V1.3 11th October 2013
COBie for All
Required Information for Facility Ownership
Buildings & Civil/Infrastructure
Understanding How COBie Works in the UK Infrastructure Market
1 v1.3 October 2013
Version Control
Date Version Lead Author
12-07-2012 V0.1 First report Paul Scarponcini 24-07-2012 V0.2 Reviewed against COBie 2.4 Nick Nisbet 29-07-2012 V0.3 Agreed content Paul Scarponcini
Nick Nisbet 01-08-2012 V0.4 Formatted for presentation to UK BIM
Task Group and BIM4Infragroup
Nick Nisbet
13-09-2012 V1.1 UC1 results included Nick Nisbet 10-10-2012 V1.2 UC2 results (provisional) included Nick Nisbet 15-10-2013 V1.3 Document Review & Introduction
section
Mark Bew
Status: DRAFT Public Release for Comment
Version: 1.3
Confidentiality: Unclassified
Copyright: © 2013 BIM Task Group
Abstract: An assessment is made of the requirements to use the COBie standard to address information exchanges for Civil / Infrastructure projects.
Important note:
This draft manual and downloads available from the ‘Labs’ area of the BIM Task Group website are for educational use and comment only. They are not yet available for production use and should not be used for contract use.
This document is technical in nature and is not aimed at Lay Users but Design and Data Professionals.
Contents
Contents 2
Authors & Acknowledgements 4
Introduction 5
1 Summary 6
2 Introduction 9
2.1 Problem Overview 9
2.2 About This Report 10
2.3 Acronyms 11
3 COBie Overview 13
Problem Decomposition 15
3.1 Problem 1: COBie Spread Sheet Format 16
3.1.1 Problem Identification 16
3.1.2 Discussion 16
3.1.3 Recommendation 17
3.2 Problem 2: COBie Schema 18
3.2.1 Problem Identification 18
3.2.2 Discussion 18
3.2.3 Recommendation 21
3.3 Problem 3: COBie Versions 22
3.3.1 Problem Identification 22
3.3.2 Recommendation 23
3.4 Problem 4: COMPONENT Geospatial Location 24
3.4.1 Problem Identification 24
3.4.2 Discussion 24
3.4.3 Recommendation 26
3.5 Problem 5: COMPONENT Linear Location 27
3.5.1 Problem Identification 27
3.5.2 Discussion 27
3.5.3 Recommendation 29
3.6 Problem 6: Continuous Objects 31
3.6.1 Problem Identification 31
3.6.2 Discussion 31
3.6.3 Recommendation 31
3.7 Problem 7: Variable Asset Values 32
3.7.1 Problem Identification 32 3.7.2 Discussion 32 3.7.3 Recommendation 32 3.8 Problem 8: IFCs 34 3.8.1 Problem Identification 34 3.8.2 Discussion 34 3.8.3 Recommendation 34 3.9 Problem 9: Classifications 35 3.9.1 Problem Identification 35 3.9.2 Discussion 35 3.9.3 Recommendation 35 3.10 Problem 10: Schedules 36 3.10.1 Problem Identification 36 3.10.2 Discussion 36 3.10.3 Recommendation 36
3.11 Problem 11: Stakeholder Requirements 37
3.11.1 Crossrail 37
3.11.2 Tube Lines 37
3.11.3 Highways Agency 38
3.12 Problem 12: Software Products 39
3.12.1 Problem Identification 39
3.12.2 Discussion 39
3.12.3 Recommendation 39
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4.1 Introduction 40
4.2 Use Case – Problem Mappings 41
4.3 Use Case Descriptions 42
4.3.1 UC 1: As-Is COBie 42
4.3.2 UC 2: Geospatial Location 44
4.3.3 UC 3: Linear Location 47
4.3.4 UC 4: Linear Identity and Attribution 47 4.3.5 UC 5: Asset-oriented COBie 48 5 Conclusions: C/I information exchange 50
5.1 Problem Identification 50
5.2 Discussion 50
5.3 Recommendation 50
6 References 51
7 Appendix A – COBieLite Extract 54
Authors & Acknowledgements
The process of developing this work has been undertaken collaboratively between the UK BIM Task Group, Bentley Systems and AEC3 Ltd. There have been a significant number of individuals and organisations involved as many as possible are mentioned below.
However the principal authors of this work were
Paul Scarponcini
Bentley Systems, Inc.
Nicholas Nisbet
BIM Task Group of UK Government Department, Business Innovation and Skills
AEC3 Ltd
Other Participants
Julian Schwarzenbach Crossrail
Jon Kirby HS2
Ross Dentten Crossrail
Phil Jackson BIM Task Group (HA)
Mark Bew BIM Task Group
Iain Miskimmin COMIT
David Philp BIM Task Group Malcolm Taylor Crossrail
John Woollett Tube Lines Mark Houghton Crossrail Neill Pawsey Crossrail Ian Childs Tube Lines Nasir Khawaja Tube Lines James Folley Tube Lines Anne Kemp Atkins (EA)
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Introduction
When we designed the concept of Level 2 BIM as a key stepping stone on the journey to the interoperable digital economy of Level 3 and beyond, we identified the need for a straight forward data structure that could be simple enough to be understood, but comprehensive enough to be useful. Our goals were to not only allow the effective transfer of information between the supply chain and client, but also to provide training and awareness of the principles of shared data to the 1.9 million people employed in our industry.
As the BIM program has developed and gathered pace to its 2016 target of all public sector projects being delivered using Level 2 BIM, the need to integrate building and infrastructure has become more and more obvious.
The age old divide between our buildings and civils businesses stretches from culture to language, but as the UK leads the way to the digital economy, construction as a whole sector has to lead the way to a new collaboration between disciplines so we can continue to deliver ambitious integrated hybrid programmes such as HS2, Crossrail and Thames Tideway. Nowhere is this need to share greater than in the creation, use and storage of data.
“COBie for all” is a project that has taken a close look at the technical issues surrounding the structural storage of data for both buildings and infrastructure. The work already done by the BIM Task Group has delivered a UK specific COBie (COBie-UK-2012) (based and compliant with COBie 2.4). The work of the “COBie for all” team is resourced in a joint team of BIM Task Group, Bentley Systems, HA, HS2 and Crossrail who posed the question;
‘’Will COBie Work for Infrastructure?’’
The work initially identified 15 ‘’issues’’ all of which are described in this document. The solutions and explanations derived satisfied the team sufficiently to say ‘’we think it will’’. So to test these findings, five “Use Cases” or scenarios have been developed to test our work.
The purpose of this document is to share the findings to date with the industry and seek views and comments. On behalf of the BIM Task Group, I would like to thank you or taking part in this exercise and thank the team that have been working hard on this project for the last six months.
Mark Bew
Chairman BIM Task Group October 2013
1 Summary
The UK government has mandated 3D BIM by 2016 on new government construction projects including Civil/Infrastructure (C/I). The expected deliverables comprise 3D models, 2D documents, and COBie UK 2012 data.
Originally created for buildings, the Construction-Operations Building information exchange (COBie) does not address C/I projects. This report outlines how COBie can be used to exchange information about C/I projects and how COBie could to be extended to further support such projects.
Interviews were held with the UK Highways Agency, Crossrail Limited, and Tube Lines to determine their asset management requirements that would dictate the COBie C/I content. Additional documentation supplied by the interviewees as well as extensive background information was used to obtain an understanding of the problem.
