2.4 - Describe the three-schema architecture. Why do we need mappings between schema levels? How do different schema definition languages support this architecture?
Answer:
DBMS defines three – schema architecture which is shown below: Internal schema at the internal level to describe physical storage structures and access paths, typically uses a physical data model.
Conceptual schema at the conceptual level describes the structure and constraints for the whole database for a community of users. These uses a conceptual or an implementation data model.
External schemas at the external level to describe the various user views. Usually uses the same data model as the conceptual schema.
The goal of the three-schema architecture is to separate
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interaction with the file manager.
No DBMS can do without this. If there is no file manager interaction then nothing stored in the files can be retrieved.
b. integrity enforcement.
Consistency constraints may not be satisfied, for example an instructor may belong to a non- existent department, two students may have the same ID, account balances could go below the minimum allowed, and so on.
c. security enforcement.
Unauthorized users may access the database, or users authorized to access part of the database may be able to access parts of the database for which they lack authority. For example, a low-level user could get access to national defense secret codes, or employees could find out what their supervisors earn (which is presumably a secret).
d. backup and recovery.
Data could be lost permanently, rather than at least being available in a consistent state that existed prior to a failure.
e. concurrency control.
Consistency constraints may be violated despite proper integrity enforcement in each transaction. For example, incorrect bank balances might be reflected due to simultaneous withdrawals and deposits on the same account, and so
1. (45 pts) For each major (CS, IT, DET, IS), identify three important and uniquely identifying characteristics and describe how the four types of professionals would work together in a professional setting. Include information learned from the various instructors for each discipline. How do professionals from these areas work together?
A model is a simplified representation of the structure and content of a phenomenon or system that describes or explains the complex relationships between concepts within the system and integrates elements of theory and practice (Creek et al 1993).
Research My first research experience took place from the Fall 2012 – Summer 2013 in a neurobiology laboratory (Dr. Daniel Plas) focused on Parkinson’s Disease. In this project an undergrad student and I were tasked with optimizing a cellular medium for neural growth of the model organism Lymnaea stagnalis. This was comprised of following established protocols and altering certain variables within the formulas (differing concentrations of ions, pH, et al.) to observe growth pattern differences in vitro.
A database is a structured collection of data. Data refers to the characteristics of people, things, and events. Oracle stores each data item in its own field. For example, a person's first name, date of birth, and their postal code are each stored in separate fields. The name of a field usually reflects...
conceptualization of the term/concept, and it also helps to show that the concept is indeed
An example of this could be when a child has a schema "wings, beak and being able to fly" (a normal bird). Every new instance of a creature with the same characteristics is assimilated into this schema. But when that child sees an aeroplane in the sky, the child asks what it is. The aeroplane challenges the current schema. This new information cannot be assimilated into the ... ...
There are different forefathers of RDF. The first who defined RDF was MCF a project started by Ramanthan V.Guha at apple computer between 1995 and 1997.he left the apple computer and joins Netscape and start working with Tim Brey on MCF to employ XML to produce first version of RDF. In 1999, RDF was defined by W3C to create RDF Data model by using XML.In2004, work on RDF is continued and produces a group of related specification. The W3C continued to work on RDF data model defined in 1999 and continue to develop new and improved specifications.W3C arrange a workshop in 2010 to discuss with their members the changes and improvements in RDF.
Later in the chapter it shows examples of the models created for the business, application and technology layer. Gives us specific techniques and terms needed that are used in the models.
While operational databases maintain state information, data warehouses typically maintain historical information. Although there are several forms of schema, e.g., star schema and snowflake schema, in the design of a data warehouse, the fact tables and dimension tables are its essential components. Users typically view the fact tables as multidimensional data cubes. The attributes of a dimension table may be organized as one or more concept hierarchies.
Mainly, there are different types sub-categorized from schemata, namely, linguistic, formal schemata, content schemata and cultural schemata which affect the comprehension and appreciation of the text.
...and stored and recorded for the person that is storing in it for whatever reason. Which is an improvement because I knew that databases were important but I didn’t properly understand how much work went in to performing one action in a system from entry to the final stage of the information be stored in a violent medium and then transfer to a more stable server And how databases are usually thought of as not important part of how a system works. But they are and it is
Better data recovery because a log is kept of disk activities so if there is a disk failure; Windows can restore the disk based on the log file.
A child’s schema can be seen as part of their inspiration for learning, their unquenchable drive to move, illustrate, discuss, and inquire about (Phillips & Pearce, 2011). According to Woolfolk, Winne and Perry, “schemas (sometimes called schemata) are abstract knowledge structures that organize vast amounts of information” (2015, p. 277). These schemas are mental structures that escort an individuals perception and comprehension of known and unknown experiences and allow an individual to symbolize large amounts of complex data, make assumptions, and make sense of new information (2015). Through the gathering of additional research, it was noted that the term schema possess several definitions as defined by various individuals. These various
Problems may also occur with the locking mechanism within concurrency control, two examples of such problems are:
The author defines schemata as how our mind relates our past experiences and reactions to the new things we perceive through our sight. Sometimes when the things we see fit our expectation and our schemata, our past experiences help us to interpret. But when we see things that are different from our experiences and unexpected, our schemata can sometimes confuses our minds and causes misinterpretation - seeing things the way we want them to be. The function of schemata can be illustrated by the following example. Some people cannot swim or even hydrophobia because they have been pushed into the water or drowned when they were small, not because they didn't learn. For these people, the first interpretation they have when they see a swimming pool would probably be "it is a very dangerous place where you might be drowned, so don't go near it!" For some of them, no matter how hard you try to make them understand that swimming doesn't equal drowning, they will never try to go into the swimming pool. But for some of them who might be persuaded to try to overcome this challenge would find out that swimming pool is actually not dangerous if you know how to swim; after that, they will have a completely different interpretation of swimming pool. In this example, people who remain terrified of the swimming pool are making a misinterpretation by selecting the wrong schemata which relates to their past experiences. People who later learned not to be afraid of swimming have selected new schemata to interpret swimming pool.