SQL

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/SQL 

SQL (Structured Query Language)

Paradigm	Declarative
Family	Query language
Designed by	Donald D. Chamberlin Raymond F. Boyce
Developer	ISO/IEC JTC 1 (Joint Technical Committee 1) / SC 32 (Subcommittee 32) / WG 3 (Working Group 3)
First appeared	1974
Stable release	SQL:2016 / December 2016
Typing discipline	Static, strong
OS	Cross-platform
Website	www.iso.org/standard/63555.html
Major implementations
Many
Dialects
SQL-86 SQL-89 SQL-92 SQL:1999 SQL:2003 SQL:2006 SQL:2008 SQL:2011 SQL:2016
Influenced by
Datalog
Influenced
CQL, LINQ, SPARQL, SOQL, PowerShell, JPQL, jOOQ, N1QL
Structured Query Language at Wikibooks

SQL (file format)

Filename extension	.sql
Internet media type	application/sql
Developed by	ISO/IEC
Initial release	1986
Type of format	Database
Standard	ISO/IEC 9075
Open format?	Yes
Website	www.iso.org/standard/63555.html

SQL (/ˌɛsˌkjuːˈɛl/ Structured Query Language) is a domain-specific language used in programming and designed for managing data held in a relational database management system (RDBMS), or for stream processing in a relational data stream management system (RDSMS). It is particularly useful in handling structured data, i.e. data incorporating relations among entities and variables. SQL offers two main advantages over older read–write APIs such as ISAM or VSAM. Firstly, it introduced the concept of accessing many records with one single command. Secondly, it eliminates the need to specify how to reach a record, e.g. with or without an index.

Originally based upon relational algebra and tuple relational calculus, SQL consists of many types of statements, which may be informally classed as sublanguages, commonly: a data query language (DQL), a data definition language (DDL), a data control language (DCL), and a data manipulation language (DML). The scope of SQL includes data query, data manipulation (insert, update and delete), data definition (schema creation and modification), and data access control. Although SQL is essentially a declarative language (4GL), it also includes procedural elements.

SQL was one of the first commercial languages to use Edgar F. Codd’s relational model. The model was described in his influential 1970 paper, "A Relational Model of Data for Large Shared Data Banks". Despite not entirely adhering to the relational model as described by Codd, it became the most widely used database language.

SQL became a standard of the American National Standards Institute (ANSI) in 1986 and of the International Organization for Standardization (ISO) in 1987. Since then, the standard has been revised to include a larger set of features. Despite the existence of standards, most SQL code requires at least some changes before being ported to different database systems.

History

SQL was initially developed at IBM by Donald D. Chamberlin and Raymond F. Boyce after learning about the relational model from Edgar F. Codd in the early 1970s. This version, initially called SEQUEL (Structured English Query Language), was designed to manipulate and retrieve data stored in IBM's original quasirelational database management system, System R, which a group at IBM San Jose Research Laboratory had developed during the 1970s.

Chamberlin and Boyce's first attempt at a relational database language was SQUARE (Specifying Queries in A Relational Environment), but it was difficult to use due to subscript/superscript notation. After moving to the San Jose Research Laboratory in 1973, they began work on a sequel to SQUARE. The name SEQUEL was later changed to SQL (dropping the vowels) because "SEQUEL" was a trademark of the UK-based Hawker Siddeley Dynamics Engineering Limited company. The label SQL later became the acronym for Structured Query Language.

After testing SQL at customer test sites to determine the usefulness and practicality of the system, IBM began developing commercial products based on their System R prototype, including System/38, SQL/DS, and IBM Db2, which were commercially available in 1979, 1981, and 1983, respectively.

In the late 1970s, Relational Software, Inc. (now Oracle Corporation) saw the potential of the concepts described by Codd, Chamberlin, and Boyce, and developed their own SQL-based RDBMS with aspirations of selling it to the U.S. Navy, Central Intelligence Agency, and other U.S. government agencies. In June 1979, Relational Software introduced one of the first commercially available implementations of SQL, Oracle V2 (Version2) for VAX computers.

By 1986, ANSI and ISO standard groups officially adopted the standard "Database Language SQL" language definition. New versions of the standard were published in 1989, 1992, 1996, 1999, 2003, 2006, 2008, 2011, and most recently, 2016.

Syntax

Main article: SQL syntax

 

${\displaystyle \left.{\begin{array}{rl}\textstyle {\mathtt {UPDATE~clause}}&\{{\mathtt {UPDATE\ country}}\\\textstyle {\mathtt {SET~clause}}&\{{\mathtt {SET\ population=~}}\overbrace {\mathtt {population+1}} ^{\mathtt {expression}}\\\textstyle {\mathtt {WHERE~clause}}&\{{\mathtt {WHERE\ \underbrace {{name=}\overbrace {'USA'} ^{expression}} _{predicate};}}\end{array}}\right\}{\textstyle {\texttt {statement}}}}$

A chart showing several of the SQL language elements comprising a single statement

The SQL language is subdivided into several language elements, including:

• Clauses, which are constituent components of statements and queries. (In some cases, these are optional.)
• Expressions, which can produce either scalar values, or tables consisting of columns and rows of data
• Predicates, which specify conditions that can be evaluated to SQL three-valued logic (3VL) (true/false/unknown) or Boolean truth values and are used to limit the effects of statements and queries, or to change program flow.
• Queries, which retrieve the data based on specific criteria. This is an important element of SQL.
• Statements, which may have a persistent effect on schemata and data, or may control transactions, program flow, connections, sessions, or diagnostics.
  • SQL statements also include the semicolon (";") statement terminator. Though not required on every platform, it is defined as a standard part of the SQL grammar.
• Insignificant whitespace is generally ignored in SQL statements and queries, making it easier to format SQL code for readability.

