Information Technology I Information Technology I Evolution of Web Technologies WorldWorld-WideWide-Web or The Triumph of Anarchy • Perhaps the most important human technological artifact that evolved more or less ad-hoc • Limited original vision of the WWW has very little to do with today’s impressive reality • Web Users have consistently innovated in figuring out new ways of leveraging this powerful medium • Web architects then try to catch up by extending (read “patching”) the Web infrastructure to support these new uses • … this lecture tells their ongoing story! Information Technology I How it all started… The Web as a Static Document Repository • Tim Berners-Lee’s original vision for the WWW (circa 1989) • An easy way to access cross-linked static documents stored in a variety of servers around the world • Initial specification defined: – A language for formatting such documents (HTML) – A simple protocol for communicating between browsers and servers (HTTP) Information Technology I How the Web works Web client (Netscape, Explorer, etc.) Internet Web server Domain Name Server WWW is a Client/Server System • Web Clients – Use HTTP protocol to connect to servers – Request and display Web pages stored in servers – Typical clients: Web browsers • Web Servers – Listen for incoming connections from clients – Use HTTP protocol to converse with clients – Store and transmit Web pages to clients Information Technology I Evolution of the WWW Business Drivers • Enable transactions • Allow interactivity between browser and server • Facilitate personalization • Support multiple browsing devices • Better organize and retrieve Web content • Support Business-to-Business applications The Web as a transaction facilitator • Business Motivation: Low-cost front-end for allowing customers to connect to corporate computers – Customer registration/Address changes – Order tracking/Customer support – Online Transactions: eCommerce ! • Problems of original Web concept – – – – Static web pages No interactivity Stateless protocol: no support for multi-step transactions Insecure communications Information Technology I Web Forms • Pages which contain fields to be filled by user • Usually contain a “Submit” button • When user presses “Submit”, server responds by sending a page containing information specific to the user-supplied parameters • Examples: – Web search tools – Order forms in commercial web sites Web Forms Under the Hood • Server sends original html page containing input fields • User types info into fields and presses submit button • Client establishes connection with handler script at server side (script filename contained in web page) • Client collects user input into a long string and sends it along with an HTTP command back to server – POST customer=John+Doe&cardno=1234567890&expires=6/98& product=123&quantity=5 • Handler script at server reads parameter string and processes it, usually producing a new page as a result Information Technology I CGI • Common Gateway Interface • Set of standards for writing handler scripts • How it works – All URLs that refer to a special directory (e.g. /cgi) cause the execution of a corresponding script at the server (for example http://web.mit.edu/cgi/test) – Scripts typically translate parameters into SQL statements for a database and translate the query results into an HTML page Example: FedEx Translate airbill number into query as expected by legacy system Server software Custom script Package results returned by legacy system into a Web page Web browser Internet Web server Database Legacy system Information Technology I Microsoft Active Server Pages (ASP) • Competing technology to CGI – Scripting Language is similar to Visual Basic • MS Access can automatically convert database tables, queries and forms into ASP pages • Requires Microsoft web server Evolution of the WWW Business Drivers • Enable transactions • Allow interactivity between browser and server • Facilitate personalization • Support multiple browsing devices • Better organize and retrieve Web content • Support Business-to-Business applications Information Technology I The Interactive Web • Business Motivation: – Allow complex interaction between user browser and corporate server – Web becomes an extension of the user’s PC – Browser becomes a window to a variety of corporate applications • Problems with Web Forms/CGI/ASP – All processing done at server side – Rapid user interaction with Web page not possible – Need local processing to create highly interactive Web pages Enter Java Applets • Programming language to enable interactive Web pages • Developed by Sun Microsystems – originally for programming intelligent microwave ovens!!! • Java programs are called applets • Applets are platform-independent – They can run equally well on Windows, Macs, Unix, etc. – Require special browsers that can support Java though Information Technology I Java Operation Servers S D Internet J Sun/UNIX • Static pages (S) • Dynamic pages (D) • Java applets (J) Windows XP Mac OS HTML page Mac OS Java applet HMTL Java Interpreter interpreter Java applet HTML page HMTL Java Interpreter interpreter Netscape (Win XP) Netscape (Mac OS) Windows XP Mac OS PC Hardware PowerMac Hardware Client environments Java Competition: Dynamic HTML • Extensions to HTML to allow Web pages to be updated without the need to communicate with a Web server • Browser must be capable of understanding them • Mutually incompatible versions have been included in Netscape Communicator, Internet Explorer } same } different SM Information Technology I Evolution of the WWW Business Drivers • Enable transactions • Allow interactivity between browser and server • Facilitate personalization • Support multiple browsing devices • Better organize and retrieve Web content • Support Business-to-Business applications Personalized Interaction • Business motivation: – Low cost medium for gathering information from customers to allow • Personalized service • Targeted advertising • Problems with current model – Does not allow easy identification of distinct customers Information Technology I Cookies • A method for identifying web users and delivering customized web sites – First time user connects to a web site, s/he is asked to fill in personal information form – Server packages information into a “cookie” file and sends cookie to browser – Browser stores cookie in local file system – Each subsequent time browser visits site, it sends cookie back to server – Server uses information stored in cookie to identify user and possibly customize the supplied web pages • Privacy implications? Information Technology I Example: Personalized recommendations at online bookstores. Evolution of the WWW Business Drivers • Enable transactions • Allow interactivity between browser and server • Facilitate personalization • Support multiple browsing devices • Better organize and retrieve Web content • Support Business-to-Business applications Information Technology I Multiple Delivery Devices • Business motivation: – Allow users to access web content from a variety of devices • • • • • PC Browsers PDAs (e.g. Palm Pilots) Mobile Phones Telephones (via voice interface) … • Problems of current Web model – Each access device has different look-and-feel requirements – HTML specifies formatting for PC browsers only Organize and Index Web Content • Web is useless unless we can easily locate relevant resources • Current solution: Search Engines – Index the Web by automatically “discovering” web pages and organizing them around keywords found in their text • Problem: – Text keywords are misleading… – HTML does not give any clues as to the true meaning of the data Information Technology I Today’s searches… Desperately seeking Wendy Cook … Dirgression: Dirgression: How Google does it: Pagerank • Pages are retrieved based on keywords • Retrieved pages are rank ordered based on a rough measure of “page significance”: – How many links point to a page – How many links point to the pointing page – Etc. for four levels of indirection • Surprisingly successful in returning relevant hits Information Technology I Support for B2B applications • Original Web was conceived as a communication medium between computers and humans • Amazing new applications will become possible if computers can automatically read and understand Web pages – Electronic purchasing – Business intelligence gathering – …. • Problem: – HTML pages are unstructured – HTML only provides information about presentation, not meaning What is the underlying issue? • When storing documents on the web, specify not only their appearance, but also their semantics (i.e. their meaning!) Information Technology I Enter: The Semantic Web • The “Next Generation Web” with well-established infrastructure for expressing information in a – – – Precise, Human-readable, and Machine-interpretable form. • Enable syntactic and semantic interoperability among independently-developed Web applications, allowing them to efficiently perform sophisticated tasks for humans. • Enable Web resources to be accessible by their semantics rather than by keywords and syntactic forms. The Origins of the Semantic Web • The information retrieval crisis beginning in the late 1990s led to a widespread interest in what has come to be called metadata. • What is metadata? – It's just data. – But it's data about other data – Data intended for machine consumption • What could metadata do for us? – Give search engines something to work with (relational triples) that is designed for their needs. – Give us all a place to record what a document, or any other resource, is for or about. Information Technology I First Requirements for Metadata • What would we need to make this work? – A standard syntax, so metadata can be recognised as such; – One or more standard vocabularies, so search engines, producers and consumers all speak the same language; – Lots of resources with metadata attached; HTML = Hypertext Markup Language • Uses tags to specify the formatting and display properties of data – Sizing of Fonts – Indentation – Etc. • Says nothing about what data means…

