Where systems thinking is held to the standard of science.
Systems thinking was built by scientists and practitioners who discovered real structure in how the world works. Many of them went against the prevailing establishment to do it. The Academy exists to make sure the field stays rooted in evidence.
“We study systems because we live inside them, we are systems ourselves, and systems live inside of us. It’s systems all the way down.”
IAdvance the science of systems thinking.Science
IIHold the field to evidentiary standards.Standards
IIIHonor the people who shape it.Members
IVRecognize those advancing it.Contributors
VSpotlight emerging work.Commendations
VITeach the field’s history and contributions, so learners can tell signal from noise.Education
How selection works
No committee selects winners.
Contributions are machine-scored on a standardized 15-point rubric, with multiple independent assessments checked for agreement. What matters is whether the work holds up under scrutiny and whether it moved the field. Anyone can recommend a candidate, and submissions are always open.
Level 1 · Promising work
Commendation
Promising work, emerging science, popularizing efforts, or application in specialized domains that advance or disseminate systems thinking.
Level 2 · Significant contribution
Contributor
Work that has significantly advanced, extended, or integrated systems thinking across domains, strengthening its development and practical use.
Level 3 · Field-shaping impact
Academy Member
Introduced or substantially reshaped enduring frameworks for systems of mind, systems of nature, and their intersection.
15points on the standardized rubric
3levels of recognition
—people recognized in the Registry
0committee votes
The AST Registry
The scientists who built systems thinking.
AST honors the people whose work gave systems thinking its scientific foundation: pioneers, boundary-crossers, and original thinkers whose contributions hold up under scrutiny, not just citation.
Each year AST evaluates the Registry against the published criteria for each honor. In years where no candidate meets the threshold, the honor is not awarded. The evidence sets the standard, not a calendar or a committee.
Academia is useful for academics. Science is useful for everyone.
Sometimes science and academia are used interchangeably. But science is not academia. Science is a method for finding out what’s true. Academia is an institution with its own culture, incentives, and politics. Sometimes they align. Often they don’t. The history of systems thinking, and of science itself, is full of people who did the best work in spite of the institution, not because of it.
Systems thinking wasn’t born in an academic department. It was born of science-based practice. Its founders were physicists who wandered into biology, mathematicians who rewired philosophy, engineers who reimagined governance, and biologists who redefined cognition. They worked across boundaries because the problems demanded it, and they were often dismissed by the disciplines they crossed into.
This is their history, and AST exists to honor the standard they set.
Support AST
Keep the evaluation independent and the Registry open.
AST is a 501(c)(3) nonprofit. Supporters help keep the evaluation process independent, the Registry open, and the field honest. Stay informed. Share the work. Recommend someone.
The AST Registry
A record of the contributions that built the field.
The Registry honors these achievements and serves as a resource for exploring the field’s scientific foundations. Selection follows explicit criteria and evidence-based review.
Academy Members
Per Bak
Denmark
Developed the theory of self-organized criticality, proposing a general mechanism by which complex systems naturally evolve toward scale-invariant dynamics, influencing foundational work on emergence, cascades, and power-law behavior.
Albert-László Barabási
USA
Discovered scale-free network structures and formalized preferential attachment, establishing a quantitative framework for understanding network topology across biological, technological, and social systems.
Ludwig von Bertalanffy
Austria
Founded General Systems Theory, providing a conceptual framework for systems as organized wholes and enabling cross-domain structural comparison.
Charles Darwin
UK
Formulated the theory of evolution by natural selection, establishing the foundational framework for adaptive, interdependent biological systems and long-term evolutionary dynamics.
Leonhard Euler
Switzerland
Founded graph theory through the Königsberg bridges problem, establishing a formal structural representation of relational systems that underpins modern network science and structural mathematics.
Heinz von Foerster
Austria
Founded second-order cybernetics and formalized observer-in-the-system perspectives, reshaping conceptual foundations of cybernetics and learning systems.
John Henry Holland
USA
Developed genetic algorithms and formal complex adaptive systems modeling, providing foundational computational mechanisms for adaptation, emergence, and evolutionary dynamics in complex systems.
Daniel Kahneman
Israel/USA
Co-developed prospect theory replacing expected utility and originated System 1/System 2 dual-process cognitive architecture.
