- ASC Proceedings of the 40th Annual Conference
- Brigham Young University - Provo, Utah
- April 8 - 10, 2004
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The Use of Extensible Markup Language (XML) in Creating Interoperable Construction Software Applications
Over the last decade the construction industry has been using several software applications in performing their day-to-day operations. From web based project management software to customized accounting packages, the industry is using highly sophisticated IT solutions. Each software package uses data that may be needed in another application. The estimated cost of an item is in the estimating application and the actual cost of the item in the project management application. The project manager needs information from both software applications to manage a project successfully. Due to similar situations in several non-construction software as well, the World Wide Web consortium has created the extensible markup language (XML). XML allows software applications to share data rather than having to re-enter it manually from one application to another. This paper describes the issues that lead to the creation of XML along with how XML can be used to integrate software applications. The inner workings of XML are discussed along with examples. This paper also examines the issues and obstacles faced by the construction industry in creating an integrated software environment. Areas of construction software that need integration are examined. Current research on the topic and progress in this area is addressed.
Keywords: Extended Markup Language (XML), Hyper Text Markup Language (HTML), aecXML, XML Schema, Integration, Database, Common Data Model, Project Management, Estimating and Accounting.
History and Introduction
In the last decade information technology has emerged as one of the most popular tools used by companies to manage their day-to-day operations. Information in the construction industry is largely produced, stored and distributed digitally (Finne, 2003). Technology is now playing a major role in the return of above average margins (Albright, Dec. 2001). In the construction industry software applications are currently used in the major departments such as the estimating, accounting, scheduling and project management. Technology is essential to the success of the construction industry in a new age of business (Stark, 2002). Construction companies spend about 17% of their operational IT budget on software (Guinta, 2003). Simply put, this is a new age of business for the construction community (Stark & Smedley, 2002).
XML technologies will lead to integrated software environments. The creation of these XML technologies requires aggressive participation by several key players in the construction industry. These include contractors, architects, engineers, sub-contractors, owners, software and hardware vendors, academicians and researchers. The major goal of this paper is to disseminate information about how XML will change future software applications in the construction industry. Another critical objective is to expose construction educators to research opportunities that exist with the IAI. It is generally regarded that academicians play a major role in the advancement of an industry. However, currently participation by educators in the IAI can be categorized as minimal at best. Only two US based educational institutions are even members of the IAI. Academicians can not only help create a robust aecXML schema but also help create it sooner.
Currently software manufacturers do not use a universal standard to define the architecture and definition of the data within their applications. Although each application within a department such as estimating applications will contain similar data, the definition of this data is different in each software application, depending on the manufacturer. Due to the lack of a common format, in most cases the data has to be manually re-entered into other applications. A typical example of this is the information from an estimate for a project needs to be re-entered into the project management software for costs to be tracked and verified against the original estimate. This data must be manually re-entered into the project management software since the two applications do not ‘speak to each other’ and hence are not interoperable (Lottaz et al, 2000). The World Wide Web consortium (W3C) created a markup language to solve the ‘Common Data Model’ problem. W3C is the organization that develops interoperable technologies including specifications and other tools (W3C, n.d). This language called the Extensible Markup Language (XML) was developed by the W3C in 1996. XML was created based on the work already done on Standard Generalized Markup Language (SGML). SGML was developed in1969 by Charles Goldfarb and was later established as an ISO standard in 1986 (Sankaranarayana, 2001). SGML is a complex modeling language that is not easily readable; however it is also very powerful in creating structured documents. The W3C established a new markup language called the hypertext markup language (HTML) to eliminate some of the complexities created by SGML. The W3C created HTML specifically for the purpose of displaying text in certain formats in internet browsers. HTML is the most popular markup language with over 800 million pages on the internet (. The latest version of XML, version 1.0 was derived from SGML; however it has several similarities to HTML. It easily readable like HTML but has the ability to describe data in a structured format like SGML. XML is already used in some construction management software such as Constructw@re (Inglesby, 1999).
