Impressive results have been achieved in the development of standardized ... business â something that the Web promised to become but failed to deliver. Gartner group ... Computing grid - multiple computers to solve one application problem.
international conference on construction information technology (incite 2004): world it for design & construction langkawi, malaysia: 18 –21 february 2004 Hosted by the Construction Industry Board of Malaysia, The Hong Kong Polytechnic University and The University of Salford, UK
SEMANTIC GRID INFASTRUCTURE FOR AEC VIRTUAL ENTERPISE – A RESEARCH AGENDA ŽIGA TURK, VLADO STANKOVSKI, MATEVŽ DOLENC AND TOMO CEROVŠEK University of Ljubljana, FGG-IKPIR, Chair of Construction Informatics Jamova 2, Ljubljana, Slovenia
Abstract. Construction activities take place in what can be called a dynamic virtual organization (VO). VOs require a secure, reliable, scalable information infrastructure that allows collaboration and the sharing of information, computation and human resources. They need an infrastructure that would ensure the interoperability of their information systems while maintaining the privacy of their data, rapid joining and parting a VO and provide a higher quality of service, more information, faster computation, than available their own infrastructure. Some of these requirements have been addressed by the research in computer integrated construction. Impressive results have been achieved in the development of standardized building information model (BIM). Infrastructures, however, on which the BIMs are being demonstrated are quite fragile. At best they rely on XML, Web services and the semantic Web technologies. In the meantime, grid technologies have been providing unpreceded computing and storage power. The paradigm is spinning off its roots and is believed to become the workhorse of networked business – something that the Web promised to become but failed to deliver. Gartner group identified grids to be driver of progress in the area of networked economy. MIT Technology Review has named grid computing one of "Ten Technologies That Will Change the World." Construction is one of the most demanding users of VO infrastructures and could potentially enormously benefit from grid computing. In this position paper we present the state of the art and outline a research agenda. We propose a particular focusing of the research work on semantic grid technology and the coupling of the ontology and structured information exchange work into the very fabric of the grid – thereby making the grid infrastructure not only technically robust and secure but also aware of the business processes that take place in construction.
1.
Introduction
The integration of the AEC industry and the interoperability of the hundreds of software applications supporting the design and construction of the built environment have been providing one of the most challenging environments for the application of information and communication technologies. The "islands of automation" problem has been identified by the AEC community in the late 1980s and several national and EU project have been tackling the problem since. Grids are expected to be the solution to the "islands of computation" problem (Hannus, 1987). Today, technical solutions for interoperability range from file format translators, local databases, document management systems, project Webs, workflows, planning and scheduling systems to complex Web services and ORB's. These need individual installation, access, configuration and expertise to be used. Integration of some these components has been demonstrated in FP4 and FP5 projects but is far from being robust and easy to implement and use. Any construction project is performed by a virtual organization consisting of dozens or even hundreds of companies, consultants, SMEs etc. It has been found out by several strategic documents (Smith, 2001) that the problem of this industry is coordinated resource sharing and problem solving in dynamic, multi-institutional virtual enterprises. The sharing includes access to computers, software, data, people and
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other resources, as is required by a range of collaborative design and problem-solving strategies. The key to an efficient collaboration is the shared semantics of the data, enabled by a common information model and/or ontology. AEC problems are often three dimensional with million degrees of freedom, which require for their handling high performance computational units. The modelling and solving often require resource sharing across institutional boundaries. Given the requirements outlined above, grids could ensure the interoperability and collaboration platform providing that they include the key ingredient required for a complex engineering virtual organization - the support for the shared semantics (Sowa, 1984, Guarino et al., 1997). It is in this area where we believe innovation and extension of the current grid architectures is required. 2.
State of the art
In this section we present the state of the art in grid computing and AEC interoperability. We believe that there is a clear convergence between the two. 2.1
GRIDS AND SEMANTIC GRIDS
client-server
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grid client
client
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server server server client
peer client
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peer
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Figure 1. Three popular networked computing paradigms.
Grid is a type of parallel and distributed system that enables the sharing, selection, and aggregation of geographically distributed "autonomous" resources dynamically at runtime depending on their availability, capability, performance, cost, and users' quality-of-service requirements (http://www.gridcomputing.com/). The term, grid computing, has become one of the latest buzzwords in the IT industry. Grid computing is an innovative approach that leverages existing IT infrastructure to optimize compute resources and manage data and computing workloads. According to Gartner, "a grid is a collection of resources owned by multiple organizations that is coordinated to allow them to solve a common problem." Gartner further defines three commonly recognized forms of grid: • • •
Computing grid - multiple computers to solve one application problem Data grid - multiple storage systems to host one very large data set Collaboration grid - multiple collaboration systems for collaborating on a common issue (http://support.sas.com/rnd/scalability/grid/).
