This work presents a novel approach for development of complex real-time systems, called the documentation-driven development (DDD) approach. This approach can enhance integration of computer aided software development activities, which encompass the entire life cycle. DDD will provide a mechanism to monitor and quickly respond to changes in requirements and provide a friendly communication and collaboration environment to enable different stakeholders to be easily involved in development processes and, therefore, significantly improve the agility of software development for complex real-time systems. DDD will also support automated software generation based on a computational model and some relevant techniques. DDD includes two main parts: a documentation management system (DMS) and a process measurement system (PMS). DMS will create, organize, monitor, analyze, and transform all documentation associated with the software development process. PMS will monitor the frequent changes in requirements and assess the effort and success possibility of development. A case study was conducted by a tool set that realized part of the proposed approach.

The major hurdle in developing distributed systems is implementing the interoperability between systems. Currently, most of the interoperability techniques require that the data or services be tightly coupled to a particular server. Furthermore, as most programmers are trained in designing stand-alone application, developing a distributed system proves to be time-consuming and difficult. The paper address the issues by creating an interface wrapper model that allows developers the feature of treating distributed objects as local objects. A tool was developed to generate a Java interface wrapper from a specification language called the Prototyping System Description Language.

We describe a distributed requirements engineering environment using computer aided software engineering tools linked together through the Internet. We created this distributed requirements engineering environment using Microsoft's Personal Web Server (PWS), Microsoft's Open Database Connectivity (OPEC) technology, Netscape Communicator, Microsoft's Internet Explorer, Microsoft's Access97 database, and a set of PERL scripts that are executed by users of the environment to perform database operations. We show how we added basic security features to the Internet accessible database.

We present a language-independent semantic model of the process of combining changes to programs. This model extends the domains used in denotational semantics (complete partial orders) to Boolean algebras, and represents incompatible modifications as well as compatible extensions. The model is used to define the intended semantics of change-merging operations on programs and to establish some general properties of software merging. We determine conditions under which changes to subprograms of a software system can be merged independently and illustrate cases where this is not possible.

The authors explore the use of software transformations for software evolution. Meaning-preserving program transformations have been widely used for program development from a fixed initial specification. They consider a wider class of transformations to support development in which the specification evolves, rather than being fixed in advance. A new and general classification of transformations based on their effect on system interfaces, externally observable behavior, and abstraction level of a system description is presented. This classification is used to rearrange chronological derivation sequences containing meaning-changing transformations into lattices containing only meaning-preserving transformations. A process model for software evolution that utilizes prototyping techniques is described. Ways in which this class of transformations can be used to support such a process are considered. A set of examples are presented to illustrate the ideas. Software tool support and directions for future research are discussed.>

The formal semantics of a prototyping language for hard real-time systems, PSDL, is given. PSDL provides a data flow notation augmented by application-orientation timing and control constraints to describe a system as a hierarchy of networks of processing units communicating via data streams. The semantics of PSDL are defined in terms of algebraic high-level Petri nets. This formalism combines algebraic specifications of abstract data types with process and concurrency concepts of Petri nets. Its data abstraction facilities are used to define the meaning of PSDL data types, while high-level Petri nets serve to model the casual and timing behavior of a system. The net model exposes potential concurrency of computation and makes all synchronization needs implied by timing and control constraints explicit and precise. Time is treated as state of clocks, and clocks are modeled as ordinary system components. The net semantics provides the basis for applying analysis techniques and semantic tools available for high-level Petri nets.>

The authors report their experiences using attribute grammars to generate pretty printers automatically for a formal specification language. This technology enables such tools to be created with a relatively small amount of effort. The resulting tools are easy to modify and are fast enough for practical use. The extension of this technique to other notations is discussed.>

Object-oriented techniques form a promising approach for realizing an integrated computer-aided software development environment capable of detection and correcting errors early in the development process. The author discusses the connection between formal specifications, object-oriented data models, reusable components, and engineering databases.>