The International Alliance for Interoperability (IAI) is an organization that is developing a framework for various software and hardware manufacturers to produce interoperable solutions for the architectural, engineering and construction (AEC) industries. The IAI consists of over 600 organizations world wide. The members of each chapter include architects, engineers, constructors, owners, researchers, and hardware and software providers. The work of the IAI in creating the first version of the architectural, engineering and construction XML (aecXML) is discussed in this study. This paper also provides a detailed account of the issues surrounding the creation of an integrated software environment in construction management. Types of software programs that need integration and the inhibitors of creating an integrated software environment are discussed in this paper. The issues in creating a shared data model versus a common database to create integrated software applications are discussed. The study includes a description of the differences between XML and HTML.
Data Integration in Construction Management Software
The construction industry is fragmented by nature (Faraj & Alshawi, 1999). This fragmentation is not restricted to the US construction market alone but is more of a global phenomenon (Kazi & Charoenngam 2003). One of the primary reasons this fragmentation exists is due the participation of various trades in developing the finished product, the ‘Building’. Priorities of these trades are not all the same and are sometimes even at odds with each other. From an information technology stand point the fragmentation exists due to the various levels of technical expertise available for these participants within their organizations. In 2001 it was estimated that approximately 75% of subcontractors did not use e-mail (Rogus, 2001).
An organization’s resources are used inefficiently due to disconnected and fragmented information, causing redundant activities (Rakow, 2002). The IAI reports that 50-85% of all construction problems are caused by missing, bad or uncoordinated information. Studies also indicate that in addition, up to 80% of construction administration processes could be saved with single entry, web-enabled, shared databases (IAI). It will be hard for companies to move ahead due to the amount of information needed to be processed the pressure to expedite the schedule, and competitive forces within the construction industry (Rakow, 2002). Although most construction professionals don’t fully agree, they would concur that failure to integrate will at least contribute to a reduced bottom line and a shrinking competitive advantage (Rakow, 2002).
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Figure 1: A typical ‘Cost Report’ that is created on every construction project. |
Project management in the last decade or so has gone from hand-written notes on paper to super-sized servers that store and mine data and the use of Internet to facilitate communications (Dubernails, 2001). In a survey conducted in 2003 by Constructech magazine of over 100 contractors, 86% of the respondents considered project management software as significantly important over other software (Guinta, 2003). Advances in the area of project management solutions such as web-based systems have helped companies reduce overall project durations allowing companies to be more profitable. However these solutions have also created some redundant activities. These activities are typically filled with human error and missing information. Many companies are now struggling with the problem of having to enter the same information into three or four databases. Consider for instance the data presented in the cost report of a project in figure 1. The estimate data in the report is in an estimating application. The percent complete data is in a project management application and the actual costs have to be tracked using an accounting application. Monitoring this cost report is very crucial to the success of a project. Most companies monitor this report on a weekly or a fortnightly basis. However the creation of this report is very tedious if the various software applications cannot share data with each other. In creating the report presented in the figure below, the estimating data has to be manually entered into a spreadsheet from the estimating software, the percent complete data has to be manually entered from the project management software and the actual costs have to be tracked using payments received from the owner and the pay applications approved for the sub-contractors.
Integrated systems will free the accounting department from time consuming, redundant data entry (Rakow, Aug. 2002). The accounting department would no longer be burdened by requests for cost reports and processing invoices. Advantages such as these lead an organization to have a competitive advantage over their peers. If construction companies do not immediately try to integrate their applications, they should at least research the issue and its impact on their specific systems, or risk falling substantially behind the competition (Stark, 2003).
aecXML and IAI
The vision and goal of the IAI is to “develop a standard universal framework to enable and encourage information sharing and interoperability throughout all phases of the whole building life cycle” (IAI, n.d). Established in 1995, the IAI is a global standards setting organization that is represented by ten chapters and six hundred members in various parts of the world. Members of the alliance represent a diverse group of professionals from the architectural, engineering and construction industries. The IAI is also involved in the development of a vendor neutral standard for software interoperability. The North American chapter of the IAI functions as a technical committee of the National Institute of Building Sciences.