Grid computing has its origins in solving computationally intensive problems and is well documented in papers and books (Foster and Kesselman, 1999). Recent developments and trends of grid computing go beyond the solving of data (petabytes) or computationally (teraflops) problems for scientists and engineers towards making grids a suitable business infrastructure for virtual organizations. Grids are increasingly
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viewed as services (Foster et al., 2002) aware of the business semantics. Semantic grids should provide to the grids what the semantic Web is providing to the Web - communication based on high level, meaningful entities. Convergence of grid technology and the Web services (Berners-Lee et al., 2001) technology is demonstrated in toolkits such as Globus (2003) that implement the Open Grid Services Architecture OGSA (2003) and are compatible with SOAP, WSDL and UDDI - the pillars of the Web services architecture. Main features of the "grid services" infrastructure are that (1) whole grids can be regarded as a Web service, (2) individual core grid functions have a Web services like interface and (3) existing Web services can become grid enabled and make use of grid's virtualization, scalability and security mechanisms. A related concept to semantic grids is "cognitive grid" (Kesselman, 2001) that is sometimes understood as intelligent management of grid resources. Among the numerous research projects in the EU, the US and beyond, some are particularly relevant: The GEODISE project (Grid Enabled Optimization and Design Search for Engineering) was one of the first to explore the possibilities of the semantic grid, however, the semantics was being attached to files as metadata. True semantic-rich information is not addressed. The myGrid project defined its architecture using the OGSA architecture but does not seem to be based on a common ontology. The COG project has similar goals to Grid research, but is addressing a different business sector and seems to be primarily concerned with the heterogonous data formats and not heterogonous information schema addressed in Grid research. Also relevant to the Grid research are the CoAKTinG (Collaborative Advanced Knowledge Technologies in the Grid) and GRENADE (Grid-Enabled Desktop Environments) projects that address the interactive collaboration using grids. The only grid project related to the AEC sector that we are aware of is the NSF funded SCEC/IT (Information Infrastructure for Earthquake Research). The rather broad and practical goal is to "provide information technology infrastructure for earthquake research, including knowledge representation and reasoning, Grid technologies, digital libraries, and interactive knowledge acquisition". 2.2
INTEROPERABILITY IN AEC
Characteristic for the AEC industry are the uniqueness of the products, the processes, the VO and the improvised virtual organization involved in the process. The items to be integrated are seldom predefined and the integrated solution is unlikely to be repeated. One stable element in this framework is the conceptual model of a building product. While buildings are different from each other, the language (and the data structures) required to describe them are believed to be stable. Both the ISO and the IAI have made a considerable investment into the building product model standard that defined the data structured required to describe any building product. European projects, such as CIMSTEEL, COMBINE, COMBI, ATLAS, eConstruct, ToCEE, ISTforCE, eCOGNOS, CONCUR, PROCURE, ICCI, prodAEC and others have demonstrated that by using these standards data created in one application may be used in another (see http://www.itcon.org/cgi-bin/special/Show?_id=2001eu for an overview). In spite of the extensive research in building information models, the industry still communicates using line drawings, files and perhaps project webs. We believe that one reason for that is that the IT infrastructures today are well suited for semantically poor data formats and file level information exchange. Semantic Web and web services technologies, built around XML have been demonstrated in research projects (eCONSTRUCT, ISTforCE) but their scalability in large complex industrial environments has not been tested. Building product model is defined, and IFC version 2.X is supported by key 3D modelling suites like ArchiCAD, Architectural Desktop and Microstation. They can produce a building information model (BIM) that will be used by hundreds of other applications that support the design, planning and maintenance of building products. These applications will need to read and write the building information model. Today, they do so in a variety of ways. The prevailing way is by reading and writing files in a format and schema conforming to the standard. Where to write data to and where to read it from needs to be managed by the human user each time a program is started (File ... Open) or closed (File ... Save as). These files may be uploaded / downloaded to / from project webs. Again, humans are to a large extent responsible for locating the right information at the right time. Building information model databases are being developed that will replace files as container of BIM data. Several such databases are entering the market, for example WebStep by Eurostep, EXPRESS Data
