input/output
Enable an AI agent to recognise what enters or leaves an activity, judge whether those inputs and outputs are usable and accounted for, and decide whether to accept, supply, transform, release or withhold them.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
Researched by: Codex + Grok
Purpose and description
Enable an AI agent to recognise what enters or leaves an activity, judge whether those inputs and outputs are usable and accounted for, and decide whether to accept, supply, transform, release or withhold them.
Input/output (I/O) is the transfer of material, energy, signals or data across the boundary of a process, device or system, treated as one concern because the same ports, channels and models ordinarily describe both what the unit receives and what it emits.
It can be Assign or inspect an input/output role relative to a specific activity boundary.; Check whether required inputs are present, suitable and timely enough to permit execution.; Request, select or substitute an input when the activity's requirements and permissions allow it.; Trace an output to the inputs and execution that produced it.; Validate and route an output, or withhold it when release conditions are unmet.; Reconcile missing, partial, duplicate, rejected or unintended boundary flows and propose recovery actions..
Distinguishing features
An input or output must be identifiable relative to a named activity and boundary; the same item can be one activity's output and another's input.
An input is supplied to or made available for use by the activity; an output is produced or emitted by it. Mere proximity or ownership does not establish either role.
The input/output is what is supplied or produced; the interface or channel is how that supply or production is exposed or transferred.
An output can be identified at the activity boundary even when its downstream outcome or benefit has not occurred.
A constraint governs how an activity may operate; it is also an input only when the activity actually receives or reads some representation of it.
Scope
+ The activity and boundary relative to which something is an input or output
+ Required, optional, actual and missing inputs and outputs
+ The form, quantity and condition needed for something to enter or leave the activity
+ Supply, consumption, production, delivery and acceptance states
+ Traceable relationships between inputs used and outputs produced
+ Unintended outputs, rejected inputs and incomplete transfers
- The internal procedure or algorithm that performs the activity
- The full identity and lifecycle of the resource, material or information carrying the input/output role
- The design and operation of an interface, channel or transport mechanism
- The wider outcomes, benefits or impacts caused by using an output
- The complete capabilities and governance of the agents supplying or receiving items
Characteristics
- Role relative to activity
- Named activity and boundary, with input or output role Prevents direction from being assigned without a reference point or treated as an intrinsic property of an item.
- Carrier category
- Information, material, energy, mixed or unresolved Determines what it means to supply, consume, copy, measure or transfer the item.
- Expectation status
- Required, optional, conditional, unintended or unresolved Separates necessary contributions and deliverables from optional or unexpected boundary flows.
- Input readiness
- Unknown, missing, available but unchecked, acceptable, unacceptable or expired Supports a decision about whether the activity can start or continue.
- Output disposition
- Expected, produced, withheld, released, delivered, accepted or rejected; distinguish concurrent conditions where needed Prevents production from being mistaken for successful delivery or acceptance.
- Quantity or extent
- Carrier-appropriate units such as items, kilograms, joules, bytes or records, with measurement basis and uncertainty Makes shortages, partial completion and unexplained differences assessable without imposing one unit on unlike flows.
- Timing and freshness
- Availability and delivery timestamps, deadlines, age and validity duration with stated time basis An otherwise suitable input or output may be unusable when it arrives late or becomes stale.
- Transformation trace
- Links between identified input instances or versions, activity executions and output instances or versions Supports explanation, reproduction and identification of outputs affected by a defective input.
Also called
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 5 bundles · 9 layers · 16 findings · 28 questions.
Activity boundary and direction Establishes what receives or produces the item and where its input/output role applies.
Input and output are relative roles; without an explicit activity boundary, direction and responsibility are ambiguous.
Reference activity
Identifies the activity and the level at which its boundary is being considered.
Role at a stated boundary
Record the receiving or producing activity and whether the role refers to a whole activity, a step or a particular execution.
- Which activity receives or produces this item, and is the reference a whole activity, a step or one execution? definition
- What makes this item an input or output at that boundary rather than an internal intermediate? boundary
Handoffs and return paths
Distinguishes connected roles when an item moves between activities or returns as feedback.
Connected input/output roles
Record the supplying and receiving sides of a handoff, including cases where an output returns as a later input.
- Whose output supplies this input, or whose input is this output intended to become? provenance
- If the item returns to the same activity, what separates its output event from its later input use? boundary
Input and output requirements Captures the conditions that make an input usable and an output acceptable.
Presence alone does not establish readiness, and production alone does not establish completion.
Input readiness
Determines which inputs are necessary and whether available candidates satisfy their intended use.
Required and usable inputs
Record mandatory or conditional inputs, their suitability criteria and the consequences of missing or unsuitable supply.
