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Analysis of Signature Generation Schemes for Multiterm Queries In Linear Hashing with Superimposed Signatures
Get PDFSignature files provide efficient retrieval of data by reflecting the essence of the data objects into bit patterns. Our analysis explores the performance of three superimposed signature generation schemes as they are applied to a dynamic signature file organization based on linear hashing: Linear
Hashing with Superimposed Signatures (LHSS). The first scheme (SM) allows all terms set the same number of bits whereas the second and third schemes (MMS aid MMM) emphasize the terms with high discriminatory power. In addition, MMM considers the probability distribution of the number of query terms. The main contribution of the study is a detailed analysis of LHSS in multiterm query environments by incorporating the term discrimination values based on document and query frequencies. The approach of the study can also be extended to other signature file access methods based on partitioning. The
derivation of the performance evaluation formulas, the simulation results based on these formulas for various experimental settings, and the implementation results based on INSPEC and NPL text databases are provided. Results indicate that MMM and MMS outperform SM in all cases in terms of access savings, especially when terms become more distinctive. MMM slightly outperforms MMS in high weight and low weight query cases. The performance gap among all three schemes decreases as the database size increases, and as the signature size increases the performances of MMM and MMS decrease and converge
to that of the SM scheme when the hashing level is fixed
Case Tool for Developing Process Control Specifications in Dairy Manufacturing
Get PDFA computer aided software engineering (CASE) tool designed to assist the task of developing the specification of control software for programmable logic controllers for dairy process manufacturing is described. The CASE tool, called the specification assistant, is a part of a larger development environment that may ultimately include automatic generation of PLC code from the specification. The specification assistant includes a set of rule bases and associated rule-base editors that permit customization of the tool to particular manufacturing sites. It aims to standardize control code specifications, support reuse of specifications, allow inspection of specifications through simulation and reports, and facilitate the long term maintenance of specifications. The specification assistant was developed to support the domain of dairy process manufacturing in New Zealand. A domain analysis was performed to identify a specification language appropriate for the particular domain. Initial experience with the specification assistant indicates that it will improve the productivity of the software engineers who are the recipients of the specifications. Results also suggest that quality of both the specifications and the control software will be improved.
Keywords: Computer Aided Software Engineering, CASE, PLC, process control, automated manufacturin
A Survey of Traditional and Practical Concurrency Control in Relational Database Management Systems
Get PDFTraditionally, database theory has focused on concepts such as atomicity and serializability, asserting that concurrent transaction management must enable correctness above all else. Textbooks and academic journals detail a vision of unbounded rationality, where reduced throughput because of concurrency protocols is not of tremendous concern. This thesis seeks to survey the traditional basis for concurrency in relational database management systems and contrast that with actual practice. SQL-92, the current standard for concurrency in relational database management systems has defined isolation, or
allowable concurrency levels, and these are examined. Some ways in which DB2, a popular database, interprets these levels and finesses extra concurrency through performance enhancement are detailed. SQL-92 standardizes de facto relational database management systems features. Given this and a superabundance of articles in professional journals detailing steps for fine-tuning transaction concurrency, the expansion of performance tuning seems bright, even at the expense of serializabilty.
Are the practical changes wrought by non-academic professionals killing traditional database concurrency ideals? Not really. Reasoned changes for performance gains advocate compromise, using complex concurrency controls when necessary for the job at hand and relaxing standards otherwise. The idea of relational database management systems is only twenty years old, and standards are still evolving. Is there still an interplay between tradition and practice? Of course. Current practice uses tradition pragmatically, not idealistically. Academic ideas help drive the systems available for use, and perhaps current practice now will help academic ideas define concurrency control concepts for relational database management systems
Intelligent Simulation Modeling of a Flexible Manufacturing System with Automated Guided Vehicles
Get PDFAlthough simulation is a very flexible and cost effective problem solving technique, it has been traditionally limited to building models which are merely descriptive of the system under study. Relatively new approaches combine improvement heuristics and artificial intelligence with simulation to provide prescriptive power in simulation modeling. This study demonstrates the synergy obtained by bringing together the "learning automata theory" and simulation analysis. Intelligent objects are embedded in the simulation model of a Flexible Manufacturing System (FMS), in which Automated Guided Vehicles (AGVs) serve as the material handling system between four unique workcenters. The objective of the study is to find satisfactory AGV routing patterns along available paths to minimize the mean time spent by different kinds of parts in the system. System parameters such as different part routing and processing time requirements, arrivals distribution, number of palettes, available paths between workcenters, number and speed of AGVs can be defined by the user. The network of learning automata acts as the decision maker driving the simulation, and the FMS model acts as the training environment for the automata