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Manager by EDM Technology, and IFC Model Server by SECOM, BSPro Server from Granlund etc. For software to work with these databases, specialised interfaces (APIs) binding the program to a location of a particular database will be needed. Again, in a multi project environment, with multiple programs being used on-demand, this may be so hard that it will effectively discourage the use of building information models. 3. 3.1
Vision, goals and research agenda STRATEGIC VISION
In a hospital project, for example, collaboration of experts from fields of urban planning, local authorities, social security and health insurance, architecture, structural engineering, medicine, medical technology, hygiene, HVAC, accounting, law etc. is required. No two hospitals are the same. For no two hospitals, the same team of experts enumerated above would be called in. The group of companies and contractors involved would be different each time. Some, like the chief designer or main contractor would stay on the project longer, some would just come in, do their job, and get out; quickly and dynamically. They need a platform, which lets them get in and out of an extremely complex virtual enterprise, built around complex, structured information. Like plugging a power cord into a wall socket for electricity. Like plugging into the grid! The vision of the use of grids in AEC is to provide infrastructure where a user would simply get building information model information from the grid and also put it there. The complexity of the IT, the internet, that will be used to physically store this information, protect it, make it available to others etc. would be totally hidden from the end user. The location of information and software resources would be “the grid” not a server on some IP number somewhere, but a robust, reliable, secure, scalable “grid”, very likely redundantly distributed across several severs around the internet. She would use terms from her professional vocabulary, from an engineering ontology, to find relevant information. Similarly, software authors would make the software semantically compliant with the standard building model and technically compliant with the grid. The "Save As ..." option would be replaced by "Send to grid" and the "Load ..." with an ontology aware query mechanism, that would search the grid for relevant information. 3.2
TACTICAL GOALS
The long term practical goal of the grid related research in AEC is to provide traditional industries such as construction stable, co-allocated, reliable, unified, adaptive, remote, ambient accessible, interoperable, pay-per-demand access to (1) information, (2) communication and (3) processing infrastructure in thus finally provide integration and interoperability infrastructure. This goal cannot be achieved by a single research project. The work should focus on the enablers for this paradigm shift - from internet and web services - to the grid. The enablers are researchers, standardization bodies and key software developers. They need a reference grid, which will be in a position to provide the strategic steering of their future developments. The key scientific question addressed to be addressed is how grid technology can be used to address the interoperability of software and services working with complex and semantically rich information, in addition to distributed processing power that can crunch this information. This should be done in an environment characterised by some standard data structures that are undergoing a dynamic evolution. Conceptually, we believe that there is a need for an ontic level above the information schema level. This should be done by extending the OGSA with common grid semantics. The key technological objective is to make the grid infrastructure available to the mostly SME companies that are providing the engineering software and whose speciality may be topics like structural mechanics or 3D solid modelling and not latest trends in middleware technology. The results of the technical work would be to show how typical server side applications or components of applications can be made grid-computing compatible and how the mostly client side applications can interface with the grid. The project will provide the necessary libraries, toolkits and guidelines.
SEMANTIC GRID INFRASTRUCTURE FOR AEC 3.3
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RESULTS OF AEC GRID RESEARCH
The AEC community is newly exposed to the grid but can provide one of the most challenging application areas. We have pointed out in Section 2.1the extensive development that is taking place. Yet the notion that the grid community has on “semantics” is so much simpler than what IFC or GPP minded construction IT researchers understands by it. The AEC community can offer the development of the shared semantics extensions to the current reference grid architectures, new middleware software based on existing grid middleware. For its SME software developers it should provide adapters that adapt software to interface to the grid, and toolkits, that will allow any SME to adapt their software. 4.