Procedural extensions

SQL is designed for a specific purpose: to query data contained in a relational database. SQL is a set-based, declarative programming language, not an imperative programming language like C or BASIC. However, extensions to Standard SQL add procedural programming language functionality, such as control-of-flow constructs. These include:

Source	Abbreviation	Full name
ANSI/ISO Standard	SQL/PSM	SQL/Persistent Stored Modules
Interbase / Firebird	PSQL	Procedural SQL
IBM Db2	SQL PL	SQL Procedural Language (implements SQL/PSM)
IBM Informix	SPL	Stored Procedural Language
IBM Netezza	NZPLSQL	(based on Postgres PL/pgSQL)
Invantive	PSQL	Invantive Procedural SQL (implements SQL/PSM and PL/SQL)
MariaDB	SQL/PSM, PL/SQL	SQL/Persistent Stored Module (implements SQL/PSM), Procedural Language/SQL (based on Ada)
Microsoft / Sybase	T-SQL	Transact-SQL
Mimer SQL	SQL/PSM	SQL/Persistent Stored Module (implements SQL/PSM)
MySQL	SQL/PSM	SQL/Persistent Stored Module (implements SQL/PSM)
MonetDB	SQL/PSM	SQL/Persistent Stored Module (implements SQL/PSM)
NuoDB	SSP	Starkey Stored Procedures
Oracle	PL/SQL	Procedural Language/SQL (based on Ada)
PostgreSQL	PL/pgSQL	Procedural Language/PostgreSQL Structured Query Language (based on reduced PL/SQL)
SAP R/3	ABAP	Advanced Business Application Programming
SAP HANA	SQLScript	SQLScript
Sybase	Watcom-SQL	SQL Anywhere Watcom-SQL Dialect
Teradata	SPL	Stored Procedural Language

In addition to the standard SQL/PSM extensions and proprietary SQL extensions, procedural and object-oriented programmability is available on many SQL platforms via DBMS integration with other languages. The SQL standard defines SQL/JRT extensions (SQL Routines and Types for the Java Programming Language) to support Java code in SQL databases. Microsoft SQL Server 2005 uses the SQLCLR (SQL Server Common Language Runtime) to host managed .NET assemblies in the database, while prior versions of SQL Server were restricted to unmanaged extended stored procedures primarily written in C. PostgreSQL lets users write functions in a wide variety of languages—including Perl, Python, Tcl, JavaScript (PL/V8) and C.

Interoperability and standardization

Overview

SQL implementations are incompatible between vendors and do not necessarily completely follow standards. In particular, date and time syntax, string concatenation, NULLs, and comparison case sensitivity vary from vendor to vendor. Particular exceptions are PostgreSQL and Mimer SQL which strive for standards compliance, though PostgreSQL does not adhere to the standard in all cases. For example, the folding of unquoted names to lower case in PostgreSQL is incompatible with the SQL standard, which says that unquoted names should be folded to upper case. Thus, Foo should be equivalent to FOO not foo according to the standard.

Popular implementations of SQL commonly omit support for basic features of Standard SQL, such as the DATE or TIME data types. The most obvious such examples, and incidentally the most popular commercial and proprietary SQL DBMSs, are Oracle (whose DATE behaves as DATETIME, and lacks a TIME type) and MS SQL Server (before the 2008 version). As a result, SQL code can rarely be ported between database systems without modifications.

Reasons for incompatibility

Several reasons for this lack of portability between database systems include:

• The complexity and size of the SQL standard means that most implementers do not support the entire standard.
• The standard does not specify database behavior in several important areas (e.g. indices, file storage...), leaving implementations to decide how to behave.
• The SQL standard precisely specifies the syntax that a conforming database system must implement. However, the standard's specification of the semantics of language constructs is less well-defined, leading to ambiguity.
• Many database vendors have large existing customer bases; where the newer version of the SQL standard conflicts with the prior behavior of the vendor's database, the vendor may be unwilling to break backward compatibility.
• Little commercial incentive exists for vendors to make changing database suppliers easier (see vendor lock-in).
• Users evaluating database software tend to place other factors such as performance higher in their priorities than standards conformance.

Standardization history

SQL was adopted as a standard by the ANSI in 1986 as SQL-86 and the ISO in 1987. It is maintained by ISO/IEC JTC 1, Information technology, Subcommittee SC 32, Data management and interchange.

Until 1996, the National Institute of Standards and Technology (NIST) data-management standards program certified SQL DBMS compliance with the SQL standard. Vendors now self-certify the compliance of their products.

The original standard declared that the official pronunciation for "SQL" was an initialism: /ˌɛsˌkjuːˈɛl/ ("ess cue el"). Regardless, many English-speaking database professionals (including Donald Chamberlin himself) use the acronym-like pronunciation of /ˈsiːkwəl/ ("sequel"), mirroring the language's prerelease development name, "SEQUEL".

The SQL standard has gone through a number of revisions:

Year	Name	Alias	Comments
1986	SQL-86	SQL-87	First formalized by ANSI
1989	SQL-89	FIPS 127-1	Minor revision that added integrity constraints adopted as FIPS 127-1
1992	SQL-92	SQL2, FIPS 127-2	Major revision (ISO 9075), Entry Level SQL-92 adopted as FIPS 127-2
1999	SQL:1999	SQL3	Added regular expression matching, recursive queries (e.g. transitive closure), triggers, support for procedural and control-of-flow statements, nonscalar types (arrays), and some object-oriented features (e.g. structured types), support for embedding SQL in Java (SQL/OLB) and vice versa (SQL/JRT)
2003	SQL:2003		Introduced XML-related features (SQL/XML), window functions, standardized sequences, and columns with autogenerated values (including identity columns)
2006	SQL:2006		ISO/IEC 9075-14:2006 defines ways that SQL can be used with XML. It defines ways of importing and storing XML data in an SQL database, manipulating it within the database, and publishing both XML and conventional SQL data in XML form. In addition, it lets applications integrate queries into their SQL code with XQuery, the XML Query Language published by the World Wide Web Consortium (W3C), to concurrently access ordinary SQL-data and XML documents.
2008	SQL:2008		Legalizes ORDER BY outside cursor definitions. Adds INSTEAD OF triggers, TRUNCATE statement, FETCH clause
2011	SQL:2011		Adds temporal data (PERIOD FOR) (more information at Temporal database#History). Enhancements for window functions and FETCH clause.
2016	SQL:2016		Adds row pattern matching, polymorphic table functions, JSON
2019	SQL:2019		Adds Part 15, multidimensional arrays (MDarray type and operators)

Current standard

The standard is commonly denoted by the pattern: ISO/IEC 9075-n:yyyy Part n: title, or, as a shortcut, ISO/IEC 9075.