network; providing realistic, yet cost-effective and risk-free feedback. Object oriented design and implementation of the simulation model with a process oriented world view, graphical animation and visually interactive simulation (using GUI objects such as windows, menus, dialog boxes; mouse sensitive dynamic automaton trace charts and dynamic graphical statistical monitoring) are other issues dealt with in the study
Integrated Expert System Development Environment With an Automatic Verification Feature: An Application To Grinding Process
Get PDFThe concerns of this Master degree project are the implementations of an expert system development environment and an application to manufacturing. The environment is given the
name of IDEA (Integrated expert system Development Environment with Automatic verification feature), and it integrates an expert system shell with a rule base verification facility and a rule base builder into a single program. The interface of IDEA has the look of a general purpose computer language. The knowledge bases referenced by IDEA consist of LF-THEN rules with
the syntax of Object-Attribute-Value (O-A-V) triples and confidence factors. An application is developed for grinding chattering diagnosis problems using the IDEA. The verification facility of IDEA realizes the main functions of CHECK, a verification tool, developed by T. Nguyen et al, 1987, so that it can identify some major problems of inconsistency and incompleteness. Different from CHECK, IDEA uses a unique approach based on rule tree algorithm to check for some logic problems in a rule base. IDEA also has the ability to draw the rule tree on a computer screen. This report discusses the problems of inconsistency and incompleteness in detail, including the influence of introducing confidence factors. Some
problems identified in this report are not reported before.
The rule base builder of IDEA uses some techniques that can greatly reduce errors in a rule base during its input phase and greatly speed up the input work. First, the builder uses
templates for rule input to eliminate the possible syntax errors of rules. Second, it uses an O-AV file for declared O-A-V triples. By checking the O-A-V file and the O-A-V triples used in the rule base, the problems of illegal O-A-V triples and unreferenced O-A-V triples can be identified. Finally, it has the ability to automatically generate the ask-part of the rule base, so that no errors will exists in the ask-part and the input work can be efficient. Grinding chattering is a kind of abnormal phenomenon in a grinding process, which greatly degrades the surface quality of the workpiece ground. The grinding chattering diagnosis rule base gives complete answers for the causes of chattering for external cylindrical grinding.
This report describes the rule base development work and its related grinding knowledge
Cell Programming Language Investigation of Extensions For Flow Control and Error Recovery in the Language
Get PDFThe Cell Programming Language (CPL) is a simple programming language which allows the students and faculty to easily program a workcell on a personal computer as the workcell
controller. However, the original version of CPL lacks programming flexibility and power since it does not support subroutines, flow control, error recovery and operator interface to the execution of a CPL program. The objective of the project is to design and implement a new version of CPL to overcome the shortcomings of the original CPL by extending the language to include flow control, error recovery and operator interface to the execution of a CPL program. In this report CPL is introduced. The problems in the original CPL are addressed, the extensions to the original CPL are defined, and the implementation of the extensions is described. Some future development tasks are also discussed
Structuring Hypertext Databases Using Hyper-Plate
Get PDFHypertext is the non-sequential access of information. The hypertext structure is powerful enough to represent informal, semiformal, and formal data. The construction of a hypertext document is a complex and laborious task. In general, hypertext documents are constructed manually. The manualmethod of construction may produce unstructured documents. It has been shown that a poor domerzt structure contributes to the lost in hyperspace syndrome. Hypertext Authoping System WypAS) was developed at the Depmtnaent of Systems Analysis, Miami University, Oxford, Ohio. In this study, Hyper-plate system was developed to structure documents created in HypAS. Hyperplate
system is used to create hyper-plates, i.e., templates for hypertext documents. A hyper-plate defines the atbributes of a collection of nodes and the relationship among those nodes. The hyper-plate concept was conceived to aa'dress the issues of structuring and automating the construction of hypertext documents. The concepts of this study can be extended to any hypertext authoring system. The paper presents the design and
implementation of Hyper-plate. The system components, data strctures, operations and its integralion with HpAS are described in detail
Visual Programming: Concepts and Implementations
Get PDFThe computing environment has changed dramatically since the advent of the computer. Enhanced computer graphics and sheer processing power have ushered in a new age of computing. User interfaces have advanced from simple line entry to powerful graphical interfaces. With these advances, computer languages are no longer forced to be sequentially and textually-based. A new programming paradigm has evolved to harness the power of today's computing environment - visual programming. Visual programming provides the user with visible models which reflect physical objects. By connecting these visible models to each other, an executable program is created. By removing the inherent abstractions of textual languages, visual programming could lead computing into a new era