The need for standards
Standardization has been the driving element of the AEC interoperability research and the future research in grid computing should contribute both to AEC as well as grid standards. 4.1
CONTRIBUTION TO INTEROPERABILITY STANDARDS AND ONTOLOGIES
AEC interoperability standards, most notably the IAI-IFC aka ISO PAS 16739 IFC, bcXML, aecXML, ISO 10303 STEP and the related STEP/SDAI protocols are at an early stage of transition from research environments towards industrial use. An adequate infrastructure on which software that would support these standards would run comfortably and smoothly, does not exist. Grids have the potential to provide that. At a recent workshop at CEN (Comité Européen de Normalisation) five areas of specifications (CWAs CEN Workshop Agreements) that may lead to CEN standardisation, were identified (resulting, in part, from the ICCI project involving three Grid research partners): 1. European eConstruction Framework. This framework will model on a high abstraction level the world of "eConstruction" with all relevant dimensions. 2. European eConstruction Architecture. A common, logical architecture fulfilling the EeF incorporating vital components like: schemas, taxonomies, APIs and software. 3. European eConstruction Meta-Schema (EeM). 4. European eConstruction Ontology (EeO) 5. European eConstruction Software Toolset (EeS) Grid research directly addresses the needs of #1 and #2. Through the development of a construction ontology in relation to the grid the needs of #4 would be addressed. Other AEC standardisation issues for the grid research include: • evolve the dated, client-server, STEP physical file based, ISO 10303-22 SDAI (Standard Data Access Interface) into a modern, grid enabled information access interface to product model data. • involve IAI-IFC development. • contribute to the harmonisation of competing ontologies currently available in the construction sector, particularly in ironing out the differences between the implicit ontology’s of IAI-IFC and those developed under the ISO 12006-2 and the ISO 12006-3 framework standards. • contribute to the development of an explicit ontology of the AEC components of the IAI-IFC. 4.2
GRID STANDARDS
Grid (Services) Computing is based on an open set of standards and protocols (i.e., Open Grid Services Architecture: OGSA) that enable communication across heterogeneous, geographically dispersed IT environments. The current trend is to produce a broader set of standards that cover all aspects of Grid technologies (computational, data storage, networking and web services). This effort is articulated through the Global Grid Forum. AEC researchers should access to these forums to promote the international relevance of Grid research and contribute to the emerging standards. The focus should be the proposal of semantic extensions to the OGSA specification. Currently OGSA's ontology is technical - it speaks of services, protocols, processes, computers etc. We suggest to build the semantic deep into the core of the grid standards so that any grid related service or protocol can have a meaningful "business" role. Our current idea is to allow for an arbitrary ontology, specified in one of the well
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established ontology languages, become part of the very fabric of the grid (Error! Reference source not found.). 5.
Draft architecture
This section outlines the initial ideas on the architecture for the AEC grid. 5.1
ONTOLOGY ENHANCEMENTS TO THE GRID
As discussed in Section 2 recent developments in the grid community extended the architecture towards the services paradigm that is a prerequisite for semantic grid. Figure 1 shows this architecture. We believe that if the grid is supposed to become an integrative element for virtual organization (VO), the notion of the business concepts of this VO should be an integral part of the grid. We suggest to achieve this by adding an ontology layer into the grid that would allow for any grid service to know what business relevant some data or process has. The layer would be made available to other functionality through an ontology server. Particularly important is this service to the database services of the grid, however, several functions of the grid (MDS, GRAM) could work more intelligently, if they are aware of the business context. GRAM
GridFTP
MDS
DataGrid ontology Services
Grid Services shared ontology HTTP, LDAP, SOAP, TLS/GSI, … IP
Figure 2. Extensions (white) of the current grid architectures (grey) to support semantic collaboration.
Interoperability in AEC today, at best relies on the management of IFC files. Attempts to use true IFC databases are academic. Environments are fragile and depend on a single server that provides such crucial functions as information and process management for a complex project. Grid research suggests to use the grid as a robust, scalable, safe infrastructure for the AEC industry. It would allow seamless integration of software committing to the IAI standards and focus the developers into the functionality and not data exchange or interfacing with this or that information server. The grid is the place for the data Currently there are a few companies providing ASP services and project webs to engineering communities that allow collaboration and information sharing. The grid will extend this concept towards true resource sharing and on-demand resource renting. This will allow for new business models to be developed as well as the rethinking of the IT infrastructures in the industry. Grids could provide the necessary robustness as well as security (through the X.509 mechanism) that would make outsourcing the IT infrastructure a more realistic option than today when they have to rely on a multitude of chaotically interwoven services. The grid research in AEC should introduce two major improvements visible to the end user as well as the application developer: 1.
The grid infrastructure eliminates the need of knowing exact locations of semantically rich data and complex problem solving services. They are "on the grid".
2.
The ontology reduces the need to know the exact structure and access paths of the data in product model databases. They can be accesses by using an engineering ontology as opposed object names and record keys.
SEMANTIC GRID INFRASTRUCTURE FOR AEC 5.2
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THE OVERALL ARCHITECTURE
CAD CAD
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CAD CAD
CAD CAD
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OGSA or similar
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generic client services
CAD CAD
CAD CAD application application (WS part) (WS part)
CAD application application (WS part) (WS part)
CAD CAD applicatio applicatio n (WS n part) (WS part) CAD
CAD CAD applicatio applicatio n (WS n (WS part) part)
CAD CAD application application (WSpart) part) (WS
CAD CAD applicatio applicatio (WS nn(WS part) part)
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application grid adapters
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CAD CAD applicatio applicatio n (WS n part) (WS part)
architectural design
structural design
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semantic grid infrastructure generic server services server grid adapters
project space
facility mngmnt.
ap pl.
