In 2015, the Korean government launched a major software education initiative. The urgency to rally the nation around the 4th Industrial Revolution is the driving force. It consists of two major components. One is to enhance software (computer science) education in universities, and another is to make coding education mandatory in elementary and middle schools.

Cloud computing has started taking root. Many vendors provide Infrastructure as a Service (IaaS), Software as a Service (SaaS), and Platform as a Service (PaaS). SaaS and PaaS are provided on top of an IaaS infrastructure. Different vendors have implemented different architectures for their IaaS and PaaS clouds. Further, the architecture of the IaaS infrastructure is multi-dimensional, consisting of virtualization architecture, cloud service and management functional architecture, network architecture, and a scale-out architecture. There are few definitive articles that provide a reference architecture for the IaaS infrastructure. In this article, I will try to provide a framework and outline for such an architecture.

The Internet and the Web have brought about a revolution in the way people live, obtain information, and interact with others. They have also brought about major changes in governance and commerce. Unfortunately, just as in the offline world, the transgressions of a minority of the people inhabiting the online world have made it costly and unhappy for the great majority of the people. This paper reviews the types of the negative byproducts of the Internet and approaches to mitigating them.

A botnet is a network of computers on the Internet infected with software robots, bots. There are numerous botnets. Some of them control millions of computers. Botnets have become the platform for the scourge of the Internet, namely, spam e-mails, launch denial of service attacks, click fraud, theft of sensitive information, cyber sabotage, cyber warfare, etc. In this paper, we review the status of the botnets, how they work, and how they may be defeated.

Cloud computing allows users to use only a Web browser to receive computing services via the Internet. Users only need to pay for the services they actually use. It appears that a wide adoption of cloud computing in the foreseeable future is inevitable, and its adoption will bring about a sea change in the pricing and distribution practices for both software and hardware. There are, however, various issues that will impede adoption of cloud computing. Most of them can be solved. We discuss the status of cloud computing today and various adoption issues. We also provide a market prognosis.

Cloud computing allows users to use only a Web browser to receive computing services via the Internet. Users only need to pay for the services they actually use. It appears that a wide adoption of cloud computing in the foreseeable future is inevitable, and its adoption will bring about a sea change in the pricing and distribution practices for both software and hardware. There are, however, various issues that will impede adoption of cloud computing. Most of them can be solved. We discuss the status of cloud computing today and various adoption issues. We also provide a market prognosis.

The Sharable Content Object Reference Model (SCORM) specification defines metadata of learning objects, which are used as the elementary reusable components in distance learning. The Content Object Repository Discovery and Registration/Resolution Architecture (CORDRA) specification provides a common architecture for the resolution, discovery, and sharing of these learning objects. These two specifications together define standardized ways in which learning objects can be discovered and reused by content designers. However, the current CORDRA and the definition of objects in SCORM only allow an object to be copied, updated, and reorganized in a new content aggregation, which is used as a delivery package to end users. This paper proposes a revised CORDRA architecture and a reusability mechanism to make instruction design easier. In particular, it proposes a structure called a reusability tree for tracking the history of reuse of learning objects in CORDRA. This paper also defines the notions of similarity, diversity, and relevancy of learning objects to make it easier for users to precisely search for and reuse learning objects.

Since the terrorist attacks of September 11, 2001, “homeland security” has become the centerpiece of U.S. domestic and foreign policies. The number of terrorists is a tiny fraction of all the people who live in or enter the U.S. However, given the enormous consequences of a repeat of the September 11 attacks, all non-terrorists have been subjected to security measures. The cost of all the security measures includes not only the cost of human resources, deployment of defensive weaponry and technology purchases, but also the time that all people waste. One of the ways to reduce costs is to make terrorist-related intelligence more precise and accurate, so that efforts to track, arrest and deter terrorists, their supporters and movements of funds and weapons can be more precisely directed. One of the ways to make such intelligence more precise is the use of data gathered and stored in databases, and database and related technologies to query, search and mine the databases. This paper first reviews the difficulties in tracking terrorist suspects and their activities. It then examines how databases, and database and related technologies, can be used and made more effective in aiding the war against terror.

