LiveView Glossary

Aggregation Table

A data table with an attached aggregation preprocessor that computes and maintains aggregations from another LiveView table that serves as a data source.

Author-Time Aggregation

Author-time aggregation is configured in a LiveView configuration file that defines a LiveView data table with an aggregation data source. Author-time aggregations run on the LiveView Server and cannot be changed once the server has started.

Collector

An application that takes data that is not in the LiveView Server and publishes it in an existing LiveView table.

Conflation

A technique for reducing the rate at which data is coming into a table. Conflation is done by periodic publication, publishing at most one update per second per key for example, with repeated updates on the same key folded together (conflated) such that clients get the result of multiple deltas as a single delta.

You configure a table to use conflation with the publish-interval-millis attribute of the aggregate table's <data-table> tag. For example, setting publish-interval-millis="250" means that data will be published in the target table row every 250 milliseconds.

To control whether the aggregated data is conflated, set the conflate-data attribute of the <aggregation> tag under the data-source in the target (aggregation) table. By default, this attribute is set to false, which means that the periodic publish will include all row updates. If you set this attribute to true, only the most recent update will be published.

Continuous Query

A query that first executes a snapshot query, and then continues to return results as records that satisfy the query are created, updated, or deleted in the target table. A continuous query provides to a client a continuously updating view of the data that satisfies the query.

Continuous Query Processor

The Continuous Query Processor manages your data. LiveView Server executes the Continuous Query Processor in the default container of the host StreamBase Server.

Data Source

A LiveView Table is populated from a data source. A data source must be one of three types:

  • A globally defined application,

  • An aggregation from another LiveView table,

  • A data transformation.

Dynamic Aggregation

Dynamic aggregation uses ad hoc aggregate functions expressed in a query sent to a LiveView Server instance over a client connection. Client connections include those made by LiveView Desktop, lv-client, and any custom querying utility or function you have made using the LiveView Client API.

Full-Active One-to-One Table Joins

A join of two tables, a local table and a foreign table, whereby join processing occurs when a row in the either the local or the foreign table is inserted or updated. As in a half-active join, when a row in the local table is inserted or updated, a lookup of a row in the foreign table is performed based on the join keys, and the lookup results update the data in the local row. Additionally, when a row in the foreign table is inserted or updated, all rows in the local table that match the join keys are updated.

Half-Active One-to-One Table Join

A join of two tables, a local table and a foreign table, whereby when a row in the local table is inserted or updated, a lookup of a row in the foreign table is performed based on the join keys, and the lookup results update the data in the local row.

LiveView Client Layer

The layer in the logical architecture that connects directly to clients.

LiveView Configuration Files

XML files that:

  • Define the table space and tables for an instance of LiveView Server.

  • Define applications and expression macros in a way that can be reused in multiple LiveView table configuration files.

When LiveView Server starts, all configuration files in the same folder where LiveView is launched are validated against a schema for semantic correctness. LiveView configuration files have file extension .lvconf and are often called lvconf files (pronounced ell-vee-conf).

LiveView Data Layer

The layer in the logical architecture where data is stored. Data is stored in continuous query processors.

LiveView Desktop

A desktop interface for viewing the data in tables managed by LiveView Server. LiveView Desktop is an Eclipse Rich Client Platform application. The charting functionality is powered by Panopticon.

LiveView HA Pair

A pair of LiveView Servers with identical configuration and data used as backups for one another, to provide high availability (HA).

LiveView Java Client Library and API

A library for Java programs to access LiveView, available on the file system at %STREAMBASE_HOME%\liveview\lib, and through StreamBase Studio as a library for Java and Studio projects.

LiveView .NET Client Library and API

A library for .NET programs to access LiveView Server. The LiveView .NET Client Library and API uses the Microsoft Reactive Extensions (Rx) library. It is available on the file system at %STREAMBASE_HOME%\liveview\sdk\bin, and through StreamBase Studio as a library for .NET and Studio projects.

LiveView Project

A StreamBase Studio project that contains LiveView configuration files at its root, along with any other files needed to start LiveView Server.

LiveView Server

A single instance of LiveView software that ingests data, runs the Continuous Query Processor, and provides services for clients.

LiveView Services Layer

The layer in the logical architecture where services (such as alerts) occur.

LiveView Table

A LiveView table (sometimes called an Active Table) is data table with a particular schema that accepts a stream of incoming data and queries.

Preprocessor

A StreamBase application that processes all data flowing into a LiveView table. Processors can be custom or built in LiveView. They may fetch data themselves using input adapters, or they may receive data from other tables.

Primary Key Merge Join

A join of two data feeds with the same primary key, such that each row contains all fields for a given primary key value.

Publisher

An application that publishes data into a LiveView table.

QueryServer

A StreamBase application that runs in the default container and forms the basis for LiveView Server.

Snapshot Parallelism

The number of parallel threads used to scan a table during the snapshot portion of a query.

Snapshot Query

A query that executes once and returns a single result set, containing all records from the target table that satisfy the query at the time of execution.

Static Aggregation

Static aggregation was provided in LiveView releases before 2.0 as another version of aggregation defined in lvconf files for running on LiveView Server. Static aggregation is still supported by LiveView 2.x servers, but this feature is now deprecated in favor of Author-Time Aggregation, and will be removed in a future release.

Transform

A StreamBase application that acts on a data source and feeds into a LiveView table.