ArcGIS Pipeline Data Model Version Core Abstract and Core Classes

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1 ArcGIS Pipeline Data Model Version Core Abstract and Core Classes An ESRI Technical Paper ESRI 380 New York St., Redlands, CA , USA TEL FAX info@esri.com WEB

2 Copyright 2007 ESRI All rights reserved. Printed in the United States of America. The information contained in this document is the exclusive property of ESRI. This work is protected under United States copyright law and other international copyright treaties and conventions. No part of this work may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying and recording, or by any information storage or retrieval system, except as expressly permitted in writing by ESRI. All requests should be sent to Attention: Contracts Manager, ESRI, 380 New York Street, Redlands, CA , USA. The information contained in this document is subject to change without notice. U.S. GOVERNMENT RESTRICTED/LIMITED RIGHTS Any software, documentation, and/or data delivered hereunder is subject to the terms of the License Agreement. In no event shall the U.S. Government acquire greater than RESTRICTED/LIMITED RIGHTS. At a minimum, use, duplication, or disclosure by the U.S. Government is subject to restrictions as set forth in FAR Alternates I, II, and III (JUN 1987); FAR (JUN 1987) and/or FAR / (Commercial technical Data/Computer Software); and DFARS (NOV 1995) (technical Data) and/or DFARS (Computer Software), as applicable. Contractor/Manufacturer is ESRI, 380 New York Street, Redlands, CA , USA. ESRI, the ESRI globe logo, ArcCatalog, ArcGIS, ArcIMS, ArcMap, ArcObjects, ArcPad, ArcSDE, ArcToolbox, are trademarks, registered trademarks, or service marks of ESRI in the United States, the European Community, or certain other jurisdictions. Other companies and products mentioned herein are trademarks or registered trademarks of their respective trademark owners.

3 ArcGIS Pipeline Data Model Version 4.0 Abstract and Core Classes An ESRI Technical Paper Contents Page Forward... 1 Executive Summary Introduction What Is the APDM? Why Use the APDM? The Business Case The Technical Case History of the APDM APDM Steering Committee APDM Technical Committee Difference Between a Standard and a Template Design Rationale Core Elements Stationing and Station Equations Distance Based Arbitrary (Pseudo-distance Based) The Centerline (Routes, Measures, and Events) Hierarchy Coincident Geometry Events Versus Features APDM Conceptual Model APDM Abstract Classes/Metadata Overview APDM Abstract Classes What is an abstract class? Why are abstract classes used? Duplication of Attributes within APDM abstract classes Inheritance (How to read the APDM Logical Model Poster) Abstract Class Definitions APDMObject ObjectArchive CenterlineObject ESRI Technical Paper i

4 Contents Page NonFacilityObject FacilityObject FeatureArchive CenterlinePolyline CenterlinePolylineEvent CenterlinePoint OfflineFeature OfflinePoint OfflineFacility OfflineNonPointFacility OfflinePointFacility OnlineFeature OnlinePolyline OnlinePolylineForOfflineFeature OnlinePoint OnlinePointForOfflineFeature OnlineFacility OnlinePolylineFacility OnlinePointFacility Fitting APDM Metadata Class-level Metadata ReferenceMode APDMClass OnlineLocationClass Feature-level Metadata Online Event Feature-Level Metadata Attributes ControlPoint Feature-Level Metadata Attributes APDM Core Classes and Relationships EventID Core Object Classes Activity ActivityHierarchy AltRefMeasure <class name>audit Company ExternalDocument LineLoop LineLoopHierarchy OwnerOperator Product SubSystem ii

5 Contents Page SubSystemHierarchy Core Feature Classes ControlPoint Site StationSeries SubSystemRange APDM Core Domains Required Domains gnoperationalstatus gnstatus clstationeditresponse clxyeditresponse clzeditresponse gnonlinelocationmechanism gnhistoricalstate gnangle cleditresponse gnapdmclasstype gnrefmodebasis gnrefmodetype gnrefmodeunits gnyesno gnrequiresgeometry APDM Compliance Non Geometric Features Topology Centerline Structure Implementation Issues The APDM and Inline History Inline History Implementation Using the APDM in a Versioned Geodatabase Environment Features as Events, Events as Features Topology and the Geometric Network Developing Applications The APDM and Other Pipeline Data Models Conversion To/From PODS and ISAT Getting Data into the Model Model Future Appendix A - Standards and Conventions Naming Conventions Class Names ESRI Technical Paper iii

6 Contents Page Foreign Keys Use of Feature Datasets Maximum String Size Documentation Standards Object or Feature Class Attributed Relationship Class Appendix B - Glossary A B C D E F G H I J K L M N O P Q R S T U V W X Y Z Appendix 3 APDM 3.0 to APDM 4.0 Conversion Utility Script Disclaimer ConvertAPDM3to iv