After a brief introduction to COBie, the problem is broken down into a dozen smaller, more manageable problems. Each is identified and explained along with a discussion about possible solutions. A simplified, expedient recommendation is made for turning each problem into an opportunity for short term enhancement to COBie, whilst a longer term approach can be identified and pursued.
1. COBie Spread Sheet Format – the COBie spreadsheet format spans across upto 20 sheets and so may need to be complemented with an XML machine readable schema and/or a concise human readable summary presentation.
2. COBie Schema – the COBie schema may need development to support asset requirements tracking and their fulfilment.
3. COBie Versions –clarity is needed as to whether COBie2.26 or COBie 2.4 is the preferred version
4. COMPONENT Geospatial Location –investigates support for locating assets with geospatial
coordinates or with geospatial features by extending the use of the coordinates spread sheet and by generalizing the current location specification (building-floor-space hierarchy) common to buildings but not applicable to most C/I projects;
5. COMPONENT Linear Location – proposes support for linearly locating project components
along the linear assets (roads, rail lines) common to most C/I projects;
6. Continuous Objects –proposes a solution for segmenting continuous assets so they can be tagged and treated similarly to the discrete assets common to buildings;
7. Variable Asset Values – adds the ability to allow attributes of linear assets to vary in value along the length of the linear asset without necessitating further segmentation;
8. Relationship to IFCs – COBie is based on Industry Foundation Classes which are currently focussed on buildings with limited support for C/I with long term efforts to develop C/I IFCs have begun;
9. Use of Classifications – COBie mandates the use of standardized classification schemes for categorizing facilities, spaces, types, systems and organizational roles; these may need extension or replacement with C/I classifications;
10. Schedules – COBie addresses manageable equipment, products, and spaces that appear in schedules (on design drawings or elsewhere). C/I assets tend to be implicit from the linework;
11. Other Stakeholder Requirements – interviewed stakeholder concerns and emerging solutions are discussed;
12. Supporting Software Products – civil has lagged behind building and plant in implementing BIM and 3D modeling; C/I software products may be able to automatically generate or consume COBie compliant files with some configuration for mapping the data ahead of time
7 v1.3 October 2013 Five Use Cases are proposed that will explore these problems and the recommended solutions. The use cases are based on actual stakeholder scenarios and will use their sample data.
An initial report [PXS-3] was distributed with limited circulation. Subsequent meetings with the interviewees provided further clarification of their requirements and feedback on the proposed solutions. Meetings with HM Government provided additional insight into their 2016 mandate. The UK mandate covers all capital improvement projects, including C/I.
COBie has been adopted as the medium for information exchange to the Client from tier 1 partners such as lead engineers and constructors for all built assets. The COBie deliverable may be expected at several stages during the project, culminating at handover, or after an extended transfer process. COBie also allows other tiers to supply information in a consistent way. Once with the client, the information is intended for use in portfolio, asset and facility management systems. A separate COBie for C/I would be confusing and cause problems for projects like Crossrail that contains buildings and C/I, and for the supply chain in general.
The challenge is to find a way to support C/I using the existing COBie entity relationship structure shown below. This may be made more amenable if using more generic names for some of the “boxes”. It would accommodate a single “COBie for All” solution, thereby supporting projects like Crossrail that contain buildings and C/I.
Figure 1: The COBie data structure (buildings)
It has been seen from the discussions that the seven types of manageable aspects (grey) are encountered throughout the built environment, but the naming of these seven aspects may cause difficulties from specific professions (such as cost consultancy) or sectors such as C/I. In order to explore the important issues and help understanding, we propose exploring some synonyms. If these synonyms prove acceptable, then the support of some synonyms could be suggested to the COBie implementers.
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2 Introduction
2.1 Problem
Overview
“The [UK] Government Construction Strategy (GCS) requires that: Government will require fully collaborative 3D BIM (with all project and asset information, documentation and data being electronic) as a minimum by 2016. This refers to all centrally procured Government projects as outlined in the GCS including new build and retained estate, vertical and linear.” [HMG-3]. The UK mandate covers all capital improvement projects, including C/I.
The HM Government BIM Task Group identifies three key deliverables: the individual domain 3D models in their native file formats, the 2D reviewable design deliverables cut from the models, and COBie UK 2012 data.
The Construction-Operations Building information exchange (COBie) was designed and named1
to focus on buildings. It delivers information about “the scheduled equipment, products, and spaces that appear on design drawings.” [NIBS-6]. It uses a buildings-oriented spatial structure hierarchy of facility / floor / space to establish placement of components. The content of the information exchange is prescribed by the Facility Management Handover [NIBS-4] Model View Definition (MVD) in accordance with ISO 16739 [ISO-1]. This ISO standard specifies Industry Foundation Classes (IFCs) for building construction information [NIBS-2]. COBie advocates the use of standard classification systems (OmniClass is mandated in the US in [NIBS-4] but is substitutable according to other documents such as [NIBS-5]) for categorizing facilities, spaces, types, systems and organizational roles [NIBS-5].
Other than perhaps rail and subway stations, Civil/Infrastructure2 (C/I) projects are not about
buildings. Most of what will become managed assets do not appear in schedules on design drawings. Objects tend to be continuous like roads, rather than discrete like windows and doors. Attributes of these continuous objects often change in value along the object. Location of objects typically is via linear referencing or geospatial coordinates or feature geometries.
There are no IFCs in ISO 16739 specifically for C/I, such as for road and rail, except generic Geographic and Civil elements, introduced at IFC4 (2013). The FM Handover documents the relationship between COBie and IFC and so notes that “project structure and component breakdown structures outside of building engineering...are outside of the scope of this MVD.” OmniClass in the US and Uniclass in the UK contain limited classes for C/I categorization, though work is underway to include C/I classes in Uniclass2. So the question to be addressed is “how can COBie be used to exchange information about C/I projects?”
1 unless we accept “Building” as a verb rather than a noun
2 Civil/Infrastructure is chosen to expand the common notion of “COBie for Civil” to include all infrastructure projects, even if they are not Civil (such as electrical power networks)
2.2
About This Report
This report attempts to answer the problem stated above. Because of the current focus of COBie on buildings and the fact that C/I projects lag behind buildings and plant facilities in the application of BIM, this most certainly needs to be a long term objective. The focus of this report is on short term solutions that would comprise the initial steps in achieving the longer term goal.
Use cases are proposed that will demonstrate the proposed solutions.
The content of this report has been derived from information obtained from the following sources:
1. Background information from buildingSMART, HM Government, The Institute of Asset Management, the National Institute of Building Sciences, and the U.S. Army Corps of Engineers, obtained from the internet and included in the References section above, 2. Formal interviews (London, March 25-28 and June 19-26, 2013) and follow up
discussions and emails with, and additional documentation collected from the following individuals, to which appreciation is hereby acknowledged:
a. Iain Miskimmin: COMIT
b. Neill Pawsey, Ross Dentten, Mark Houghton: Crossrail Limited,
c. Phil Jackson, consultant to UK Highways Agency and Bentley Systems, Inc., d. Julian Schwarzenbach, Data and Process Advantage (consultant to Crossrail
Limited),
e. Ian Childs, Nasir Khawaja, John Woollett, Alex Berry, James Foley: Tube Lines, f. Mark Bew: Engineering Construction Strategies Ltd,
g. Jon Kerbey: hs2, and h. Anne Kemp: Atkins
3. Standards from the International Organization for Standardization (ISO). a. ISO 16759:2012 IFC
b. ISO 15926 Process plant
c. ISO 10303 Express and step standard
The report was initially prepared by Paul Scarponcini and then developed with Nick Nisbet. It is published as a working paper for industry discussion, and for implementers involved with the use-case demonstrations and involved with Government departments.
