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BACnet’s New Data Modeling Initiatives and their Relationship to

Project Haystack

Bob JohnsonSiemens Building Technologies

Data Modeling #1

Tuesday, May 19, 2015

2

Content

•Introduction, Background

•Current BACnet

•The Extended Data Model (=> BACnet XD)

•BACnet WS Extensions

•Support for Classic BACnet

•Conclusion

3

BACnet and Project Haystack

BACnet

Project Haystack

BACnet and Haystack are on parallel paths regarding the definition of descriptive tagging models for BAS information and ‘IT-friendly’ network services designed to take advantage of this information.

4

Our Perspective

• Siemens strongly supports sharing and cooperation between Project Haystack and BACnet, in order to drive expansion and acceptance of descriptive data models and services in the BACS industry

• We believe that descriptive data models and services provide clear benefits to operation and monitoring applications and workflows

5

A Main Objective

Haystack Clients

Other Client

Control System

Analytics ClientOperation and Monitoring Client

BACnet

Haystack Services

Control System

BACnet

Siemens’ goal is to support ‘Classic BACnet’, BACnet Web Services, and Haystack with a minimal amount of redundant configuration.

To achieve this goal, Siemens and other vendors desire a level of similarity between tagging models.

6

BACnet Steps

Over the years, BACnet has taken several steps toward an extensible data model with descriptive tagging…

1995 – Present: Classic BACnet

2006 – Present: The Structured View Object

2006 – Present: BACnet/WS (SOAP Web Services)

2010 – Present: CSML (Control System Modeling Language)

BACnet Extended Data Model (BACnet XD)

BACnet/WS Extensions and Support for Classic BACnet

7

Content


•Current BACnet




•Conclusion

8

Classic BACnet – 1995 to Present

Device 7: AI 77

Room.260:Space.Temppoint, sensor

unit: °F, fault: false:

Some descriptive tagging information can be derived from the object model and naming conventions.

AI, AV, AOBI, BV, BO

MI, MV, MODevice

ScheduleTrend Log

:

Objects

ReadProperty, RPMWriteProperty, WPM

SubscribeCOVCOVNotification

EventNotification:

Services

MSTP (485)ARCnetLonTalk

PTPEthernet

IP

Networks

9

The Structured View Object – 2006 to Present

Node_Type:SYSTEM, NETWORK, DEVICE, ORGANIZATIONAL, AREA,EQUIPMENT, POINT, COLLECTION, PROPERTY, FUNCTIONAL, OTHER

Node_Subtype is intended to provide additional information describing the element represented by the SVO

Subordinate_Annotations are intended to provide additional information describing the child objects

SVONodeTypeNodeSubtype

AnnotationAnnotationAnnotation

:

ReferenceReferenceReference

:

Object

Object

SVOObject

Object

10

Structured View Object Example

The SVO adds descriptive information, but standardization is limited.

SVOs are useful for:• Constructing user views and

traversing the object model• Application modeling and

application library management

SVOEQUIPMENTVAV

RoomTempRoomCO2

AirFlowOpMode

::

SVOEQUIPMENTLighting

LightBtnLightCmdDelayOff

::

AI:SpaceTemp

AI:CO2

AI:AirFlow

MV:Mode

BI:LightBtn

MV:LightCmd

AV:Delay

SVODEVICERoomControl

HVACLighting

11

BACnet/WS Web Services – 2006 to Present

•BACnet/WS specifies the use of Simple Object Access Protocol (SOAP) over HTTP, and encodes data for transport using XML.

•BACnet/WS supports traversal and data access via node paths such as:

/Geographic/EastWing/AHU_5/DischargeTemp [:Description]

•Services include getValue, getValues, setValue, setValues, and getHistoryPeriodic. The general form of a service is

Service(options, path(s), [value(s)])

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BACnet/WS Web Services (cont.)

•BACnet/WS defines "normalized points.“ Common attributes of points available in the majority of BAS models are exposed using a common set of names.

•BACnet/WS node attributes include NodeType, NodeSubtype, DisplayName, Description, Units, HasHistory, Children, Minimum, Maximum, and many others.

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XML Data Formats (CSML) – 2010 to Present

The Control System Modeling Language (CSML) defines XML formats for data to be exchanged between BAS systems. This data may be transferred through files or by other means.

CSML is designed to provide a common syntax and data model that can be used to represent both standard and proprietary object, property, and data type definitions, along with descriptive information.

CSML may also be used to transfer instance data (database content).

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XML Data Formats (CSML)

Example:

<BitString type="0-BACnetEventTransitionBits" value="to-offnormal;to-fault;to-normal" />

All BACnet data elements represented in CSML share a common set of optional attributes, such as name, type, displayName, writable, value, units, etc.

Each data element may also define a specific set of required or optional attributes of its own.

15

Content


•Current BACnet




•Conclusion

16

The Extended Data Model (=> BACnet XD)

•Past: MODBUS Registers

•Today: BACnet Objects & Properties

This slide covers content from a public review addendum that is not yet part of the standard

•Future: BACnet XD Allows Arbitrary Data & Data Structures + Semantics

Extended Data Model (BACnet XD)

BACnet Objects and Properties

RESTful BACnet Interface

Classic BACnet Services

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Extended Data Model Content

Characteristics: Writability, volatility, range, length, type, choices, etc.

Semantics: Semantic and value tags from multiple sources

Relationships: Hierarchies and associations between data items

Multimedia: Support for media types beyond control system data: PDFs, Graphics, CSV, foreign XML, etc.