7 Forward It has always been the intent of the ArcGIS Pipeline Data Model (APDM) Technical Committee to keep pace with the technology released by Environmental Systems Research Institute (ESRI). One of the primary purposes of the APDM is to explore how ESRI technology can be best utilized for the pipeline industry. Every year ESRI unfolds new approaches to spatial analysis, new data structures, and new desktop and server tools. These new capabilities impact the APDM in wonderful and challenging ways. The question often arises When will the APDM become stable? The uniform response is It is stable, but it will always evolve. It is fair to say that the APDM Version 4.0 represents a significant step forward from the APDM Version 3.0. The APDM Version 1.0 strove to capture the salient information about the pipeline world. Version 2.0 sought to define the APDM as a customizable template that could be extended to meet end user needs, and Version 3.0 sought to refine the information captured in the previous two releases and align it with the ArcGIS 9.0 technology offered by ESRI. The focus of Version 4.0 has been to define, capture and store the behavior of pipeline systems, particularly that of reference modes (stationing) and response to centerline editing. In addition, Version 4.0 is designed to take advantage of ArcGIS 9.2 technology. A byproduct of encapsulating behavior is the concept and rule of APDM compliance. As more operators adopt the APDM and more vendors develop applications for the APDM, the need for interoperability becomes paramount. Interoperability can be loosely defined as the exchange of and description of data, schema and behavior between different implementations, and within a single APDM implementation. A requirement for interoperability is compliance to the rules of the APDM. What was called the core in the APDM 3.0 is still the core in the APDM 4.0. Core refers to those schema items that are required. What were called the conceptual classes in the APDM 3.0 are now referred to as abstract classes in the APDM 4.0. The abstract classes denote the set of required attributes, domains and relationships that make an APDM 4.0 model compliant. The APDM 4.0 abstract classes are expanded and refined in comparison to Version 3.0. The whitepaper, the logical model diagram and the physical Unified Modeling Language (UML) model have all been re-worked to consistently reflect the compliance structure within the APDM. If all feature and object classes within a particular APDM implementation properly inherit from the APDM abstract classes and metadata structures, then the implementation is considered compliant. Compliant APDM implementations facilitate data sharing and easier application development since the root behavior is now defined within the model. Essentially, the APDM Version 4.0 still adheres to the principal that an end user editing and updating features within an APDM geodatabase can do so using out-of-the-box ESRI software tools. ESRI Technical Paper 1

8 Another question common to operators considering adoption of the APDM is whether any one vendor owns the APDM and controls it. The answer to this question is Yes, ESRI owns the APDM. However, while ESRI owns the APDM, control of the APDM rests with the pipeline industry at large via the APDM Steering and Technical committees. ESRI does not consider itself a standards body, nor does the APDM consider itself a standard data model. The APDM is available on the web for free to all ESRI users ( The model is open to everyone, even to competing interests. The APDM is founded on the supposition that an open and free model, supported by the volunteer efforts of ESRI pipeline users, will confer lasting benefits on the entire ESRI pipeline community. The goal of the APDM is to publish a data model that can be used to facilitate consensus and interaction between various pipeline interests working with ESRI technology. The APDM is a template-based model (just like every other model available from ESRI) that works on a common abstract model that can be expanded to suit the needs of any pipeline operation. This allows operators to create value-added data model implementations that can support the tools and applications specific to their organization, and yet still remain APDM compliant. Lastly, you will soon discover the APDM is rife with its own peculiar, pipeline-specific terminology and nomenclature. Every effort has been made to present the material in a readable and understandable fashion. This document contains a wealth of information describing the structure, content and semantic behavior of the APDM. Please let us know if the material requires revision or clarification. Submitted on behalf of the APDM Technical and Steering Committees. May,