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2.3 Acronyms
AD4 (CRL) Asset Data Dictionary Definition Document ADMM (HA) Asset Data Management Manual
AIMS (CRL) Asset Information Management System AM Asset Management
AMO (HA) Asset Management Office BIM Building Information Modeling bSa buildingSMART alliance bSI buildingSMART International C/I Civil / Infrastructure
CERL (USACE) Construction Engineering Research Laboratory COBie Construction-Operations Building information exchange CRL Crossrail Limited
CRS Coordinate Reference System DBMS Data Base Management System DfT (UK) Department for Transport ELR Engineering Line of Reference
ERDC Engineering Research and Development Center GIS Geographic Information System
FM Facilities Management
GCS (UK) Government Construction Strategy HA (UK) Highways Agency
HMG Her Majesty's Government
IAM The Institute of Asset Management ie information exchange
IFC Industry Foundation Class
ifcXML, ifc4XML Alternate XML representations for IFC2X3 and IFC4 IM Information Modeling
IS International Standard
ISO International Organization for Standardization LCS (LU) Location Coding System
LRM Linear Referencing Method LRS Linear Referencing System LU London Underground
MMHW (HA) Method of Measurement for Highway Works MVD Model View Definition
NBIMS (US) National Building Information Modeling Standard NIBS (US) National Institute of Building Sciences
NIEM National Information Exchange Model SDO Standards Developing Organization SPFF (IFC) STEP Physical File Format
STEP Standard for the Exchange of Product model data TL Tube Lines
UC Use Case
UML Unified Modeling Language
USACE United States Army Corps of Engineers XML eXtensible Markup Language
XSLT eXtensible Stylesheet Language Transformations XSP Cross Section Positions
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3 COBie
Overview
COBie is “an information exchange specification for the life-cycle capture and delivery of information needed by facility managers” [NIBS-1]. COBie provides a format for the publication of a subset of a building model referred to as a "model view." The definition of this model view (Model View Definition - MVD) is contained in the Facilities Management Handover [NIBS-4]. COBie information can be contained in any of three formats: the IFC STEP Physical File Format (IFC SPFF), ifcXML, or SpreadsheetML. The latter is used by Microsoft Excel™ and most other spreadsheet tools including OpenOffice. Long term, the expectation is that COBie type data would be held in a Data Base Management System (DBMS) from which a spread sheet or other view (report) could be extracted. But as a first step, it was felt that, for people not familiar with the concept of BIM data, spread sheets provide a simple introduction.
Though the expectation is that the spread sheets would be written and read by software, the reason this format was chosen was that it is the easiest to read by humans of the three. But this is relative – the COBie spread sheets are certainly not easily read, especially by novices.
A COBie file (workbook) contains information about a single facility. The COBie Responsibility Matrix [NIBS-5] lays out the spread sheet schema. The schema is spread out across 20 work sheets in the workbook. For newcomers to COBie, it may be easier to look first at one of the three filled out examples [NIBS-8]. The spread sheets include3:
INSTRUCTION – header information and instructions
CONTACT – information about people who create COBie information or act as a SPARE
supplier or a TYPE manufacturer, parts warranty guarantor, or labor warranty guarantor (IfcPersonAndOrganization)
FACILITY – project, site, and building (IfcProject, IfcSite, IfcBuilding) - a distinct operational unit, along with the project and site details.
FLOOR – vertical levels and exterior areas (IfcBuildingStorey) - a primary spatial subdivision SPACE – spaces on a floor (IfcSpace) - a location for activity such as use, inspection or maintenance.
ZONE – sets of spaces sharing a specific attribute (IfcSpatialZone) TYPE – types of equipment, products, and materials (IfcTypeObject)
COMPONENT – individually named or schedule items (IfcProduct)
SYSTEM – sets of components providing a service (IfcSystem)
ASSEMBLY – constituents for TYPES, COMPONENTS (IfcRelAggregates)
CONNECTION – logical connections between COMPONENTS (IfcRelConnectsElements)
SPARE – onsite and replacement parts (IfcConstructionProductResource)
RESOURCE – required materials, tools, and training (IfcConstructionEquipmentResource)
JOB – PM, safety, and other operational plans (IfcTask)
IMPACT – economic, environmental and social Impacts at various stages in the life cycle
(IfcProperty)
DOCUMENT – all applicable document references (IfcDocumentInformation)
ATTRIBUTE – properties of referenced item (IfcProperty)
COORDINATE – spatial locations in box, line, or point format for FLOOR,SPACE or COMPONENT
(IfcCartesianPoint)
ISSUE – other issues remaining at handover (IfcApproval)
PICKLISTS – fixed enumerations and customizable code lists (IfcClassificationReference)
3 Package names appear in upper case; spread sheet / COBie concept names appear in UPPERCAMELCASE
Some of the literature [e.g., NIBS-3] presents these worksheets into DESIGN (FACILITY,FLOOR,
SPACE, ZONE, TYPE, COMPONENT, SYSTEM), BUILD (extending TYPE, COMPONENT and SYSTEM
and adding SPARE,RESOURCE,JOB), and COMMON (CONTACT,DOCUMENT,ISSUE,COORDINATE,
ATTRIBUTE,CONNECTION, IMPACT). These are deliberately overlapping boundaries since some
COMPONENT data is not entered until the BUILD life-cycle phase. Data is collected into the
spread sheets at various steps along the building life-cycle process culminating in the Construction-Operation handover. The essential spread sheets are those contained in DESIGN and BUILD with COMMON spread sheets containing supplementary information.
Within each spread sheet, the columns are pre-defined. They are color-coded to signify whether the column content is required, a reference to another sheet or pick list, an external reference, if specified as required, or secondary information when preparing product data. “Regional, owner, or product specific data may be added as new columns to the right of standard template columns” according to the example spread sheets but information in any such supplementary columns is not checked by the standard quality assurance programs.
The Responsibility Matrix [NIBS-5] workbook contains a Spreadsheet Schema spread sheet with the following information for each COBie spreadsheet column: sheet, column letter, column name, unique key (primary or compound), foreign key, requirement on value (required, system, or as-specified), allowed values (type and maximum length), constraints/notes, IFC object, description, IFC 2.4 URL, and IFC to COBie Notes (issue, object iterations, alternative processing). Though extremely helpful in understanding the COBie schema, it should be noted that the Responsibility Matrix is informative only (not normative).
Optionalities and multiplicities for COBie spread sheet rows are not always obvious nor easily ascertainable from the documentation. For example, the FACILITY spread sheet can only contain a single row – multiple facilities must each appear in its own workbook. A FLOOR can contain
multiple SPACES but each SPACE can only exist on a single FLOOR.
