Disjoint vs overlapping constraint

IN disjoint states an entity instance of a supertype can only be a member of one subtype. Ask your question!

Help us make our solutions better Rate this solution on a scale of below We want to correct this solution. Tell us more Hide this section if you want to rate later. Explain the difference between a weak and a strong entity set.

Give an example for each of them 2. Please explain the difference between Disjoint and Overlapping in regards to develop databases? With some examples please. Disjoint and Overlapping Events Describe the difference between the probability of two mutually exclusive events, two complementary events, and two events that are not mutually exclusive.

disjoint vs overlapping constraint

Questions Courses. Explain the distinction between disjoint and overlapping constraints. May 18 AM. IN disjoint states an entity instance of a supertype can only be a member of one subtype the overlap states an entity Do you need an answer to a question different from the above?

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It only takes a minute to sign up. I'm building an inventory database that stores IT hardware, such as desktop computers, laptops, switches, routers, mobile phones, etc. My dilemma is choosing between the following two designs:. In the top diagram all devices share common subtypes. For example, desktop computers and laptops would have records in the following tables: Device, NetworkDevice. A switch would have records in: Device, NetworkDevice.

Any device for which we track location will have a record in Location. Some pros and cons that I thought of for this setup:. In the bottom diagram all devices have their own subtype There are more classes of device that are not shown here. In this situation, it is obvious which tables records get inserted to or selected from. Desktop computers and laptops go in Computer, etc. In both situations, the ClassDiscriminator field is placed in subtype tables for use with a CHECK constraint to control which types can be inserted.

Are there any recommendations for which design is better, or is it completely a matter of opinion and dependent on the intended purpose of the database? Is the overlapping nature of this table something that could cause problems, or is it okay to implement it this way? Physical implementation of subtyping in a database is a complex issue.

Unless you have a situation where it offers compelling advantages see below for one or two examples it adds complexity into implementation while providing relatively little value. Having done this with really complex subtyping applicaitons and sentences on a court case management system, disparate combined-risk commercial insurance contract structures I guess I have some observations on this. Some significant corner cases are:.

If the total number of database fields across the subtypes is relatively low say: less than or there is significant commonality between subtypes then splitting the subtypes out into separate physical tables is probably of little value.

It will add significant overhead to reporting queries and searches. In most cases it's best to have a single table and manage your subtyping within the application. Probably the closest to your problem. If your subtyping is very disjoint, and different subtypes have type-dependent data structures hanging off them i. In this case, each subtype probably has relatively little commonality within the application i. Most reporting and querying will probably occur within a given sub-type, with cross-type queries mainly being restricted to a handful of common fields.

Court case management system. See this SO posting for a rundown on some possible approaches. Insurance policy administration system. If you have a very large number of fields with little commonality across your sub-types and little requirement to query across sub-type tables i.

Pathologically complex version of your problem. In most cases physical sub-type tables in a DB schema are a bit of a solution in search of a problem, as they potentially have undesirable side-effects. In your case, I assume you have a relatively modest number of sub-types and a manageable number of attributes. Your diagram and question don't indicate any intention to hang child tables off the records.

I would suggest that you consider going with the first option suggested above and maintaining one table and manage the sub-typing within your application.

Consider first developing a sound logical data model using the rules of data modeling classification hierarchy found in Enterprise Model Patternsa book by David Hay. When creating a classification hierarchy, each occurrence row must be of one and only one sub-type.Why don't fictional characters say "goodbye" when they hang up a phone? If we can't tunnel through the Earth, how do we know what's at its center? All Rights Reserved. The material on this site can not be reproduced, distributed, transmitted, cached or otherwise used, except with prior written permission of Multiply.

Hottest Questions. Previously Viewed. Unanswered Questions. Needs a Topic. What Difference between disjoint and overlapping constraints? We need you to answer this question! If you know the answer to this question, please register to join our limited beta program and start the conversation right now!

Subtype Discriminator

In a disjointness design constraint, an entity can belong to not more than one lower-level entity set. In overlapping generalizations, the same entity may belong to more than one lower-level entity sets. For example, in the employee-workteam example of the book, a manager may participate in more than one work-team. Asked in The Difference Between What are the difference between joint set and disjoint set?

The difference between joint sets and disjoint sets is the number of elements in common. A disjoint set, in math, does not any elements in common. A joint set must have at least one number in common.

disjoint vs overlapping constraint

Asked in Database Programming What is the difference between constraints and criteria? Asked in Algebra Difference betweenDisjoint sets and pairwise disjoint sets?

Assuming that, by 'disjoint', you mean that a collection of sets has an empty intersection, here is the difference between pairwise disjoint and 'disjoint': If a collection of sets is pairwise disjoint, it implies that the collection is 'disjoint': If no two sets overlap, then no k sets would overlap for any k, since this would require the overlap of at least two sets i.