March 25, 1998 08:00

Seattle, WA

Partly Cloudy Skies

Temperature: 46 degrees

Information Technology I XML = eXtensible Markup Language • • • • Represents data as a list of hierarchically structured fields Syntax similar to HTML Uses tags to delimit the and of a field Can be easily extended with more tags to represent additional kinds of data March 25, 1998 08:00 Seattle WA partly cloudy 46 XML is just a syntax… • … for describing the meaning of data stored on a Semantic Web page • In order for XML to be useful, organizations must agree on common ontologies – Concepts of interest to their domain • E.g. product, quantity, price, weight, size, delivery date – Relationships among concepts • Product-has-price, Order-has-delivery date – Vocabularies of XML tags to represent the above • This is an organizational not a technical problem! Information Technology I Industry support for XML • Organizations developing standard vocabularies – commerce.net -- e-commerce processes – rosettanet.org -- supply chain processes • Vendors incorporating XML support in their products – Microsoft -- XML support in IE 5.0 and Office 2000 – Oracle -- XML support in databases – IBM -- leading in XML parsers and viewers • XML-based business2business networks – Ariba procurement network – New York times syndication network – IFX (Charles Schwab and others) Semantic Web Technological Layers XML Customized tags, like: Nena + RDF Relations, in triples, like: (Nena) (is_dog_of) (Chris) + Ontologies Hierarchies of concepts, like animal -> mammal -> dog + Inference rules Like: If (person) (owns) (dog), then (person) (cares_for) (dog) = Semantic Web!