A UML model of the COBie spread sheet schema is being developed [PXS-1] to capture these relationships in a single document. As a Physical Model, it depicts the COBie concepts as they are implemented in the spread sheets. Packaging is introduced for clarity, though again, the boundaries are fuzzy:
class Overview Packages
Build (from COBie2.4) Common (from COBie2.4) Design (from COBie2.4) Design:: Facility Design::Floor Design:: Space Design::Zone Design:: Component Design::Type Design:: System Build::Job Build:: Resource Build:: Spare Common::Contact Common::Document Common::Issue Common::Coordinate Common::Attribute Common::Connection Common::Impact 1..* +floor 1 #spaceNames 1..* 0..* #componentNames 1..* 0..* +space 1 +typeName 1 +typeName 1 0..* #typeName 1..* 0..* +resourceNames 1..*
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Problem Decomposition
The easiest way to solve a complex problem (like the one in Clause 2 above) is to decompose it into smaller, more easily solvable problems. Once these are solved, one can check to see if the original problem has been solved. The Problem Statement is therefore decomposed into a set of smaller problems. Each problem is identified and explained. A discussion about possible solutions follows. Finally, a recommendation is made. The recommendation is based on a simple, short term expedient, typically flagged as short term by the keyword “initially”. Longer term, more complex solution direction may also be included.
3.1
Problem 1: COBie Spread Sheet Format
3.1.1 Problem
Identification
COBie information can be contained in any of three formats, the IFC STEP Physical File Format (IFC SPFF), ifcXML, or SpreadsheetML (open XML schema used by Microsoft Office Excel 2003 and other spreadsheet applications such as OpenOffice.). When people think of COBie, it is usually about the spread sheet version. Compared to IFCs, the COBie spreadsheet is easier to grasp and is therefore often portrayed as a good first step in capturing asset information. It is at least potentially human readable, checkable and editable, though most production is achieved through software mappings and tools.
Because Excel spread sheets are most often used to show COBie data, it is easy to confuse this “view” with the actual internal schema as defined by the FM Handover.
3.1.2 Discussion
With COBie, each facility requires up to 20 spread sheets combined into a single workbook file. Users must realize that the first sheet you see when you open the file is one of many, each accessible by a tab along the bottom of the screen.
Many of the spread sheets are too wide and long to be readable on screen or in print, unless columns and rows are filtered or hidden. Related information may be spread out across multiple spread sheets. To find all of the information relevant to a single COMPONENT, for example, it may be necessary to visit upto10 other sheets: CONTACT, SPACE, TYPE, SYSTEM, ASSEMBLY, CONNECTION,,IMPACT,DOCUMENT,ATTRIBUTE,andISSUE.
If an attribute of an entity in COBie is not pre-defined as a column on any of the spread sheets, the attribute name and value can be added as a row in the ATTRIBUTE spread sheet along with the entity (spread sheet row) the attribute is attached. This means that attributes from any of the rows in all of the other spread sheets appear in this single ATTRIBUTE spread sheet.
There is the potential for redundant or overriding information. Consider a property of a TYPE
(e.g., COLOR) held in a column of the TYPE spread sheet. An instance of TYPE (row in that table) might have a COLOR of “blue”. Perhaps at construction time, only “red” ones are available. It is
possible to override the COLOR value by creating a COLOR ATTRIBUTE for the TYPE in the
ATTRIBUTE spread sheet and giving it a value of “red”. Then the contractor purchases instances
of this TYPE (called COMPONENTS) for installation. To record these instances, rows in the
COMPONENT spread sheet are created. There is no COLOR column for these rows since the
COMPONENT refers back to the TYPE spread sheet for COLOR. However, if you look there, you
find “blue”. You may also look in the ATTRIBUTE spread sheet for the override.Suppose one of the purchased items is actually “green”. Then a COLOR ATTRIBUTE needs to be added to the
ATTRIBUTE spread sheet for just that one COMPONENT. Unless you find the TYPE, COMPONENT,
and ATTRIBUTE rows, you have no idea what the color of each instance is.
Having information structured across different sheets may make it hard to visualize the overall content, especially if the current practice compounds component and type, or system and system classification. Different kinds of data may need to be entered in multiple places. Therefore, if human data entry and review is to be supported, then a more intuitive user-friendly front end needs to be developed. All of the information about an asset, including the lists of supplementary information could be presented to the user as if it were contained on a single spread sheet. This is not the case with the proposed Crossrail AD4’s and the Tube Lines TLF-447’s.
17 v1.3 October 2013 Clearly, where possible COBie content should be generated by the contractor’s software and then read by the owner’s software, with minimal direct human intervention4. If this is indeed the intent, then XML might be a better choice than a spread sheet. It provides a more cohesive structure to the data (albeit it mostly hierarchical) and therefore the information is less scattered. It may be easier for software to interact with an XML file. For example, most civil design software can read and write LandXML. XSLT (Extensible Stylesheet Language Transformations) can be used to translate XML documents into another XML document and thus accommodate schema differences. Transformations and tools exist for mapping ifcXML to and from COBie spread sheets.
COBieLite is a candidate XML representation of COBie designed as an alternative to ifcXML, though closer to ifc4XML. It was born out of a need to support hand-held and remote sensing devices. It “is a National Information Exchange Model (NIEM) compliant XML specification for COBie that simplifies the delivery and use of facility asset information for those outside the typical architects, engineers, builders, and managers who already use COBie in IFC or SpreadsheetML formats.” [NIBS-9].
The Clinic building from the 2012 COBie Challenge [NIBS-8] has been formatted using the COBieLite XSD schema definition. The resultant XML document is about ten times the size as the spread sheet version file and is over 200,000 lines long. Though complex at first glance, the stripped down version included in Appendix A appears relatively straight forward. It obviates the concern about scattered data that is apparent in the spread sheet version. The extract in Appendix A demonstrates all of the schema structure but eliminates all but one occurrence of each COBie concept. Further simplification of the XML schema should be investigated.
COBieLite contains the same information as the spread sheet file. COBieLite’s similarity to ifc4XML may make its future uncertain if it is transferred to buildingSMART International (see
Problem 3: COBie Standard, Discussion, below).
3.1.3 Recommendation
Given the interoperability of IFC, COBie, ifcXML, ifc4XML, COBieLite , other XML schemas such as LandXML, and of generic spreadsheet arrangements, it is of decreasing importance which structured form data is originated in. However the supply chain and demand side need a common target and COBie may fulfil that role. It might be advisable to use any of the above forms as a short term expedient to collect the information to demonstrate how COBie can be used to exchange information on C/I projects from construction to operations.
4 The BIM Task Group believes that “on small projects COBie UK 2012 may also be created or updated by hand directly in the spreadsheet version of the COBie UK 2012 data” [HMG-3]
3.2
Problem 2: COBie Schema
3.2.1 Problem
Identification
Two issues have been raised about the COBie schema which relate to C/I, as well as to buildings. Firstly, packaging into DESIGN, BUILD, and COMMON may be an oversimplification of incremental data drops. Secondly, the asset management view supported may not be consistent with the requirements voiced by the interviewed stakeholders.
3.2.2 Discussion
3.2.2.1 Packaging
[NIBS-3] uses the following graphic to provide a high level view of when each COBie concept (spread sheet) is relevant during the facility life-cycle:
Treating DESIGN, BUILD, and COMMON as packages may be inappropriate, as they are not mutually exclusive, and not all inclusive. It makes sense to have TYPE andCOMPONENTS under DESIGN because TYPE provides the requirements for COMPONENTS. COMPONENTS are
instances which eventually get serial numbers and installation date and therefore logically are also included in BUILD which is why orange BUILD overlaps into DESIGN. Similarly TYPE assets may become products with known manufacturer and model numbers.
