Glossary

data policy

A data policy provides additional metadata that can be associated with a tagged component. For more details on tags and tagging, see the Niagara Tagging Guide.

Haystack

An extensible Semantic Web Browser developed by the Haystack research group at the MIT Computer Science and Artificial Intelligence Laboratory (http://haystack.lcs.mit.edu). The project explores how the Semantic Web data model (a Resource Description Framework — RDF) can be applied by users to better organize, navigate, and retrieve information, both personal and shared (www.w3.org/2005/04/swls/BioDash/Demo/What is Haystack.html).

Haystack tag dictionary

A smart tag dictionary (namespace) containing a collection of tags developed by Project Haystack, which can be used for semantic modeling of building control entities, i.e. site tags, building tags, equipment tags, point tags, geo-location tags, etc.

The Haystack dictionary is indicated by the hs character, followed by a colon character (:).

The Haystack dictionary is a result of the work of the Open Source Initiative (OSI) hosted on the website http://project-haystack.org.

implied tags index

In Niagara you can manually enable indexing on individual tags in the tag definitions of a custom smart tag dictionary. The index primarily improves performance of NEQL searches and speeds-up hierarchy refreshing.

namespace

A container for a set of names in a naming system. A tag dictionary is a namespace.

Niagara tag dictionary

A tag dictionary (namespace) containing a collection of tags developed for Niagara systems, that are used for semantic modeling of specific building control entities, i.e. networks, devices, equipment, points, sites, buildings, geo-location, histories, etc.

The Niagara dictionary is a type of Smart Tag dictionary, therefore it applies Implied Tags and Implied Relations to components and links. This allows queries to find these components based on type, linkage, hierarchy or combinations of these. The Niagara tag dictionary is included by default in all stations created using the New Station tool.

The Niagara dictionary is indicated by the n character, followed by a colon character (:).

scoped tag rule

In Niagara tag rules have a scope in which they apply. This means that an entity will only have tags implied by a tag rule if the entity is within the tag rule's scope. This focuses evaluation of NEQL queries on applicable entities, which reduces the amount of time it takes to complete a search or hierarchy refresh.

semantic information

Metadata used to indicate the purpose of a device, that is, what the device is, what each of its data points means, and how devices are related to each other.

tag

A piece of semantic information (metadata) associated with a device or point (entity) for the purpose of filtering or grouping entities. Tags identify the purpose of the component or point and its relationship to other entities. For example, you may wish to view only data collected from meters located in maintenance buildings as opposed to those located in office buildings or schools. For this grouping to work, the metering device in each maintenance building includes a tag that associates the meter with all the other maintenance buildings in your system.

JACEs are associated with Supervisors based on tags; searching is done based on tags.

Tags are contained in tag dictionaries. Each tag dictionary is referenced by a unique namespace.

tag dictionary

Tag dictionaries contain a set of tag definitions, and may contain tag group definitions, relation definitions, as well as tag rules for smart tags.

taggable spaces

The implementation of tags for all common data types: components, files, histories and alarms.

tag rule index

In Niagara the tag rule index is an index on the station’s Tag Dictionary Service which improves performance in evaluating tag rules for implied tags during NEQL searches.