Concepts

This page provides an overview of Senfi concepts.

Measurement, Metric, Tag

Measurement

Senfi deals with data in a time series. Each sample in this time series consists of:

• a timestamp indicating when the data was sampled
• a fixed set of tags
• a fixed set of metrics

All these samples are kept in a dataset called a measurement.

Metric

A metric is a discrete reading or unit of data. It can be produced/measured by sensors, equipment, or complex systems. An example of a metric is temperature (eg. 37). A metric may or may not have units associated (eg. degrees Celsius).

Tag

A tag is an attribute of the sample. It is usually used as a way to identify where is the metrics are taken from (eg. device ID). It is also useful for filtering (eg. select all samples from this region).

Sensor

Unlike applications like Prometheus or InfluxDB which deals purely with temporal data in a time series, Senfi associates such data with physical objects in the real world.

A sensor in Senfi represents a physical object/system of interest. A sensor may produce one or more measurements, or it may not produce any measurements. There are 3 types of sensors in Senfi:

Managed sensors

Sensors that produces at least one measurement

Specialized sensors

Sensors with special behaviour, eg. lift controller

Unmanaged sensors

Sensors that does not produce measurement

Site

A site represents a place whereby sensors are physically located. A site usually comprise of one or more buildings. A site in Senfi has a geographical location and usually a 3D representation. Users may choose to use the CMS to trace out the building outline and generate a quick 3D building, or they can also upload a 3D building modelled using modelling software such as Autodesk 3DS Max, SketchUp etc.

Sample building generated from building outline

Sample building modelled using 3D software

Rule, Alert

In an operating environment such as a smart building, it is important that organizations are able to keep track and be aware of what is going on in and around their assets. The way to do that is through monitoring and alerting.

Sensors produce measurements which contain data in the form of metrics and tags. Senfi provides multiple ways for users to monitor metric and tag values for conditions which require attention - such as abnormally high values, or when a combination of values indicates something is down - and to take action when it happens.

Rule

User can make use of Senfi's flexible rule engine to be alerted of abnormality in the system they are monitoring.

A rule in Senfi comprises of:

• Inputs
• Conditions
• Output
• Actions
• Rule execution options

Computed measurement

Frequently, incoming metrics represent raw values that are read from the sensing device (eg. door open status, door closed status). To be able to derive better insights and to formulate more complex rules, it is useful to be able to calculate new metrics that are derived from the raw metrics. We refer to these metrics as derived metrics and the set of metrics as computed measurement.

Similar to measurement, a computed measurement comprises of:

• timestamp
• tags
• metrics (derived)

Following from the above example, a computed measurement could compute the duration that a door remains opened by taking the timestamp between a door open and door closed metric.

Organization, User, Access Group

An organization represents the entity (eg. company, individual) that is responsible for managing the account that uses Senfi. An organization comprises at least one user with Administrator role. Users with Administrator role are able to manage other users, including user account creation/deletion, user roles etc.

Think of access group as a subset of the assets under the organization. Users can be placed into access groups to have access to those assets. Currently assets that can be assigned to an access group are:

• user
• site
• rule