The authors describe the semantics of the real-time language PSDL, which was designed for prototyping real-time systems. They focus on the aspects of the language relating to hard real-time constraints, scheduling, and functional behavior. They present the aspects of PSDL that simplify the description of real-time constraints and clarify the relationships between periodic and data-driven operators and the interactions between timing and control constraints in a language that combines these features.>

Prototype system description language is a high-level real-time language with special features for hard real-time system specification and design. It can be used to firm up requirements through execution of its software prototypes. The language design is based on a real-time model merging data and control flow, and its implementation is beyond conventional compiler technology because of the need to meet real-time constraints. A special scheme used to meet the hard real-time constraints and the guidelines used to implement such a language in the target language Ada are described and illustrated. The required software tools for automated translation and scheduling are also discussed. These tools have been designed, and a prototype version has been partially implemented.>

The uses and advantages of a language tailored specifically for the description and construction of translators are considered. The major features of the Kodiyak language prototyping language are described. The Kodiyak language was designed to be a comprehensive translator development system. The language is intended to support a simple, unambiguous conceptual model of translation, to allow the construction of nontrivial translators, and, to be easy to use.>

The authors introduce a clustering concept called component aggregation which considers assemblies having the same types of parts as equivalent objects. The notion of equivalent objects is used to develop a mathematical model of composite objects. It is shown that the set of equivalence classes of objects form a Boolean algebra whose minterms represent the objects that are not considered composite at the current viewing level. The algebraic structure of composite objects serves as a basis for developing a technique for organizing composite objects and supporting materialization of explosion views. The technique provides a clustering mechanism which partitions the database into meaningful and application-oriented clusters, and allows any desired explosion view to be materialized using a minimal set of stored views. A simplified relational database for design data and a set of frequent access patterns in design applications are outlined and used to demonstrate the benefits of database organizations based on the mathematical model of composite objects.>

PSDL is a language for describing prototypes of real-time software systems. It is most useful for requirements analysis, feasibility studies, and the design of large embedded systems. PSDL has facilities for recording and enforcing timing constraints, and for modeling the control aspects of real-time systems using nonprocedural control constraints, operator abstractions, and data abstractions. The language has been designed for use with an associated prototyping methodology. PSDL prototypes are executable if supported by a software base containing reusable software components in an underlying programming language (e.g. Ada).>

An implementation technique for design databases is introduced. The technique is based on the component aggregation abstraction, which ignores the details of assembly structures of objects and considers assemblies which have exactly the same type of parts as equivalent assemblies. Component aggregation allows structural properties of design objects to be explored and utilized to achieve efficient organization of design data. A mathematical model of design objects is developed, and used to demonstrate the benefits of component aggregation in the execution of frequent operations in design applications.

Optical flow can be used to locate dynamic occlusion boundaries in an image sequence. We derive an edge detection algorithm sensitive to changes in flow fields likely to be associated with occlusion. The algorithm is patterned after the Marr-Hildreth zero-crossing detectors currently used to locate boundaries in scalar fields. Zero-crossing detectors are extended to identify changes in direction and/or magnitude in a vector-valued flow field. As a result, the detector works for flow boundaries generated due to the relative motion of two overlapping surfaces, as well as the simpler case of motion parallax due to a sensor moving through an otherwise stationary environment. We then show how the approach can be extended to identify which side of a dynamic occlusion boundary corresponds to the occluding surface. The fundamental principal involved is that at an occlusion boundary, the image of the surface boundary moves with the image of the occluding surface. Such information is important in interpreting dynamic scenes. Results are demonstrated on optical flow fields automatically computed from real image sequences.

Model building is identified as the most important part of the analysis and design process for software systems. A set of primitives to support this process is presented, along with a formal language, MSG.84, for recording the results of analysis and design. The semantics of the notation is defined in terms of the actor formalism, which is based on a message passing paradigm. The automatic derivation of a graphical form of the specification for user review is discussed. Potentials for computer-aided design based on MSG.84 are indicated.