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Logical Data Model
A logical data model or logical schema is a data model of a specific problem domain expressed independently of a particular database management product or storage technology (physical data model) but in terms of data structures such as relational tables and columns, object-oriented classes, or XML tags. This is as opposed to a conceptual data model, which describes the semantics of an organization without reference to technology. Overview Logical data models represent the abstract structure of a domain of information. They are often diagrammatic in nature and are most typically used in business processes that seek to capture things of importance to an organization and how they relate to one another. Once validated and approved, the logical data model can become the basis of a physical data model and form the design of a database. Logical data models should be based on the structures identified in a preceding conceptual data model, since this describes the semantics of the informa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Data Model
A data model is an abstract model that organizes elements of data and standardizes how they relate to one another and to the properties of real-world entities. For instance, a data model may specify that the data element representing a car be composed of a number of other elements which, in turn, represent the color and size of the car and define its owner. The corresponding professional activity is called generally ''data modeling'' or, more specifically, '' database design''. Data models are typically specified by a data expert, data specialist, data scientist, data librarian, or a data scholar. A data modeling language and notation are often represented in graphical form as diagrams. Michael R. McCaleb (1999)"A Conceptual Data Model of Datum Systems". National Institute of Standards and Technology. August 1999. A data model can sometimes be referred to as a data structure, especially in the context of programming languages. Data models are often complemented by function ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Impact Evaluation
Impact evaluation assesses the changes that can be attributed to a particular intervention, such as a project, program or policy, both the intended ones, as well as ideally the unintended ones. In contrast to outcome monitoring, which examines whether targets have been achieved, impact evaluation is structured to answer the question: how would outcomes such as participants' well-being have changed if the intervention had not been undertaken? This involves counterfactual analysis, that is, "a comparison between what actually happened and what would have happened in the absence of the intervention." Impact evaluations seek to answer cause-and-effect questions. In other words, they look for the changes in outcome that are directly attributable to a program. Impact evaluation helps people answer key questions for evidence-based policy making: what works, what doesn't, where, why and for how much? It has received increasing attention in policy making in recent years in the context of b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Database Schema
The database schema is the structure of a database described in a formal language supported typically by a relational database management system (RDBMS). The term "wikt:schema, schema" refers to the organization of data as a blueprint of how the database is constructed (divided into database tables in the case of relational databases). The formal definition of a database schema is a set of formulas (sentences) called integrity constraints imposed on a database. These integrity constraints ensure compatibility between parts of the schema. All constraints are expressible in the same language. A database can be considered a structure in realization of the database language. The states of a created conceptual schema are transformed into an explicit mapping, the database schema. This describes how real-world entities are Data modeling, modeled in the database. "A database schema specifies, based on the database administrator's knowledge of possible applications, the facts that can ent ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Database Design
Database design is the organization of data according to a database model. The designer determines what data must be stored and how the data elements interrelate. With this information, they can begin to fit the data to the database model.Teorey, T.J., Lightstone, S.S., et al., (2009). Database Design: Know it all.1st ed. Burlington, MA.: Morgan Kaufmann Publishers A database management system manages the data accordingly. Database design is a process that consists of several steps. Conceptual data modeling The first step of database design involves classifying data and identifying interrelationships. The theoretical representation of data is called an ''ontology'' or a '' conceptual data model''. Determining data to be stored In a majority of cases, the person designing a database is a person with expertise in database design, rather than expertise in the domain from which the data to be stored is drawn e.g. financial information, biological information etc. Therefore, the da ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DODAF
The Department of Defense Architecture Framework (DoDAF) is an architecture framework for the United States Department of Defense (DoD) that provides visualization infrastructure for specific stakeholders concerns through viewpoints organized by various views. These views are artifacts for visualizing, understanding, and assimilating the broad scope and complexities of an architecture description through tabular, structural, behavioral, ontological, pictorial, temporal, graphical, probabilistic, or alternative conceptual means. The current release is DoDAF 2.02. This Architecture Framework is especially suited to large systems with complex integration and interoperability challenges, and it is apparently unique in its employment of "operational views". These views offer overview and details aimed to specific stakeholders within their domain and in interaction with other domains in which the system will operate. Overview The DoDAF provides a foundational framework for dev ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Process Model
The term process model is used in various contexts. For example, in business process modeling the enterprise process model is often referred to as the ''business process model''. Overview Process models are processes of the same nature that are classified together into a model. Thus, a process model is a description of a process at the type level. Since the process model is at the type level, a process is an instantiation of it. The same process model is used repeatedly for the development of many applications and thus, has many instantiations. One possible use of a process model is to prescribe how things must/should/could be done in contrast to the process itself which is really what happens. A process model is roughly an anticipation of what the process will look like. What the process shall be will be determined during actual system development. Colette Rolland and Pernici, C. Thanos (1998). ''A Comprehensive View of Process Engineering. Proceedings of the 10th Internation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Physical Data Model
A physical data model (or database design) is a representation of a data design as implemented, or intended to be implemented, in a database management system. In the Project lifecycle, lifecycle of a project it typically derives from a logical data model, though it may be reverse-engineered from a given database implementation. A complete physical data model will include all the database artifacts required to create Relational database, relationships between tables or to achieve performance goals, such as index (database), indexes, constraint definitions, Associative entity, linking tables, Partition (database), partitioned tables or Data cluster, clusters. Analysts can usually use a physical data model to calculate storage estimates; it may include specific storage allocation details for a given database system. seven main databases dominate the commercial marketplace: Informix Dynamic Server, Informix, Oracle Database, Oracle, PostgreSQL, Postgres, Microsoft SQL Server, SQL S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Data Redundancy
In computer main memory, auxiliary storage and computer buses, data redundancy is the existence of data that is additional to the actual data and permits correction of errors in stored or transmitted data. The additional data can simply be a complete copy of the actual data (a type of repetition code), or only select pieces of data that allow detection of errors and reconstruction of lost or damaged data up to a certain level. For example, by including computed check bits, ECC memory is capable of detecting and correcting single-bit errors within each memory word, while RAID 1 combines two hard disk drives (HDDs) into a logical storage unit that allows stored data to survive a complete failure of one drive. Data redundancy can also be used as a measure against silent data corruption; for example, file systems such as Btrfs and ZFS use data and metadata checksumming in combination with copies of stored data to detect silent data corruption and repair its effects. I ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