The COMMON items are intended to be “supplementary” and include ASSEMBLY and IMPACT at
COBie 2.4. CONNECTIONS can connect either TYPES or COMPONENTS. ASSEMBLY aggregates TYPES or COMPONENTS. CONNECTION and ASSEMBLY are “supplemental” in the sense that they are optional, and reference the DESIGN and BUILD assets. Various Operations such as maintenance, start-up, shut-down, inspection and so on) are documented in the JOB package. This reflects the constructor’s responsibility to handover the operational information for the products in the facility.
Some of these questions are answered in the FM Handover [NIBS-4] which provides further refinement of the life-cycle processes and allocates schema content based on this further refinement.
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3.2.2.2 Asset View
Perhaps the biggest complaint about the COBie schema, is that it does not support the asset management perspective voiced by the interviewed stakeholders. Both CRL [CRL-1] and Tube Lines speak in terms of a requirement for an asset vs. the fulfillment of that requirement with an actual asset instance. This separation enables the installation of any of a set of supplied assets anywhere that they fulfill the requirement. More significantly, this separation supports the notion of substitution of asset instances over time (temporary or long-term) when the requirements themselves have not changed. The key to the success of this strategy is to not over specify the requirement (e.g., mandating a particular manufacturer’s model) but to allow “approved equals” to meet a more loosely defined requirement.
The requirement for an asset includes classification of the asset type. This is implemented in COBie as TYPE.CATEGORY and SYSTEM.CATEGORY. TYPE.CATEGORY is specified by OmniClass Table 23 (category-product PICKLIST) or Uniclass L classification, supporting a
maintenance view.
However, from the interviewed stakeholders’ perspective, an asset requirement also specifies function. Function is the duty performed by the asset (e.g., building structure) and supports an operator’s view. In COBie, SYSTEM is a functional aggregation of COMPONENTS.
SYSTEM.CATEGORY is specified as OmniClass Table 21 (category-element PICKLIST), or Uniclass G/H supporting a functional view.
Also from the client perspective, an asset requirement also specifies location. This is discussed below.
CRL calls the combined classification (TYPE category) / function (SYSTEM category)/ location (SPACE) requirement an Asset Tag. So a boiler TYPE (with product category) to be located in the basement SPACE (location) is required to provide heating SYSTEM (with function category). Most of the information defining an asset tag is held in COBie in each COMPONENT row: the COMPONENT, the TYPE, the SPACE. Only the SYSTEM assignment(s) are held separately, pointing to the COMPONENT.
A COMPONENT can have a serial number and an installation date so it also behaves as an asset
instance fulfilling a particular asset requirement at some point in time. It has a COBie TYPE as the asset requirement with a product classification and it is in a SPACE (location) as part of a
SYSTEM (function). It can be substituted for another like COMPONENT if necessary, without
changing the asset requirements defining its classification, location and function. This matches the CRL notion of a Serialization: a specific instance of Equipment (TYPE) that exists at the Asset Tag location at a particular point in time and characterized by a serial number or batch number.
Equipment (TYPE) ultimately may represent a specific manufacturer’s model which can fulfill the requirements defined by the Asset Tag. Equipment will therefore have a manufacturer and model. COBie holds the manufacturer and model with the TYPE, not COMPONENT. What you really want to be able to do is swap out a piece of equipment (not just a serialization) that satisfies the Asset Tag requirement. In other words, you may wish to use the same type of thing, an “approved equal” that has a different model number and is from a different manufacturer. This takes substitutability beyond just being a new instance of the same manufacturer/model but having a new serial number. With COBie, this would need to be a new TYPE so you have to go back and re-define the asset requirement, not just the fulfilling asset instance. So perhaps COBie TYPE is over specified.
A distinction is being made regarding cast-in-place assets. They have classification, location, and function so constitute what CRL is calling an Asset Tag. However, the notion of substitutability does not apply. Because they were cast in place, there are no equivalent items from a manufacturer that can be brought in to replace them. In this case, CRL would not have an Equipment or Serialization for this Asset Tag [CRL-2].
The Figure below shows a correspondence between COBie TYPE, COMPONENT, SYSTEM, and SPACE and CRL Asset Tag, Equipment, and Serialization.
Bottom line is that all of the client required information is in the COBie schema, but not necessarily in the preferred place.
The disparity in where information is located, as seen in the above figure, is exacerbated by the already scattered nature of the spread sheet layout presented as Problem 1: COBie Spread Sheet Format above. It is further complicated when an attempt is made to aggregate assets into nestable groups.
COBie 2.4 introduces ASSEMBLY as an aggregation of either TYPES or COMPONENTS. It is defined
as having a single parent TYPE or COMPONENT with multiple child TYPES or COMPONENTS, respectively. The parent is itself either a TYPE or COMPONENT, appearing in that spread sheet. This enables nesting of ASSEMBLIES.
CRL has Functional Units as aggregations of Asset Tags. Since Functional Units are Asset Tags themselves, nesting is possible. Furthermore, as an Asset Tag, they represent an asset requirement which can then be fulfilled: “If a system has been supplied as a single entity and has a specific manufacturer’s number, for example, lifts and escalators, then Equipment will be created against the Functional Unit to record these details.” [CRL-1]
On the surface then, it appears that a COBie ASSEMBLY is equivalent to a CRL Functional Unit. However, because of the differences between the COBie TYPE,COMPONENT,SYSTEM,andSPACE
and the CRL Asset Tag, Equipment, and Serialization, the relationship between COBie
ASSEMBLY and CRL Functional Unit is even less straight forward from an asset management
point of view.
One could argue that COBie is only an information exchange and therefore, as long as it contains all of the necessary information, it fulfills its role. It is the responsibility of the contractor’s software to create the COBie file and the owner’s software to be able to read it. Therefore, it is the responsibility of the CRL software to map COBie TYPES, COMPONENTS,
SYSTEMS, SPACES, and ASSEMBLIES into CRL Asset Tags, Equipment, Serializations, and
21 v1.3 October 2013 However, if an asset-oriented view is being introduced earlier on in the life-cycle, then designers and contractors should be aware of the distinction between asset requirement and fulfilment. This then means they are forced to distribute the asset-oriented information across incompatible COBie spread sheets. Because this will be less intuitive to them, there would be higher risk for error. This is further exacerbated by the data fragmentation enforced by the COBie spread sheet layout. It does not make sense to map from an asset view into a COBie view when writing the COBie file only to have to map back to the asset view when reading it.
3.2.3 Recommendation
One proposal considered would be that Columns of MANUFACTURER and MODELNUMBER should be moved from TYPE to COMPONENT, or else they should be relabeled as
EXAMPLEMANUFACTURER and EXAMPLEMODEL. EQUIPMENT (and perhaps CAST-IN-PLACE) needs
to be added, preferably as part of a new Operate package. Serial number would then be moved from COMPONENT to EQUIPMENT. Then COMPONENT truly does become the asset requirement (Asset Tag) and EQUIPMENT and CAST-IN-PLACE are the fulfillment of that requirement.