Secret group communication can be achieved by encryption messages with a group key. Dynamic groups face the problem of changing the group key whenever members join or leave. One of the solutions to this problem is to send updated group keys to members via rekey messages in a secure manner. The recovery of lost group keys consequently becomes important because a member cannot decrypt the group data if she loses the rekey messages. Also, any rekey messages lost while a member is logged off cannot be recovered in real-time. Saving recent rekey messages and resending them by the key distribution center not only requires large storage space, but also can cause unnecessary transmission and decryption of keys. Furthermore, the keys in the unsaved rekey messages cannot be recovered. This paper analyzes the problem of rekey message loss and proposes an efficient scheme for recovering group keys based on a logical key hierarchy. The group key generation method used in the scheme makes it possible to recover group keys without transmission and decryption of useless keys.

XML allows users to define elements using arbitrary words and organize them in a nested structure. These features of XML offer both challenges and opportunities in information retrieval, document management, and data mining. In this paper, we propose a new methodology for preparing XML documents for quantitative determination of similarity between XML documents by taking into account XML semantics (i.e., meanings of the elements and nested structures of XML documents). Accurate quantitative determination of similarity between XML documents provides an important basis for a variety of applications of XML document mining and processing. Experiments with XML documents show that our methodology provides a 50-100% improvement in determining similarity over the traditional vector-space model that considers only term-frequency and 100% accuracy in identifying the category of each document from an on-line bookstore.

Develops a formal basis for research into the reliability aspects of transaction processing in multidatabase systems (MDBSs). We define a new correctness notion called 'global committability' for the correct unilateral commit and the retry recovery of global transactions in an autonomous MDBS environment. This notion makes it easier to ensure the isolation property of global transactions when the retry approach is applied. The formalization work illustrates that the conventional serializability and recoverability notions are not sufficient to specify the correct execution (i.e. isolated execution and recovery) of global transactions when the unilateral commit and the retry recovery are used to ensure the atomicity of global transactions. This work is significant because the unilateral commit and the retry recovery are an attractive complementary means to the undo recovery (whose correct schedule is specified by the conventional recoverability notion) for advanced transaction applications with the characteristics of site autonomy and long-lived execution.

Proposes a formal approach for translating OODB queries to equivalent relational queries. The translation is accomplished through the use of relational predicate graphs and OODB predicate graphs. One advantage of using such a graph-based approach is that we can achieve bidirectional translation between relational queries and OODB queries.>

In a heterogeneous database system, a query for one type of database system (i.e., a source query) may have to be translated to an equivalent query (or queries) for execution in a different type of database system (i.e., a target query). Usually, for a given source query, there is more than one possible target query translation. Some of them can be executed more efficiently than others by the receiving database system. Developing a translation procedure for each type of database system is time-consuming and expensive. We abstract a generic hierarchical database system (GHDBS) which has properties common to database systems whose schema contains hierarchical structures (e.g., System 2000, IMS, and some object-oriented database systems). We develop principles of query translation with GHDBS as the receiving database system. Translation into any specific system can be accomplished by a translation into the general system with refinements to reflect the characteristics of the specific system. We develop rules that guarantee correctness of the target queries, where correctness means that the target query is equivalent to the source query. We also provide rules that can guarantee a minimum number of target queries in cases when one source query needs to be translated to multiple target queries. Since the minimum number of target queries implies the minimum number of times the underlying system is invoked, efficiency is taken into consideration.>

No abstract available.