9 Executive Summary Today s pipeline operating environment is more demanding than ever. In order to be successful, pipeline companies must not only provide a competitive return on investment to shareholders, but also ensure healthy relationships with other stakeholders including regulatory agencies, the public at large, emergency responders, environmental interest groups, customers and suppliers. In response to these pressures, many operators are focusing on a strategy of operational excellence. Operational excellence implies an effective infrastructure for knowledge and data management, data analysis, and reporting. For many pipeline companies, a deployment of ESRI s Geographic Information System (GIS) technology utilizing the ArcGIS Pipeline Data Model (APDM) can provide a superior platform for data management. Superior data management results in improved pipeline integrity management, together with attendant improvements in productivity, cost reduction and cost avoidance. The APDM is designed to store information found in gathering and transmission pipelines, particularly gas and liquid systems. The APDM is expressly designed for implementation as an object-relational ESRI geodatabase for use with ESRI's ArcGIS and ArcSDE products. The APDM is the only pipeline data model designed to take full advantage of ESRI s advanced GIS spatial data management and analysis technology. Unlike other available pipeline data models, the APDM can only be implemented with ESRI geodatabase technology. The APDM is intended to be a flexible data model template that any pipeline company can readily modify to suit its own needs. Companies with existing relational databases may choose to migrate to the APDM to take advantage of the ESRI geodatabase data management environment. Such companies are expected to extensively modify the APDM template to conform the APDM to the requirements of their existing data stores. For companies without an existing data model, the APDM ships with a variety of optional, example classes (analogous to relational database tables) which can be used to store many types of pipeline information. All of the features in the APDM can be organized into one of three categories: 1) Abstract classes, 2) Core classes, and 3) Optional Classes. The abstract classes define the framework of the APDM; all other classes in the APDM inherit properties, relationships and behaviors from one of the APDM abstract classes. The APDM abstract classes are required elements of the model. The core classes are those object, feature and relationship classes, together with associated domains, that are required to maintain APDM compliance. The core classes define the APDM centerline features, stationing attributes, and supporting model elements. The optional classes are defined in a separate document (ArcGIS Pipeline Data Model Version 4.0 Optional Classes). The optional classes are included as implementation examples, but none of them are required elements of the model. The optional classes are included to provide a starting template for companies with no existing pipeline data model. ESRI Technical Paper 3

10 The APDM was initiated in The intellectual property of the APDM is owned by ESRI. Ongoing maintenance and enhancement of the content and structure of the APDM is governed by and performed by the elected members of the pipeline industry managed APDM Steering and Technical committees, respectively. 4

11 ArcGIS Pipeline Data Model Version 4.0 Abstract & Core Classes 1.0 Introduction This technical paper explains the ArcGIS Pipeline Data Model (APDM) and is intended for those interested in implementing a transmission pipeline geodatabase using ESRI ArcGIS software. The document is written for pipeline GIS professionals, company managers, developers, and graphic system operators. It provides a detailed description of the objects in the model, how the model is organized, and suggestions on how the model can be implemented within an organization. The document assumes that the reader has a working knowledge of common pipeline terminology and pipeline-specific GIS terms, such as stationing, centerline, station series, and control points, and a working knowledge of ESRI linear referencing technology. A glossary is provided to explain terms pertinent to the APDM. This document concentrates on the abstract and core classes of the APDM; the optional classes that are distributed as implementation examples are discussed in a separate document, ArcGIS Pipeline Data Model Version 4.0 Optional Classes. 2.0 What Is the APDM? The ArcGIS Pipeline Data Model is designed for storing information pertaining to gathering and transmission pipelines, particularly gas and liquid systems. The APDM was expressly designed for implementation as an ESRI geodatabase for use with ESRI's ArcGIS and ArcSDE products. A geodatabase is an object-relational construct for storing and managing geographic data as features within an industry-standard relational database management system (RDBMS). The APDM is developed and governed by Steering and Technical Committees under the umbrella of ESRI. The Steering and Technical committees include representatives from pipeline and pipeline vendor companies. ESRI helps facilitate the development and use of the APDM to serve the needs of their client base. While ESRI owns the APDM, control of the APDM is vested in the user community. The APDM model and supporting documentation is freely available and accessible to everyone via the web at ESRI does not consider itself a standards body; therefore, in keeping with the spirit of other published ESRI models, the APDM is not intended to be a comprehensive or all encompassing model. Rather, the APDM is designed to be a starting template of core elements from which a pipeline company can craft a model tailored to its business needs by adding features or refining existing features within the rules defined by the APDM template. A primary objective of the model is to account for linear referencing of features (stationing). Most transmission pipeline companies refer to the location of features or ESRI Technical Paper 5