However, if a collection of sets is 'disjoint' so the overall intersection is emptyit doesn't mean that the collection is pairwise disjoint. For instance, you could have a collection of 4 sets containing two overlapping pairs, where no set in one pair overlaps with a set in the other. So the intersection of the whole thing would be empty without pairwise disjointness. You could have a few things in contact with each other without all of them sharing a point of contact.

Asked in Math and Arithmetic When are sets disjoint in math? When two sets do not have any elements common between them,they are said to be disjoint. A constraint has a limit as for criteria: to end a loop Excel Questions. Asked in Physics, Waves Vibrations and Oscillations What is the difference between a bow wave and a shock wave?

A bow wave is produced by overlapping circles that form a V, a shock wave is produced by overlapping spheres that form a cone. Depending on what its functional dependencies are, a 3NF table with two or more overlapping candidate keys may or may not be in BCNF.

Asked in The Difference Between What is the difference between scope of study and limitation of study? Scope is the extend in which the study will cover while limitation are the constraints affecting the study. Asked in Computer Programming What is the difference between backtracking and dynamic programming?

The only difference between dynamic programming and back tracking is DP allows overlapping of sub problems.One entity type might be a subtype of another--very similar to subclasses in OO programming. A relationship exists between a Freshman entity and the corresponding Student entity. This relationship is called IsA. Some texts will call this an IsA relationship, but do not confuse with relationship between entities. Advantage : Used to create a more concise and readable E-R diagram.

It best maps to object oriented approaches either to databases or related applications. Any of the entities or sub-entities can participate in a relationship as appropriate. Covering constraint : Union of subtype entities is equal to set of supertype entities. An entity is an element of at least one subtype. Disjointness constraint : Sets of subtype entities are disjoint from one another i.

An entity can be an element of at most one entity. Specialization -needed when an entity set has subsets that have additional attributes or that participate in special, separate relationships Process of breaking up a class into subclasses Ex: Faculty contains AdjunctFac and FullTimeFac All Faculty have attributes facid, lastName, firstName, rank.

AdjunctFac also have coursePayRate FullTimeFac have annualSalary Specialization can be total every member of superclass must be in some subclass or partial. Student and Faculty are both people Bottom-up process, as opposed to top-down process of specialization Probably the covering constraint applies, but not disjointedness. EER diagram is similar for specialization s. Can have different specializations for the same class See undergraduates specialized by year and by residence.

These are independent of each other Can have shared subclasses — have multiple inheritance from two or more superclasses. Subclass related to a collection of superclasses Each instance of subclass belongs to one, not all, of the superclasses Superclasses form a union or category Ex. Total union can often be replaced by hierarchy Choose hierarchy representation if superclasses have many common attributes.

Specialization Abstraction Specialization -needed when an entity set has subsets that have additional attributes or that participate in special, separate relationships Process of breaking up a class into subclasses Ex: Faculty contains AdjunctFac and FullTimeFac.

All Faculty have attributes facid, lastName, firstName, rank. Multiple Specializations Can have different specializations for the same class See undergraduates specialized by year and by residence.This chapter builds on the previous chapter which addressed the basic concepts of Entity-Relationship ER modelling. The chapter discussed the concepts of an entity, participation, recursive relationships, weak entities and strong entities.

It also illustrated how these concepts can be represented in the ER diagrams. Improved computer speed and memory has, in recent years, triggered the development of sophisticated software applications like Geographical Information Systems GIS. The basic features of ER modelling are not sufficient to represent all the concepts in such applications. To address these needs, many different semantic data models have been proposed and some of the most important semantic concepts have been successfully incorporated into the original ER model.

This chapter continues to address the top-down database design concepts. Like the previous chapters, it links closely with the other chapters on database design, Normalisation and other design topics. The chapter also has considerable relevance for the material in the module on performance tuning, such as the chapter on indexing, as the decisions made during database design have a major impact on the performance of the application.

In the previous chapter, we discussed basic concepts of ER modelling. This sections revisits some of the important concepts covered. An entity may represent a category of people, things, events, locations or concepts within the area under consideration. An entity can have one or more attributes or characteristics. Two notations for representing an entity are common: box notation, and the notation that employs ellipses to represent the attributes belonging to an entity.

These express the number of entities with which another entity can be associated via a relationship. The relationships that exist between two entities can be categorised by the following:. The participation condition defines whether it is mandatory or optional for an entity to participate in a relationship. This is also known as the membership class of a relationship.

There are two kinds of participation conditions: mandatory and optional.

Completeness Constraint

Most entities are involved in binary relationships, so it follows that there are four main types of membership relationships:. Note: We have used the one-to-many relationship type to illustrate participation. Refer to the previous chapter for more details on how to model participation for other relationship types.

Chapter 4 - Enhanced Entity Relatioship Model - EER - Part 1

We have discussed different types of relationships that can occur between entities. Some entities have relationships that form a hierarchy. For example, a shipping company can have different types of ships for its business.