Rudolf E. Kálmán
USA
Developed the Kalman filter and modern state-space control theory, establishing foundational mathematical tools for estimation, feedback, and control in complex engineered and cyber-physical systems.
Edward Lorenz
USA
Discovered deterministic chaos and sensitive dependence on initial conditions, founding chaos theory.
Niklas Luhmann
Germany
Developed a communication-centered theory of autopoietic social systems, providing a comprehensive conceptual architecture for understanding society as self-producing systems of communication across domains such as law, politics, and organizations.
Warren McCulloch
USA
Co-founded computational neuroscience by linking logic, neural networks, and cybernetics, shaping early systems approaches to cognition and brain modeling.
John von Neumann
Hungary
Founded core computation and automata theory (including self-reproduction), providing formal architectures that underpin modern computation-based systems modeling.
Elinor Ostrom
USA
Discovered the structural design principles of polycentric governance and common-pool resource systems, establishing a durable institutional systems architecture for how cooperation, constraints, and collective action self-organize across ecological and social domains.
C.S. Peirce
USA
Originated triadic semiotics, abductive reasoning, and pragmaticism, providing an architecture of relational meaning-making and inference.
Jean Piaget
Switzerland
Founded genetic epistemology: schemas, assimilation, accommodation, equilibration as architecture of cognitive development and structural thinking.
Ilya Prigogine
Belgium
Discovered dissipative structures and advanced non-equilibrium thermodynamics, providing empirically grounded foundations for self-organization and modern complexity science.
Xuesen Qian
China
Developed Open Complex Giant Systems and meta-synthetic methodology, proposing structured approaches for integrating qualitative judgment with quantitative modeling at large scale.
Claude Shannon
USA
Formulated information theory, defining information as a measurable quantity and establishing a formal basis for communication and computation in systems contexts.
Herbert A. Simon
USA
Developed bounded rationality and hierarchical organization as core concepts in decision-making and organizations, shaping conceptual and empirical work on complex systems behavior.
Alan Turing
UK
Founded core theory of computation and proposed reaction–diffusion morphogenesis models, contributing formal and modeling foundations relevant to complex systems and pattern formation.
Amos Tversky
Israel/USA
Co-developed prospect theory and the heuristics-and-biases program, providing structural models of systematic cognitive error in judgment and decision-making.
Lotfi Zadeh
USA
Founded fuzzy set theory and fuzzy logic, creating an entirely new mathematical formalism for reasoning under vagueness with transdisciplinary reach.
Ernst von Glasersfeld
Ireland
Developed radical constructivism as a conceptual foundation for learning and knowledge, shaping second-order cybernetics and systems epistemology.
Alfred North Whitehead
UK/USA
Developed process philosophy, replacing substance ontology with process ontology as a systemic architecture for understanding reality as relational events.
Christopher Alexander
UK/USA
Originated Pattern Language and articulated structural properties of “wholeness” in design, influencing architecture, urbanism, and software pattern methodology.
W. Ross Ashby
UK
Formulated the Law of Requisite Variety and core ideas in regulation and control, providing a foundational theoretical basis for adaptation in complex systems.
Derek Cabrera
USA
Discovered O-Theory and MIO and RIO Laws, establishing a formal, empirical theory of model–world alignment and demonstrating that distinctions, part–whole organization, relationships, and perspectives (DSRP) constitute the universal structure of mind and nature.
C. West Churchman
USA
Founded the systems approach to inquiry and boundary concepts, providing generative architecture for scoping systems interventions.
John Dewey
USA
Developed pragmatist epistemology of inquiry as structured process and reflective thinking, providing architecture for experiential and transactional cognition.
Gerald Edelman
USA
Developed Neural Darwinism as a biologically grounded theory of brain development and cognition, proposing system-level mechanisms (e.g., selection, reentry) used in neuroscience discourse.
Kurt Lewin
Germany/USA
Developed field theory for social systems (B=f(P,E)), topological psychology, and action research as systemic methodology for change.
Benoit Mandelbrot
France/USA
Originated fractal geometry and formalized self-similarity and non-integer dimensional scaling, establishing a mathematical regime for analyzing irregular and scale-invariant phenomena.
James Grier Miller
USA
Developed Living Systems Theory identifying 20 critical subsystems operating isomorphically across 7 hierarchical levels of living systems.