12 events that occur along the pipeline system as events occurring along a route (station series) at a certain distance (measure). Stationing is handled in the model using out-ofthe-box ESRI technology referred to as routes and measures. The APDM is designed as a starting point. It is neither the purpose nor the focus of the APDM technical committee to design a model that is a comprehensive description of all possible features found in a pipeline system. Nor is it the intention of the model to prescribe a rigorous methodology or standard approach to modeling pipeline systems. The model s intent is to provide a set of core objects and attributes that describe and effectively handle stationing, plus a core set of abstract classes by which most, if not all, pipeline features can be categorized. The purpose behind providing a core set of features is to provide pipeline and vendor companies with a consistent framework for developing applications against the model, and for data transfer between existing databases. By this approach, any pipeline company can add features to the model, modify existing features in the model, or subtract features from the model as required by business needs. The core elements of the model remain a small subset of the features found in the model. Any new features added must fall into one of the abstract APDM classes including referenced and non-referenced features, and online and offline features. Another focus of the APDM is to develop a model that end users can implement and add data to without the need for custom code or development efforts. This is achieved by using core ESRI technology that allows any pipeline company to develop a tailored data model that meets its business needs while maintining compatibility with ESRI tools. 3.0 Why Use the APDM? A variety of factors are driving pipeline operators towards more advanced and effective pipeline data management tools; these business drivers provide the ultimate impetus for a pipeline company to adopt ESRI geodatabase technology and the APDM. Of course, there are other options besides ESRI geodatabase technology and the APDM for managing pipeline data, but an APDM geodatabase implementation offers several advantages over available alternatives in terms of efficiency, effectiveness, reliability, cost, and capability. The business and technical cases for the APDM are outlined below. 3.1 The Business Case The pipeline operating environment is more demanding than ever. In order to be successful, pipeline companies must not only provide a competitive Return on Investment (ROI) to shareholders, but also ensure healthy relationships with other stakeholders including regulatory agencies, the public at large, emergency responders, environmental interest groups, customers and suppliers. Any successful pipeline company must develop effective strategies for dealing with the following challenges: Profitability The ultimate goal of a pipeline operator is to achieve maximum profitability while maintaining safe and reliable system that meets or exceeds industry and regulatory standards. 6

13 Regulatory Pressure In the wake of tragic accidents such as the Bellingham, WA incident of 1999, public outcry elicited a response from the federal government in the form of increasingly demanding and prescriptive regulations. The Pipeline Safety Improvement Act of 2002 resulted in amendments to CFR Title Subpart O Pipeline Integrity Management, and CFR Title Subpart F Operations & Maintenance ( High Consequence Areas, and Pipeline Integrity Management) for interstate gas and liquids transmission pipeline operators, respectively. These new regulations require operators to develop an unprecedented level of knowledge regarding their pipelines and environments in which they operate in order to create highly detailed pipeline Integrity Management Programs (IMP s). Annual audits performed by the Pipeline and Hazardous Materials Safety Administration s (PHMSA) Office of Pipeline Safety (OPS) under the auspices of the U.S. Department of Transportation (DOT) are designed to enforce regulatory compliance. Failure to comply can result in spectacular fines and disruption of business operations; this makes the IMP a critical element of any pipeline company s profitability strategy. Effective integrity management also implies optimized availability of pipeline assets for operations resulting in increased revenue and increased opportunities for operational cost reduction through improved operational efficiency and reliability. Operational Complexity As technology and business management practices evolve, organizations such as pipeline companies are becoming increasingly complex in nature. Increasingly the activities of a business unit are dependent upon and/or affect the activities of other units. For example, Control Centers interact with Engineering departments to design and monitor line pressures, likewise relying on Emergency Response and Environmental groups to respond to incidents, further demanding a tight integration with frontline Field and ROW personnel to execute on site activities. Almost every activity within a pipeline organization requires coordination across multiple business units. This evolving complexity presents challenges and opportunities for cost reduction by increasing efficiency and greater output through discovering and realizing synergies. Aging Infrastructure Much of the nation s pipeline infrastructure is approaching the latter stages of its original designed service life. Successful management of aged pipelines requires extraordinary diligence and attention to detail. Modern inline inspection, direct assessment, and close interval survey methods are all critical elements of an effective Baseline Assessment Plan (BAP) and ongoing mitigation plans, but these tools and processes all produce tremendous volumes of information. Failure to effectively manage and analyze this information leads to inefficient or even fatally flawed mitigation plans. Thus, effective data analysis and management is key to service reliability, operational cost reduction and cost avoidance strategies. Suburban expansion Formerly rural pipeline Rights Of Way (ROW) are being increasingly encroached on by suburbia. This trend can dramatically increase One Call ESRI Technical Paper 7

