Canary Axiom: trends, dashboards and asset templates on the Canary Historian, Views, aggregates and folders

Axiom is the Canary System's client for trend charts and dashboards. It runs as a service on a server, usually the Historian machine, users open it in a web browser, and every tag it shows comes through the Views service. This article explains, from Canary's knowledge base (mostly version 26 articles, with two version 25 articles) and product pages, where Axiom runs, how tags are browsed, why trends show aggregated values, how dashboards and asset templates are built, how files and permissions work, and what the Excel Add-in adds. How the whole Canary System is built: Canary Historian architecture.

1. Where Axiom runs

Canary's Axiom product page says the client is built in HTML, so a user needs only a modern web browser. Processing is done on the Canary server, and charts and applications are stored there instead of on each computer. When the server is upgraded, each client receives the new release the next time it connects. The same page states that every Canary System includes a licence for Axiom.

The Axiom service is installed first, usually on the same machine as the Historian. Users then browse to the Axiom server name over HTTPS, or to localhost on the server itself; Internet Explorer is not supported. Login goes through the identity providers set in the Identity tile. In version 26, Active Directory is enabled by default, Anonymous and Kerberos are disabled by default, and other providers are added through OAuth 2.0 or OpenID Connect. The first time someone logs in with a Canary client such as Axiom, an internal Canary user is created and linked to that external account.

2. Browsing tags through Views

Axiom does not read the Historian files itself. Canary describes the Views service as the gateway between clients and the Historian: a client sends its request to Views, Views reads the Historian's HDB files, aggregates or processes the data, and returns it encrypted over gRPC. Axiom Core, the Excel Add-in, the ODBC server, the Read API, Publisher and Calcs & Events all read through it. For systems with more than 50 concurrent clients, Canary's architecture article suggests one Views service for Axiom and a second one for APIs and third-party applications.

In a chart, the Add Trends menu shows the Views server on the left, with the raw Historian view and the Virtual Views built on it. By default Axiom uses the Views service on localhost; a gear icon points it at another server, a layout Canary calls uncommon. Selecting a branch lists its tags, including those of its sub-nodes unless that option is cleared, and Include Properties adds each tag's description and engineering units. The search box takes several keywords separated by spaces, ignores case, returns only tags that contain all of them, and excludes tags that match a keyword starting with "!". How Virtual Views rename tags and define assets is covered in Canary Virtual Views and Calcs & Events.

3. Trend charts

A chart screen holds the trends and their legend, the chart duration, a live mode, buttons to scroll back and forward in time, cursor modes and annotations. The Edit Trends menu sets, for each trend:

From the chart menu, Export Data writes the chart data to a CSV file, Statistics gives values such as the mean, standard deviation and quartiles, and Playback replays the chart from a chosen time at a set rate.

4. Why a trend shows aggregated values

Canary states that Axiom trends aggregated data, one value per pixel of chart width, for performance reasons. The shortest aggregate period is the chart duration divided by the chart width in pixels. Canary's examples:

Changing the duration or resizing the chart changes what each point stands for, so a volatile signal can look different from one view to the next, and an average can smooth away a short peak or dip. For such tags Canary suggests the minimum or maximum aggregate, or a combination of minimum, maximum and average. Axiom's ad hoc calculations also work only on aggregated data; for calculations on raw values Canary points to its Calculations service. Historian basics such as deadband and compression: What is a process historian. Trends that stop updating: Canary Historian troubleshooting.

5. Applications: dashboards and asset templates

An Axiom application is a set of screens built in the browser. The designer switches between Edit and Live mode, controls are dragged onto a screen, and each control can be given a source tag or a calculation. The version 26 control articles include the bar chart, circular, linear and donut gauges, data table, grid, events table, scatter plot, button, data entry, image and Trend Graph controls. A Value Box, in Canary's version 25 article, shows a tag's value, timestamp and quality, can apply an aggregate over a set interval, and changes colour against a limit that is a fixed number or another tag. A Trend Graph can import an existing chart, but the chart is copied into the application when the application is saved, so later edits to the chart file do not reach it.

Asset-based controls depend on Virtual Views. The Asset Template, Grid, Panel, Screen and Trend Graph controls can be linked to an asset type defined in a Virtual View, and without a Virtual View these asset properties do not appear. Canary's example is one templated screen for twenty assets instead of twenty screens. The Asset Template control draws one panel per asset instance, applies whatever is placed in the panel to every instance, shows a dash where an asset lacks a tag, filters instances with an expression and splits them into pages. Canary's product page adds that when the Canary System discovers new assets, Axiom includes them.

6. Files, folders and who can see what

Charts and applications are saved in folders on the server. The defaults in version 26:

Folder permissions are set under Axiom Security in the Identity tile and are evaluated from the top down; if file security is turned off, Everyone and Anonymous can read and write every folder. Separate access control lists decide who may log in to Axiom (Everyone and Anonymous by default), who may use scripting (Administrators), who may use the Data Entry control (Administrators) and who may create automated reports (Everyone and Anonymous). While the Anonymous provider is disabled, which is the default, Anonymous fails for every function.

Each user's preferences set the theme, the locale and the time zone. The time zone defaults to the local time of the client computer, and a change takes effect after logging out and in again. Automated reports run saved charts or applications on a schedule; the Viewer lists the reports that have run, and each one can be opened or downloaded as a PDF.

7. The Excel Add-in

The Excel Add-in is another Views client. Its functions include Tag List, Raw Data, Processed Data (values on regular timestamps from an aggregate and an interval), Last Value, Find Events and AdHoc Events, and its settings choose the Historian, the time zone of the returned data and API token authentication. Formulas with relative times such as Now - 1h are refreshed with Recalculate Workbook. Canary's product page counts more than 30 aggregates for Processed Data.

What TDL checks first

These are our own working habits on a Canary system, not Canary requirements:

• We check the tag names and the Virtual Views before any screen is built, because asset templates and asset-based trends need asset types from a Virtual View.
• We check which time zone the Axiom preferences and the Excel Add-in settings use against the plant's local time, so that shift reports line up.
• We check the Aggregate Kind on trends of fast or spiky signals, and use a minimum or maximum where an average would hide a peak.
• We check the Axiom Security folders and access control lists: what belongs in Public, what belongs in ReadOnly, and whether Anonymous is enabled at all.
• We check whether Views and Axiom share a server, and how many concurrent clients are expected.

How TDL approaches it

TDL Industrial Automation is a Canary Certified Partner. Our historian work so far has been on Rockwell Automation platforms, for example FactoryTalk View SE with FactoryTalk Historian at the Vinh Hoan FeedOne aquafeed plant. On a Canary system we settle the tag names and the asset model before building Axiom screens. More on this service: Canary Historian in Vietnam.