ISO/IEC 9075 is complemented by ISO/IEC 13249: SQL Multimedia and Application Packages (SQL/MM), which defines SQL-based interfaces and packages to widely spread applications such as video, audio, and spatial data. Interested parties may purchase SQL standards documents from ISO, IEC, or ANSI. A draft of SQL:2008 is freely available as a zip archive.

Anatomy of SQL Standard

The SQL standard is divided into 10 parts, but with gaps in the numbering due to the withdrawal of outdated parts.

• ISO/IEC 9075-1:2016 Part 1: Framework (SQL/Framework). It provides logical concepts.
• ISO/IEC 9075-2:2016 Part 2: Foundation (SQL/Foundation). It contains the most central elements of the language and consists of both mandatory and optional features.
• ISO/IEC 9075-3:2016 Part 3: Call-Level Interface (SQL/CLI). It defines interfacing components (structures, procedures, variable bindings) that can be used to execute SQL statements from applications written in Ada, C respectively C++, COBOL, Fortran, MUMPS, Pascal or PL/I. (For Java see part 10.) SQL/CLI is defined in such a way that SQL statements and SQL/CLI procedure calls are treated as separate from the calling application's source code. Open Database Connectivity is a well-known superset of SQL/CLI. This part of the standard consists solely of mandatory features.
• ISO/IEC 9075-4:2016 Part 4: Persistent stored modules (SQL/PSM). It standardizes procedural extensions for SQL, including flow of control, condition handling, statement condition signals and resignals, cursors and local variables, and assignment of expressions to variables and parameters. In addition, SQL/PSM formalizes the declaration and maintenance of persistent database language routines (e.g., "stored procedures"). This part of the standard consists solely of optional features.
• ISO/IEC 9075-9:2016 Part 9: Management of External Data (SQL/MED). It provides extensions to SQL that define foreign-data wrappers and datalink types to allow SQL to manage external data. External data is data that is accessible to, but not managed by, an SQL-based DBMS. This part of the standard consists solely of optional features.
• ISO/IEC 9075-10:2016 Part 10: Object language bindings (SQL/OLB). It defines the syntax and semantics of SQLJ, which is SQL embedded in Java (see also part 3). The standard also describes mechanisms to ensure binary portability of SQLJ applications and specifies various Java packages and their contained classes. This part of the standard consists solely of optional features. Unlike SQL/OLB JDBC defines an API and is not part of the SQL standard.
• ISO/IEC 9075-11:2016 Part 11: Information and definition schemas (SQL/Schemata). It defines the Information Schema and Definition Schema, providing a common set of tools to make SQL databases and objects self-describing. These tools include the SQL object identifier, structure and integrity constraints, security and authorization specifications, features and packages of ISO/IEC 9075, support of features provided by SQL-based DBMS implementations, SQL-based DBMS implementation information and sizing items, and the values supported by the DBMS implementations. This part of the standard contains both mandatory and optional features.
• ISO/IEC 9075-13:2016 Part 13: SQL Routines and types using the Java TM programming language (SQL/JRT). It specifies the ability to invoke static Java methods as routines from within SQL applications ('Java-in-the-database'). It also calls for the ability to use Java classes as SQL structured user-defined types. This part of the standard consists solely of optional features.
• ISO/IEC 9075-14:2016 Part 14: XML-Related Specifications (SQL/XML). It specifies SQL-based extensions for using XML in conjunction with SQL. The XML data type is introduced, as well as several routines, functions, and XML-to-SQL data type mappings to support manipulation and storage of XML in an SQL database. This part of the standard consists solely of optional features.
• ISO/IEC 9075-15:2019 Part 15: Multi-dimensional arrays (SQL/MDA). It specifies a multidimensional array type (MDarray) for SQL, along with operations on MDarrays, MDarray slices, MDarray cells, and related features. This part of the standard consists solely of optional features.

Extensions to the ISO/IEC Standard

ISO/IEC 9075 is complemented by ISO/IEC 13249 SQL Multimedia and Application Packages. This closely related but separate standard is developed by the same committee. It defines interfaces and packages based on SQL. The aim is unified access to typical database applications like text, pictures, data mining, or spatial data.

• ISO/IEC 13249-1:2016 Part 1: Framework
• ISO/IEC 13249-2:2003 Part 2: Full-Text
• ISO/IEC 13249-3:2016 Part 3: Spatial
• ISO/IEC 13249-5:2003 Part 5: Still image
• ISO/IEC 13249-6:2006 Part 6: Data mining
• ISO/IEC 13249-7:2013 Part 7: History
• ISO/IEC 13249-8:xxxx Part 8: Metadata Registry Access MRA (work in progress)

Technical reports

ISO/IEC 9075 is also accompanied by a series of Technical Reports, published as ISO/IEC TR 19075. These Technical Reports explain the justification for and usage of some features of SQL, giving examples where appropriate. The Technical Reports are non-normative; if there is any discrepancy from 9075, the text in 9075 holds. Currently available 19075 Technical Reports are:

• ISO/IEC TR 19075-1:2011 Part 1: XQuery Regular Expression Support in SQL
• ISO/IEC TR 19075-2:2015 Part 2: SQL Support for Time-Related Information
• ISO/IEC TR 19075-3:2015 Part 3: SQL Embedded in Programs using the Java programming language
• ISO/IEC TR 19075-4:2015 Part 4: SQL with Routines and types using the Java programming language
• ISO/IEC TR 19075-5:2016 Part 5: Row Pattern Recognition in SQL
• ISO/IEC TR 19075-6:2017 Part 6: SQL support for JavaScript Object Notation (JSON)
• ISO/IEC TR 19075-7:2017 Part 7: Polymorphic table functions in SQL
• ISO/IEC TR 19075-8:2019 Part 8: Multi-Dimensional Arrays (SQL/MDA)
• ISO/IEC TR 19075-9:2020 Part 9: Online analytic processing (OLAP) capabilities

Alternatives

A distinction should be made between alternatives to SQL as a language, and alternatives to the relational model itself. Below are proposed relational alternatives to the SQL language. See navigational database and NoSQL for alternatives to the relational model.