14 response and public notification burdens, potential for third party damage, complexity of risk analysis, and the financial, operational, litigable and regulatory consequences of an unintended product release. Effective strategies for dealing with suburban encroachment are a critical aspect of any pipeline company s cost optimization strategy. Mergers, Acquisitions & Restructuring As pipeline systems change hands, many companies find themselves faced with the tasks of integrating staffs, business processes and workflows, and data management systems. Failure to do so results in increased operating costs through staff inefficiency, and increased regulatory exposure. Graying of the Workforce For many pipeline companies, much of the corporate knowledge base is stored in the brains of senior staff. As these employees retire, critical knowledge is irretrievably lost. Whenever such knowledge is lost, unnecessary cost is incurred to reproduce it. In some cases the consequences of lost knowledge can be dire from both an operational and financial standpoint. Thus, an effective knowledge and data management infrastructure becomes an important cost reduction and cost avoidance tool. In response to above challenges, many operators are focusing on a strategy of operational excellence achieved through the incorporation of new technology and processes to integrate and optimize the organization. In the Information Age, operational excellence implies an effective infrastructure for knowledge and data management, data analysis and reporting. Increasingly, operators are realizing that the traditional hardcopy-based or CAD-based data management environment is simply not up to the task. Indeed, for some of the more prescriptive regulations such as gas or liquids High Consequence Area (HCA) analysis, a GIS-based platform is practically required. As discussed below, ESRI geodatabase technology and the APDM provide a superior foundation for data and knowledge management. For pipeline operators, an effectively implemented data management system based on the APDM can becomes an integral part of the operations and asset management framework. Effective implementation enables increased productivity, cost reduction and cost avoidance. Increased productivity is achieved through optimized maintenance planning and execution with reduced downtime, resulting in greater output and increased available capacity for operations. Cost reduction is achieved through increased staff and operational efficiency and reductions in rework and unnecessary work. Cost avoidance is improved through increased operational safety and reliability, and through reductions in regulatory fines, unfavorable litigation judgments, and ultimately, avoidance of consent decrees and corrective actions. An effective data management platform such as APDM can reduce the time it takes to perform tasks such as data maintenance and integration, freeing company personnel to spend more time on critical functions such as analysis of and response to information. More time is available for preventive maintenance activities, project planning and oversight, and other work in need of completion. Likewise, by automating traditionally 8

15 manual and inefficient functions, overtime can be reduced and in some cases, headcount can be reduced as well, thereby reducing operating costs. For example, the APDM enables deployment of advanced mobile electronic field data collection and communication. In many cases, the conversion from paper forms to electronic data capture can result in a 20-40% reduction in time spent on a given activity by field inspectors and technicians. For a full time inspector paid $50K per year, the net savings can range from $10-20K per inspector. Based on the size of the organization, this alone can amount to significant savings when implemented throughout the company. Other expenses typically reduced with implementation of the APDM include the reduction and in many cases elimination of time spent integrating disparate data sets and the time and cost to create and update maps and drawings. Further, advanced data integration and analysis is enabled and can be used to justify project deferrals or even avoidance. For example, the integration and assessment of Close Interval Survey (CIS) data combined with InLine Inspection (ILI) data can be used to develop engineered criteria for adequate cathodic protection levels, which many times justifies the deferral of projects such as Cathodic Protection (CP) installations, excavations and rehabilitation projects. It should not be unexpected that a mature implementation of an enterprise data management system based on the APDM can reduce pipeline maintenance costs by as much as 5-10%. For a pipeline company with an annual maintenance budget of $20 MM, this can result in savings in excess of $1MM per year. Eventually, the extension of the system to facilities and tank farms may further extend the ability to reduce operating expenses. A significant benefit from any solution is the ability for it to lead to increased revenues. In the case of the APDM, it is a platform that when implemented effectively will lead to better informed decision making, faster data collection, communication and processing and rapid response to identified needs. New capabilities can enable the monitoring of anomalies versus shutdown and excavation, the optimization of maintenance planning and scheduling to reduce unnecessary work and the better coordination of needed work. Over time, it should be expected that an enterprise-wide improvement in information management, communication and decision making will lead to improvements in capacity availability and utilization of anywhere from 2-10%. Conservatively speaking, if available capacity can be increased by 1% on a gasoline system that on average transports 1MM barrels per day at a revenue of 1$ per barrel, then increased revenue could amount to on average over $10,000 per day. Increased productivity, cost reduction and cost avoidance are important factors in improving ROI, but ROI is only one part of a balanced scorecard. Many pipeline companies are focused on being excellent corporate citizens. An effective platform based on the APDM can become an important tool for maintaining a positive image and good relationships with all of the pipeline s important stakeholders: regulatory agencies, the public, emergency responders, environmental groups, customers and suppliers. ESRI Technical Paper 9

