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-3
votes
0answers
15 views

Oracle Database [on hold]

n an Oracle database with standard configuration, if transaction T1 is reading a row of data, and transaction T2 wants to read the entire table (the table that includes the row T1 is reading), T2 ...
-3
votes
0answers
15 views

Difference between ER Diagram and Database design [on hold]

what is difference between ER Diagram and Database Design?whether we could put differ attributes in database design as compared to ER Diagram.
0
votes
0answers
7 views

Grouping operator in DBMS (Ɣ) is duplicate impervious. Why?

I'm reading Database Systems by Ullman where its mentioned that Ɣ is duplicate impervious. I dont understand why a simple group operation should cause elimination of duplicates. Aliter, ...
2
votes
2answers
26 views

Restricting capabilities of admin role in database schema

Suppose I have to design database for learning management system. Which will going to have user having roles such as admin, teacher, tutor, student etc. In a system student can submit solution for an ...
1
vote
0answers
125 views

What is the difference between a R-tree and a BVH?

I've just read about R-Trees: The key idea of the data structure is to group nearby objects and represent them with their minimum bounding rectangle in the next higher level of the tree; the "R" ...
0
votes
1answer
12 views

Lookup complexity in B-trees [Database]

Given that: B = n/R blocks in the file 2d index records per block (blocking factor): 2d > R an extra block access from the index to the datafile I am not able ...
-1
votes
0answers
8 views

Ms Access Query [migrated]

If there are two tables. Table A has table_code as PK and its FK in Table B. How can query be designed so that the results display all those values of table_code which is in Table A but not in Table ...
1
vote
1answer
411 views

Need help with ER diagram

I am making database on Disaster Management. There are four tables. ...
-4
votes
0answers
15 views

Needed Help Improving Database Design? [duplicate]

I am making database to map things affected by a natural disaster in a certain place. In the ER diagram shown below Disaster has one to one relationship with the People, Infrastructure and Homes. ...
0
votes
0answers
37 views

What is the difference between physical level and internal level of a database according to ANSI/SPARC?

According to ANSI/SPARC model a database consists of three (or four?) levels. These are internal (and/or physical?), conceptual and external levels. Most information resources say like physical and ...
0
votes
2answers
42 views

What is the difference between F+ (closure of F) and F* (cover of F) for Functional Dependencies?

F+ and F* is defined as follows: F+: closure of F F+ = {fd | F |= fd} Set of all FDs deduced from inference rule (normally: Armstrong axioms) F: cover of F {fd | F |- fd} cover of F Set of ...
0
votes
1answer
59 views

An ID (auto increment integer) always as primary key for each db-table? [closed]

Till now, I always gave each db-table an id-column (generally with the table name and an underscore as a prefix, e.g. employee_id), and I also never have seen another approach to unique a ...
0
votes
1answer
71 views

Why isn't there a universal separator character for data files? [closed]

I am not sure if this is the correct forum for this question, but... After so much time and usage of spreadsheets and data files in general, there is a need to cater for all types of files containing ...
0
votes
0answers
28 views

Pointers to schema evolution and semi-automated instance migration

QUESTION EDITED Since this question wasn't clear, I'll rephrase. See question-history for original. I'm looking for academic papers that describe schema evolution on documents (1) in a generic way. ...
0
votes
1answer
27 views

How can I solve this Functional Dependency?

Consider R(A, B, C) with FDs F ={A→B, B→C, A→C} Prove or disprove F |= C → A There are 7 inference rules from Armstrong's Axiom. Which one is to use here?
0
votes
0answers
13 views

Question about 3NF Form

So I was given set of productions and have ocmputed minimal cover. However, I have to change the set to 3NF form. I know that a production(X->A) is in 3NF form if one of these statements is true: ...
0
votes
0answers
40 views

2 phase locking with added increment mode

Suppose that a DBMS recognizes increment as an atomic operation, in addition to the read and ...
3
votes
2answers
60 views

The finer details of Meek's STV

Meek's version of the Single Transferable Vote system [.pdf] is used in multiple big elections including those of New Zealand and Stack Exchange. Demonstration (with thanks to the Department of ...
1
vote
0answers
812 views

Difference between conflict serializability and view serializability

In my understanding both of them can be converted to serial schedules. (This helps with consistency by isolation property while also giving the performance boost by concurrency). I'm unable to ...
2
votes
0answers
37 views

Using cross-products with relational algebra

I have some questions about something that I'm working on in an assignment for my database class. Here is the schema for the questions I'm working on, so that you know what to refer to: ...
0
votes
1answer
91 views

A schedule is not conflict-serializable. Is it serializable?

While reading this solved quiz on concurrency control, I got stuck on exercise 2, which reads as follows: 2) Consider the following schedule: S: r1(X), w2(X), r3(X), r1(Y), w2(Z), r3(Y), ...
-3
votes
2answers
39 views

An application where we always delete the oldest object? [closed]

In what king of application, in which we insert or delete objects, we always delete the oldest one (the least recently stored, more precisely which was the first object stored) ?
10
votes
2answers
157 views

Good snapshottable data structure for an in-memory index

I'm designing an in-memory object database for a very specific use case. It is single writer, but must support efficient concurrent reads. Reads must be isolated. There is no query language, the ...
1
vote
1answer
68 views

Data versioning in a relational database

I've been working on an industrial project where my job was to design a data model in-memory and in a relational database in such a way, that can capture the time-varying nature of the production ...
5
votes
1answer
281 views

How to find a basis which is guaranteed to need 9 or less characters to represent a 12 digits number?