• .QL: object-oriented Datalog
• 4D Query Language (4D QL)
• Datalog: critics suggest that Datalog has two advantages over SQL: it has cleaner semantics, which facilitates program understanding and maintenance, and it is more expressive, in particular for recursive queries.
• HTSQL: URL based query method
• IBM Business System 12 (IBM BS12): one of the first fully relational database management systems, introduced in 1982
• ISBL
• jOOQ: SQL implemented in Java as an internal domain-specific language
• Java Persistence Query Language (JPQL): The query language used by the Java Persistence API and Hibernate persistence library
• JavaScript: MongoDB implements its query language in a JavaScript API.
• LINQ: Runs SQL statements written like language constructs to query collections directly from inside .Net code
• Object Query Language
• QBE (Query By Example) created by Moshè Zloof, IBM 1977
• QUEL introduced in 1974 by the U.C. Berkeley Ingres project, closer to tuple relational calculus than SQL
• Tutorial D
• XQuery

Distributed SQL processing

Distributed Relational Database Architecture (DRDA) was designed by a workgroup within IBM from 1988 to 1994. DRDA enables network-connected relational databases to cooperate to fulfill SQL requests.

An interactive user or program can issue SQL statements to a local RDB and receive tables of data and status indicators in reply from remote RDBs. SQL statements can also be compiled and stored in remote RDBs as packages and then invoked by package name. This is important for the efficient operation of application programs that issue complex, high-frequency queries. It is especially important when the tables to be accessed are located in remote systems.

The messages, protocols, and structural components of DRDA are defined by the Distributed Data Management Architecture. Distributed SQL processing ala DRDA is distinctive from contemporary distributed SQL databases.

Criticisms

Design

SQL deviates in several ways from its theoretical foundation, the relational model and its tuple calculus. In that model, a table is a set of tuples, while in SQL, tables and query results are lists of rows; the same row may occur multiple times, and the order of rows can be employed in queries (e.g. in the LIMIT clause). Critics argue that SQL should be replaced with a language that returns strictly to the original foundation: for example, see The Third Manifesto.

Orthogonality and completeness

Early specifications did not support major features, such as primary keys. Result sets could not be named, and subqueries had not been defined. These were added in 1992.

The lack of sum types has been described as a roadblock to full use of SQL's user-defined types. JSON support, for example, needs to be added by a new standard in 2016.

Null

The concept of Null is the subject of some debates. The Null marker indicates the absence of a value, and is distinct from a value of 0 for an integer column or an empty string for a text column. The concept of Nulls enforces the 3-valued-logic in SQL, which is a concrete implementation of the general 3-valued logic.

Duplicates

Another popular criticism is that it allows duplicate rows, making integration with languages such as Python, whose data types might make accurately representing the data difficult, in terms of parsing and by the absence of modularity.

This is usually avoided by declaring a primary key, or a unique constraint, with one or more columns that uniquely identify a row in the table.

Impedance mismatch

In a similar sense to object–relational impedance mismatch, a mismatch occurs between the declarative SQL language and the procedural languages in which SQL is typically embedded.

SQL data types

The SQL standard defines three kinds of data types:

• predefined data types
• constructed types
• user-defined types.

Constructed types are one of ARRAY, MULTISET, REF(erence), or ROW. User-defined types are comparable to classes in object-oriented language with their own constructors, observers, mutators, methods, inheritance, overloading, overwriting, interfaces, and so on. Predefined data types are intrinsically supported by the implementation.

Predefined data types

• Character types

• Character (CHAR)
• Character varying (VARCHAR)
• Character large object (CLOB)

• National character types

• National character (NCHAR)
• National character varying (NCHAR VARYING)
• National character large object (NCLOB)

• Binary types

• Binary (BINARY)
• Binary varying (VARBINARY)
• Binary large object (BLOB)

• Numeric types

• Exact numeric types (NUMERIC, DECIMAL, SMALLINT, INTEGER, BIGINT)
• Approximate numeric types (FLOAT, REAL, DOUBLE PRECISION)
• Decimal floating-point type (DECFLOAT)

• Datetime types (DATE, TIME, TIMESTAMP)
• Interval type (INTERVAL)
• Boolean
• XML
• JSON

Property rights (economics)

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Property_rights_(economics) 

Property rights have developed over ancient and modern history, from Abrahamic law to todays Universal Declaration of Human Rights article 17. Property rights can be understood as constructs in economics for determining how a resource or economic good is used and owned. Resources can be owned by (and hence be the property of) individuals, associations, collectives, or governments. Property rights can be viewed as an attribute of an economic good. This attribute has three broad components and is often referred to as a bundle of rights in the United States:

1. the right to use the good
2. the right to earn income from the good
3. the right to transfer the good to others, alter it, abandon it, or destroy it (the right to ownership cessation)

Conceptualizing Property in Economics Vs Law

The fields of economics and law do not have a general consensus on conceptions of property rights. Various property types are used in law but the terminology can be seen in economic reports. Sometimes in economics, property types are simply described as private or public/common in reference to private goods (excludable and rivalrous goods, like a phone) and public goods (non-excludable and non-rivalrous goods, like air) respectively. Below is a list of the several property types defined and their relation to the economic concepts of excludability (the ability to limit the consumption of the good) and rivalry (a person's consumption of the good reduces the ability of another to consume it).