16 Many of the cost justifications developed above for an APDM implementation can be equally applied to an effective, spatially enabled implementation of a relational pipeline database such as Integrated Spatial Analysis Techniques (ISAT), Pipeline Open Data Standard (PODS), or Industry Standard for Pipeline Data Management (ISPDM). However, the APDM and ESRI geodatbase technology offers additional cost benefits over these relational technology alternatives. Reduced entry cost For smaller operators, the APDM can be implemented in a personal, file or workgroup geodatabase, eliminating the need for enteprise RDBMS software such as Oracle or SQL Server, together with attendant Database Adminstrator (DBA) and System Adminstrator (SA) personnel costs. To spatially enable a relational pipeline database, an enterprise RDBMS is effectively required. Thus, for smaller operators, significant support staff headcount reduction and software capital expenditure savings can be achieved with an APDM implementation relative to a relational pipeline database implementation. Reduced software development / software purchase expenditures Spatially enabling a relational pipeline database with ESRI technology calls for the use of extended stored procedures (utilizing ArcObjects or ArcSDE C API coding in the case of ArcSDE), database triggers and/or scheduled services to synchronize the database with the GIS. Also, relational pipeline databases have no built-in capability for long transaction management, or history management. Such funcitionality is not included out-of-the-box with any of the relational pipeline models, and therefore must either be developed inhouse or purchased from a vendor. In-house development of such functionality may require several staff years (or more) of effort; purchase from a vendor requires some fraction thereof in equivalent capital software expenditure. This extra code requires maintenance, so some attendant support staff headcount is required. Because the APDM is a geodatabase, the need for such database synchronization software is eliminated; long transaction capability and history management (archiving) are built in. Relative to a relational pipeline database implementation, the APDM enables reduced support staff headcount and/or reduced capital expenditures for third-party software. To equal out-of-the-box APDM geodatabase functionality requires excessive investment in in-house software development. Practically, the only viable way to an effective spatially enabled relational pipeline database implementation is through third-party vendor tools. However, with the APDM it is possible to maintain the geodatabase with out-of-the-box ESRI tools. This frees an operator to reserve capital and staff resources for higher value activities than simply maintaining the pipeline database. 3.2 The Technical Case As discussed above, most pipeline operators have arrived at the conclusion that hardcopy-based and simple CAD-based data management systems are insufficient to meet the demands of today s operating environment. Some kind of advanced databasedriven data management system is required. Several database-driven data management 10

17 options are currently available to pipeline operators: 1) a pure relational database implementation using ISAT, PODS, ISPDM, or a proprietary model, 2) a spatially enabled implementation of one or the aforementioned relational models using GIS technology, and 3) a pure ESRI geodatabase implementation utilizing the APDM. ESRI geodatabase technology is still relatively new compared to traditional RDBMS technology. SQL access to a versioned geodatabase is somewhat complicated, and SQL edit capability is somewhat limited. Some feel that geodatabase implementations are more difficult to integrate with existing relational enterprise databases than an equivalent relational database implementation. The prime consideration in determining whether to select the APDM in lieu of a standard or GIS-enabled relational database model is this: Do the benefits of ESRI geodatabase technology analytical, cartographic, and editing functionality override the need to integrate the database with other enterprise relational applications and data access technologies? The primary advantage of the geodatabase over a relational model is summarized by the following observations: The RDBMS enforces referential data integrity, but not spatial data integrity. The geodatabase enforces both referential and spatial data integrity. The RDBMS cannot easily enforce the link between feature geometry and attribute data. To use a GIS with relational pipeline data models such as ISAT or PODS, the GIS is typically grafted on to the relational model. When ESRI technology is used to spatially enable a relational ISAT or PODS database, spatial information is usually stored twice: once in the relational coordinate tables present in these models, and again in ArcSDE layers or feature classes derived from the relational coordinate tables. Editing operations in the RDBMS require application logic to drive updates of relational database attributes, which in turn are followed by feature geometry updates (or the reverse). Data synchronization is a constant, error-prone, time-consuming, costly and troublesome issue for spatially enabled relational pipeline data models: feature geometries in ArcSDE are typically snapshots derived from the database; each time the database is modified, the feature geometries are potentially out of date and must be rebuilt. The geodatabase seamlessly enforces the linkage between feature geometry and attribute data; in addition, it allows the construction of more complex relationships that simplify and streamline editing operations. Because of this, an APDM geodatabase implementation avoids the problems with spatial data updates and synchronization that are typical of a GIS-enabled relational model. The geodatabase (and the APDM) offers less expensive data maintenance for interrelated spatial features and attributes as a function of the underlying data structure. As a result, the reliance on data integrity logic built into custom applications is minimized. Ultimately, these advantages result in lower data maintenance costs and greater data reliability. Utilizing a geodatabase for storage of GIS data provides end user access to all the powerful ESRI GIS analytical technology. While a spatially enabled relational database ESRI Technical Paper 11