The work of the alliance is accomplished in the ‘Domain Committees’ of each chapter. The aecXML domain, architectural domain, building services domain, codes and standards domain, facilities management domain, libraries domain and project management domain are the seven domain committees in the IAI. These committees are responsible for the creation of the ‘aecXML schema’ and the ‘Industry Foundation Classes’ (IFCs). The IFCs are the end product of the work of the domain committees. The latest (second) version of the IFCs was released in May 2003 in Washington, D.C. It is a high level data modeling tool for the AEC industries (Froese, 2003). It is used by software and hardware providers to produce IFC conforming products. These applications can share data among themselves as long as they are IFC compliant. An example of IFC complaint software is the new Timberline CAD integrator. The CAD Integrator allows the transfer of information from electronic CAD drawings into a Timberline estimates seamlessly (Timberline, n.d). It allows estimators to directly import CAD drawings and have the quantities of material transfer over to the estimate. This integration is possible since both the CAD drawings and the estimating software are IFC compliant.
aecXML schema is a derivative of the IFCs. A schema in XML terms refers to the structural definition of an object or a collection of objects. While the IFCs are a conceptual model, the business model of implementing the IFCs for business-to-business (B2B) transactions especially that over the internet is the aecXML. The IFCs address the transactions of the entire AEC industry; the aecXML facilitates interoperability between software applications. An example of this would be the integration of a specific project management application (like Constructw@re) with a specific accounting application (like Timberline Gold). The IAI hopes that future versions of these applications will be aecXML compliant and use the common schema to share data. Figure 2 shows a representation of the relationship between the IFCs and the aecXML. Readers should note that the IFCs were created to deal with the whole building lifecycle whereas aecXML is created to address the issue of only B2B transactions. aecXML can be considered as a subset of both the IFCs and the XML standard defined by the W3C. The aecXML domain committee of the IAI is currently working to the development of the first version of a common schema.
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Figure 2: Relationship between IFCs and aecXML (IAI, n.d) |
XML versus HTML
The purpose of HTML was to render text in a browser. It contains standard tags that are used to modify the way text is displayed on the screen, such as making text of a certain font or making text left aligned and so on. There are no user defined tags in HTML; instead HTML authors can only use tags that are in the HTML standard as defined by the W3C.
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Figure 3: An HTML file describing a car. |
The code presented in figure 3 is an HTML file that is describing the attributes of a used car. Notice in line 8 that the html document specifies the font and the font size for the text to be displayed in an internet browser. The use of standard HTML tags such as the tag ‘B’ for bold text and ‘I’ for italic text is shown above. A parser program looks at a file and searches for specific text within the file. Complicated parser programming is needed to get the information about this car into some other program. It must also be noted that if the user causes an error in entering this information such as typing ‘Modal’ instead of ‘Model’ the parser program will not work. The HTML program cannot check itself to verify if the user has entered all the required information.
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Figure 4: An XML file describing the same car shown in figure 1. |
The XML code presented in figure 4 describes the attributes of the same used car as done in the HTML file presented in figure 3. Notice however that the code does not contain any information about how this data will be formatted. The tags presented in the XML file are user defined. XML is created to define data in a structured format that can be verified and data that is extensible. Data in an XML file is referred as elements. In this instance the <car> is the root element and attributes are the child elements that are nested inside the root. It is important to note that unlike HTML, XML does not do anything. It is simply a way to create structured data that can be shared across applications. XML is not meant to replace HTML; instead it complements HTML (W3schools, n.d). HTML and XML files can be used together where the data can be in XML format and the formatting of the data can be done using HTML tags. Unlike HTML the tags in XML are user defined along with the structure of the data, such as the definition of the <car> element in the example in figure 4. The data in an XML file can be verified against a ‘schema’ which is essentially a definition for the data in the XML file. A detailed discussion of XML schemas along with the extensibility feature of XML is included later in this paper.
