--- title: "OPC UA DataValues: A New Server Time Can Carry an Older Value" description: "Leviathan Systems — Technical content Published 2026-10-21; updated 2026-10-21." canonical: "https://www.leviathansystems.co/articles/industrial-ai-opcua-value-status-source-server-time" last-updated: "2026-10-21" --- # OPC UA DataValues: A New Server Time Can Carry an Older Value Leviathan Systems — Technical content Published 2026-10-21; updated 2026-10-21. An OPC UA server timestamp can advance because the server knows an unchanged value is still accurate, without receiving a new source-value instance. That can be useful current-state evidence. Keep the value, its StatusCode and both timestamp meanings together before treating it as a new AI observation. A recent timestamp and a Good status answer different questions; neither alone establishes the input your application requires. ## Buy the value with the information needed to use it An industrial AI consumer may receive a number and a time column while the source protocol supplied more meaning. OPC UA's DataValue combines a value with status and source/server timestamps. Flattening that structure into a single updated-at field leaves the consumer to guess which time survived and whether the value was usable. The reference here is OPC10000-4, Part 4: Services, displayed as v1.05.07 and checked October 21, 2026. Its definitions explain the returned information; they do not establish that a particular exporter preserves it or that a device implements every feature. Decide what the purchase must support: the server's knowledge of current state, identifiable source-value history, or an application requirement for particular observations. Those can be related deliverables, but increasing the number of exported rows does not make them equivalent. References: [DV1](https://reference.opcfoundation.org/Core/Part4/v105/docs/7.11) ## Source time belongs to the value instance Part 4 says a source timestamp is applied by the data source and does not change for that value instance. Instance means the received value instance, independently of its numeric content. The timestamp should reflect the last change of value or status. An upstream OPC UA source timestamp is passed through rather than replaced by a downstream server's clock. Consequently, equal numbers alone do not establish repeated delivery of one instance, and different source timestamps do not automatically establish changed physical measurements. A status change can affect the time's meaning. In a non-Good condition, the source timestamp can concern recognition of that condition or an attempted recovery. Where the timestamping source is unavailable, the specified source time is null. Copying a server time into that absence would create an unsupported source-time assertion. Keep the source identity and its timestamping behavior attached to retained data. The field is not a universal unique observation identifier, and the specification's UTC representation does not prove actual clock agreement. References: [TS1](https://reference.opcfoundation.org/Core/Part4/v105/docs/7.11.3) ## A server can know an unchanged value is still accurate The server timestamp reflects when the server received the Variable value or knew it to be accurate. Part 4 describes a server subscribing to another server: with no errors, an unchanged value need not arrive as a new update, yet the receiving server advances its server timestamp on the described cycle. Exception-based sources provide another named example. A later server time can therefore convey useful knowledge about an unchanged state. Calling every such return stale would discard that meaning. Calling it a newly received source value would add a different claim. In a non-Good condition, server time can instead reflect receipt of the status or a recovery attempt. For an offer, establish which of those meanings the supplied time represents. A field labelled latest, received or measured is insufficient if the exporter has collapsed them. The related sampling-and-queue guide addresses which changes reach the consumer; this article concerns the meaning retained with each returned DataValue. References: [SV1](https://reference.opcfoundation.org/Core/Part4/v105/docs/7.11.4) ## DV-8: three export rows, one stipulated source instance DV-8 is a fictional input comparison for one identified Variable, V-A. At 09:00:00 a source supplies one value instance, U1, whose numeric value is 17 in the example's stated unit. Its source timestamp is 09:00:00 and its status severity is Good. U1 is a teaching label, not an additional OPC UA field. Stipulate the exception-based behavior just described, a connection without errors, an unchanged value, and server knowledge times of 09:00:00, 09:01:00 and 09:02:00. An exporter produces three rows with the same source timestamp and numeric value but those successive server times. The case explicitly supplies one source instance; that conclusion is not deduced from timestamp equality alone. No device, measurement, publishing deadline or actual clock performance is represented. At a review time of 09:02:05, the last server-knowledge time is five seconds earlier. The source timestamp is 125 seconds earlier. All times share a stipulated comparable UTC clock basis solely for this arithmetic. The two ages describe different facts. The 125-second interval does not erase the example's later server knowledge, and the five-second interval does not create a new source instance. For a state view under these premises, the last row preserves the server's knowledge at 09:02 that the value remains accurate. For a requirement to supply three independently acquired process observations, three exported rows do not satisfy it: the case supplied only U1. Nor does it provide a newly acquired physical observation at 09:02. Those different conclusions should survive the data handoff. ## Quality does not follow the newest clock Part 4 assigns Good severity to good-quality values, Uncertain to uncertain quality for the indicated reason, and Bad to unusable values. Its client rules require the status to be checked before using results; Bad results must not be used. Uncertain results require care and their actual condition, rather than treatment