# Architecture principles whose category is Coordination Surfaces

> 28 records

This index as JSON: https://banes-lab.com/json/api/facets/architecture/category/coordination-surfaces

## Entries

- [Stated Invariant](https://banes-lab.com/records/architecture/stated-invariant.md): A design rule that an invariant a topology relies on is written with its property in a form that could be false, the set it ranges over, the parties it binds and the thing that would object if it stopped holding.
- [Derived Record State](https://banes-lab.com/records/architecture/derived-record-state.md): A design rule that a record's state is a query over the edges it carries, open while its satisfying artifact is unresolved, blocked while a blocker is open and absorbed once the artifact exists, so no party writes a state.
- [Declared Subject](https://banes-lab.com/records/architecture/declared-subject.md): A rule or precondition that a record carries an allocated id and a declared subject key as two fields, so a moved surface keeps the id, a renamed subject keeps the key, and two records sharing a key are a finding.
- [Write Barrier](https://banes-lab.com/records/architecture/write-barrier.md): A mechanism that lets a planned exclusive write to a shared surface proceed only once every peer is observed parked, beside a compare-and-swap that covers every other write.
- [Operand-Free Outcome Surface](https://banes-lab.com/records/architecture/operand-free-outcome-surface.md): A rule or precondition that a surface carrying one jointly authored product declares that one writer per record has no operand there, and settles a collision by announcement and by each author cutting its own duplicate.
- [Projection Channel](https://banes-lab.com/records/architecture/projection-channel.md): A rule or precondition that the projection a host injects into every bounded reader is refreshed in the same change as the fact it carries, in a shape a check reads.
- [Two-Direction Index](https://banes-lab.com/records/architecture/two-direction-index.md): A mechanism that generates an index from the directory on every run and checks it both ways, reporting an entry with no file and a file with no entry, with every scan independent of depth.
- [Independent Lifetime Axes](https://banes-lab.com/records/architecture/independent-lifetime-axes.md): A design rule that a surface's lifetime is declared on three independent axes, retention, mutability and removal authority, each taking a value from a closed set, so no single word stands for all three.
- [Section Lifetime Divergence](https://banes-lab.com/records/architecture/section-lifetime-divergence.md): A rule or precondition that a file states a default lifetime and each section declares only the axes on which it differs, since the narrower unit is the more constrained one.
- [Write Scope and Read Population](https://banes-lab.com/records/architecture/write-scope-and-read-population.md): A design rule that a run declares the paths it writes and publishes the set it read as two declarations, because collision is decided by the first and a published result's validity by the second.
- [Read-Time Join](https://banes-lab.com/records/architecture/read-time-join.md): A mechanism that lets a caller whose question a live declared scope already covers read that run's published result and its standing, writing nothing, so it cannot deadlock, be orphaned or need cleanup.
- [One-Sided Liveness](https://banes-lab.com/records/architecture/one-sided-liveness.md): A design rule that a process's absence proves it is dead while its presence proves nothing, so liveness is derived once, from the witness first and from a generous window only where the witness cannot decide.
- [Reversible Channel Encoding](https://banes-lab.com/records/architecture/reversible-channel-encoding.md): A rule or precondition that a channel name is a total and invertible encoding of the scope it belongs to, with an alphabet that excludes the separator, so a retention check can read the scope back out of the name.
- [Declare-Before-Read Order](https://banes-lab.com/records/architecture/declare-before-read-order.md): A mechanism that orders two simultaneous starters without a lock by writing each entry before reading the set, with the start stamp and then the party identity breaking a tie.
- [Period-Decided Disposition](https://banes-lab.com/records/architecture/period-decided-disposition.md): A design rule that a duplicate is first counted by its distinguished copies and then read by the period of each derivation edge, so a periodic copy owes a comparator and a one-shot copy is a record whose source is repaired instead.
- [Derived Party Count](https://banes-lab.com/records/architecture/derived-party-count.md): A design rule that the number of parties a body of work implies is derived from how the work is partitioned into concerns, so two parties holding one partition reach one count.
- [Fan-In Ceiling](https://banes-lab.com/records/architecture/fan-in-ceiling.md): A rule or precondition that the useful number of parties is bounded by the fan-in of the most contended surface, where claims resting on it go stale faster than they help.
- [State-Arity Limit](https://banes-lab.com/records/architecture/state-arity-limit.md): A rule or precondition that a property relating two states of content, such as growing but never shrinking, is enforced only by a mechanism holding both readings, in the layer that already spans runs.
- [Carrier and Payload Split](https://banes-lab.com/records/architecture/carrier-and-payload-split.md): A design rule that a surface read through a tool types the fields a mechanism joins on and leaves the fields only a reader consumes as prose, deciding the line per field.
- [Joinable Mandated Field](https://banes-lab.com/records/architecture/joinable-mandated-field.md): A rule or precondition that a mandated field takes a value from a closed set or an identifier, or declares that it is written for readers, so a governed surface never looks measured on a property nothing can read.
- [Single Aggregate](https://banes-lab.com/records/architecture/single-aggregate.md): A rule or precondition that a shared measurement keeps one aggregate, overwritten by each run that can honestly replace it, while a run that cannot streams its verdict instead of writing a second report.
- [Contradicted Invariant](https://banes-lab.com/records/architecture/contradicted-invariant.md): A defect in which one surface states the opposite of an invariant another relies on, so every mechanism faithfully implementing either statement stays green while the invariant is violated.
- [Written Status Marker](https://banes-lab.com/records/architecture/written-status-marker.md): A defect in which a party writes a record's state as a marker instead of deriving it from the record's edges, so the marker goes stale and asserts a state that no longer holds.
- [Invocation-Keyed Report](https://banes-lab.com/records/architecture/invocation-keyed-report.md): A defect in which a run writes its result under a name derived from how it was invoked, beside the shared aggregate, so documents accumulate that each describe a moment and none the state.
- [Narrowed Aggregate](https://banes-lab.com/records/architecture/narrowed-aggregate.md): A defect in which a run over a narrowed scope overwrites the whole-scope aggregate, so the aggregate reports a smaller population as though it were the whole.
- [Cyclic Tiebreak](https://banes-lab.com/records/architecture/cyclic-tiebreak.md): A defect in which a tiebreak picks a source among copies none of which is distinguished, turning a correct refusal into a direction no copy supports.
- [Destructive Closure](https://banes-lab.com/records/architecture/destructive-closure.md): A defect in which closing a converged venue deletes it instead of moving it to the archive, keeping the outcome and destroying the argument it came from.
- [Hand-Kept Index](https://banes-lab.com/records/architecture/hand-kept-index.md): A defect in which an index is written by hand beside what it indexes, so it drifts silently because nothing compares the two.