Proposes a solution for the construction of a relational front-end for object-oriented database systems (OODBs). Rules are provided to transform the structural part of an OODB scheme to an equivalent relational scheme to provide relational users with a relational view of the OODB scheme. A mechanism based on a relational predicate graph and an OODB predicate graph is provided to translate relational queries to OODB queries to allow relational users access to data stored in an OODB database system.>

The authors investigate principles of translating relational queries to hierarchical queries. Instead of using a specific hierarchical database system they abstract a generic hierarchical database system (GHDBS) which has properties common to database systems whose schema contain hierarchical structures. Principles of query translation with GHDBS as the receiving database system are developed. Rules that guarantee the correctness of the translated queries are described. Rules are provided that can guarantee a minimum number of target queries in a case when a user-submitted source query needs to be translated to multiple target queries.>

We present a novel language for querying object-oriented databases. The language is built around the idea of extended path expressions that substantially generalize [ZAN83], and on an adaptation of the first-order formalization of object-oriented languages from [KW89, KLW90, KW92]. The language incorporates features not found in earlier proposals; it is easier to use and has greater expressive power. Some of the salient features of our language are: ffl Precise model-theoretic semantics. ffl A very expressive form of path expressions that not only can do joins, selections and unnesting, but can also be used to explore the database schema. ffl Views can be defined and manipulated in a much more uniform way than in other proposals. ffl Database schema can be explored in the very same language that is used to retrieve data. Unlike in relational languages, the user needs not know anything about the system tables that store schema information. ffl The notions of a type and type-correctness have precise meaning. It accommodates a wide variety of queries that might be deemed well- or ill-typed under different circumstances. In particular, we show that there is more than one way of settling the issue of type correctness. For expository purposes and due to space limitation, we chose to make a number of simplifying assumptions and left some features out. A more complete account can be found in [KSK92].

An active database system reacts to a set of external events such as a timer interrupt or access to a particular object in the database. A trigger is a general mechanism for active data management, both in the context of a centralized system or a distributed system (including that of autonomous and cooperating agents). It consists of three parts; event specification, integrity constraint specification, and action specification. The event specification in a trigger is a set of events which will cause the condition in the constraint specification to be checked. If the condition is true, the actions in the action specification will be initiated. In this paper, we develop a framework for supporting triggers in object-oriented database systems. The framework consists of a categorization for each of the three components of a trigger. The framework is first cast in the context of the relational model of data, and is then extended to account for object-oriented concepts that constitute an object-oriented data model, including nested objects, methods, and inheritance hierarchy.

A scheduler producing quasi-serializable executions for concurrency control in multidatabase systems (MDBSs) is presented. An algorithm is proposed which ensures quasi-serializability by controlling submissions of global transactions. The algorithm groups global transactions in such a way that transactions in a group affect each other in a partial order. Transaction groups are executed separately and in a consistent order at all local sites. The algorithm differs from the others in that it does not violate local autonomy, provides a high degree of concurrency, and is globally deadlock-free.>

The conventional models of authorization have been designed for database systems supporting the hierarchical, network, and relational models of data. However, these models are not adequate for next-generation database systems that support richer data models that include object-oriented concepts and semantic data modeling concepts. Rabitti, Woelk, and Kim [14] presented a preliminary model of authorization for use as the basis of an authorization mechanism in such database systems. In this paper we present a fuller model of authorization that fills a few major gaps that the conventional models of authorization cannot fill for next-generation database systems. We also further formalize the notion of implicit authorization and refine the application of the notion of implicit authorization to object-oriented and semantic modeling concepts. We also describe a user interface for using the model of authorization and consider key issues in implementing the authorization model.

ORION-2 is a commercially available, federated, object-oriented database management system designed and implemented at MCC. One major architectural innovation in ORION-2 is the coexistence of a shared databese and a number of private databases. The shared database is accessible to all authorized users of the system, while each private database is accessible to only the user who owns it. A distributed database system with a shared database and private databases for individual users is a natural architecture for data-intensive application environments on a network of workstations, notably computer-aided design and engineering systems. This paper discusses the benefits and limitations of such a system and explores the impact of such an architecture on the semantics and implementation of some of the key functions of a database system, notably queries, database schema, and versions. Although the issues are discussed in the context of an object-oriented data model, the results (at least significant portions thereof) are applicable to database systems supporting other data models.