Types of Property/Regimes

• Property rights can be categorized with excludability and rivalry. Excludability describes the characteristic regarding whether a good can be withheld from certain consumers. In terms of the same good, rivalry describes its accessibility to competing consumers. The combination of excludability and rivalry as parameters is reflected through various types of property rights.
• Open-access property is owned by nobody (res nullius). It is non-excludable, as excluding people is either impossible or prohibitively costly, and can be rivalrous or non-rivalrous. Open-access property is not managed by anyone, and access to it is not controlled. This is also known as a common property resource, impure public good or a common pool resource. Examples of this can be air, water, sights, and sounds. Tragedy of the commons refers to this title. An example would be unregulated forests as there's limited resources available and therefore rivalrous, but anyone may access these resources. If non-rivalrous, it would be a public good (cannot be rivalrous, no matter how much it is used, for example, the ocean (outside of territorial borders)).

Open-access property may exist because ownership has never been established, granted, by laws within a particular country, or because no effective controls are in place, or feasible, i.e., the cost of exclusivity outweighs the benefits.

— Encyclopedia of Law and Economics

• Public property (also known as state property) is excludable and can be rivalrous or non-rivalrous. This type of property is publicly owned, but its access and use are managed and controlled by a government agency or organization granted such authority. For example, a government pavement is non-excludable as anyone may use it but rivalrous as, the more people using it, the more likely it will be too crowded for another to join. Public property is sometimes used interchangeably with public good, usually impure public goods. They may also be a club good, which is excludable and non-rivalrous. An example would be paying to go to an uncongested public bathroom, as the price excludes those who can't afford it but there is ample utilities for more people to use making it non-rivalrous.
• Private property is both excludable and rivalrous. Private property access, use, exclusion and management are controlled by the private owner or a group of legal owners. This is sometimes used interchangeably with private good. An example would be a cellphone as it only one person may use it, making it rivalrous, and it has to be purchased, which makes it excludable.
• Common property or collective property is excludable and rivalrous. Not to be confused with common property in reference to economics, this is in reference to law. It is property that is owned by a group of individuals where access, use, and exclusion are controlled by the joint owners. Unlike private property, common property has multiple owners which allows for a greater ability to manage conflicts through shared benefits and enforcement. This would still be related to private goods. An example of common property would be any private good that is jointly owned.

Property Rights Theory

Introduction

Property rights theory is an exploration of how providing stakeholders with ownership of any factors of production or goods, not just land, will increase the efficiency of an economy as the gains from providing the rights exceed the costs. A widely accepted explanation is that well-enforced property rights provide incentives for individuals to participate in economic activities, such as investment, innovation and trade, which lead to a more efficient market. Implicit or explicit property rights can be created through government regulation in the market, either through prescriptive command and control approaches (e.g. limits on input/output/discharge quantities, specified processes/equipment, audits) or by market-based instruments (e.g. taxes, transferable permits or quotas), and more recently through cooperative, self-regulatory, post-regulatory and reflexive law approaches. In economics, depending on the level of transaction costs, various forms of property rights institutions will develop. In economics, an institution is

"a complex of positions, roles, norms and values lodged in particular types of social structures and organising relatively stable patterns of human activity with respect to fundamental problems in producing life-sustaining resources, in reproducing individuals, and in sustaining viable societal structures within a given environment."

— Johnathon Turner, The Institutional Order

For specificity in the case of economic property rights, this is a system or structure that has value and stability. Transaction costs are the costs of defining, monitoring, and enforcing property rights. Each institutional form can be described by the distribution of rights. This video provides examples of why enforcing property rights is more efficient for the market than not doing so https://www.youtube.com/watch?v=AJy7pWK0W8g&ab_channel=KhanAcademy.

Exploration

Ronald Coase

proposed that clearly defining and assigning property rights would resolve environmental problems by internalizing externalities and rely on incentives of private owners to conserve resources for the future. He asserts transaction costs are ideally zero because they cause inefficiencies; due to those who would be allocatively efficient with the ownership being unable to afford or receiving less private benefit than they gain from it, as the transaction costs on top of the cost of purchasing and maintaining the property. This is known as Coase theorem. Critics of this view argue that this assumes that it is possible to internalize all environmental benefits, that owners will have perfect information, that scale economies are manageable, transaction costs are bearable, and that legal frameworks operate efficiently.

John Locke, Adam Smith and Karl Marx

are classical economists that generally recognize the importance of property rights in the process of economic development, and modern mainstream economics agree with such a recognition. John Locke supposed that one's labour was their own property and, consequently, property was any land maintained and sustained through one's own labour as long as there was sufficient and similar quality land to meet the needs of everyone's labour. Using this ideology, property in a broader sense would be taken as any good a person produced or maintains with their own labour. This was later elaborated on by Adam Smith who believed that the amount of labour it takes to produce a good does not provide its value but instead the labour the good commands or the value of goods people will be willing to trade for the good. He felt the division of labour to produce products for others was better for the whole of society.^[28] This was later critiqued by Karl Marx.

Sanford Grossman, Oliver Hart, and John Moore

developed the property rights approach to the theory of the firm based on the incomplete contracting paradigm. These authors argue that in the real world, contracts are incomplete and hence it is impossible to contractually specify what decisions will have to be taken in any conceivable state of the world.  There will be renegotiations in the future, so parties have insufficient investment incentives (since they will only get a fraction of the investment's return in future negotiations); i.e., there is a hold-up problem. Hence, property rights matter, because they determine who has control over future decisions if no agreement will be reached. In other words, property rights determine the parties' future bargaining positions (while their bargaining powers, i.e. their fractions of the renegotiation surplus, are independent of the property rights allocation). The property rights approach to the theory of the firm can thus explain pros and cons of integration in the context of private firms. Yet, it has also been applied in various other frameworks such as public good provision and privatization. The property rights approach has been extended in many directions. For instance, some authors have studied different bargaining solutions, while other authors have studied the role of asymmetric information.

Three important criteria for efficiency of property rights are

(1) universality—all scarce resources are owned by someone;

(2) exclusivity—property rights are exclusive rights;

(3) transferability—to ensure that resources can be allocated from low to high yield uses

— Joseph Mahoney, Economic Foundations of Strategy, pg 109

Benefits of Implementing Property Rights

Opportunism is discouraged as it is harder to exploit a good protected by enforced property rights. For example, a song can be easily pirated from purchased copies and, with no punishment, this form of the free-rider problem likely occurs. This causes the price mechanism to be less effective at finding the true market equilibrium and hurts the owners of the good who did not get it through opportunism.