Howard T. Odum
USA
Created emergy theory and energy systems language (circuit diagrams for ecosystems), providing a new formalism for systems ecology.
Gordon Pask
UK
Developed Conversation Theory and cybernetic learning architectures, formalizing knowledge construction as recursive interaction between participants and systems, influencing second-order cybernetics and educational systems design.
Walter Pitts
USA
Co-originated the McCulloch-Pitts neuron formalizing neural computation as logic, foundational to neural network theory.
Karl Pribram
USA
Developed systems-level theories of memory and cognition (including holonomic proposals), contributing conceptual alternatives to localized, reductionist brain models.
René Thom
France
Originated catastrophe theory, a topological classification of discontinuous change in dynamical systems.
Norbert Wiener
USA
Founded cybernetics, formalizing feedback, control, and communication as general concepts spanning biological and engineered systems.
Russell Ackoff
USA
Developed Interactive Planning and a practical theory of organizational problem formulation (“messes”), shaping applied systems thinking in management and design practice.
Gregory Bateson
UK
Developed a systems-oriented account of mind and learning (“ecology of mind”), advancing concepts of recursion, communication, and epistemology used across systems discourse.
Stafford Beer
UK
Developed management cybernetics (including POSIWID) and the Viable System Model, providing a structured methodology for organizational diagnosis and recursive governance.
Alexander Bogdanov
Russia
Authored Tektology, an early general science of organization proposing structural similarities across biological, social, and economic systems, anticipating later developments in general systems theory and cybernetics.
Kenneth E. Boulding
USA
Developed the General Systems hierarchy framework and advanced systems thinking within economics and social science, contributing to cross-disciplinary conceptual integration in systems theory.
Laura Cabrera
USA
Co-developed O-Theory/DSRP applications and led validation of the TQ instrument, advancing empirical measurement of systems thinking as a cognitive skill and translating findings into education, policy, and applied practice.
Peter Checkland
UK
Developed Soft Systems Methodology (SSM), establishing a learning-oriented methodological approach for ill-structured problem situations in organizations and public systems.
Terrence Deacon
USA
Developed teleodynamics and a theory of absential causation linking thermodynamics, biology, and cognition, proposing a naturalized account of purpose and symbolic capacity.
Jay W. Forrester
USA
Founded system dynamics and introduced stock–flow–feedback modeling as a general method for analyzing complex system behavior in policy and organizations.
Karl Friston
UK
Developed the Free Energy Principle and formalized the Markov blanket as an architectural boundary linking thermodynamics, inference, and cognition, an integrative bridge between mind and nature in complex adaptive systems.
Murray Gell-Mann
USA
Co-founded modern complexity science through foundational theoretical contributions and institution-building that established interdisciplinary study of complex adaptive systems.
Stuart Kauffman
USA
Developed NK models and autocatalytic set theory, formalizing mechanisms of self-organization and evolutionary innovation within complex adaptive systems.
George Klir
USA
Created the formal hierarchy of systems modeling (GSPS architecture), providing a mathematical backbone for systems problem solving and clarifying levels of model representation across domains.
Alfred Korzybski
Poland/USA
Originated General Semantics and the “map vs territory” representational grammar, establishing a foundational epistemic architecture for distinguishing models from reality across cognition, language, and systems discourse.
Vladimir Lefebvre
Russia
Developed reflexive models of decision and social interaction, providing formal tools used in parts of psychology, social science, and influence analysis.
Humberto Maturana
Chile
Co-developed autopoiesis and a biology of cognition, providing a conceptual framework for living systems and observer-involved cognition.
Edgar Morin
France
Developed a transdisciplinary philosophy of complex thought, providing a conceptual framework for understanding interdependence, uncertainty, and self-organization across domains.
Anatol Rapoport
Canada/USA
Advanced mathematical biology, evolutionary game theory (including early articulation of Tit-for-Tat dynamics), and formal modeling of social interaction, strengthening quantitative social systems analysis.
Robert Rosen
USA
Originated Metabolism-Repair-systems and relational biology, proposing a non-mechanistic structural architecture for living systems (metabolism–repair closure) that reframed what it means for a system to be “alive.”
Steven H. Strogatz
USA
Co-developed small-world network theory and advanced nonlinear dynamics education and modeling, strengthening formal understanding of synchronization and network structure in complex systems.
