Data and Applications Security Developments and Directions Dr Bhavani Thuraisingham The University of Texas at Dallas Lecture 8 Trustworthy Semantic Webs February 2011 Outline Semantic web XML and XML security RDF and RDF security Ontologies Rules Applications Reference Building trustworthy semantic web Thuraisingham CRC Press 2007 From Today s Web to Semantic web Today s web High recall low precision Too many web pages resulting in searches many not relevant Sometimes low recall Results sensitive to vocabulary Different words even if they mean the same thing do not results in same web pages Results are single web pages not linked web pages Semantic web Machine understandable web pages Activities on the web such as searching with little or no human intervention Technologies for knowledge management e commerce interoperability Solutions to the problems faced by today s web Knowledge Management and Personal Agents Knowledge Management Corporation Need Searching extracting and maintaining information uncovering hidden dependencies viewing information Semantic web for knowledge management Organizing knowledge automated tools for maintaining knowledge question answering querying multiple documents controlling access to documents Personal Agent John is a president of a company He needs to have a surgery for a serious but not a critical illness With current web he has to check each web page for relevant information make decisions depending on the information provided With the semantic web the agent will retrieve all the relevant information synthesize the information ask John if needed and then present the various options and makes recommendations E Commerce Business to Consumer Users shopping on the web wrapper technology is used to extract information about user preferences etc and display the products to the user Use of semantic web Develop software agents that can interpret privacy requirements pricing and product information and display timely and correct information to the use also provides information about the reputation of shops Business to Business Organizations work together and carrying out transactions such as collaborating on a product supply chains etc With today s web lack of standards for data exchange Use of semantic web XML is a big improvement but need to agree on vocabulary Future will be the use of ontologies to agree on meanings and interpretations Semantic Web Technologies Explicit metadata Metadata is data about data Need metadata to be explicitly specified so that different groups and organizations will know what is on the web Metadata specification languages include XML and RDF Ontologies Explicit and formal specification of conceptualization describes a domain of discourse relationships Ontology languages include XML RDF OWL Logic Logic can be used to specify facts as well as rules New facts and derived from existing facts based on the inference rules Descriptive Logic is the type of logic that has been developed for semantic web applications Layered Approach Tim Berners Lee s Vision www w3c org What is XML all about XML is needed due to the limitations of HTML and complexities of SGML It is an extensible markup language specified by the W3C World Wide Web Consortium Designed to make the interchange of structured documents over the Internet easier Key to XML used to be Document Type Definitions DTDs Defines the role of each element of text in a formal model XML schemas have now become critical to specify the structure XML schemas are also XML documents XML Elements XML Statement John Smith is a Professor in Texas This can be expressed as follows Professor name John Smith name state Texas state Professor XML Elements Now suppose this data can be read by anyone then we can augment the XML statement by an additional element called access as follows Professor name John Smith name state Texas state access All Read access Professor XML Elements If only HR can update this XML statement then we have the following Professor name John Smith name state Texas state access HR department Write access Professor XML Elements We may not wish for everyone to know that John Smith is a professor but we can give out the information that this professor is in Texas This can be expressed as Professor name John Smith Govt official Read name state Texas All Read state access HR department Write access Professor XML Attributes Suppose we want to specify to access based on attribute values One way to specify such access is given below Professor Name John Smith Access All Read Salary 60K Access Administrator Read Write Department Security Access All Read Professor Here we assume that everyone can read the name John Smith and Department Security But only the administrator can read and write the salary attribute XML DTD DTDs essentially specify the structure of XML documents Consider the following DTD for Professor with elements Name and State This will be specified as ELEMENT Professor Officer Name State ELEMENT name PCDATA ELEMENR state PCDATA ELEMENT access PCDATA XML Schema While DTDs were the early attempts to specify structure for XML documents XML schemas are far more elegant to specify structures Unlike DTDs XML schemas essentially use the XML syntax for specification Consider the following example ComplexType name ProfessorType Sequence element name name type string element name state type string element name access type strong Sequence ComplexType XML Namespaces Namespaces are used for DISAMBIGUATION CountryX Academic Institution DTD Xmlns CountryX http www CountryX edu Instution Xmlns USA http www USA edu Instution DTD Xmlns UK http www UK edu Instution DTD USA Title College USA Name University of Texas at Dallas USA State Texas UK Title University UK Name Cambridge University UK State Cambs CountryX Acedmic Instiution XML Namespaces Country Academic Institution Access Government official Read Access DTD Xmlns CountryX http www CountryX edu Instution Xmlns USA http www USA edu Instution DTD Xmlns UK http www UK edu Instution DTD USA Title College USA Name University of Texas at Dallas USA State Texas UK Title University UK Name Cambridge University UK State Cambs CountryX Academic Institution Federations Distribution Site 1 document Professor name ID 111 ID Name John Smith name State Texas state Professor name Site 2 document Professor salary ID 111 ID salary 60K salary Professor salary Credentials in XML Professor credID 9 subID 16 CIssuer 2 name Alice Brown name university