The set of object-oriented concepts found in object-oriented programming languages forms a good basis for a data model for post-relational database systems which will extend the domain of database applications beyond conventional business data processing. However, despite the high level of research and development activities during the past several years, there is no standard object-oriented data model, and criticisms and concerns about the field still remain. In this paper, I will first provide a historical perspective on the emergence of object-oriented database systems in order to derive a definition of object-oriented database systems. I will then examine a number of major challenge which remain for researchers and implementers of object-oriented database systems.

An object-oriented database is defined and justified on the basis of a small set of central object-oriented concepts. A number of common misconceptions about object-oriented databases are discussed. The results of relevant recent research in object-oriented databases are outlined. Directions for future research in object-oriented databases are provided.>

Various architectural components of ORION-1 and ORION-1SX are described and a review of the current implementation is provided. The message handler receives all messages sent to the ORION system. The object subsystem provides high-level data management functions, including query optimization, schema management, long data management (including text search) and support for versionable objects, composite objects, and multimedia objects. The transaction management subsystem coordinates concurrent object accesses and provides recovery capabilities. The storage subsystem manages persistent storage of objects and controls the flow of objects between the secondary storage device and main memory buffers. In ORION-1, all subsystems reside in one computer. The ORION-1SX architecture is significantly different from ORION-1 in the management of shared data structures and distribution of these subsystems and their components.>

Cyclic query processing issues in object-oriented databases are investigated. A data and cyclic query model is defined for an object-oriented database system, using a graph model. Then the efficient processing of a general object-oriented cyclic query is discussed. For efficient processing, a general cyclic query and the access plans generated for a given query are defined and a cost model is developed to determine the cost for each access plant generated. The retrieval algorithms used for actual data retrieval are also investigated.>

In object-oriented systems, an object may recursively reference any number of other objects. The references, however, do not capture any special relationships between objects. An important semantic relationship which may be superimposed on a reference is the IS-PART-OF relationship between a pair of objects. A set of objects related by the IS-PART-OF relationship is collectively called a composite object.

Three index organizations are introduced for use in the evaluation of a query in an object-oriented or nested relational database. Detailed models of the three indexes are developed. Using the models, the storage cost, retrieval cost, and update cost of these indexes are evaluated, and a number of observations are made about the use of these indexes for evaluating queries for object-oriented or nested relational databases. A comparison of the combined retrieval and update costs for the three indexes is also included. It is shown that the degree of reference sharing among objects for the various classes in the path influences both the retrieval and update costs.>

A query under an object-oriented data model exhibits characteristics which one finds in a relational query and those which clearly separate it from a relational query. The differences in turn have interesting impacts on the complexity of and strategy for query evaluation in object-oriented databases. The authors develop a model of a query under an object-oriented data model, and analyze the fundamental differences in the semantics of queries in object-oriented databases and relational databases.>

There are two major issues to address to achieve integration of an object-oriented programming system with a database system. One is the language issue: an object-oriented programming language must be augmented with semantic data modeling concepts to provide a robust set of data modeling concepts to allow modeling of entities for important real-world applications. Another is the computational-model issue: application programmers should be able to access and manipulate objects as though the objects are in an infinite virtual memory; in other words, they should not have to be aware of the existence of a database system in their computations with the data structures the programming language allows. This paper discusses these issues and presents the solutions which we have incorporated into the ORION object-oriented database system at MCC.

In this paper, we describe transaction management in ORION, an object-oriented database system. The application environments for which ORION is intended led us to implement the notions of sessions of transactions, and hypothetical transactions (transactions which always abort). The object-oriented data model which ORION implements complicates locking requirements. ORION supports a concurrency control mechanism based on extensions to the current theory of locking, and a transaction recovery mechanism based on conventional logging.

