Information Systems and the World Wide Web

International School of New Media at the University of Lübeck

Erik Wilde, UC Berkeley School of Information

January 2007

Date Subject Slides Resources
2007-01-02 Overview and Introduction: Information Systems are a large class of computer applications which revolve around information as a resource. The World Wide Web (WWW) is the most popular and biggest information system available today. Many other information systems are designed as stand-alone systems, but increasingly are integrated into the Web architecture, leveraging the popularity and global availability of the Web. Because of this integration, it is important to understand the Web as an information system, rather than a delivery system for Web pages. Introduction (15 Slides) Erik Wilde
2007-01-02 Uniform Resource Identifier (URI): A Uniform Resource Identifier (URI) identifies a resource in the context of the Web. A URI has several parts, most generally speaking a scheme (which indicates the way resources can be accessed), and a scheme-specific part. Rather than exposing a file system or similar resources through URIs, the namespace of a set of resources on the Web should be designed and maintained. This way, URIs can be used in a way which breaks fewer links by keeping URIs stable even when a Web site is completely redesigned and uses a different technology in its new incarnation. URI (22 Slides) Spec · Cool URIs
2007-01-02 Hypertext Transfer Protocol (HTTP): The Hypertext Transfer Protocol (HTTP) is the protocol which transports Web contents. It is based on the Internet's reliable transport protocol, the Transmission Control Protocol (TCP). HTTP is more than a simple file retrieval protocol, it provides content negotiation and other features which turn the Web into a flexible and scalable information system. The other basic infrastructure building block of the Web is the Domain Name System (DNS), which provides a naming system for the number-oriented addressing scheme of the Internet protocols. HTTP (54 Slides) Spec
2007-01-03 Hypertext Markup Language (HTML): The Hypertext Markup Language (HTML) is the language for providing Web content. It is based on the idea of structuring content, while the layout should be controlled using stylesheet languages. HTML document have a document head which allows HTML documents to contain document metadata. One of the most important tasks of HTML is to serve as an interface for data input for Web-based applications. This can be done by using HTML Forms. HTML (50 Slides) HTML Spec · XHTML Spec · Validator
2007-01-03 Cascading Stylesheets (CSS): Cascading Stylesheets (CSS) have been designed as a language for better separating presentation-specific issues from the structuring of documents as provided by HTML. However, CSS can be applied to XML as well, either directly (by applying a CSS stylesheet to an XML document), or as an supplement to basic HTML layout structures generated from an XML document. CSS uses a simple model of selectors and declarations. Selectors specify to which elements of a document a set of declarations (each being a value assigned to a property) apply; in addition there is a model of how property values are inherited and cascaded. The biggest limitation of CSS is that it cannot change the structure of the displayed document. CSS (39 Slides) Specs · Validator
2007-01-03 Representational State Transfer (REST): Representational State Transfer (REST) is an architectural style for building distributed systems. The WWW is an example for such a system. REST-style applications can be built using a wide variety of technologies. REST's main principles are that of resource-oriented states and functionalities, the idea of a unique way of identifying resources, and the idea of how operations on these resources are defined in terms of a single protocol for interacting with resources. REST-oriented system design leads to systems which are open, scalable, extensible, and easy to understand. REST (36 Slides) · RESTwiki
2007-01-04 Information Models and Systems: Information systems are based on the two basic principles of structured information and well-defined ways of handling this information. While the Web as an information system has a number of well-designed ways to handle information, the foundation of Web-based applications, how information should be structured, are less clear. When considering information structures, the most important aspects are the question of classification systems and how to apply these to existing information, and the question of how classified information can be composed into structures which can be regarded as useful and self-contained representations for relevant information. InfoSys (30 Slides) Bob's Course
2007-01-04 Extensible Markup Language (XML): The Extensible Markup Language (XML) defines a simple way for structuring data. The power and popularity of XML can be explained by its versatility, the platform-independence, the standards and technologies leveraging it, and the number of tools and products supporting it. Understanding XML itself is rather simple, it only depends on a very small set of other technologies. Unicode and URIs are the most important foundations of XML. XML itself specifies two different things: on the one hand the format for structured data, which are called XML documents, and on the other hand a constraint language for XML documents, which is called Document Type Definition (DTD) XML (54 Slides) Press · Spec
