Streams

SdsStreams are collections of sequentially occurring values indexed by a single property, typically time series data. You define SdsStreams to organize incoming data from another system into the CONNECT data services. To define an SdsStream, you must first define an SdsType, which defines the structure of the data you want to stream into a selected namespace.

Sequential Data Store (SDS (Sequential Data Store)) stores collections of events and provides convenient ways to find and associate events. Events of consistent structure are stored in streams. Streams are referenced by their identifier or Id field. Stream identifiers must be unique within a namespace.

A stream must include a TypeId that references the identifier of an existing type. Stream management using the .NET SDS (Sequential Data Store) client libraries is performed through ISdsMetadataService. Create the ISdsMetadataService using one of the SdsService.GetMetadataService() factory methods.

The following table shows the required and optional stream fields. Fields not listed are reserved for internal SDS (Sequential Data Store) use.

Note: You can access stream metadata and tags through Metadata API (Application Programming Interface) and Tags API (Application Programming Interface) respectively. Because they are associated with SdsStream objects, you can use them as search criteria.

Rules for the stream identifier (SdsStream.Id)

The stream identifier, SdsStream.Id, has the following requirements:

• Is not case sensitive.

• Cannot just be whitespace.

• Cannot contain leading or trailing whitespace.

• Cannot contain forward slash ("/").

• Contains a maximum of 100 characters.

Indexes

While you define the primary index on the type, the stream is where you define secondary indexes. If the primary index defined on the type is a compound index, secondary indexes on the stream are allowed as long as that compound index does not have more than two properties. For more information on compound indexes, see Indexes.

Interpolation and extrapolation

The InterpolationMode, ExtrapolationMode, and PropertyOverrides can be used to determine how a specific stream reads data. These read characteristics are inherited from the type if they are not defined at the stream level. For more information about type read characteristics and how these characteristics dictate how events are read, see Types.

SdsStreamPropertyOverride

The SdsStreamPropertyOverride object provides a way to override interpolation behavior and unit of measure for individual SdsType Properties for a specific SdsStream.

The SdsStreamPropertyOverride object has the following structure.

The unit of measure can be overridden for any type property defined by the stream type, including primary keys and secondary indexes. For more information about type property units of measure, see Types.

Read characteristics of the stream are determined by the type and the PropertyOverrides of the stream. The interpolation mode for non-index properties can be defined and overridden at the stream level. For more information about type read characteristics, see Types.

If the SdsType InterpolationMode is set to Discrete, it cannot be overridden at any level. When InterpolationMode is set to Discrete and an event is not defined for that index, a null value is returned for the entire event.