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product data grid
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Figure 3. The AEC grid infrastructure (middle) with grid-side servers (below) and workstation side clients.
In Figure 3, the users are using the applications. These applications need information and functionality from the outside of the user's workstation, from the grid. The applications therefore have a workstation component and the grid based component. The communication media between the workstation and the grid is the Internet and the workstation applications, their grid based counterparts, as well as the grid only services are connected to the grid with a series of interfaces. At the very bottom there are numerous computers on which these "grid side" services run. Workstations would typically not know on which machine the service is running. Computationally intensive services would run on several in parallel, big databases would be spread across several machines. Simple services would have redundant backups in case of computer or network failures. Any prototyping should therefore develop these components: grid enabled workstation applications (the first three from the left) that connect to a grid through a
specialised semantic grid adapter for each application. This adapter talks to the workstation-side semantic grid client common to all applications on a workstation. Over the internet, this client connects to
server side semantic grid server. It would run on machines providing grid-enabled services.
semantic grid adapter will be used by services that are to made grid enabled.
specialised core servers, such as the product database and an ontology server. This software may not have a workstation component other than some administration interface
Together the above forms a semantic collaboration grid.
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Discussions
In spite of successful pilots, the AEC industry lack a robust collaboration infrastructure. Grids are the latest hyped technology that promises the solution to this decades old problem allowing both the researchers as well as the industry to capitalize on the development in standards of the past decades. A grid is a natural transition path for the project webs and application service providers. In this paper we have not been mentioning a very clear potential that the grid has for the providers of complex numerical and modeling software that is truly hungry for processing power and gigaflop computers. Research in the field of grids in AEC is just starting. An EU project has been proposed, AEC partners have been involved in the preparation of a Grid integrated project. There is at least one national grid related project (in Slovenia – www.gridforum.si) seriously is focusing on the AEC aspects of the grid. However, grid research in AEC is still rather new. The vision shared by the authors of this paper is that the AEC community should work towards a single AEC grid in which or various services and software could be plugged in and not repeat the mistakes of the various “integration” projects that developed their own collaboration infrastructures from scratch. This paper is therefore proposing the establishing of aec.gridforum , to coordinate and harmonize grid efforts in AEC as well as to show the general grid community, that to support, with grid technology, virtual organizations of a particular domain, domain specific solutions, particularly those related to domain ontologies, should be built into the fabric of the grid. 7.
Acknowledgement
The authors would like to acknowledge the contribution of Jarek Nabrzyski, Matti Hannus and Peter Katranuschkov who took part in the discussions leading to this paper.
8.
References
Berners-Lee T, Hendler J, Lassila O (2001). The Semantic Web, A new form of Web content that is meaningful to computers will unleash a revolution of new possibilities, Scientific American, May 2001. De Roure D, Jennings N, Shadbolt N (2003). The Semantic Grid: A Future e-Science Infrastructure : in Grid Computing: Making the Global Infrastructure a Reality, Wiley & Sons, England. Foster I and Kesselman C editors (1999). The Grid: Blueprint for a New Computing Infrastructure. Morgan-Kaufmann. Foster I, Kesselman C, Nick J, Tuecke S (2002). The Physiology of the Grid: An Open Grid Services Architecture for Distributed Systems Integration, Open Grid Service Infrastructure WG, Global Grid Forum, June 22, 2002. Guarino N, Borgo S and Masolo C (1997). "Logical modeling of product knowledge: towards a well-founded semantics for STEP," in Proceedings of the European Conference on Product Data Technology, Sophia Antipolis, France. Globus (2003) http://www-unix.globus.org/toolkit/ Hannus and Sernen (1987) Islands of automation, updated by Hannus, 2000. John F. Sowa (1984) "Conceptual Structures: Information Processing in Mind and Machine", Addison-Wesley, Reading, MA. Kesselman K (2001). The Cognitive Grid: Grid Services Meet the Semantic Web, University of Southern California. OGSA (2003) http://www.ggf.org/ogsa-wg/ Smith, H. (2001). The implications of the Latham, Egan and Urban Task Force reports for interdisciplinary working, Heriot Watt University.
