Synchronized Multimedia Integration Language (SMIL)
• SMIL Enables simple authoring of interactive audiovisual presentations– Utilized for rich media/multimedia presentations that integrate streaming
audio and video with images, text or any other media type• Window controls (in <head>)
– Controlling layout: <region>, <root-layout>• Timeline controls (in <body>)
– Sequence control: <seq>, <excl>, <par>– Timing control: <begin>, <end>, <dur>
• Content types (in <body>)– <audio>, <video>, <img>, <ref>
• http://www.w3.org/AudioVideo/• Example:
– http://www.umiacs.umd.edu/~oard/teaching/603/spring12/slides/13/media.html
Ajax• Traditional interaction with web server
• Nothing happens until we submit data• We must wait until the server request is processed (cannot do
anything with the page)• A page must be completed loaded even if most of the content
identical to previous page• Compare with a desktop application• Can we do better? Can the page be updated without requiring a
page load?• Ajax is the answer• Example (AjaxExamples):
• directoryLookup.html, directory.php, processMemo.php in TypicalASynchronous folder
Ajax
Ajax
Ajax• Ajax Asynchronous JavaScript and XML• Combination of technologies• Adds a layer between the browser and the web server, handling
server requests and processing the results• Layer Name Ajax Framework/Ajax Engine
• The requests are not synchronized with user actions (e.g., clicking on links, buttons, etc.). User can continue interacting with the browser while request is being processed
Ajax• In the traditional client/server model we submit server requests by
clicking on a link or via submit (this generates the HTTP request for us)• Notice we get a new web page as a result
• XMLHTTPRequest• JavaScript object that will issue the HTTP request• No page load is generated as a result of the request• Can only issue request to URLs within the same domain• Cannot directly access a remote server
• There is nothing the server needs to do just because the request is associated with AJAX. The server is just receiving an HTTP request
• Ajax application just care about receiving an HTTP response
Ajax Examples• HTML Ajax
– http://test.deitel.com/examples/iw3htp4/ajax/fig15_05/SwitchContent.html
• XML Ajax– http://test.deitel.com/examples/iw3htp4/ajax/fig15_08/PullImagesOntoPage.html
• Jason Ajax– http://test.deitel.com/examples/iw3htp4/ajax/fig15_09_10/addressbook.html
Database
Server-side Programming
Interchange Language
Client-side Programming
Web Browser
Client Hardware
Server Hardware (PC, Unix)
(MySQL)
(PHP)
(HTML, XML)
(JavaScript)
(IE, Firefox)
(PC)
Bus
ines
sru
les
Inte
ract
ion
Des
ign
Inte
rfac
eD
esig
n
• Relational normalization• Structured programming• Software patterns• Object-oriented design• Functional decomposition
Model-View-Controller
• Web Service • Web API (Application Programming Interface) that can be accessed over a
network and executed at a remote system• Allows client applications to build interfaces to the service
• From webopedia.com • Web services allow different applications from different sources to
communicate with each other without time-consuming custom coding, and because all communication is in XML, Web services are not tied to any one operating system or programming language
• Web services do not provide the user with a GUI. Web services instead share business logic, data and processes through a programmatic interface across a network
• Web Service (From Wikipedia)• W3C defines a "Web service" as a software system designed to support
interoperable machine-to-machine interaction over a network• Example:
• http://code.google.com/apis/maps/documentation/webservices/#WebServices
Web Services
• Services can range from simple requests to complicated business processes• Payment processing• Content Syndication• Currency conversion• Language translation
• Any internet protocol can be used to build web services but HTTP and XML are often used
• By using web services, your application can publish its function to the world
• Web services can be created in any programming language• Web services enable us to solve interoperability problems between
systems by allowing data exchange between different applications and different platforms.• With web services a company billing system can connect with a
supplier server
Web Services
• Several protocols and techniques have been developed to create and utilize web services. Two main ones:• REST Representational State Transfer• SOAP Simple Object Access Protocol
• In General• REST light-weight interactions• SOAP secure, reliable interactions• Each has its advantages
• From Wikipedia• REST primary purpose of the service is to manipulate XML
representations of Web resources using a uniform set of "stateless" operations
• SOAP the service may expose an arbitrary set of operations