I'm trying to map a 12 digit number into a fixed width file. For a number of reasons, it must be compressed in such a way that it is guaranteed to be less than or equal to 9 characters (alpha numeric ...
3
votes
1answer
67 views

Algorithm for automatic/optimal database joins?

I'm curious if there is existing literature or well known algorithms out there for a problem I am working on. Given a normalized relational database with valid foreign key constraints and a list of ...
5
votes
1answer
390 views

A relational algebra extended to model the full DML (“CRUD”) domain

There are multiple references about the relational algebra for modeling queries (SELECT) but I have found very very little on the expanded algebra that would ...
2
votes
0answers
27 views

How to store linguistic data?

I'm both interested in practical and theoretical aspects of the problem. How do you store linguistic data. Suppose you have stemmed, parsed, tagged and, perhaps even did some preliminary analysis, ...
0
votes
1answer
67 views

Database normalization impractical

After third form normalization, extra tables shall be created. And the functional determinant are used as primary key in the new table, as foreign key in the modified old table. My question is that ...
0
votes
1answer
1k views

What is the difference between a prime attribute and a proper subset of the candidate key? [closed]

I am taking DBMS classes and am currently studying the various normal forms. The following is the definition of a Prime Attribute I learned in class: ...
1
vote
0answers
73 views

two phase locking and a contest question?

In 2PL (two phase locking), what advantage(s) does the rigorous model have over the strict model? I) There is no advantage over the strict model. II) In contrast to the strict model, it ...
0
votes
1answer
45 views

How can I formalize key value stores with set theory?

I'm currently developing a simple key-value NoSQL store and want to build its formal model. I found article about key value formalisation with category theory, but I'm interested are there some works ...
3
votes
2answers
195 views

Linearizability and Serializability in context of Software Transactional Memory

I've been trying to grasp serializability and linearizability in the context of software transactional memory. However, I think both notions can be applied to transactional memory in general. At this ...
3
votes
0answers
114 views

How to generate globally unique timestamps for transactions in distributed database systems?

According the paper [1] (Section 4), timestamp ordering (T/O) is a technique whereby a serialization order is selected a priori and transaction execution is forced to obey this order. In the ...
0
votes
1answer
84 views

Information Systems (IS) and Data Warehouse

I'm working on a research project about the adoption of DWH systems and doing some literature review I find many documents that refer to Information System. I tried to find the right definition of ...
2
votes
1answer
120 views

Rollback and Timestamp Ordering in Database

If we use the Timestamp Ordering for concurrency control in following scheduling: My TA says T2,T3,T5 is Run and T4,T5 is Rollback. I think it's false. any expert could help us?
4
votes
1answer
79 views

n closest points in a set of lat/long coordinates

Here's my problem: I have a website where people can search based on their location (which is converted to lat/long coordinates). I have many products stored in a database with their lat/long ...
-1
votes
0answers
52 views

Could there be an end of (human-organized) databases? [closed]

I'm not a computer science guy but just curious about a potential decline of databases. I believe there will always be data, that's for sure, but would there always be databases? Databases are a ...
0
votes
1answer
38 views

Terminology for describing a kind of server [closed]

What is the adjective used to describe the fact that a server keep track of queries made by a user. I take the example of a database server.
2
votes
2answers
284 views

When should you use the existential and universal quantifiers for Relational Calculus?

Could someone explain to me WHEN do you use existential and universal quantifiers for Relational Calculus? Given this schema: Hotel(hotelNo, hotelName, city) ...
3
votes
1answer
374 views

Can a schedule with cyclic precedence graph still be serialisable?

We know Every conflict serializable schedule is serializable, but not all serializable schedules conflict-serializable. (*) so it means there is at least one serializable schedule that not conflict ...
1
vote
0answers
39 views

1-serializability theorem in database theory

In the paper "MVCC@TODS'1983 by Bernstein et al.", 1-serializability ($1$-$\text{SR}$) problem is defined as a decision problem: To decide whether an MV (multi-version) log $L$ is $1$-$\text{SR}$. ...
1
vote
1answer
112 views

A relationship in a UML class diagram

I am investigating a small database in a paper: Each line is a selling record. For instance, Line 2 expresses that ...
2
votes
1answer
111 views

What actually is the concept of transparency? Why not call it Abstraction?

I searched this over Google few times but ended up with articles on transparency rather than an answer. With relation to distributed database study(or distributed OS), what is the concept of ...
0
votes
1answer
177 views

Automatically generate meaningful queries for a data table

My field of research is not Database or AI. But I have some problems to solve, and would like to know which branch this kind of problems belong to, and what are the results. The main question is: ...
1
vote
2answers
608 views

B-Tree and how it is used in practice

I understand what a B-Tree is (I already implemented a B-Tree in Java with insert and delete methods that preserve the invariant). However I do not understand exactly how it is used for example for ...
3
votes
1answer
6k views

Difference between data duplication and data redundancy

My Computing teachers talk about data duplication and data redundancy in terms of databases as different things, but I'm struggling to differentiate them. The context is database normalisation, and in ...
1
vote
1answer
50 views

Partial Range Query on Inverted File with Combined Index

I am currently reading Multidimensional and Metric Data Structures by Hanan Samet for fun. The combined index is discussed on page 5-6. I do understand it in the sense that the inverted file itself is ...
0
votes
2answers
28 views

Determine Epsilon for identification [closed]

I have a project in which I need to compare different distances in a database with a distance in input in order to identify a person. For that I use this expression: DistanceDB - DistanceInput < ...
2
votes
1answer
91 views

Does “serializable” also mean that it's lockable

Here's an final exam question for a Database Fundamentals class. I've read the book, stuff online.. I can't figure out if "serializable" also means that the schedule is ...