18 implementation can take advantage of some of ESRI s advanced GIS capabilities, the same cannot be said for a pure relational implementation, and neither can take full advantage of ESRI technology like a geodatabase. Compelling technology included in the geodatabase includes multi-user, long transaction versioned editing; coincident feature editing via topology; geoprocessing; raster-based spatial analysis; geo-statistical analysis; state-of-the-art map display/cartographic production tools; 3D Visualization using ArcGIS Explorer ; integration with the Web via ArcIMS and ArcGIS Server ; disconnected editing via Tablet PC and handheld personal digital assistants (PDAs) running ArcPad ; and dynamic annotation. All of these factors combine to make an APDM geodatabase implementation more efficient, more reliable and less costly than a relational database implementation. Other ESRI data models could potentially be applied to pipeline; the ESRI Gas Distribution Model is one potential candidate. The APDM is designed for pipeline companies whose primary means of locating features is by linear referencing (or stationing). Ultimately, the ability to locate, edit, analyze, and organize features on or along a pipeline via stationing is what differentiates the APDM from the standard ESRI Gas Distribution Model. The APDM is developed for ESRI enterprise software ArcGIS/ArcSDE technology, which is entirely predicated on the geodatabase. The APDM returns lower cost, more effective, efficient and reliable data creation and management, and superior data analysis. All of these elements are important to the highly regulated and important transmission pipeline industry. 4.0 History of the APDM The APDM is developed and maintained jointly by the ESRI APDM steering and technical committees. The technical committee is responsible for developing the structure, content, and technological aspects of the model. The steering committee is responsible for the organizational/promotional aspects of the model. Ultimately both committees fall under the umbrella of the ESRI Petroleum User Group. The core elements of the APDM embody many of the same concepts found in the ISAT, PODS, and ISPDM models. Every attempt is made to make the APDM open to data transfer between each model. The steering and technical committees strive to balance the interests of each pipeline model group, the pipeline companies, and the pipeline vendor community. Participation in both committees is divided between operator and vendor communities, and ISAT/PODS data model members. Below is a brief chronology of the model's development: March 2002 M.J. Harden starts the initial work on the model. July 2002 The model is presented at the ESRI User Conference in San Diego, California. An open invitation to participate in the design of the model is extended to the pipeline community. August 2002 The initial meeting of interested member groups occurs at ESRI, Redlands, California. 12

19 October 2002 The steering and technical committees are officially formed at the ESRI Electric/Gas Utility User Group Conference (EGUG), Coeur d'alene, Idaho. December 2002 June 2003 Monthly technical and steering committee meetings occur at various member organizations. Development of the intellectual property agreement, steering committee charter, technical committee mandate, operational procedures, and APDM content and structure proceed. March 2003 The APDM is released for public comment at the ESRI Petroleum Users Group (PUG) meeting in Houston, Texas. July 2003 Version 1 of the APDM is officially released at the ESRI International User Conference in San Diego, California. October 2003 The model is reviewed and Version 2 is proposed by the APDM technical committee at the ESRI EGUG Conference in Galveston, Texas. August 2004 The model is reviewed and Version 3 is released by the APDM technical committee at the first APDM Pre-conference workshop at the 24 th annual ESRI International User Conference in San Diego, California. March 2005 The model is reviewed and Version 4 is proposed by the APDM technical committee at the ESRI PUG meeting in Houston, Texas. July 2005 The second annual APDM pre-conference workshop held at the 25 th annual ESRI International User Conference in San Diego, California. June 2006 The model is reviewed and Version 4 is released for review by the APDM technical committee via the APDM web site ( September 2006 Work begins on APDM v5.0. The final draft of APDM v4.0 is released via the APDM web site ( Active members of the Pipeline Interest Group (PIG) elect the members of the APDM steering and technical committees. Elections occur at the annual PUG meetings (March of each year). Steering committee terms are one year in length; technical committee terms are two years in length. 5.0 APDM Steering Committee A ten (10) person committee is charged with setting the organizational direction of the APDM within the context of the pipeline industry. The Steering Committee meets once per month via phone conference on the second Wednesday of the month. Craig Wilder (Craig.Wilder@bp.com) is the current chairperson of the APDM Steering Committee. 6.0 APDM Technical Committee A ten (10) person committee charged with developing the technical content of the APDM model. The technical committee meets three times per year during the ESRI Petroleum User Group Conference (PUG) in February/March, the annual ESRI User Conference held in July/August and the GITA Oil & Gas Conference (September). Technical committee meetings are open to anyone interested in furthering the model. However, only ESRI Technical Paper 13

20 the technical committee members are allowed to vote on changes to the APDM. Peter Veenstra is the current chairperson of the APDM Technical Committee. 7.0 Difference Between a Standard and a Template The APDM is intended to be a template, not a standard. There is no governing organization that has officially approved the APDM as a standard. The features and relationships included in the model are deemed critical or common to 80 percent of all pipeline companies' typical implementations of geographic information system technology. The APDM, similar to most other published models on the ESRI Web site, represents core features found in almost every pipeline system. The intent of the model is not to create a database standard, but rather to create a database template from which custom models can be created and evolved. However, one of the design criteria of the model is to create and delineate core elements that must be maintained in order to preserve a standard for data transfer, application development, and conversion efforts between APDM implementations. 8.0 Design Rationale The APDM is a geodatabase model developed for managing transmission and gathering (gas and liquid) pipelines. This section outlines the design rationale considered at every stage in development of the APDM. These justifications served as guidelines for ensuring the model meets the needs of the pipeline industry. Each justification describes some of the considerations and background material measured and weighed to determine the final model. This section is divided into the following parts, each of which describes the driving forces behind how the APDM was developed. Core Elements Stationing and Station Equations The Centerline (Routes, Measures, and Events) Hierarchy Coincident Geometry Events Versus Features Later sections of this document describe in more detail the content and structure of the APDM. It is important to realize that no single pipeline data model can do everything for all organizations. Realizing the variation in how data is modeled between different pipeline companies, the technical committee developed the APDM according to four guiding principles: 1. The APDM is designed to provide a set of core elements that remain consistent for any APDM implementation. The core elements are designed to ease data 14

