Scott A. Hendrickson’s research while affiliated with University of California, Irvine and other places

Privacy-enhancing personalized (PEP) systems address individual users' privacy preferences as well as privacy laws and regulations. Building such systems entails model- ing two different domains: (a) privacy constraints as man- dated by law, voluntary self-regulation, or users' individ- ual privacy preferences, and modeled by legal profession- als, and (b) software architectures as dictated by available software components and modeled by software architects. Both can evolve independently, e.g., as new laws go into effect or new components become available. In prior work, we proposed modeling PEP systems using a product line ar- chitecture (PLA). However, with an extensional PLA, these domain models became strongly entangled making it diffi- cult to modify one without inadvertently affecting the other. This paper evaluates an approach towards modeling both domains within an intensional PLA. We find evidence that this results in a clearer separation between the two domain models, making each easier to evolve and maintain.

Knowledge of why some product line architecture (PLA) consists of the specific features and feature interactions that constitute its overall structure is an invaluable resource for an architect. However, most PLA modeling techniques do not model these concepts explicitly. This requires that the architect express rationale separately, which increases the likelihood that it diverges and slowly but surely loses its value. To address this, we present an approach to capturing rationale that relies on a particular form of PLA modeling, namely PLAs modeled using change sets and relationships. In so doing, we enable the architect to express rationale concerning the PLA at three different tiers, covering individual elements in the PLA, change sets and their raison d'être, and the relationships that govern how individual product architectures are composed.

We will demonstrate ArchStudio, an environment for software architecture modeling and meta-modeling. We will also showcase a set of innovative architecture-centric applications that use ArchStudio technologies as their basis.

The essence of any modeling approach for product line architectures lies in its ability to express variability. Existing approaches do so by explicitly specifying variation points inside the architectural specification of the entire product line, usually with optional and alternative elements of some form. This, however, leads to a sizable mismatch between conceptual variability (i.e., the features through which architects logically view and interpret differences in product architectures) and actual variability (i.e., the modeling constructs through which the logical differences must be expressed). We contribute a new product line architecture modeling approach that unites the two. Our approach uses change sets to group related architectural differences and relationships to govern which change set combinations are valid when composed into a particular product architecture. The result lifts modeling of variability out of modeling architectural structure, consolidates related variation points, and explicitly and separately manages their compatibilities.

Class diagrams model a system's classes, their inter-relationships, op- erations, and attributes and are used for a variety of purposes including explora- tory design, communication, and evaluation. However, traditional diagrams, and the tools used to create them, focus on capturing a single configuration - the product of the design process - rather than supporting the explorative design process itself that is used to create and evolve a design over time. This process involves iteration over multiple alternatives and evaluation of those alternatives. We present a layered approach and environment that encourages this process by capturing a design and its alternatives using layers. Layers may be combined with other layers to compose and explore new design alternatives for evaluation. Our tool provides mechanisms for creating, composing, and visualizing layers as well as detecting dependencies and conflicts among layers and managing seman- tic relationships among layers.

This paper addresses issues involved when an architect explore alternative designs including non-functional requirements; in our approach, non-functional requirements are expressed as state- charts. Non-functional requirements greatly impact the resulting design of a system because they naturally conflict with each other, crosscut the system at multiple points, and may be satisfied in a number of different ways. This makes correctly designing them early in the software lifecycle critical, since correcting them later can be extremely costly. Our approach supports an architect generating and evaluating many different design alternatives. This explorative process is not well supported by current techniques, which focus on documenting the result of this process, but not on assisting the designer during this process. We present an architec- ture-based approach that supports exploration of non-functional requirements expressed as statecharts. Our approach captures design alternatives of non-functional requirements separately, composes different system designs from these alternatives using a novel weaving technique, and analyzes the resulting design for specific qualities using simulation.

The solid state thermochemical decomposition kinetics and activation energy of neat 1,3,5,5-tetranitrohexahydropyrimidine (DNNC) and its DNNC-d6 deuterium labeled analogue were obtained by isothermal differential scanning calorimetry (IDSC) at 142, 145, and 148°C. Global rate constants and kinetic deuterium isotope effect (KDIE) data from the exothermic decomposition process suggest that homolytic CH bond rupture, in one or both types of chemically non-equivalent methylene (CH2) groups of the DNNC ring structure, constitutes the exothermic rate-controlling step. A DNNC-d6 energy of activation equal to 115kJ/mol was determined for this initial autocatalytic exothermic energy release from which a 106kJ/mol activation energy was calculated for unlabeled DNNC. This exothermic autocatalytic decomposition process follows an extended endothermic induction period for DNNC which shows a higher 128kJ/mol activation energy during which a catalytic initiating species may form by a rate-controlling step different from CH bond rupture.

Previous research eorts into creating links between software architecture and its implementations have not explicitly addressed ver- sioning. These earlier eorts have either ignored versioning entirely, cre- ated overly constraining couplings between architecture and implemen- tation, or disregarded the need for versioning upon deployment. This situation calls for an explicit approach to versioning the architecture- implementation relationship capable of being used throughout design, implementation, and deployment. We present ArchEvol, a set of xADL 2.0 extensions, ArchStudio and Eclipse plug-ins, and Subversion guide- lines for managing the architectural-implementation relationship through- out the entire software life cycle.

Applications built in a strongly decoupled, event-based interaction style have many commendable characteristics, including ease of dynamic configuration, accommodation of platform heterogeneity, and ease of distribution over a network. It is not always easy, however, to humanly grasp the dynamic behavior of such applications, since many threads are active and events are asynchronously (and profusely) transmitted. This paper presents a novel, complete approach that aids in the understanding, debugging, and visualization of the behaviors of event-based applications. It applies to real, implemented systems, without requiring the presence of component source code, and supports partial or incomplete, heuristic behavior specifications. A prototype implementation of our approach was applied to two systems, including the prototype itself, indicating that our approach is feasible, scalable, and shows promising results in terms of increasing the understandability of these types of systems.

Distributed applications that lack a central, trustworthy authority for control and validation are properly termed decentralized. Multiple, independent agencies, or "partners", cooperate to achieve their separate goals. Issues of trust are paramount for designers of such partners. While the research literature has produced a variety of trust technology building blocks, few have attempted to articulate how these various technologies can regularly be composed to meet trust goals. This paper presents a particular, event-based, architectural style, PACE, that shows where and how to incorporate various types of trust-related technologies within a partner, positions the technologies with respect to the rest of the application, allows variation in the underlying network model, and works in a dynamic setting. Initial experiments with variants of two sample decentralized applications developed in the PACE style reveal the virtues of dealing with all aspects of application structure and trust in a comprehensive fashion.