- Which inputs are required under the current conditions, and what form, quantity, quality or freshness must each have? definition
- What evidence shows that the available inputs satisfy those requirements? measurement
- If an input is missing or unsuitable, may the activity wait, proceed partially or use an approved substitute? action
Output acceptance
Defines what counts as a satisfactory output for the receiving party or next activity.
Deliverable and acceptance conditions
Record expected outputs and the checks and authority needed to accept them.
- What must be produced, in what form and quantity, and by what deadline for the output obligation to be met? definition
- Which checks establish acceptability, and who or what can accept or reject the output? action
- Which expectations concern the output itself, and which concern downstream outcomes outside this model? boundary
Supply, production and transfer Tracks what has actually become available, been used, been produced and reached its destination.
An agent must distinguish intended flows from observed events and avoid treating availability, use, production and receipt as equivalent.
Input availability and use
Separates offered or accessible inputs from those actually used by an execution.
Observed input use
Record when and how much input was available and used, including whether use consumed, changed or merely read it.
- What quantity or version was available when needed, and what quantity or version was actually used? measurement
- Did use consume, alter, copy or read the input, and what remained available afterward? measurement
Output release and receipt
Separates creation of an output from permission to release it and evidence of receipt.
Verified output handoff
Record production, release and receipt evidence, including partial or repeated transfers.
- What evidence establishes that the output was produced, released and received, and when did each occur? provenance
- What destination and release conditions apply before the agent may transfer this output? action
- How can a partial, failed or repeated handoff be detected before deciding whether to retry? measurement
Transformation trace and reconciliation Connects actual inputs to actual outputs and examines gaps, defects and unintended production.
Input/output modelling must support explanations of what was produced from what, while exposing discrepancies that require intervention.
Input/output dependencies
Captures the evidence connecting particular inputs, executions and outputs.
Supported transformation links
Record which inputs contributed to an output and the strength and limits of the available trace.
- Which input instances or versions and which execution produced this output, and what records support those links? provenance
- If an input is corrected, withdrawn or found defective, which outputs require review or regeneration? action
Discrepancies and unintended outputs
Accounts for missing results, excess production, rejected material and other boundary flows beyond the intended deliverable.
Accounted and unexplained differences
Record expected versus observed flows using a valid comparison basis, without assuming that all input and output quantities must balance.
- Which expected outputs are missing, and which unintended, excess or rejected outputs were observed? measurement
- What balance or correspondence, if any, should hold between these inputs and outputs, and what evidence explains deviations? measurement
- Which discrepancies require containment, rework, disposal or escalation before the activity can be considered complete? action
Evidence and external alignment What the world already says about this thing, gathered so the model can be checked against it.
A model that cannot be lined up against existing standards, identifiers and practice cannot be adopted by anyone who already uses them.
Reported evidence
Findings from the breadth pass, kept separate from the structural claims.
Kinds and varieties
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Blocking (synchronous) versus non-blocking or asynchronous I/O
- Memory-mapped versus port-mapped hardware I/O
- Digital versus analogue process I/O on industrial controllers
- Standard character streams (stdin, stdout, stderr)
- Human-computer I/O (keyboards, displays, pointing, speech)
- Activity-boundary I/O in function modelling (IDEF0 inputs and outputs, as distinct from controls and mechanisms)
- Network and socket I/O versus local device or file I/O
- Inter-industry economic input-output flows in national accounts
- Which of these kinds and varieties hold for the sense of input/output this model covers, and on what evidence? provenance
Identifiers and schemes
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- POSIX / ISO C stdio - file descriptors 0 (stdin), 1 (stdout), 2 (stderr) - Canonical stream identifiers on Unix-like systems and hosted ISO C implementations
- Unix device node - /dev/* (e.g. /dev/stdin, /dev/tty, character and block devices) - Filesystem names for I/O devices, not a globally unique product code
- Which of these identifiers and schemes hold for the sense of input/output this model covers, and on what evidence? provenance
Standards and regulation
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- ISO/IEC 2382:2015 Information technology - Vocabulary (ISO/IEC) - defines input-output and related IT terms
- IEEE Std 1003.1 (POSIX) (IEEE / The Open Group) - portable file, stream and device I/O
- ISO/IEC 9899 (C language) (ISO/IEC) - stdio and hosted I/O library
- FIPS PUB 183 IDEF0 (NIST, withdrawn as a FIPS in 2008 but still the IDEF0 reference) - inputs and outputs of a function box
- IEC 61131 series, especially 61131-1 and 61131-2 (IEC) - programmable controllers and their I/O equipment
- IEC 61158 (IEC) - industrial fieldbus communications that carry process I/O
- USB specifications (USB Implementers Forum) - host-to-peripheral I/O interconnect