Werner Ulrich
Switzerland
Developed Critical Systems Heuristics and formalized boundary critique, providing a structured methodology for surfacing assumptions, defining system boundaries, and improving ethical and practical rigor in complex interventions.
Francisco Varela
Chile
Co-developed autopoiesis and advanced enactive cognition and neurophenomenology, strengthening conceptual links between living systems, cognition, and observer-involved approaches.
Duncan J. Watts
USA
Co-developed small-world network theory, demonstrating how clustered local structure and short global path lengths coexist in complex networks, reshaping modern network science across disciplines.
Hector Zenil
UK
Developed Algorithmic Information Dynamics, including the Coding Theorem and Block Decomposition Methods for estimating algorithmic complexity and a perturbation-based algorithmic causal calculus for inferring the causal structure of networks and biological systems. He was awarded the IASCYS Prize for his work.
Recognized Contributors
Urie Bronfenbrenner
USA
Founded ecological systems theory (micro/meso/exo/macro/chronosystem), a nested structural grammar for how layered contexts shape human development.
Douglas Hofstadter
USA
Developed strange loops and self-reference as cognitive architecture, formalizing how recursive structure generates mind and meaning.
George Lakoff
USA
Originated conceptual metaphor theory showing abstract thought is structured by embodied image schemas, reframing cognitive architecture.
Margaret Mead
USA
Applied cybernetics to social and cultural analysis, contributing early second-order perspectives on learning, observation, and social systems.
Donella Meadows
USA
Advanced sustainability-oriented systems practice by applying system dynamics and communicating stock–flow–feedback modeling and leverage concepts for socio-environmental policy and public understanding.
John D. Sterman
USA
Advanced and consolidated system dynamics through formal behavioral modeling, policy feedback analysis, and large-scale application, strengthening the empirical and methodological foundations of dynamic systems modeling across domains.
Stephen Wolfram
USA
Developed a computational approach to complexity using rule-based models, contributing formal and methodological tools for studying emergent behavior in complex systems.
Chris Argyris
USA
Developed double-loop learning as architecture for how thinking changes its own premises, with theories of action for organizational learning.
W. Brian Arthur
USA
Developed increasing returns, path dependence, and complexity economics, reframing economic systems through complexity science.
Charles François
Belgium
Created a field-level reference synthesis (International Encyclopedia of Systems and Cybernetics) that stabilized terminology and improved cross-tradition coherence.
Arthur Koestler
Hungary/UK
Originated the holon concept and holarchy, providing structural vocabulary for part-whole organization across systems thinking.
Ervin László
Hungary
Advanced systems philosophy and evolutionary systems perspectives, contributing conceptual integration across science, society, and global discourse.
Magoroh Maruyama
Japan/USA
Formalized deviation-amplifying mutual causal processes (‘the second cybernetics’), extending cybernetic theory to positive feedback.
Gerald R. Midgley
UK
Developed systemic intervention and methodological pluralism in applied systems practice, integrating critical reflection with participatory, evidence-informed intervention design across domains.
Karl H. Müller
Austria
Advanced sociocybernetics and second-order systems discourse through conceptual work on reflexivity, constructivism, and the observer in social systems.
Peter Senge
USA
Developed widely adopted organizational learning frameworks and advanced the diffusion of system dynamics–based systems thinking in management, education, and organizational development.
Robert Vallée
France
Advanced systems and cybernetics scholarship within the French tradition, contributing conceptual continuity, interpretation, and historical coherence across cybernetics work.
John Warfield
USA
Developed Interactive Structural Modeling (ISM) and the Science of Generic Design, providing reusable structural methodology for complex problem-structuring.
Andrzej P. Wierzbicki
Poland
Developed decision and knowledge methodologies (including multi-criteria approaches) used in complex systems planning, evaluation, and governance contexts.
Commendations
Yaneer Bar-Yam
USA
Developed multiscale complexity framework and founded NECSI, applying complexity science across public health, military, and urban systems.
Mary Catherine Bateson
USA
Extended cybernetics and systems ideas into cultural analysis and human development, applying systems thinking in anthropology, communication, and education contexts.
Søren Brier
Denmark
Developed cybersemiotics as a conceptual synthesis linking systems theory, semiotics, and philosophy to address meaning-making in complex systems.
Tom R. Burns
Sweden
Developed actor-system dynamics and related institutional systems concepts, contributing sociological systems theory used in governance and social systems analysis.