The relationship that exists between the concept of the ship and the specific types of ships forms a hierarchy. The ship is called a superclass. The specific types of ships are called subclasses.Why don't fictional characters say "goodbye" when they hang up a phone? If we can't tunnel through the Earth, how do we know what's at its center? All Rights Reserved. The material on this site can not be reproduced, distributed, transmitted, cached or otherwise used, except with prior written permission of Multiply.

Hottest Questions. Previously Viewed. Unanswered Questions. Database Design. Difference between disjoint and overlapping design constraints? Wiki User In a disjointness design constraint, an entity can belong to not more than one lower-level entity set. In overlapping generalizations, the same entity may belong to more than one lower-level entity sets. For example, in the employee-workteam example of the book, a manager may participate in more than one work-team.

The difference between joint sets and disjoint sets is the number of elements in common. A disjoint set, in math, does not any elements in common. A joint set must have at least one number in common.

Asked in Database Programming What is the difference between constraints and criteria? Asked in Algebra Difference betweenDisjoint sets and pairwise disjoint sets? Assuming that, by 'disjoint', you mean that a collection of sets has an empty intersection, here is the difference between pairwise disjoint and 'disjoint': If a collection of sets is pairwise disjoint, it implies that the collection is 'disjoint': If no two sets overlap, then no k sets would overlap for any k, since this would require the overlap of at least two sets i.

However, if a collection of sets is 'disjoint' so the overall intersection is emptyit doesn't mean that the collection is pairwise disjoint. For instance, you could have a collection of 4 sets containing two overlapping pairs, where no set in one pair overlaps with a set in the other. So the intersection of the whole thing would be empty without pairwise disjointness. You could have a few things in contact with each other without all of them sharing a point of contact.

Asked in Math and Arithmetic When are sets disjoint in math? When two sets do not have any elements common between them,they are said to be disjoint. A constraint has a limit as for criteria: to end a loop Excel Questions. Asked in Physics, Waves Vibrations and Oscillations What is the difference between a bow wave and a shock wave? A bow wave is produced by overlapping circles that form a V, a shock wave is produced by overlapping spheres that form a cone.

Depending on what its functional dependencies are, a 3NF table with two or more overlapping candidate keys may or may not be in BCNF. Asked in The Difference Between What is the difference between scope of study and limitation of study? Scope is the extend in which the study will cover while limitation are the constraints affecting the study.

Asked in Computer Programming What is the difference between backtracking and dynamic programming? The only difference between dynamic programming and back tracking is DP allows overlapping of sub problems. Asked in Industrial Engineering, Geometry, The Difference Between What is the difference between a geometric constraint and a numeric constraint?Which detail from Heart of Darkness shows the ineffectiveness of the colonizers. All Rights Reserved. The material on this site can not be reproduced, distributed, transmitted, cached or otherwise used, except with prior written permission of Multiply.

Hottest Questions. Previously Viewed. Unanswered Questions. Database Design. Difference between disjoint and overlapping design constraints? Wiki User November 21, PM. In a disjointness design constraint, an entity can belong to not more than one lower-level entity set. In overlapping generalizations, the same entity may belong to more than one lower-level entity sets.

For example, in the employee-workteam example of the book, a manager may participate in more than one work-team. The difference between joint sets and disjoint sets is the number of elements in common. A disjoint set, in math, does not any elements in common.

A joint set must have at least one number in common. Asked in Database Programming What is the difference between constraints and criteria? Asked in Algebra Difference betweenDisjoint sets and pairwise disjoint sets?

Assuming that, by 'disjoint', you mean that a collection of sets has an empty intersection, here is the difference between pairwise disjoint and 'disjoint': If a collection of sets is pairwise disjoint, it implies that the collection is 'disjoint': If no two sets overlap, then no k sets would overlap for any k, since this would require the overlap of at least two sets i. However, if a collection of sets is 'disjoint' so the overall intersection is emptyit doesn't mean that the collection is pairwise disjoint.

For instance, you could have a collection of 4 sets containing two overlapping pairs, where no set in one pair overlaps with a set in the other. So the intersection of the whole thing would be empty without pairwise disjointness. You could have a few things in contact with each other without all of them sharing a point of contact.

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Asked in Math and Arithmetic When are sets disjoint in math? When two sets do not have any elements common between them,they are said to be disjoint. A constraint has a limit as for criteria: to end a loop Excel Questions. Asked in Physics, Waves Vibrations and Oscillations What is the difference between a bow wave and a shock wave? A bow wave is produced by overlapping circles that form a V, a shock wave is produced by overlapping spheres that form a cone.

disjoint vs overlapping constraint

Depending on what its functional dependencies are, a 3NF table with two or more overlapping candidate keys may or may not be in BCNF. Asked in The Difference Between What is the difference between scope of study and limitation of study? Scope is the extend in which the study will cover while limitation are the constraints affecting the study.

Asked in Computer Programming What is the difference between backtracking and dynamic programming? The only difference between dynamic programming and back tracking is DP allows overlapping of sub problems.


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