The Extended Data Model is an abstract model for defining, transmitting, and storing BMS and other application data. The model consists of ‘data’ (values) and ‘metadata’ (attributes). Metadata includes:

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Hierarchies and Virtual Objects

Extended Data Model metadata can express hierarchies without requiring Structured View objects in controllers.

The model can also include ‘virtual objects’, allowing SVOs and other objects to be represented, even if these objects do not exist as BACnet objects in the controller.

EQUIPMENTVAV

RoomTempRoomCO2

AirFlowOpMode

:

EQUIPMENTLighting

LightBtnLightCmdDelayOff

:

AI:SpaceTemp

DEVICERoomControl

HVACLighting

attributesattributesattributes




AI:CO2attributesattributesattributes

AI:AirFlowattributesattributesattributes

MV:Modeattributesattributesattributes

BI:LightBtnattributesattributesattributes

MV:LightCmdattributesattributesattributes

AV:Delayattributesattributesattributes

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Tagging in the Extended Data Model

The Data Model supports semantic and value tags from multiple sources. ASHRAE-defined tags require no prefix. Tags from other sources are prefixed with either a reversed DNS name or an ASHRAE-assigned vendor ID.

<Real name="flow" value="1030.0“ tags="sensor;com.siemens.flow;555-air">

<ValueTags>

<String name=“com.siemens.sensorType” value=“xyz”/>

</ValueTags>

</Real>


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Content


•Current BACnet




•Conclusion

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Changes from BACnet/WS

Public Review Addendum am includes the following new BACnet/WS extensions:• Migration from SOAP to a simple RESTful API (node path ->

REST URI)• The ability to send Extended Data Model content encoded

using XML, JSON, or plain text• The ability to configure Extended Data Model content on the

server• Support for COV, Trending, and Event subscriptions

This slide covers content from an public review addendum that is not yet part of the standard

22

Changes from BACnet/WS

One important benefit of semantic tagging is to find data based on its tags. Therefore, it is required that all servers support filtering with the 'filter' query parameter to find items with particular tag values.

For example, the following query returns a list of objects with the semantic tag "meter”:

GET /.sysdata/objects?filter=$target/$tags/contains(meter)

This slide covers content from an public review addendum that is not yet part of the standard

23

Content


•Current BACnet

•BACnet Web Services & XML Data Formats (CSML)



•Conclusion

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Support for “Classic BACnet”

Methods for adding descriptive tagging and Extended Data Model definitions to BACnet devices are planned, providing access to tagging and extended data via classic BACnet services.

• semantic tags on objects and properties

• discoverable arrangements of objects and properties

• descriptions of objects, properties, and data types

• property metadata like writability, range, volatility, etc.


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Support for “Classic BACnet”

xdd files provide XML-encoded Extended Data Model information, allowing clients to read and use this information without requiring use of the RESTful API.




xdd File Objects

Object Tagging Properties

RESTful BACnet Web Services

xdd File Location Properties

Classic BACnet Services

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Extended Data Access via “Classic BACnet”




xdd File Objects



xdd File Objects


Classic BACnet Device

BACnet Object

Object_ID

Object_Name

Description

Present_Value

Profile_Location

...

...

...

...

: ...

Profile_Name ...

BACnet File Object

object reference

URL

<CSML xmlns=”http://bacnet.org/csml/1.1> <Definitions> <Object name="555-myActuator" extends="0-BaseObject" > <Real name="command-position" writable="true" commandable="true" units="percent" minimum="0.0" maximum="100.0" displayName="Command Position" description="The commanded position for the actuator - see feedback for actual position" propertyIdentifier="1001" tags="control;safety"/> <Real name="feedback-position" units="percent" displayName="Actual Position" description="The actual position of the actuator based on confirmation measurement" propertyIdentifier="1002" tags="feedback;safety"/> <Boolean name="horn-enable" writable="true" tags="safety;indicator" propertyIdentifier="1007" </Object> <Definitions></CSML>

xdd File

xdd

27


Interoperability will be greatly enhanced by adding standardized descriptive tagging information to BACnet objects.




xdd File Objects




AI:77

Object_Name SpaceTempDescription Room 260 Space TemperaturePresent_Value 70.0Units °F: :

Tags point;sensor;temp;com.siemens.room

Value_Tags com.siemens.sensorType “xyz”

: :

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Content


•Current BACnet

•BACnet Web Services & XML Data Formats (CSML)

•The Extended Data Model (=> BACnet XD) and Support for Classic BACnet


•Conclusion

29

Conclusion

• Read/Modify descriptive data, hierarchies and associations

• Multi-language, context-aware user views, beneficial for single or multi-vendor systems (normalization across subsystems on a job, across jobs, between vendors, etc.)

• Paths to extend “Classic BACnet” systems

• New services allowing descriptive data to be used in queries and other operations

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References

This presentation only touched on a subset of BACnet data modeling topics.

For more information, public review and final versions of BACnet addenda are available at no cost from ASHRAE (www.ashrae.org) and the BACnet website (www.bacnet.org).

http://www.ashrae.org/

http://www.bacnet.org/

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References

•Addendum 135-2012am

The common extended data model for BACnet (BACnet XD), plus RESTful Web Services for accessing the model.

•Addendum 135-2012ba

Support for ‘Classic BACnet’ devices

•Addendum 135-2012ap

An approach for defining application interfaces through the use of semantic tags

data modeling #1 anet’s new data modeling initiatives … · anet’s new data modeling...

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