However The following two short term recommendations are made to use the COBie schema to better suit the requirements voiced by the interviewed stakeholders.
Firstly to address the desire to separate the requirements on a Component from the fulfilment 1. TYPE can hold both requirement Types and product TYPES: Extend the AssetType
enumeration to offer Requirement in addition to the current Fixed (Cast-in-place) or Moveable (Equipment). A ‘requirement’ type is not expected to be purchased, but may be compared against the available TYPES.
Secondly to document the allowed substitutions of one Component for another, or for one Type for another.
2. Add column to the TYPE.AllowableSubstitutions
a. This field then documents equivalent product TYPEs that satisify the requirement
b. This is only expected on ‘Requirement’ TYPEs c. This is blank for cast-in-place TYPEs
d. This is blank for manufactured product TYPEs
3. Add column to the COMPONENT rows to document COMPONENT.RequirementType a. COMPONENT TypeName remains the installed Type
Long term, a proper data modeling exercise should be done for the information exchange, including accommodation for the impact of C/I projects and an asset management view. If multiple schemas persist, then perhaps ISO 15926 should be evaluated as a possible solution for handling them.
3.3
Problem 3: COBie Versions
3.3.1 Problem
Identification
It is difficult to say what exactly constitutes the COBie standard. It suffers from distributed, dynamic documentation, suspect version control, and distributed governance.
3.3.1.1 Documentation
COBie has not been formally standardized as an ISO standard. Meanwhile aspects of the COBie standard are distributed across the internet. The references section of this document attempts to capture the most significant of these various documents. [NIBS-1] introduces COBie. [NIBS-3] provides an overview and links to other relevant internet sites. [NIBS-2] Clause 4.2.4 appears to be the official balloted COBie 2.26 standard in the US but is at too high a level to be implementable by itself. Instead, it cites the ISO/PAS 16739:2005 [ISO-1] industry foundation class (IFC) model and the FM Handover MVD [NIBS-4] as normative references. An extensive Bibliography includes (non-normative) references to some 38 other documents, describing the development and application of COBie. Critical among these are the COBie
Responsibility Matrix [NIBS-5] and the COBie Guide [NIBS-6], but these are assumed to be informative only.
The COBie Responsibility Matrix [NIBS-5] lays out the spread sheet schema but is missing some key optionality’s and cardinalities between concepts (spread sheets). It also enables the allocation of responsibility for populating the spread sheets at different stages in the project life-cycle. Unfortunately, it keeps getting updated (now at version 16) with no indication (or availability) of the version that goes with the balloted COBie 2.26.
The COBie Guide [NIBS-6] is extremely helpful for elucidating schema details missing from the
Responsibility Matrix. Unfortunately it remains a document in progress. Being non-normative, it suggests further requirements (e.g., provision of CURRENT, VOLTAGE, and FREQUENCY attributes to electrical TYPES).
It has been suggested that “the open standard Schematron-based source code for the COBie tool kit that shows the -exact- testing of data integrity checks that are being done in the COBie Tool Kit” would be a good source for further information about the schema. This source has yet to be checked. If different to content elsewhere then this content should be included in a part of the normative standard. It would not have been voted upon as part of the standard’s acceptance by NBIMS-US since was developed after [NIBS-2].
3.3.1.2 Version Control
COBie version 2.26 was adopted last year as a standard in the US as part of the National BIM Standard-United States™ Version 2 [NIBS-2]. It is based on the FM Handover which uses IFC 2x4. However, this version of IFC was not approved until this year.
For International acceptance, additional functionality has been added (e.g., ASSEMBLY and
IMPACT worksheets) as COBie 2.4 (sometimes cited as 2.405) [NIBS-7]. The additions are
backward compatible with COBie 2.26, and do not alter the existing structure. COBie 2.4 is being balloted in the US as part of NBIMS-US V3 during the summer of 2013. COBie UK 2012 [HMG-2] expects COBie 2.4, although some documentation references to earlier COBie 2.26 material. Versions of the Responsibility Matrix do not appear to be coordinated with versions of the standard.
The following changes were introduced between COBie 2.26 and COBie 2.4 . There is 1. Additional columns on the Type sheet .
2. Introduction of the Issues sheet for H&S and other concerns
3. Introduction of the Impact sheet for cost, carbon and other environmental measures affecting stages of the asset life-cycle.
5 Excel would show 2.40 as 2.4 if the cell format specified one decimal place. This may be the origin of this confusion. Or it could really be 2.4 since it implements IFC 2x4. From a versioning viewpoint, it is confusing that 2.4 would follow 2.26.
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3.3.1.3 Governance
COBie is jointly controlled by buildingSMART alliance (North America) and buildingSMART UKI (UK and Ireland) under a Memorandum of Understanding. It was originally developed in the US at the US Army Corps of Engineers (USACE) Engineering Research and Development Center (ERDC) Construction Engineering Research Laboratory (CERL) and approved as a NBIMS-US V2 standard under the buildingSMART alliance, a council of the National Institute of Building Sciences.
The COBie UK 2012 site [HMG-1] is hosted by the Building Information Modelling (BIM) Task Group, a part of HM Government Department for Business Innovation & Skills. The SDO for COBie UK is buildingSMART UKI. The site directs you to [NIBS-1], [NIBS-4], and [NIBS-5] for details on the standard. Discussion
COBie 2.4 includes international input.
The FM Handover is updated for COBie 2.4. It is derived from the full ISO 16739:2013 IFC standard by:
1) filtering out only those IFC’s needed for the COBie information exchange 2) adding appropriate constraints
The new FM Handover is interactive, facilitating search and internal links. As a normative reference for COBie 2.4, it should provide the complete COBie schema definition.
An NBIMS US Technical Committee member has stated that CERL funding has been reduced and therefore buildingSMART International (bSI) will be taking over COBie. Neither bSa, bsUKI or bSI has not yet adopted COBieLite, an XML version of COBie.
buildingSMART International have their own ifc4XML, which implements an international standard ISO-10303 part28 ed2. . There has a mechanism for creating simplified subsets reflecting selected hierarchies and relationships. It is not apparent what will happen to COBieLite if COBie moves to bSI.
3.3.2 Recommendation
It appears as though COBie 2.4 may become a more proper standard. It would therefore seem prudent to focus on it instead of 2.26. This will also form the basis for the proposed BS1192:4:2014 document.
3.4
Problem 4: COMPONENT Geospatial Location
3.4.1 Problem
Identification
C/I projects also tend to have larger spatial extents than individual building projects. Individual C/I managed assets typically exist across a much broader spatial extent than do building assets. It is no surprise then that Geographic Information Systems (GIS) play a more significant role in C/I asset management [IAM-1].
C/I components may be located at a geospatial position or by using a geospatial feature. Use of a geospatial position requires the specification of a Coordinate Reference System (CRS) which is typically more global than a local Cartesian building coordinate system.
COBie needs to be able to store information about geospatial locations for use in locating components. Examples of geospatial features include station footprints, areas of interest or sensitivity (e.g., sound levels), and buffers around linear features.
Also from the client perspective, an asset requirement also specifies location. Location defines where the asset is to be located in support of the building manager’s view. COBie specifies locations as SPACES.