Fritjof Capra
USA
Produced influential syntheses linking systems ideas with contemporary science, ecology, and culture, contributing broad public and interdisciplinary uptake.
Mary Parker Follett
USA
Developed integrative thinking, circular response, and power-with concepts, providing early systemic architecture for organizational and social thought.
Ranulph Glanville
UK
Advanced second-order cybernetics in design and education, formalizing reflexive practice and observer-inclusion as core principles in systemic design and learning.
Jifa Gu
China
Created the WSR (Wuli-Shili-Renli) methodology integrating physical, rational, and human dimensions into systems problem-solving, bridging Eastern philosophy with systems methodology.
Debora Hammond
USA
Advanced historical and conceptual integration of general systems theory and cybernetics, clarifying intellectual lineages and epistemological foundations and strengthening coherence across systems traditions.
Wolfgang Hofkirchner
Austria
Formulated a Unified Theory of Information as systems philosophy, providing conceptual structure for information, society, and complexity in systems contexts.
Louis H. Kauffman
USA
Developed formal work linking topology, logic, and self-reference, contributing mathematical foundations relevant to cybernetics, computation, and systems modeling.
Matjaz Mulej
Slovenia
Developed requisite holism and systems innovation approaches in management and organization, supporting applied uptake and field stewardship in systemics.
Bjarne Berg
Norway
Applied learning-organization and systems practice in organizations, supporting adoption, capability-building, and operational use across Norwegian contexts.
Klaus Krippendorff
USA
Developed a systems-oriented theory of communication and meaning, shaping conceptual and methodological approaches in information, design, and human-centered systems contexts.
Loet Leydesdorff
Netherlands
Developed scientometric and innovation-systems models (including triple-helix dynamics) used for empirical analysis of knowledge production and systems of innovation.
Melanie Mitchell
USA
Advanced complexity science and genetic algorithms through formal analysis, computational modeling, and conceptual synthesis, contributing to understanding of emergence, adaptation, and artificial life within complex systems.
Roberto Moreno-Díaz
Spain
Developed neurocybernetic retinal theory and advanced natural and artificial visual perception research, extending McCulloch's neural framework to robotic vision systems.
Constantin Virgil Negoita
Romania/USA
Co-founded the first journal on fuzzy sets and systems with Zadeh and Zimmermann, authored the first textbook on fuzzy sets, and contributed to early structural development of fuzzy set theory.
José Perez-Rios
Spain
Advanced system dynamics and management methodology through applied practice and teaching, supporting uptake of SD methods in organizational and educational contexts.
David Silberman
USA
Led applied programs in trauma and PTSD-focused work relevant to systems-oriented practice, contributing community-facing impact and program development.
Linda Booth Sweeney
USA
Advanced systems education and pedagogy, developing curricula and tools that supported broad learning in K–12, higher education, and professional practice.
Jennifer Wilby
UK
Contributed systems methodology scholarship and field stewardship through sustained leadership supporting systems community development and applied practice.
Rainer Ernst Zimmermann
Germany
Contributed to systems philosophy and science education through conceptual and historical analysis of systems thinking, cybernetics, and interdisciplinary knowledge structures.
Membership is honorific, carries no benefits or obligations, and implies no participation in or endorsement of AST. Recognition may be conferred on living or deceased individuals without application or acceptance.Registry update form
AST Honors
Honors for field-shaping achievement, exceptional contribution, and promising new work.
AST honors excellence in systems thinking, complexity, and systems science. Each year, AST evaluates the eligible pool in the Registry against the published criteria for each honor using machine scoring. Of those who meet the criteria and have not already received the honor for the same contribution, the most noteworthy is identified.
In years where no candidate meets the threshold, the honor is not awarded. The evidence sets the standard, not a calendar or a committee.
Know someone whose work merits an AST Honor?
Anyone can nominate a contribution for the Medal, a Prize, or the Promising Research Award, including their own.
AST evaluates contributions to systems thinking and the systems sciences, never individuals, credentials, or status. The unit of evaluation is the contribution itself. Submissions are always open and are reviewed in the next scheduled cycle.
Step 1Submit
Anyone can nominate. Self-submissions and third-party submissions are both accepted.
Step 2Score
The contribution is machine-scored on the 15-point rubric by multiple independent assessments.