The moral hazard is less likely to influence the actions of consumers, meaning they will be less likely to exploit resources unsustainably or inefficiently as property is protected. This will lead to a lower group cost overall as people will not be able to exploit these resources as easily, causing less inefficiency issues. For example, if a person's car doesn't have property rights, people will be more likely to mistreat it or steal it for a drive, as there is no real repercussions for doing so.

Property rights are also believed to lower transaction costs by providing an efficient resolution for conflicts over scarce resources. Empirically, using historical data of former European colonies, Acemoglu, Johnson and Robinson find substantial evidence that good economic institutions – those that provide secure property rights and equality of opportunity – lead to economic prosperity.

Real-world Interconnectivity

As a nation grows the necessity for a well-defined property rights grows as well. This is due to the underlying assumption that within property rights other people must be present in order to have the rights over somebody else. Additionally, property rights are foundational for a capitalist system, allowing for growth and wealth creation.

North, Wallis and Weingast argue that property rights originate to facilitate elites' rent-seeking activities. Particularly, the legal and political systems that protect elites' claims on rent revenues form the basis of the so-called "limited access order", in which non-elites are denied access to political power and economic privileges. In a historical study of medieval England, for instance, North and Thomas find that the dramatic development of English land laws in the 13th century resulted from elites' interests in exploiting rent revenues from land ownership after a sudden rise in land price in the 12th century. In contrast, the modern "open access order", which consists of a democratic political system and a free- market economy, usually features widespread, secure and impersonal property rights. Universal property rights, along with impersonal economic and political competition, downplay the role of rent-seeking and instead favor innovations and productive activities in a modern economy.

Further Literature

In 2013, researchers produced an annotated bibliography on the property rights literature concerned with two principal outcomes: (a) reduction in investors risk and increase in incentives to invest, and (b) improvements in household welfare; the researchers explored the channels through which property rights affect growth and household welfare in developing countries. They found that better protection of property rights can affect several development outcomes, including better management of natural resources.

Incomplete property rights allow agents with valuation lower than that of the original owners of economic value to inefficiently expropriate them distorting in this way their investment and effort exertion decisions. When instead, the state is entrusted the power to protect property, it might directly expropriate private parties if not sufficiently constrained by an efficient political process. The necessity of strong protection of property for efficiency has been however criticized by a vast legal scholarship, originated from the seminal contribution by Guido Calabresi and Douglas Melamed.

Calabresi and Melamed argue that in the face of transaction costs sufficiently sizeable to prevent consensual trade, legalized private expropriation in the form of, for instance, liability rules can be welfare-increasing. To elaborate, when property is fully protected, some agents with valuation higher than that of the original owners will be unable to legally acquire value because of sizable transaction costs. When the protection of property is weak instead, low-valuation potential buyers inefficiently expropriate original owners. Hence, a rise in the heterogeneity of the potential buyers' valuations makes inefficient expropriation by low-valuation potential buyers be more important from a social welfare point of view than inefficient exclusion from trade and so induces stronger property rights. Crucially, this prediction survives even after considering production and investment activities and it is consistent with a novel dataset on the rules on the acquisition of ownership through adverse possession and on the use of government takings to transfer real property from a private party to another private party prevailing in 126 jurisdictions. These data measure “horizontal property rights” and thus the extent of protection of property from “direct and indirect private takings,” which are ubiquitous forms of expropriation that occur daily within the rule of law and are thus different from predation by the state and the elites, which is much less common but has been the focus of the economics literature. To capture preference diversity, the author uses the contemporary genetic diversity, which is a primitive metric of the genealogical distance between populations with a common ancestor and so of the differences in characteristics transmitted across generations, such as preferences. Regression analysis reveals that the protection of the original owners' property rights is the strongest where contemporary genetic diversity is the largest. Evidence from several different identification strategies suggests that this relationship is indeed causal.

Retrograde and prograde motion

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Retrograde_and_prograde_motion 

Retrograde orbit: the satellite (red) orbits in the direction opposite to the rotation of its primary (blue/black)

Retrograde motion in astronomy is, in general, orbital or rotational motion of an object in the direction opposite the rotation of its primary, that is, the central object (right figure). It may also describe other motions such as precession or nutation of an object's rotational axis. Prograde or direct motion is more normal motion in the same direction as the primary rotates. However, "retrograde" and "prograde" can also refer to an object other than the primary if so described. The direction of rotation is determined by an inertial frame of reference, such as distant fixed stars.

In the Solar System, the orbits around the Sun of all planets and most other objects, except many comets, are prograde. They orbit around the Sun in the same direction as the sun rotates about its axis, which is counterclockwise when observed from above the Sun's north pole. Except for Venus and Uranus, planetary rotations are also prograde. Most natural satellites have prograde orbits around their planets. Prograde satellites of Uranus orbit in the direction Uranus rotates, which is retrograde to the Sun. Nearly all regular satellites are tidally locked and thus have prograde rotation. Retrograde satellites are generally small and distant from their planets, except Neptune's satellite Triton, which is large and close. All retrograde satellites are thought to have formed separately before being captured by their planets.

Most low-inclination artificial satellites of Earth have been placed in a prograde orbit, because in this situation less propellant is required to reach the orbit.

Formation of celestial systems

When a galaxy or a planetary system forms, its material takes a shape similar to that of a disk. Most of the material orbits and rotates in one direction. This uniformity of motion is due to the collapse of a gas cloud. The nature of the collapse is explained by conservation of angular momentum. In 2010 the discovery of several hot Jupiters with backward orbits called into question the theories about the formation of planetary systems. This can be explained by noting that stars and their planets do not form in isolation but in star clusters that contain molecular clouds. When a protoplanetary disk collides with or steals material from a cloud this can result in retrograde motion of a disk and the resulting planets.