Web Services
• REST (Representational State Transfer)• Resources are represented by URLs
• Resource document, person, location• Each resource has a unique URL
• Each resource does not need to have an actual page/document. It can be generated dynamically
• A resource is considered a “noun”• Operations are performed via HTTP methods (GET, POST, PUT,
DELETE)• Methods are considered “verbs”
• REST designed to operate with resource-oriented services (locate/manipulate resource)
Web Services (REST)
• Example:• Web service that allows individuals to manage file backups• Each backup has an URL
http://backupFake.doesnotexist.org/backups/1938• Server responses will use XML• Using HTTP GET we can get the backup• Using HTTP PUT we can update a backup• Using HTTP POST we can upload a backup
• We can receive a URL that corresponds to the new backup• Using HTTP DELETE we can delete a backup
• Notice that REST relies on a familiar approach (HTTP methods) to ask for services (we don’t need to create a new interface/approach)
Web Services (REST)
• SOAP (Simple Object Access Protocol)• SOAP Designed for action-oriented services (actions a web server
can carry out)• Designed as a way to package remote procedure calls into XML
wrappers• SOAP is an XML-based messaging protocol• SOAP request
• XML document• Has three components
• Envelop defines document as SOAP request• Body provides information about the call and responses• Optional header and fault elements
• SOAP response is an XML document
Web Services(SOAP)
• Web Service example• http://www.w3schools.com/webservices/ws_example.asp• Using web service example http://
www.w3schools.com/webservices/ws_use.asp• Many popular organizations provide web services
• Amazon http://aws.amazon.com/• Netflix http://developer.netflix.com/docs
• Netflix Web API allows you to• Search movies, TV series, etc.• Retrieve catalog titles• Manage and displaying queues for users
• Yahoo• http://developer.yahoo.com/everything.html
• eBay http://developer.ebay.com/products/shopping/
Web Services (Examples)
• WSDL (Web Services Description Language)• XML-based language for describing and locating web services• W3C standard• It is machine-readable
• UDDI (Universal Description, Discovery and Integration)• Directory service where companies can search and register for
web services described by WSDL• Service Broker
• Wikipedia Image for Service Broker/Requester/Provider• http://en.wikipedia.org/wiki/File:Webservices.png
Web Services (Platform Elements)
• http://www.youtube.com/watch?v=v3OMEAU_4HI• http://spf13.com/post/soap-vs-rest
REST vs. SOAP
• Frapi• FRAPI is a RESTful API Framework that allows
developers to develop RESTful APIs that• http://getfrapi.com/
Frapi (RESTful API Framework)
• Mashup• Web page or application that uses and combines data and/or
functionality from several sources. Sources are often based on web services.
• Relies on open APIs• Allow us to create new views of data
• Mashup Genres• Video and Photo Mashups• Mapping Mashups
• Big player Google Maps API• Search and Shopping Mashups• News Mashups
• Example: Diggdot.us (combines news from Digg.com, Del.icio.us and Slashdot.org)
Mashups
• Google vs Yahoo• http://www.langreiter.com/exec/yahoo-vs-google.html
• Popular MashUp Listing• http://www.programmableweb.com/popular
Mashup Examples
• From:• http://www.cs.umd.edu/~golbeck/LBSC690/SemanticWeb.html
• Semantic web• Adds structure to the meaningful content of web pages• Most data in the web is for human consumption, rather than data that can
be processed automatically by computers. Semantic Web will enable computers to be able to understand the data, instead of just displaying it
• Allows for complex queries. For example:• How many stores are open when I am not at work or traveling in
June?• It is not a separate web, but an extension of our present web
• Semantic web – Term coined by Tim Berners-Lee• http://www.w3.org/People/Berners-Lee/
Semantic Web
• Semantic web needs• Access to structured collections of information• Sets of inference rules to conduct automated reasoning
• Semantic Web Challenge• Provide a language that expresses both data and rules for
reasoning about data• Allowing rules from knowledge-representation system to be
exported to the web• Technologies for developing the semantic web
• XML – Allows users to add arbitrary structure to their documents• RDF – Allows users to add meaning to their documents
Semantic Web
• RDF Resource Description Framework• Allow us to express meaning
• In RDF a document makes assertions that particular entities (people, web pages, etc.) have properties (e.g., “father of”) with certain values (e.g. another person)
• Meaning is encoded in triples• Triple has subject, verb/predicate and object (all expressed
using URIs)• <#john> pref:loves <#cheescake>.