XML Schemas versus Shared Database Model
An XML schema consists of the structural definition of an object or collection of objects. An object is defined in the schema and it contains definitions for the attributes of the object along with the data type of each attribute. Every schema must have at least one root object and any number of child objects may be embedded inside the root object. Consider the schema for the used car presented in figure 5 below. In this example the ‘car’ element is the root object and its attributes are ‘maker’, ‘model’, ‘year’, ‘miles’, ‘condition’ and ‘price’. Also notice that the type of the data other properties such as number of occurrences for each attribute are also defined in the schema. The XML file presented in figure 4 can be verified against the schema in figure 5 to validate the data. Once the XML file is validated, it may be used in any application that might need that data. For instance, two used car web-sites can advertise the same car provided both sites use the same schema. This process is exactly like the implementation of the aecXML. An XML file from an accounting application will be verified against an existing schema and the required data can then be imported into the project management application. The definition of the schemas is where disagreements between software providers are being worked out prior to the release of aecXML by the IAI aecXML domain committee.
Once a common schema is created, each manufacturer can use the ‘Extensible’ feature in XML to add data definitions specific to their product. The extensibility of XML schemas allows the addition of more data to an XML document. This is done by declaring the original XML schema as the base and creating a new schema to include additional data. Software manufacturers find this to be an attractive feature since they can maintain the privacy of their data while producing software applications that can integrate with other applications. In the used car example presented earlier, this can be useful when one of the sales web-sites’ wants to include details about accident history in their advertisement. They would use the ‘car’ schema as the base and create a new schema which would include all the data in the ‘car’ schema and additional information. The new document would still be a valid XML document.
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Figure 5: An XML schema describing the attributes of the car shown in figure 3. |
Another way to create an integrated environment is by using a single database that is shared by several applications. This may be achieved by commercially available databases such as ‘Microsoft SQL server’ or ‘Oracle SQL server’. However, this idea is much harder to sell to the software providers. The two major problem areas are that proprietary features in individual applications could be compromised and that manufacturers may have to change their programming platforms to allow their systems to interact with the database. This also has creates the problem of ownership of the database and the data within it. A unified database might also throttle innovative research due to the complexity of changing a well defined database. For example if a particular solution requires a relationship in the database to be changed, it would affect all manufacturers who then have to modify their software. This is not a problem with a shared XML schema since they only have to export data into a verifiable XML document while including more data using the ‘extensible’ feature. The author favors the use of a common data model similar to the one proposed by the IAI over the use of a shared database to integrate software applications.
Conclusions
Construction firms are heavily using information technology solutions in conducting their day-to-day operations. These tools have radically changed several processes in the industry. Web-based project management is a typical example of the changes in the last decade. While construction firms have benefited tremendously by adopting new technologies, these solutions have also created a problem in that they are not interoperable. Organizations spend significant amount of resources in manually entering data from one software application to the other. Future estimating, accounting, and project management applications must share data among themselves for construction firms to take full advantage of new technology. The integration of electronic CAD drawings with estimating packages will revolutionize the way ‘take-off’ process in estimating is done today.
Few software applications exist in isolation in any industry. There is always a need to connect process specific applications with similar applications in an organization. The W3C recognized this problem and created a new programming language called the XML. This language allows software applications to share data by sharing a common data model. This is accomplished by using XML schemas. An XML schema is a way to define the structure of data in an XML document. XML documents are created using raw data and the documents are verified against the schema for validity. Once the data is deemed valid, applications can share the data with each other. XML allows for these schemas to be expandable by using the ‘extensible’ feature of XML. The construction community has been aware of the integration issue for while and the IAI is currently developing a schema to be used in sharing data for B2B transactions. This schema called the aecXML will allow software providers for construction companies to share data. In the immediate future, participation by academicians and researchers could prove to be crucial in making the aecXML a reality.
An integrated software environment is also possible with a unified database for all software applications. However, due to the diverse nature of software providers in the construction industry and the costs of rebuilding all applications, this is not a practical solution. The author predicts that aecXML will be an industry standard in the years to come and it will be used to create an integrated software environment for the architectural, engineering and construction industries.
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