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Barbara Liskov

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TLDR: Barbara Liskov is an computer scientist known for her pioneering contributions to programming languages, distributed systems, and data abstraction. She was born November 7, 1939, and became one of the first women in the United States to earn a Ph.D. in computer science, awarded by Stanford University in 1968.

Barbara Liskov made significant contributions to the concept of data abstraction in programming, introducing key ideas that underpin modern software engineering. Her work on the CLU programming language, developed in 1974, introduced constructs like abstract data types and iterators, shaping the development of object-oriented programming.

A central principle associated with Barbara Liskov is the Liskov Substitution Principle (LSP), introduced in 1987. It states that objects of a subclass should be replaceable with objects of the parent class without affecting the correctness of the program. This principle is foundational in designing reliable and scalable object-oriented systems.

In addition to programming languages, Barbara Liskov contributed to the field of distributed systems through her work on the Argus programming language, introduced in 1987. Argus integrated features like atomic transactions and fault tolerance, enabling the development of robust distributed applications.

Her achievements have been widely recognized. In 2008, she received the Turing Award, often referred to as the “Nobel Prize of Computing,” for her contributions to the theory and practice of programming language and system design. This honor solidified her legacy as a leading figure in computer science.

Through her research, teachings, and publications, Barbara Liskov has influenced generations of computer scientists and software developers. Her groundbreaking work continues to impact areas such as programming, data abstraction, and distributed computing, ensuring her place in the history of technological advancements.

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

Snippet from Wikipedia: Barbara Liskov: Barbara Liskov (born November 7, 1939, as Barbara Jane Huberman) is an American computer scientist who has made pioneering contributions to programming languages and distributed computing. Her notable work includes the introduction of abstract data types and the accompanying principle of data abstraction, along with the Liskov substitution principle, which applies these ideas to object-oriented programming, subtyping, and inheritance. Her work was recognized with the 2008 Turing Award, the highest distinction in computer science.
Liskov is one of the earliest women to have been granted a doctorate in computer science in the United States, and the second woman to receive the Turing award. She is currently an Institute Professor and Ford Professor of Engineering at the Massachusetts Institute of Technology.

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Snippet from Wikipedia: Liskov substitution principle

The Liskov substitution principle (LSP) is a particular definition of a subtyping relation, called strong behavioral subtyping, that was initially introduced by Barbara Liskov in a 1987 conference keynote address titled Data abstraction and hierarchy. It is based on the concept of "substitutability" – a principle in object-oriented programming stating that an object (such as a class) may be replaced by a sub-object (such as a class that extends the first class) without breaking the program. It is a semantic rather than merely syntactic relation, because it intends to guarantee semantic interoperability of types in a hierarchy, object types in particular. Barbara Liskov and Jeannette Wing described the principle succinctly in a 1994 paper as follows:

Subtype Requirement: Let ⁠ $\phi (x)$ ⁠ be a property provable about objects ⁠ $x$ ⁠ of type T. Then ⁠ $\phi (y)$ ⁠ should be true for objects ⁠ $y$ ⁠ of type S where S is a subtype of T.

Symbolically:

$S\leq T\to (\forall x{:}T.\phi (x)\to \forall y{:}S.\phi (y))$

That is, if S subtypes T, what holds for T-objects holds for S-objects. In the same paper, Liskov and Wing detailed their notion of behavioral subtyping in an extension of Hoare logic, which bears a certain resemblance to Bertrand Meyer's design by contract in that it considers the interaction of subtyping with preconditions, postconditions and invariants.