as ordinary Good data. There is also an important limit to a Good badge: the DataValue rules permit Good severity where a server does not support status information. Good alone is not proof of independent sensor validation, complete diagnostic coverage or fitness for the AI task. Change DV-8's premises in a separate return at 09:03. Suppose the numeric content remains 17 but the source now reports Uncertain and a source timestamp associated with recognizing that non-Good condition. The recent source time is not a newly measured Good 17. The receiving application needs the actual status reason and its intended-use policy. If a subsequent return is Bad with null value, it supplies no usable numeric 17 or zero. Retaining an earlier Good value, assuming a value or excluding an input are different application decisions to identify; the new Bad return must not be presented as a valid current number. References: [QS1](https://reference.opcfoundation.org/Core/Part4/v105/docs/7.11.5), [ST1](https://reference.opcfoundation.org/Core/Part4/v105/docs/7.38.1) ## Compare what survives the export into AI input Consider two fictional offers for DV-8. Offer Flat returns only 17 with updated-at 09:02. It leaves the clock's meaning and quality condition unresolved. Offer Full preserves the source and server times, the associated status and the source's stipulated update behavior. It lets the buyer distinguish current-state knowledge from a new source observation and later recognize the changed quality condition. Neither is evidence of measured model quality. Flat can be a suitable deliverable if the buyer deliberately contracts for that limited state projection and its meaning is established elsewhere. It is insufficient for an unchanged request to retain the source/quality relationships it discarded. Full makes those relationships inspectable; the supplier still needs to demonstrate what its actual implementation returns. More columns alone are not a compliance certificate. Carry the chosen meaning into the consumer's input and retained history. If values are flattened, carried forward or converted to a common time axis, identify that transformation rather than silently calling its rows fresh measurements. The worked case offers a concrete question for the data provider: what does each returned 17 establish, and what evidence distinguishes the later Uncertain return? Resolve that before judging an AI dataset by its row count or its newest timestamp. The Modbus guide covers numeric interpretation; Redfish separates report, metric and health meanings. Those interfaces have their own definitions. Do not transfer their timestamp or status rules to OPC UA merely because dashboards present similar columns. ## Discuss a separate physical equipment connection on its own scope If the equipment project also needs physical IT network cabling, Leviathan's Structured Cabling & Fiber Installation service is the relevant route to discuss agreed installation, endpoint identification, labels and physical handoff records. Share a nonconfidential equipment, connection, supplied-material and required-record outline through the related project inquiry. OPC UA software integration, industrial automation, source validation, AI data handling and process operation remain with the appointed equipment, software and process owners. This data-meaning comparison does not supply those services or a field procedure. References: [L1](https://www.leviathansystems.co/services/structured-cabling) ## Primary sources - [DV1 — OPC Foundation: OPC10000-4 Part 4 v1.05.07, DataValue](https://reference.opcfoundation.org/Core/Part4/v105/docs/7.11). Checked 2026-10-21. DataValue structure and value/status relationship. The requested versioned reference redirects to the Foundation specs page displaying v1.05.07; no offered-product compliance is established. - [TS1 — OPC Foundation: Part 4 v1.05.07, 7.11.3 SourceTimestamp](https://reference.opcfoundation.org/Core/Part4/v105/docs/7.11.3). Checked 2026-10-21. Value-instance, source/status and null-time semantics as displayed on the checked reference. No unique-ID or clock-accuracy guarantee. - [SV1 — OPC Foundation: Part 4 v1.05.07, 7.11.4 ServerTimestamp](https://reference.opcfoundation.org/Core/Part4/v105/docs/7.11.4). Checked 2026-10-21. Receipt/knowledge time and conditional unchanged-value examples. Their assumptions are not a general refresh deadline or physical-sensor observation guarantee. - [QS1 — OPC Foundation: Part 4 v1.05.07, 7.11.5 StatusCode assigned to a value](https://reference.opcfoundation.org/Core/Part4/v105/docs/7.11.5). Checked 2026-10-21. Good/Uncertain/Bad severity, minimum checking and the no-status-information Good provision. No application-specific quality policy or sensor certification. - [ST1 — OPC Foundation: Part 4 v1.05.07, 7.38.1 StatusCode general rules](https://reference.opcfoundation.org/Core/Part4/v105/docs/7.38.1). Checked 2026-10-21. Use of Good, Uncertain and Bad results. No operational handling recipe, particular SubCode diagnosis or actual equipment-state assessment. - [L1 — Leviathan Systems: Structured Cabling & Fiber Installation](https://www.leviathansystems.co/services/structured-cabling). Checked 2026-10-21. Separately agreed physical network-cabling and record scope, without OPC UA integration or process operation. ## Related Leviathan resources - [OPC UA sampling, queues and retained change history](/articles/industrial-ai-opcua-sampling-queue-publishing) - [Modbus words and application quantities](/articles/industrial-ai-modbus-register-value-encoding-units) - [Redfish report times, metric times and resource health](/articles/redfish-metric-report-time-versus-resource-health) - [Structured Cabling & Fiber Installation](/services/structured-cabling) - [Discuss a separate physical network-cabling project](/contact?service=structured-cabling&from=%2Farticles%2Findustrial-ai-opcua-value-status-source-server-time) ## Does the equipment need a separate physical connection? Share a nonconfidential equipment, IT connection and physical-handoff outline to discuss cabling scope, requirements and availability. [Discuss the scope](/contact?service=structured-cabling&from=/articles/industrial-ai-opcua-value-status-source-server-time)