2007-01-05 Document Type Definition (DTD): The XML specification defines a format for structured data (XML documents) and a grammar-based constraint language for these (DTD). In SGML-based systems, DTDs were often very complex and feature-rich constructs, which controlled a lot of the processing of SGML documents. XML greatly simplified DTDs, and de-facto usage of DTDs today simplified them even more. In many systems today, DTDs are not used at all or generated from sample documents. In this lecture, it is argued that DTDs (or schemas, to be more general) should be taken seriously in any non-trivial XML application, because they are a representation of the underlying (and often underspecified) data model of the application. DTD (37 Slides) QuickRef
2007-01-05 XML Path Language (XPath): XML structures data into a rather small number of different constructs, most notably elements and attributes. The XML Path Language (XPath) defines a way how to select parts of XML documents, so that they can be used for further processing. XPath's primary use in in XSL Transformations (XSLT), but other XML technologies use it as well, e.g. XML Schema. XPath is a very compact language with a syntax that resembles the path expressions which are well-known from file systems. These path expressions, however, are generalized and therefore much more powerful than the rather simple path expressions in file systems. Because of its use in different XML technologies, XPath is one of the most important XML core technologies. XPath (46 Slides) Chapter · QuickRef
2007-01-08 Meike KlettkeRelational Database Management Systems (RDBMS): Databases are used in all important systems handling information, they are the best method for storing, managing, and querying large amounts of structured data. The most important data model for databases today is the relational model, which in database systems is represented by tables. Relational Database Management Systems (RDBMS) require data modeling according to the relational model, and normalization plays an important role in the modeling process. The Structured Query Language (SQL) can be used to query information stored in relational databases. RDBMS
2007-01-09 XML Namespaces: XML is successful because it can be used in many different scenarios, and because it is easy to define a schema (such as a DTD) for new scenarios, producing a tailored XML data model for this scenario. This means that names in XML documents must be interpreted as belonging to a certain schema. As long as a document uses names from only one schema, this can be done rather easily. However, in many scenarios today documents combine names from different schemas, and XML Namespaces provide a mechanism how the names in an XML document can be associated with a namespace. Namespaces (26 Slides) FAQ · Spec
2007-01-09 XML Schema: XML Schema is the most popular schema language for XML today. It has been introduced to overcome some of the commonly observed limitations of DTDs, most notably the lack of typing. Simple Types describe content which is not structured by XML markup, which means it describes attribute values and element content. Simple types can be defined by deriving new types from existing types by using type restriction. Complex Types describe element content if this content is using attributes and/or element content other than only character data. Using XML Schema's type concepts, it is easier to represent model-level information in a schema, because type hierarchies can represent model-level specializations. XSD (65 Slides) Specs · QuickRef
2007-01-10 XSL Transformations (XSLT): Because XML can be used to represent any vocabulary (often defined by some schema), the question is how these different vocabularies can be processed and maybe transformed into something else. This something else may be another XML vocabulary (a common requirement in B2B scenarios), or it may be HTML (a common scenario for Web publishing). Using XSL Transformations (XSLT), mapping tasks can be implemented easily. XSLT leverages XPath's expressive power in a rather simple programming language, the programs are often called stylesheets. For easy tasks, XSLT mappings can be specified without much real programming going on, by simply specifying how components of the source markup are mapped to components of the target markup. XSLT (84 Slides) Spec
2007-01-11 Web Programming: Web Programming can be loosely defined as any programming activity that somehow is related to the Web. This opens up a wide range of programming environment, but strictly speaking in many cases these programming environments lie outside of the Web's core. However, some programming tasks are an integral part of the Web, for example scripting code and Asynchronous JavaScript and XML (AJAX), the ability of scripting code to request servers. Using some examples, this final part of the course explores the whole range of Web programming activities. Programming (77 Slides)
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