A DAG (direct acyclic graph) is an important data structure which requires efficient support in CAD (computer-aided design) databases. It typically arise from the design hierarchy, which describes complex designs in terms of subdesigns. A study is made of the properties of the three types of clustered sequences of nodes for hierarchies and DAGs, and algorithms are developed for generating the clustered sequences, retrieving the descendants of a given node, and inserting new nodes into existing clustered sequences of nodes which preserve their clustering properties. The performance of the clustering sequences is compared.>

A model of a complex object is presented and a set of meaningful operations, both basic and advanced, on a single complex object and on a configuration of complex objects is defined. A set of requirements is presented for storage subsystems that support complex objects. Implementation of complex objects and operations on a single complex object are described, and a detailed performance analysis is provided which establishes the merit of complex objects. Finally, storage techniques are proposed for supporting advanced operations on a configuration of complex objects.>

Many applications in the CAD/CAM and AI domains require the capability to define and manipulate a structured collection of records as a single logical entity, called a complex object. A complex object is the unit of sharing among many configurations of higher level entities. In this paper, we present a model of complex object and define a set of meaningful operations, both basic and advanced, on a single complex object and on a configuration of complex objects. We then present a set of requirements for storage subsystems that support complex objects. We also describe our implementation of complex objects and operations on a single complex object; and provide a detailed performance analysis which establishes the merit of complex objects. Finally, we propose storage techniques for supporting advanced operations on a configuration of complex objects.

In this paper, we elaborate on three major enhancements to the conventional object-oriented data model, namely, schema evolution, composite objects, and versions. Schema evolution is the ability to dynamically make changes to the class definitions and the structure of the class lattice. Composite objects are recursive collections of exclusive components that are treated as units of storage, retrieval, and integrity enforcement. Versions are variations of the same object that are related by the history of their derivation. These additional features are strongly motivated by data management requirements of object-oriented applications from the AI, CAD/CAM, and OIS (office information systems with multimedia documents) domains. An object-oriented data model, with these enhancements, has been incorporated into ORION, a prototype database system developed at MCC as a vehicle of research into object-oriented databases.

Many applications in such domains as computer-aided design require the capability to define, store and retrieve as a single unit a collection of related objects known as a composite object. A composite object explicitly captures and enforces the IS-PART-OF integrity constraint between child and parent pairs of objects in a hierarchical collection of objects. Further, it can be used as a unit of storage and retrieval to enhance the performance of a database system.

Object-oriented programming is well-suited to such data-intensive application domains as CAD/CAM, AI, and OIS (office information systems) with multimedia documents. At MCC we have built a prototype object-oriented database system, called ORION. It adds persistence and sharability to objects created and manipulated in applications implemented in an object-oriented programming environment. One of the important requirements of these applications is schema evolution, that is, the ability to dynamically make a wide variety of changes to the database schema. In this paper, following a brief review of the object-oriented data model that we support in ORION, we establish a framework for supporting schema evolution, define the semantics of schema evolution, and discuss its implementation.

Presented in this paper is the data model for ORION, a prototype database system that adds persistence and sharability to objects created and manipulated in object-oriented applications. The ORION data model consolidates and modifies a number of major concepts found in many object-oriented systems, such as objects, classes, class lattice, methods, and inheritance. These concepts are reviewed and three major enhancements to the conventional object-oriented data model, namely, schema evolution, composite objects, and versions, are elaborated upon. Schema evolution is the ability to dynamically make changes to the class definitions and the structure of the class lattice. Composite objects are recursive collections of exclusive components that are treated as units of storage, retrieval, and integrity enforcement. Versions are variations of the same object that are related by the history of their derivation. These enhancements are strongly motivated by the data management requirements of the ORION applications from the domains of artificial intelligence, computer-aided design and manufacturing, and office information systems with multimedia documents.