3.4.2 Discussion
The FM Handover MVD, upon which COBie is based, is limited to “non-geometric building information” [NIBS-2], but nonetheless does support some geometric information. Alternatively This information may be held separately in a GIS or geospatial database, like Oracle Spatial, just as CAD drawings and 3D building models are held in external systems separate from the COBie spread sheets.
COBie currently allows the locating of components in both a spatial hierarchy and also in a coordinate hierarchy. Geospatial support needs to be added.
3.4.2.1 Existing Spatial Hierarchy
COBie needs to be able to specify where COMPONENTS are located. In accordance with IFCs, containment is achieved via an assignment of a COMPONENT to a SPACE, where SPACES are contained on FLOORS without defining their precise geometry.
In order to respect the generalized spatial hierarchy, COBie for C/I could retain the Facility-Floor-Space structure and allows C/I projects to use Floor as a synonym for Region and Facility-Floor-Space as a synonym for Location. As an example, The COBie Guide [NIBS-6, pg. 20] offers the following recommendation for site features:
For each facility compound or campus with shared site work, a separate COBie file shall be submitted. A single COBie.Floor row will be created for this site file and identified as a COBie.Floor.FloorType of “Site.” Definable areas within that site will be identified in rows in the COBie.Space worksheet. Examples of typical COBie.Space rows within COBie.Floor=Site’s are parking lots, utility pads, loading docks, etc… The default list of Site spaces that shall be included for a given client are identified in Appendix A.
This informative advice is in direct contrast to the normative FM Handover which states that “Spaces are areas or volumes that provide for certain functions within a building.” [NIBS-4, 5.3.3.43 IfcSpace], and “A building storey has an elevation and typically represents a (nearly) horizontal aggregation of spaces that are vertically bound.” [NIBS-4, 5.3.3.5 IfcBuildingStorey] – (underlining added for emphasis). Elsewhere the generalized concept of the spatial hierarchy makes clear that spaces may occur within the site.
It should be noted that all COMPONENTS must be located in a SPACE, even if they are located
more precisely with COORDINATES.
3.4.2.2 Existing Coordinate Support
Currently in COBie, COORDINATES can be defined for SPACES , FLOORS AND COMPONENTS. Coordinate types as an enumeration are limited to “point”, “line-end-one”, “line-end-two”, “box-lowerleft”, and “box-upperright”. Any type of point can be used with any of these objects.
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3.4.2.3 Geospatial Coordinates
The identified need is to use a single point location, specified by its coordinates, to locate a
COMPONENT. This can be solved by the COORDINATE spread sheet. This sheet includes
specification of X, Y, and Z coordinates for COORDINATETYPE = “point”.
This leaves the Coordinate Reference System(s) – CRS. This could be done as a property at the facility level if all points have the same CRS. Otherwise this could be specified as the facility default geospatial CRS which can then be overridden with a property of the coordinates for individual points.
These CRS properties can either be added as columns to the FACILITY and COORDINATES spread
sheets or as attached attributes in the ATTRIBUTE spread sheet. But it is probably reasonable to expect that there is some area within which these COORDINATES exist and this can be used to satisfy the COMPONENT SPACE requirement.
On a similar note, COBie says that SPACES occur on a FLOOR in a FACILITY. Renaming FLOOR to
REGION with floor as one type of REGION would allow the preservation of the COBie spatial
hierarchy whilst still supporting this C/I requirement. Even in C/I, there is most likely some physical area breakdown of a FACILITY before getting to the more specific LOCATION.
3.4.2.4 Geospatial Feature Location
Following the advice in the Guide, the geospatial locations should be treated as COBie SPACES.
COMPONENTS can then be specified as occurring in these geospatial “spaces”. Perhaps SPACE
can be renamed LOCATION. This would accommodate geospatial locations that are points, curves, surfaces, solids, and collections of these. This would also help with linear locations (see 4.5, Problem 5: COMPONENT Linear Location, below).
Again, by renaming FLOOR to REGION with floor as one type of REGION would allow the preservation of the COBie spatial hierarchy whilst still supporting this C/I requirement. Even in C/I, there is most likely some physical area breakdown of a FACILITY before getting to the more specific geospatial feature LOCATION.Fortunately, most GIS and geospatial databases today
conform to ISO TC211 and OGC software standards. These standards prescribe a feature model where a feature instance is the representation (abstraction) of some real world phenomenon, such as a building, a road or a catch pit. Hierarchically structured feature classes define properties for features. Geometry/location is one of these properties and can occur zero or more times per feature instance. Feature instances have a unique id within some scope. The result of this is that the geometry/location can be kept in the GIS or geospatial database and then be referenced by COBie via the feature id. Though multiple geometry/locations can exist for the same feature id (e.g., a tube station can be represented as a point or a polygon), COBie probably does not need to concern itself with this level of detail.
Mandatory columns in the SPACE spread sheet are: NAME, CREATEDBY, CREATEDON, CATEGORY,
FLOORNAME, and DESCRIPTION. The NAME would be the COBie name used to refer to the
geospatial feature. It would be the SPACE name contained in the COMPONENT spread sheet. It
may not be the same as the geospatial feature name in the GIS or geospatial database (see external discussion below).
The FLOORNAME refers to the building floor in the FLOOR spread sheet. As suggested above, if
FLOOR is renamed REGION, then this column becomes REGIONNAME. The allowable values for
the CATEGORY column in the FLOOR spread sheet will need to be expanded, but currently does
include “floor”.
The CATEGORY is currently limited to the SpaceFunctionClassification code list for
Category-Space. This most likely will need to be expanded beyond just building-oriented spaces. The remaining mandatory columns are already sufficiently generic to support C/I.
Optional columns are ROOMTAG, USEABLEHEIGHT, GROSSAREA, NETAREA, EXTSYSTEM,
EXTOBJECT, and EXTIDENTIFIER. The first four of these are building-oriented but are not a
problem since they are optional and can therefore be ignored for C/I. The external columns can be used as the (GIS or geospatial database) source of the SPACE information. The EXTSYSTEM
column could be used to specify the GIS or geospatial database. Then EXTOBJECT could be used to specify the feature class except that it is currently restricted to ifcSpace Class Name so the pick list would have to be extended for C/I. The EXTIDENTIFIER could be used to specify the feature id in the GIS or geospatial data which may or may not be the same as the SPACENAME. i.e., the COBie geospatial feature name.
Because the geometry of the geospatial feature is retained in the GIS or geospatial database, it may not be necessary to include the CRS in the COBie file. This could be problematic anyway, if a feature has multiple geometric representations and they are not all in the same CRS.
3.4.3 Recommendation
The short (and long) term recommendation is to work within the existing COBie schema structure:
1. Provide more generic names for the Floor and Space spread sheets to support C/I facilities by supporting synonyms:
a. spread sheet FLOOR and REGION;
b. columnFLOORNAME AND REGIONNAME;
c. spread sheet SPACE to LOCATION;
d. columnSPACENAME AND LOCATIONNAME
2. For locating a COMPONENT by geospatial point coordinates:
a. the coordinates shall be entered into the COORDINATES spread sheet and
attached to that COMPONENT
b. an optional FACILITYCRS column needs to be added to the FACILITY spread sheet or as an ATTRIBUTE of the FACILITY
c. an optional overriding CRS column may be needed to be added to the
COORDINATES spread sheet.