Orbital and rotational parameters

Orbital inclination

A celestial object's inclination indicates whether the object's orbit is prograde or retrograde. The inclination of a celestial object is the angle between its orbital plane and another reference frame such as the equatorial plane of the object's primary. In the Solar System, inclination of the planets is measured from the ecliptic plane, which is the plane of Earth's orbit around the Sun. The inclination of moons is measured from the equator of the planet they orbit. An object with an inclination between 0 and 90 degrees is orbiting or revolving in the same direction as the primary is rotating. An object with an inclination of exactly 90 degrees has a perpendicular orbit that is neither prograde nor retrograde. An object with an inclination between 90 degrees and 180 degrees is in a retrograde orbit.

Axial tilt

A celestial object's axial tilt indicates whether the object's rotation is prograde or retrograde. Axial tilt is the angle between an object's rotation axis and a line perpendicular to its orbital plane passing through the object's centre. An object with an axial tilt up to 90 degrees is rotating in the same direction as its primary. An object with an axial tilt of exactly 90 degrees, has a perpendicular rotation that is neither prograde nor retrograde. An object with an axial tilt between 90 degrees and 180 degrees is rotating in the opposite direction to its orbital direction. Regardless of inclination or axial tilt, the north pole of any planet or moon in the Solar System is defined as the pole that is in the same celestial hemisphere as Earth's north pole.

Solar System bodies

Planets

All eight planets in the Solar System orbit the Sun in the direction of the Sun's rotation, which is counterclockwise when viewed from above the Sun's north pole. Six of the planets also rotate about their axis in this same direction. The exceptions – the planets with retrograde rotation – are Venus and Uranus. Venus's axial tilt is 177°, which means it is rotating almost exactly in the opposite direction to its orbit. Uranus has an axial tilt of 97.77°, so its axis of rotation is approximately parallel with the plane of the Solar System. The reason for Uranus's unusual axial tilt is not known with certainty, but the usual speculation is that during the formation of the Solar System, an Earth-sized protoplanet collided with Uranus, causing the skewed orientation.

It is unlikely that Venus was formed with its present slow retrograde rotation, which takes 243 days. Venus probably began with a fast prograde rotation with a period of several hours much like most of the planets in the Solar System. Venus is close enough to the Sun to experience significant gravitational tidal dissipation, and also has a thick enough atmosphere to create thermally driven atmospheric tides that create a retrograde torque. Venus's present slow retrograde rotation is in equilibrium balance between gravitational tides trying to tidally lock Venus to the Sun and atmospheric tides trying to spin Venus in a retrograde direction. In addition to maintaining this present day equilibrium, tides are also sufficient to account for evolution of Venus's rotation from a primordial fast prograde direction to its present-day slow retrograde rotation. In the past, various alternative hypotheses have been proposed to explain Venus's retrograde rotation, such as collisions or it having originally formed that way.

Despite being closer to the Sun than Venus, Mercury is not tidally locked because it has entered a 3:2 spin–orbit resonance due to the eccentricity of its orbit. Mercury's prograde rotation is slow enough that due to its eccentricity, its angular orbital velocity exceeds its angular rotational velocity near perihelion, causing the motion of the sun in Mercury's sky to temporarily reverse. The rotations of Earth and Mars are also affected by tidal forces with the Sun, but they have not reached an equilibrium state like Mercury and Venus because they are further out from the Sun where tidal forces are weaker. The gas giants of the Solar System are too massive and too far from the Sun for tidal forces to slow down their rotations.

Dwarf planets

All known dwarf planets and dwarf planet candidates have prograde orbits around the Sun, but some have retrograde rotation. Pluto has retrograde rotation; its axial tilt is approximately 120 degrees. Pluto and its moon Charon are tidally locked to each other. It is suspected that the Plutonian satellite system was created by a massive collision.

Natural satellites and rings

The orange moon is in a retrograde orbit.

If formed in the gravity field of a planet as the planet is forming, a moon will orbit the planet in the same direction as the planet is rotating and is a regular moon. If an object is formed elsewhere and later captured into orbit by a planet's gravity, it can be captured into either a retrograde or prograde orbit depending on whether it first approaches the side of the planet that is rotating towards or away from it. This is an irregular moon.

In the Solar System, many of the asteroid-sized moons have retrograde orbits, whereas all the large moons except Triton (the largest of Neptune's moons) have prograde orbits. The particles in Saturn's Phoebe ring are thought to have a retrograde orbit because they originate from the irregular moon Phoebe.

All retrograde satellites experience tidal deceleration to some degree. The only satellite in the Solar System for which this effect is non-negligible is Neptune's moon Triton. All the other retrograde satellites are on distant orbits and tidal forces between them and the planet are negligible.

Within the Hill sphere, the region of stability for retrograde orbits at a large distance from the primary is larger than that for prograde orbits. This has been suggested as an explanation for the preponderance of retrograde moons around Jupiter. Because Saturn has a more even mix of retrograde/prograde moons, however, the underlying causes appear to be more complex.

With the exception of Hyperion, all the known regular planetary natural satellites in the Solar System are tidally locked to their host planet, so they have zero rotation relative to their host planet, but have the same type of rotation as their host planet relative to the Sun because they have prograde orbits around their host planet. That is, they all have prograde rotation relative to the Sun except those of Uranus.

If there is a collision, material could be ejected in any direction and coalesce into either prograde or retrograde moons, which may be the case for the moons of dwarf planet Haumea, although Haumea's rotation direction is not known.

Asteroids

Asteroids usually have a prograde orbit around the Sun. Only a few dozen asteroids in retrograde orbits are known.

Some asteroids with retrograde orbits may be burnt-out comets, but some may acquire their retrograde orbit due to gravitational interactions with Jupiter.

Due to their small size and their large distance from Earth it is difficult to telescopically analyse the rotation of most asteroids. As of 2012, data is available for less than 200 asteroids and the different methods of determining the orientation of poles often result in large discrepancies. The asteroid spin vector catalog at Poznan Observatory avoids use of the phrases "retrograde rotation" or "prograde rotation" as it depends which reference plane is meant and asteroid coordinates are usually given with respect to the ecliptic plane rather than the asteroid's orbital plane.