21 transfer between existing pipeline data models and for the development of portable APDM applications by third party vendors. 2. The APDM provides a mechanism for locating features on or along the pipeline centerline by both absolute positioning and by linear referencing (commonly referred to as stationing). It is not the purpose of the APDM to prescribe the approach to implementation for the model. These features can exist as geometric features in feature classes, dynamic events in event tables, or a combination of both. 3. Features (or tables or objects) are included in the APDM if they are required by 80 percent of all pipeline companies and by the United States government regulatory agencies The APDM can be implemented and maintained within a geodatabase without the need for custom application code. 9.0 Core Elements The prime object of the technical committee is to promulgate a small, well-defined set of core objects with required attributes. These core elements provide the mechanism for linear referencing to locate events as geometric features or dynamic events. The core also provides a foundation from which other features can be added to the model, or from which existing features in the model can be customized as required (provided that the core elements remain intact and immutable). The core elements are required for maintenance of the centerline and stationing. The core elements are classified into a set of conceptual features (abstract classes) that provide an aid to determining how additional model elements can be classified and organized within the APDM. If the core objects (tables, feature classes) and attributes are immutable, then the remainder of the geodatabase is optional and totally customizable. The feature classes, other than the core feature classes, that are distributed with the model provide examples of the most common features, rather than being an all-inclusive description of every possible feature found on or along a pipeline system. The purpose of the APDM is to allow pipeline companies to build geodatabases to suit their business needs. The core elements of the model provide a standard set of features the rest is up to the end user. Users may pick and choose which elements to include, which to remove, and which to alter to suit their needs. Other than the core elements of the model, it is up to the user to determine what is or is not included in the model. 1 The APDM technical committee is aware the APDM will be implemented in international settings. Every attempt is made to avoid an American-centric view of the model. It is the carefully weighed opinion of the committee that transmission pipeline regulations in the United States are some of the most rigorous in the world. Many of the companies participating in the development of the model have holdings and operations outside of the United States and are consulted during model development to facilitate the requirements of the international pipeline community. ESRI Technical Paper 15

22 The amount of data that pipeline companies are able to access has exponentially increased within the last decade. In the historical paper world it was conceivable to manage thousands of features. With the advent of faster computers, better integration between disparate systems, and the proliferation of readily available digital data in a wide variety of formats, the potential for the management of millions, if not billions, of features is quite conceivable for many large pipeline companies. By keeping a small core of required elements, the APDM is very open and flexible to integration with larger corporate or enterprise data systems. In this manner, the APDM can be implemented as the front door to the enterprise repository of data. By spatially modeling a detailed, rich set of features, the GIS can be seen as an extension of the entire enterprise data warehouse. 9.1 Stationing and Station Equations Traditionally, the location of pipeline features on a pipeline was determined by station series and station value. A station series is a linear path representing a portion of the centerline of the pipeline or the route that the pipeline follows across the surface of the earth. The cumulative measure of 'stationing values' from the start of the station series to the terminus of the station series is called station position. An infinite number of events can be located along a station series representing the location of a feature, or the start and end of a linear feature. At each point along the station series (including the start and endpoints) where the centerline bends either horizontally or vertically, a control point is placed. Control points are known points of stationing (measured distance along the station series) and have known coordinate values. Each control point forms the vertex of a station series linear feature. Each station series is thus composed of two or more known points of stationing. Stationing monotonically increases or decreases without gaps from the begin point to the endpoint of a station series. Once stationing is assigned to the centerline, the stationing values for known points along the centerline usually do not change. When the pipeline is first built, the stationing measurements are uninterrupted and continuous along the length of the entire pipeline. When a pipeline is rerouted (i.e. the path of the centerline is altered), discontinuities are introduced into the stationing. The points of the breaks in stationing are known as station equations. Once an equation is introduced into the centerline, the stationing is altered for the portion of the centerline that has been rerouted with the addition of a new station series. Any event occurring between two control points has a station value calculated by the interpolation of station values of the known control points on either side of the event. Traditional GIS implementations store point, linear, and polygon features by absolute coordinates for each vertex of the feature. Using stationing (linear referencing or relative positioning), a dynamic method for determining the location of a feature (or event) is available. The ESRI geodatabase supports both of these methods. Once the location of a feature is determined using either absolute or relative positioning, the alternative positioning values can be determined (provided an underlying centerline of station series 16