Access control enforcement for conversation-based web services
Service Oriented Computing is emerging as the main approach to build distributed enterprise applications on the Web. The widespread use of Web services is hindered by the lack of adequate security and privacy support. In this paper, we present a novel framework for enforcing access control in conversation-based Web services. Our approach takes into account the conversational nature of Web services. This is in contrast with existing approaches to access control enforcement that assume a Web service as a set of independent operations. Furthermore, our approach achieves a tradeoff between the need to protect Web service's access control policies and the need to disclose to clients the portion of access control policies related to the conversations they are interested in. This is important to avoid situations where the client cannot progress in the conversation due to the lack of required security requirements. We introduce the concept of k-trustworthiness that defines the conversations for which a client can provide credentials maximizing the likelihood that it will eventually hit a final state.

title: An integrated approach to federated identity and privilege management in open systems
abstract: Online partnerships depend on federations of not only user identities but also of user entitlements across organizational boundaries.

title: Index configuration in object-oriented databases
abstract: In relational databases, an attribute of a relation can have only a single primitive value, making it cumbersome to model complex objects. The objectoriented paradigm removes this difficulty by introducing the notion of nested objects, which allows the value of an object atribute to be another object or a set of other objects. This means that a class consists of a set of attributes, and the values of the attributes are objects that belong to other classes; that is, the definition of a class forms a hierarchy of classes. All attributes of the nested classes are nested attributes of the root of the hierarchy. A branch of such hierarchy is called apath. In this article, we address the problem of index configuration for a given path. We first summarize some basic concepts, and introduce the concept of index configuration for a path. Then we present cost formulas to evaluate the costs of the various configurations. Finally, we present the algorithm that determines the optimal configuration, and show its correctness.

title: Objects with Multiple Most Specific Classes
abstract: In most object-oriented data models objects must belong to a single most specific class. This exclusive link between an instance and a class is often not adequate to model real-world situations. In this paper, we present an approach where objects can belong to several most specific classes. We formally address how the resulting conflicts can be handled, both for structural and behavioral components of objects. In particular, we formalize a notion of context and characterize the state of an object in terms of the set of its most specific classes. Moreover, we discuss two different dispatching approaches, one allowing context-dependent behavior, the other one ensuring behavior identity.

title: An advanced commit protocol for MLS distributed database systems
abstract: The classical Early Prepare commit protocol (EP), used in many commercial systems, is not suitable for use in multilevel secure distributed database systems that employ a locking protocol for concurrency control. This is because EP requires that read locks be not released by a subtransaction during its window of uncertainty; however, it is not possible for a locking protocol to provide this guarantee in a multilevel secure system (since read lock of a higher level transaction on a lower level data object must be released whenever a lower level transaction wants to write it). The Secure Early Prepare protocol (SEP) overcomes this difficulty by aborting those distributed transactions that release their low level read locks prematurely. We see this approach as being too restrictive. One of the major benefits of distributed processing is its robustness to failures, and SEP fails to take advantage of this. In this work, we propose the Advanced Secure Early Prepare commit protocol (ASEP) together with a number of language primitives that can be used as system calls in distributed transactions. These language primitives permit features like partial rollback and forward recovery, and allow a distributed transaction to proceed even when a subtransaction has released its low level read locks prematurely. This not only offers flexibility, but also can be used, if desired, by a sophisticated programmer to tradeoff consistency for atomicity of the distributed transaction. •Partially supported by National Science Foundation under grants

title: Index Organizations for Object-Oriented Database Systems
abstract: We present an indexing technique providing support for queries involving complex, nested objects and inheritance hierarchies. This technique is compared with two techniques obtained from more traditional organizations. The three techniques are evaluated using an analytical cost model. The discussion is cast in the framework of object-oriented databases. However, results are applicable to data management systems characterized by features such as complex objects and inheritance hierarchies.