VLSI layout systems perform various operations on design data describing the layouts of geometries (rectangles) on different mask layers. In this paper, we identify a basic set of such operations and show a formulation of these operations in terms of expressions of predicates that are suitable for processing by a database system. We then describe the operations and properties of a 4-D (four-dimensional) tree structure for efficiently supporting these operations. We also provide a qualitative analysis of the time complexity of the data structure, which compares favorably against various existing proposals.

This paper identifies data modelling and data access and sharing requirements which multimedia applications impose on a database system. It shows the capabilities of an object-based data model and indicates extensions which are needed to meet the data modelling aspects of these requirements. A logical implementation of the operations on the model is described. The model generalizes the notions of instantiation and generalization in the standard object-oriented paradigm, and augments it with the notions of aggregation and relationships which are specialized for a multimedia application environment. Objects may exist in aggregation hierarchies which provide the capability to integrate diverse types of multimedia information such as text, sound, bit-mapped images, and complex graphics drawings. Objects may also be linked through other user-defined relationships to capture such application functions as voice annotation and referencing of one document by another. Using this model, the semantics of aggregation and relationships in a multimedia application environment can be understood and efficiently supported by a database system.

No abstract available.

VLSI CAD applications deal with design objects that have an interface description and an implementation description. Versions of design objects have a common interface but differ in their implementations. A molecular object is a modeling construct which enables a database entity to be represented by two sets of heterogeneous records, one set describes the object's interface and the other describes its implementation. Thus a reasonable starting point for modeling design objects is to begin with the concept of molecular objects. In this paper, we identify modeling concepts that are fundamental to capturing the semantics of VLSI CAD design objects and versions in terms of molecular objects. A provisional set of user operations on design objects, consistent with these modeling concepts, is also defined. The modeling framework that we present has been found useful for investigating physical storage techniques and change notification problems in version control.

This paper outlines the overall architecture of a query processor for relational queries and describes the design and control of its major processing modules. The query processor consists of only four processing modules and a number of random-access memory modules. Each processing module processes tuples of relations in a bit-serial, tuple-parallel manner for each of the primitive database operations which comprise a complex relational query. The query processor is designed to be manufacturable using existing VLSI technology, and to support in a uniform manner both the numeric and nonnumeric processing requirements a high-level query language like SQL presents.

This paper presents the design of a relational query processor. The query processor consists of only four processing PIPEs and a number of random-access memory modules. Each PIPE processes tuples of relations in a bit-serial, tuple-parallel manner for each of the primitive database operations which comprise a complex relational query. The design of the query processor meets three major objectives: the query processor must be manufacturable using existing and near-term LSI (VLSI) technology; it must support in a uniform manner both the numeric and nonnumeric processing requirements a high-level user interface like SQL presents; and it must support the query-processing strategy derived in the query optimizer to satisfy certain system-wide performance optimality criteria.

SQL is a high-level nonprocedural data language which has received wide recognition in relational databases. One of the most interesting features of SQL is the nesting of query blocks to an arbitrary depth. An SQL-like query nested to an arbitrary depth is shown to be composed of five basic types of nesting. Four of them have not been well understood and more work needs to be done to improve their execution efficiency. Algorithms are developed that transform queries involving these basic types of nesting into semantically equivalent queries that are amenable to efficient processing by existing query-processing subsystems. These algorithms are then combined into a coherent strategy for processing a general nested query of arbitrary complexity.

This paper presents a new method of computing the product or join of n relations in a paged-memory environment. The method, termed the nested-block method, is an attempt to take maximum advantage of available main-memory buffer space. The problem of finding an optimal allocation of main-memory buffer space for the nested-block method of scanning n relations poses a nonlinear integer-programming problem. This paper first describes the operation of the nested-block method, and derives corresponding cost formula. It then presents an efficient heuristic algorithm for determining a near-optimal allocation of main-memory buffer space. The need to compute the product of relations arises naturally in processing n-relation queries. Conventional techniques for computing the join of relations can be complemented by the nested-block method. This paper examines these two important applications of the nested-block method.