Asteroids with satellites, also known as binary asteroids, make up about 15% of all asteroids less than 10 km in diameter in the main belt and near-Earth population and most are thought to be formed by the YORP effect causing an asteroid to spin so fast that it breaks up. As of 2012, and where the rotation is known, all satellites of asteroids orbit the asteroid in the same direction as the asteroid is rotating.

Most known objects that are in orbital resonance are orbiting in the same direction as the objects they are in resonance with, however a few retrograde asteroids have been found in resonance with Jupiter and Saturn.

Comets

Comets from the Oort cloud are much more likely than asteroids to be retrograde. Halley's Comet has a retrograde orbit around the Sun.

Kuiper belt objects

Most Kuiper belt objects have prograde orbits around the Sun. The first Kuiper belt object discovered to have a retrograde orbit was 2008 KV42. Other Kuiper belt objects with retrograde orbits are (471325) 2011 KT₁₉, (342842) 2008 YB3, (468861) 2013 LU28 and 2011 MM₄. All of these orbits are highly tilted, with inclinations in the 100°–125° range.

Meteoroids

Meteoroids in a retrograde orbit around the Sun hit the Earth with a faster relative speed than prograde meteoroids and tend to burn up in the atmosphere and are more likely to hit the side of the Earth facing away from the Sun (i.e. at night) whereas the prograde meteoroids have slower closing speeds and more often land as meteorites and tend to hit the Sun-facing side of the Earth. Most meteoroids are prograde.

Sun

The Sun's motion about the centre of mass of the Solar System is complicated by perturbations from the planets. Every few hundred years this motion switches between prograde and retrograde.

Planetary atmospheres

Retrograde motion, or retrogression, within the Earth's atmosphere is seen in weather systems whose motion is opposite the general regional direction of airflow, i.e. from east to west against the westerlies or from west to east through the trade wind easterlies. Prograde motion with respect to planetary rotation is seen in the atmospheric super-rotation of the thermosphere of Earth and in the upper troposphere of Venus. Simulations indicate that the atmosphere of Pluto should be dominated by winds retrograde to its rotation.

Artificial satellites

Further information: Artificial satellites in retrograde orbit

Artificial satellites destined for low inclination orbits are usually launched in the prograde direction, since this minimizes the amount of propellant required to reach orbit by taking advantage of the Earth's rotation (an equatorial launch site is optimal for this effect). However, Israeli Ofeq satellites are launched in a westward, retrograde direction over the Mediterranean to ensure that launch debris does not fall onto populated land areas.

Exoplanets

Stars and planetary systems tend to be born in star clusters rather than forming in isolation. Protoplanetary disks can collide with or steal material from molecular clouds within the cluster and this can lead to disks and their resulting planets having inclined or retrograde orbits around their stars. Retrograde motion may also result from gravitational interactions with other celestial bodies in the same system (See Kozai mechanism) or a near-collision with another planet, or it may be that the star itself flipped over early in their system's formation due to interactions between the star's magnetic field and the planet-forming disk.

The accretion disk of the protostar IRAS 16293-2422 has parts rotating in opposite directions. This is the first known example of a counterrotating accretion disk. If this system forms planets, the inner planets will likely orbit in the opposite direction to the outer planets.

WASP-17b was the first exoplanet that was discovered to be orbiting its star opposite to the direction the star is rotating. A second such planet was announced just a day later: HAT-P-7b.

In one study more than half of all the known hot Jupiters had orbits that were misaligned with the rotation axis of their parent stars, with six having backwards orbits.

The last few giant impacts during planetary formation tend to be the main determiner of a terrestrial planet's rotation rate. During the giant impact stage, the thickness of a protoplanetary disk is far larger than the size of planetary embryos so collisions are equally likely to come from any direction in three dimensions. This results in the axial tilt of accreted planets ranging from 0 to 180 degrees with any direction as likely as any other with both prograde and retrograde spins equally probable. Therefore, prograde spin with small axial tilt, common for the solar system's terrestrial planets except for Venus, is not common for terrestrial planets in general.

Stars' galactic orbits

The pattern of stars appears fixed in the sky, insofar as human vision is concerned; this is because their massive distances relative to the Earth result in motion imperceptible to the naked eye. In reality, stars orbit the center of their galaxy.

Stars with an orbit retrograde relative to a disk galaxy's general rotation are more likely to be found in the galactic halo than in the galactic disk. The Milky Way's outer halo has many globular clusters with a retrograde orbit and with a retrograde or zero rotation. The structure of the halo is the topic of an ongoing debate. Several studies have claimed to find a halo consisting of two distinct components. These studies find a "dual" halo, with an inner, more metal-rich, prograde component (i.e. stars orbit the galaxy on average with the disk rotation), and a metal-poor, outer, retrograde (rotating against the disc) component. However, these findings have been challenged by other studies, arguing against such a duality. These studies demonstrate that the observational data can be explained without a duality, when employing an improved statistical analysis and accounting for measurement uncertainties.

The nearby Kapteyn's Star is thought to have ended up with its high-velocity retrograde orbit around the galaxy as a result of being ripped from a dwarf galaxy that merged with the Milky Way.

Galaxies

Satellite galaxies

Close-flybys and mergers of galaxies within galaxy clusters can pull material out of galaxies and create small satellite galaxies in either prograde or retrograde orbits around larger galaxies.

A galaxy called Complex H, which was orbiting the Milky Way in a retrograde direction relative to the Milky Way's rotation, is colliding with the Milky Way.

Counter-rotating bulges

NGC 7331 is an example of a galaxy that has a bulge that is rotating in the opposite direction to the rest of the disk, probably as a result of infalling material.

Central black holes

The center of a spiral galaxy contains at least one supermassive black hole. A retrograde black hole – one whose spin is opposite to that of its disk – spews jets much more powerful than those of a prograde black hole, which may have no jet at all. Scientists have produced a theoretical framework for the formation and evolution of retrograde black holes based on the gap between the inner edge of an accretion disk and the black hole.