• Written in XML
• RDF Example http://www.cs.umd.edu/~golbeck/INFM743/sample.owl
• RDF triples form web of information about related things
Semantic Web
• Document that formally defines terms and inference rules as to how terms relate
• Used for reasoning about data• Typical ontology for the web has taxonomy and inference rules• Example of page marked up for ontology use:• http://www.cs.rpi.edu/~hendler/• Notice the <USE-ONTOLOGY> tag• Using ontology’s concepts, information about where Dr.
Hendler obtained his PhD is provided• Allows a computer to answer the question: “Where Dr.
Hendler received his degree?”
Semantic Web: Ontology
• Impact of semantic web will be seen when:• Programs are created that combine information from
different sources, process the information and exchange results with other programs
• Providing web-based services with semantics will • Allow for service discovery• Understanding of functions offered and how to take
advantage of such functionality
Semantic Web
Microformats
<div id="contact" class="vcard"><h2>Contact Me</h2> <h3 class="fn">Jane Doe</h3> <p> You can contact me via email to <a class="email" href="mailto:[email protected]">[email protected]</a>, or reach me at the following address:</p> <div class="adr"> <div class="street-address">255 Some Street</div> <div class="locality">Some Town</div> <div class="region">Some Place</div> </div> </div>
<div id="contact"> <h2>Contact Me</h2> <p> You can contact me via email to <a href="mailto:[email protected]">[email protected]</a>, or send stuff to me at the following address:</p> <p>255 Some Street,<br /> Some Place,<br /> Some Town</p> </div>
Human-Readable Human- and Machine-Readable
• From Wikipedia• Process of automatically collecting information from the web
• From www.webopedia.com• Application that processes HTML of a web page to extract data• Web scrapping applications simulate a person viewing a web site
• You may need to rely on web scrapping when no API is provided to access data
• ScraperWiki• Platform that enables building of programs to extract and
analyze data
• https://scraperwiki.com/
Web Scraping
• Introduction• http://www.youtube.com/watch?v=OGg8A2zfWKg
• Demo of Semantic Web Portal• http://www.youtube.com/watch?v=X6WcpG5EEeI&feature=related
• Semantic Web of Data Tim Berners-Lee• http://www.youtube.com/watch?v=HeUrEh-nqtU&feature=related
• Tim Berners-Lee: The next Web of open, linked data• http://www.youtube.com/watch?v=OM6XIICm_qo&feature=related
• RDF Basics• http://www.youtube.com/watch?v=ldl0m-5zLz4&feature=related
• http://videolectures.net/training06_sure_stsw/• Notice slides on the side move automatically
Semantic Web Videos
• http://en.wikipedia.org/wiki/Hypertext_Transfer_Protocol• http://www.w3schools.com/webservices/• AJAX in 10 Minutes ISBN-10: 0672328682• http://en.wikipedia.org/wiki/Mashup_%28web_application_hybrid%29• http://www.ibm.com/developerworks/xml/library/x-mashups.html• Sams Teach Yourself Perl in 24 Hours
• Great Reference to learn Perl• ISBN: 0-672-32793-7
References
References• http://www.cs.umd.edu/~golbeck/INFM743/xml.ppt
• http://www.xml.com/• XML in 10 Minutes (ISBN: 0-672-32471-7)• http://www.xmlhack.com/• http://www.w3.org/XML/• http://www.w3schools.com/xml/xml_whatis.asp• http://blogspace.com/rss/readers• http://www.w3.org/TR/REC-xml/• http://cyber.law.harvard.edu/rss/rss.html
