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Computerized Maintenance Management Systems (CMMS): The Evolution of a Maintenance Management Program
Published in Barney L. Capehart, Lynne C. Capehart, Paul J. Allen, David C. Green, Web Based Energy Information and Control Systems:, 2021
The client-server concept was extended to mean breaking logic and data apart into modules and deploying the data across a network. Initially there were two layers: the application and a database server. The application consisted of a graphical user interface (GUI) and the code to control the data retrieval and updating. The GUI is exposed to a user; it is the screen or web page, a place to enter or read information. The design of the GUI determines a system’s usability or user-friendliness. The data access layer is simply the database or a collection of files where the data is stored. Web applications introduced the three-tier model by default: the browser is the client tier, the database the back-end tier, and the web server and its extensions became the middle tier. [12]
Computerized Maintenance Management Systems (CMMS): The Evolution of a Maintenance Management Program
Published in Barney L. Capehart, Timothy Middelkoop, Paul J. Allen, David C. Green, Handbook of Web Based Energy Information and Control Systems, 2020
The client-server concept was extended to mean breaking logic and data apart into modules and deploying the data across a network. Initially there were two layers: the application and a database server. The application consisted of a graphical user interface (GUI) and the code to control the data retrieval and updating. The GUI is exposed to a user; it is the screen or web page, a place to enter or read information. The design of the GUI determines a system’s usability or user-friendliness. The data access layer is simply the database or a collection of files where the data is stored. Web applications introduced the three-tier model by default: the browser is the client tier, the database the back-end tier, and the web server and its extensions became the middle tier. [12]
Software design for building model servers: Concurrency aspects
Published in Manuel Martínez, Raimar Scherer, eWork and eBusiness in Architecture, Engineering and Construction, 2020
The most recent state of the model is always kept in memory as an object graph. Previous versions of objects are stored in a relational database by an ObjectStorageMgr component, where each object is serialised in binary form with additional ID and “ticket” (pseudo-timestamp) fields. In-memory References to other objects are converted to IDs which may be resolved upon retrieval. The main advantage of this approach – as opposed to an explicit field-by-field object-relational mapping – is a simplified data access layer and vastly improved flexibility, as the database schema does not have to be changed in accordance with object model changes. The disadvantage is that this makes certain types of queries on the model history very inefficient (e.g. “find all times in the past 7 days when the reading of temperature sensor A was below 15 degrees”). In such cases, all past versions of the object must be deserialised to memory and checked for the search criteria. It is however expected that such queries are relatively rare and generally not time-critical.
MarineMAS: A multi-agent framework to aid design, modelling, and evaluation of autonomous shipping systems
Published in Journal of International Maritime Safety, Environmental Affairs, and Shipping, 2019
Zhe Xiao, Xiuju Fu, Liye Zhang, Wanbing Zhang, Manu Agarwal, Rick Siow Mong Goh
The prototype system is developed using J2EE framework with integration of cluster supporting in-memory caching and concurrent computing libraries. The prototype system has a layered architecture as complying with J2EE convention. Data access layer defines the fundamental operations such query and update that interface with the underlying database or in-memory caching. For performance consideration, the frequently used data will be loaded into in-memory data structure when the system is booted up. Basically, the modelling data can be classified as the core data for agent-based modelling such as maritime traffic knowledge and GIS data and the supporting data to persist the modelling configuration parameters, indexes, and states for efficient operation. Function layer, i.e., service layer, has higher level processing logic encapsulation (planning, SA, and actions), which may invoke the basic DAO methods in the data access layer if any data operation is required. Except from the core functionalities of MAS modelling, if the simulation is running over a cluster, the cluster features and in-memory data grid (across the cluster) are managed in this layer to achieve system scalability. Visualization layer provides the user interface for dynamic modelling animation, illustration of analytic results, or other system configuration info display. The prototype system is implemented as a web-based B/S application; however, such a modularized design makes it easier to be transformed to a desktop version.
Application of Human-Computer Interaction Technology in Remote Language Learning Platform
Published in International Journal of Human–Computer Interaction, 2023
③ Data access layer. The main function of the data access layer is to access the database, add, delete, modify and query the database. The platform architecture mainly includes user database, adaptive question database, business database, document database and learner model database. Among them, the adaptive question bank stores all the test contents and adaptive parameters for adaptive test extraction. The learner model library stores all learners’ learning models for personalized course resource recommendation.