Step 3Check agreement
Assessments are compared. The work must hold up under scrutiny and show it moved the field.
Step 4Record
Selected contributions enter the Registry as a Commendation, Contributor, or Academy Member.
What to have ready
Academy Membership, if applicable, is evaluated separately over time based on sustained and durable impact. Posthumous recognition is permitted. All recognition is honorary and archival and confers no duties, authority, or material benefit.
Your name and email as recommender, and the contributor’s name, email, country, and field.
The contribution’s title and a link to the artifact. It must be concrete, reviewable, and accessible.
An abstract of up to 1,500 characters and a summary under 200 characters.
Your assessment of the recognition level, and of any honor it may merit.
Accepted contribution types
Scholarly paper or preprintEmpirical study or datasetTheoretical framework or formal modelTool, method, or standardDemonstrated practice with generalizable structureTranslational or public-facing workOther
AST contribution nomination
Nominate a contribution
AST evaluates contributions, not credentials. Submissions are always open. Fields marked * are required.
The official journal of the Academy
Journal of Systems Thinking (JoST)
Advancing systems thinking through evidence, openness, and transparency.
Unlike traditional journals, JoST uses Post-Publication Peer Review (PPPR). Articles are published after meeting clear criteria for rigor, clarity, and relevance. They are then opened to transparent, ongoing peer review where claims are scrutinized, tested, and refined in public view.
JoST distinguishes conceptual influence from empirical support and places particular emphasis on work that is testable, measurable, and useful in practice. Systems thinking advances by evidence and performance, not reputation or tradition.
Each year the International State of Systems Thinking® Conference takes stock of where the field stands. It brings together the field's top scientists, its best practitioners, and its newest researchers, along with anyone who wants to do systems thinking better: business leaders, educators, policymakers, students, parents, mechanics. Anyone who thinks.
Format
Online, worldwide
Cost
Free
For
Anyone who thinks
Theme
Register
Save your place.
Registration is free. You'll get a confirmation by email, and the link to join before the conference starts.
A day of evidence and practice. Attendees leave able to:
01
Know what works.
What the research shows, with evidence.
The SoSTR
02
Tell science from noise.
Separate evidence from fluff and opinion.
The SoSTR · selected talks
03
Know their baseline.
A skillometer test sets their starting point.
Baseline test · sponsored by the STSI Foundation
04
Practice the essentials.
Hands-on QuickDraws and OTIS.
Practice sessions
05
Leave with a plan.
A plan for practice, and materials to keep.
Practice sessions · take-home materials
06
Be inspired.
By the people whose work moved the field.
The AST Honors · speakers
Academy of Systems Thinking
SoSTR · 2027
The State of Systems Thinking Report
What works. What there is evidence for. Where the field stands, and the biggest open problems.
Published in JoSTJan 15, 2027
The centerpiece
What works.
The State of Systems Thinking Report® (SoSTR)
The field's report on what there is scientific evidence for. A State of the Union for systems thinking, delivered by the AST President.
ResearchExistence and effect studies from the year
HonorsThe year's AST Medal, Prizes, and Award
RegistryStatistics on who built the field
Open problemsWhat the field still can't do
Free to registrants in print. Published in the Journal of Systems Thinking (JoST) on the day of the conference.
With thanks to the sponsors of SoST 2027
Formerly the Cornell University International Systems Thinking Conference.
For years it ran as the Cornell University International Systems Thinking Conference, a scientific research conference. In 2025 it drew more than 9,000 participants online, scientists and practitioners alike, in the largest gathering of its kind. It is now hosted by the Academy of Systems Thinking and has broadened its audience to anyone interested in the science and practice of systems thinking.
Call for speakers
Propose a talk.
Speakers can propose a talk or a practice session. Every approach presented must be supported by scientific evidence, so each proposal names the evidence behind it.
Proposals close November 30, 2026. Speakers hear back by December 15, 2026.
Talk proposals for this conference are closed.
Contact AST
Get in touch with the Academy.
For questions about the Registry, Honors, nominations, partnerships, or supporting AST. To correct an existing Registry entry, use the Registry update form.
Registry update form
Correct or update a Registry entry.
Recognized individuals, their estates, and colleagues can submit corrections or additions to an existing entry in the AST Registry. An admin reviews every change before it appears.