3. For locating a COMPONENT using a geospatial feature: a. the feature shall be uniquely named in COBie
b. the feature shall be entered as a row in the SPACE/LOCATION spread sheet
c. then referenced in the COMPONENTSPACE/LOCATION column
d. the feature geometry and CRS will not be copied into the COBie file
e. the EXTSYSTEM, EXTOBJECT and EXTIDENTIFIER columns in the SPACE/LOCATION
spread sheet can reflect the geospatial database or GIS from which the feature geometry (and CRS) can be obtained.
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3.5
Problem 5: COMPONENT Linear Location
3.5.1 Problem
Identification
Many C/I managed assets tend to be linear (roads, rail) and project components consequently tend to be linearly located along existing or proposed linear assets, instead of within spaces on floors in buildings. Such locations can be specified using linearly referenced locations. In accordance with ISO 19148 [ISO-2], a linearly referenced location requires the specification of the linear entity along which a measurement is made, the method of measurement called a Linear Referencing Method (LRM), and the measured value along (and optionally offset from) the linear entity. See Appendix B for examples.
COBie would need to store information about linear entities along which COMPONENTS are
located and possibly about LRMs. The COMPONENTS being located would then require an “at” linearly referenced location or else “from” and “to” linearly referenced locations as alternatives to space or geospatial locations.
3.5.2 Discussion
A linearly referenced location requires three components (linear element, LRM, and measured value which may include offsets) [ISO-2]. To use linear referencing to locate a COMPONENT, that is, with respect to a linear entity, one or two linearly referenced locations are required. The
COMPONENT may either be at a single linearly referenced location or from one linearly referenced
location to another. In the latter case, this may be simplified by adding constraints on the two linearly referenced locations, such as requiring a common LRM or even a common linear element, but this is not without compromising the full flexibility of ISO 19148.
3.5.2.1 Linear Element
Linearly referenced locations must specify the linear element along which the measurement is made. This is similar to an axis in a CRS (though the LRM and measurement can be quite different than just a single numeric value). Somewhere COBie will need to keep a list of allowable linear elements. These may be assets (COMPONENTS) such as a road. More likely, they will be some reference line, such as an Engineering Line of Reference (ELR) in the case of Network Rail, a London Underground (LU) Location Coding System (LCS) coded entity in the case of Tube Lines, or a Section [HA-2] in the case of the UK Highways Agency.
In keeping with the COBie Guide’s strategy of using SPACES to locate COMPONENTS regardless of the location type, linear elements would end up in the SPACES spread sheet. Aside from needing to expand the list of allowable SPACE categories, this would work if you can live with the
notion of one-dimensional spaces. However, ISO 19148 [ISO-2] requires that linear elements support a measurability interface which, in the case of a data-only representation, would entail certain mandatory attributes. These include a default LRM, default (overall) length, and start values for each expected LRM. The type of linear element (feature, geometric curve, or topological edge) must also be specified. These would have to be added as ATTRIBUTES. Alternatively, a LINEARELEMENTS spread sheet could be proposed as an additional spread sheet in the COBie workbook, with columns for NAME, CREATEDBY, CREATEDON, CATEGORY (“feature”, “curve”, or “edge”), DESCRIPTION, EXTSYSTEM, EXTOBJECT, EXTIDENTIFIER, DEFAULTLRM,
DEFAULTLENGTH, and STARTVALUES. The last one is tricky, as it would need to be a list of (LRM,
startValue) pairs. Assigning a FLOORNAME to SPACES would be problematic, since the linear element may not be wholly contained within the Site defined by the FACILITY, for example, I-95 or the M-1. Perhaps a more global region beyond the scope of the facility should be allowed? If a relative LRM (e.g., reference post) is to be used to measure along a linear element, then the referents from which the measurements are made must be at known locations along the linear element. ISO 19148 prescribes that these referents be “owned” by the linear element. If, as part of an automated reading of a COBie file, linearly referenced locations need to be translated into locations that use a different LRM or linear element, referent locations along their owning linear elements need to be available, presumably from the COBie file.
3.5.2.2 LRM
The Linear Referencing Method (LRM) specifies how measurements are made. The LRM provides a context for the measured value, specifying how (absolute, relative, interpolated) the measurement is made (including the unit of measure).
During design and construction and often in maintenance/operation of railways, an absolute type of LRM called stationing is common. This says that a measured value of 1+05 means 105 feet measured along a linear element such as an engineering survey line or ELR, measured from its beginning (or 105 meters for a metric stationing LRM). Another absolute type of LRM is chainage which says that a measured value of 1023 means 1023 meters along a linear element such as a roadway or LCS section, measured from its beginning. In some cases, a more literal interpretation of “chainage” is used such that the unit of measure is “chains”.
A relative type of LRM, milepost, says to interpret a measured value of 2+.50 as one half (.50) mile beyond milepost 2, the post being exactly 2 miles from the start of the linear element being measured. More likely, another relative type of LRM called reference post would be used because it would allow reference post 2 to be something other than exactly 2.000 miles from the start of the linear element perhaps due to realignment. This demonstrates the need to have pre-defined the location of the referent (referent post 2 in this case) from which the measured along incremental distance (.50) is to be measured.
Percentage is an interpolated type of LRM which says that a measured value of .50 means 50% of the distance along the linear element. This would be based on the default length value of the linear element.
For greatest flexibility, the LRM of each linearly referenced location should be specified as part of that location specification. However, this is typically simplified by adopting a default LRM for each linear element or even for the FACILITY at large. This decision will impact where LRM is held: with each linearly referenced location, with each linear element, or with the FACILITY. Though ISO 19148 is adamant about de-coupling the LRM from the linear element, the standard will allow a linear element to have a default LRM which will be used to measure the linear elements in the absence of an explicitly stated LRM.
In accordance with ISO 19148, the specification of an LRM includes the following attributes: name, type (“absolute”, “relative, “interpolative”), units, constraints, and, if it supports offsets, then additionally offset units, positive lateral offset direction, and positive vertical offset direction. Unfortunately, there is no universal agreement on what LRMs are called or what each one means. If they are to be defined in COBie, an LRM spread sheet would need to be added, with the normal COBie columns like CREATEDBY plus columns to support the above listed attributes.
Otherwise, like geospatial location CRSs, the definition can be held outside of COBie proper, perhaps even in a COBie DOCUMENT. This decision would be dependent upon the variety of LRMs used and the requirement that, as part of an automated reading of a COBie file, linearly referenced locations need to be translated into equivalent locations that use a different LRM.
3.5.2.3 Measured Value
Based on the LRM, the value of the distance measured along the linear element might be a numeric value (e.g., chainage LRM) or an alphanumeric string (e.g., reference post LRM). The units of measure are defined by the LRM.
Presumably, the measured distance along would be an attribute of the COMPONENT, either as a newly added COMPONENT column or as an ATTRIBUTE with a SHEETNAME = “Component” and a ROWNAME equal to the COMPONENT.NAME. ATTRIBUTE.UNIT would only be used to override the LRM units value.
3.5.2.4 Offsets
Once the measured value is measured along the linear element, it is possible to then measure an offset distance to arrive at the linearly referenced location. ISO 19148 supports optional lateral (perpendicular left or right) offsets and vertical (up or down) offsets or offset vectors measured in any direction. The first two can be measured absolutely from the linear element position established by the measured along distance or can be relative from some offset referent, such as “five feet back of sidewalk” [see ISO-2].