- Which of these standards and regulation hold for the sense of input/output this model covers, and on what evidence? provenance
Real-world use
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- A Unix pipeline connecting one process's stdout to the next process's stdin
- A PLC scan that reads a limit-switch as a digital input and writes a 4-20 mA analogue output to a control valve
- An IDEF0 activity box with left-edge arrows (inputs transformed by the activity) and right-edge arrows (outputs produced)
- An instrumentation I/O list on a plant project, enumerating every signal from field device to controller channel
- A program reading a file or writing a printer, disk or network socket
- National-accounts input-output tables recording how one industry's outputs become another's inputs
- Which of these real-world use hold for the sense of input/output this model covers, and on what evidence? provenance
Typical measurements
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Data throughput - kilobytes per second (serial/legacy) to tens of gigabytes per second (modern buses and NVMe) - B/s (usually reported as MB/s or GB/s)
- I/O operations per second - about 10^2 (spinning disk) to 10^6 (NVMe SSD) - IOPS
- I/O latency - microseconds (local SSD or memory-mapped register) to milliseconds (disk, many networks) to seconds (human I/O) - s
- Analogue current-loop signal - 4-20 (live) with 0 or <4 often meaning fault/break - mA
- Analogue voltage signal - 0-10 or 0-5, sometimes ±10 - V
- Controller I/O update / scan interval - about 1-100 - ms
- Which of these typical measurements hold for the sense of input/output this model covers, and on what evidence? provenance
Failure modes and hazards
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Process hang or deadlock from blocking I/O that never completes
- Silent data loss when writes are not flushed before crash or close
- Buffer overrun or truncation on reads and writes of unbounded streams
- Electrical overvoltage, short or miswiring of field I/O channels
- Ground-loop noise and drift on analogue I/O
- Stuck-at faults on digital inputs (welded contact, broken wire read as the safe or the unsafe state)
- Priority inversion or thread starvation while waiting on I/O
- Modelling error: treating an IDEF0 control or mechanism as an input, so constraints or resources are drawn as consumed material
- Which of these failure modes and hazards hold for the sense of input/output this model covers, and on what evidence? provenance
Regional variation
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- French practice names it entrée/sortie (E/S); German Ein-/Ausgabe (E/A); Japanese 入出力 (nyūshutsuryoku), often still written I/O
- Computing writes input/output or I/O; economics writes input-output (hyphen) for Leontief tables - same words, different objects
- Analogue field I/O is commonly 4-20 mA in process plants and 0-10 V in many building-automation and OEM machine panels
- Remote versus local I/O is a plant-architecture distinction (I/O dropped in the field versus in the controller cabinet) that naming in office IT does not make
- Which of these regional variation hold for the sense of input/output this model covers, and on what evidence? provenance
Neighbouring kinds and how to tell them apart
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Interface (port or contract) - An interface is the named boundary and its rules; I/O is the traffic that actually crosses it
- IDEF0 control - A control constrains or governs the activity (conditions, setpoints, procedures) but is not transformed into the output; an input is
- IDEF0 mechanism (resource) - A mechanism performs the activity (people, machines, software) and is not consumed as material; an input is consumed or transformed
- Throughput (bandwidth) - Throughput is a performance measure of I/O, not the I/O itself
- Main-memory access - Load/store to RAM is not I/O on architectures that separate the memory bus from I/O space, even though memory-mapped I/O uses load/store encodings to reach devices
- Input-output model (economics) - Leontief tables record inter-industry commodity flows in accounts; they do not name device or process ports
- API - An API is a software contract that may hide I/O; calling an API is not by itself an I/O operation unless it crosses a process, device or network boundary
- Which of these neighbouring kinds and how to tell them apart hold for the sense of input/output this model covers, and on what evidence? provenance
Sources
- Input/output - Computing sense of I/O, device classes, and the blocking/memory-mapped distinctions
- Input-output model - That the same name also denotes Leontief inter-industry accounts, a neighbour rather than a subtype of device I/O
- IEEE Std 1003.1-2017, Standard for Information Technology - Portable Operating System Interface (POSIX®) Base Specifications, Issue 7 - Standard stream identifiers and the file-descriptor model of I/O
- FIPS Publication 183: Integration Definition for Function Modeling (IDEF0) - Activity-model I/O as left-edge inputs and right-edge outputs, distinct from controls and mechanisms
- IEC 61131-1, Programmable controllers - Part 1: General information - Process I/O as a defined part of programmable-controller equipment
What the second pass must settle
- Does the registry intend activity inputs and outputs generally, computing I/O specifically, or another meaning of the combined name?
- Is the primary modelled instance an individual input/output role, a handoff event or the complete input/output profile of an activity?
- Which existing world model, if any, already owns this concept and should be linked instead of creating a separate publication?
- Where should this registry draw the boundary between inputs, enabling resources and governing constraints, especially for tools, labour and standing instructions?
- Which domain-specific conventions are needed for continuous flows, copying, shared inputs and unintended outputs without assuming conservation or one-to-one transformation?