Digital libraries are changing the way that we search for, find and use resources in traditional libraries. In the networked information environment they allow users to access information anywhere and anytime. They are also leading to innovative ways for teaching and learning opportunities. For example, an instructor can develop learning objects based on traditional static text-based materials by using multimedia (images, videos, sounds, and animations) technology. Learners can explore these digital learning objects in dynamic and interactive ways at their own pace, rather than by following textual instructions.
This article provides a general overview of the Geotechnical, Rock and Water Digital Library (GROW) , a part of the US National Science, Mathematics, Engineering and Technology Digital Library (NSDL) . This article demonstrates GROW's role as a learning object repository and its role as a high-quality civil engineering Web portal. Metadata standards, related authority control, and learning objects using Flash technology are reported. The learning objects design philosophy and the hierarchical structure of granularity (element, learning unit, module and theme) are described in detail. Finally, achievements including awards and site statistics are reported.
GROW started in 2001 with a $900,000 grant from the National Science Foundation (NSF) . The mission of the NSDL is to "provide organized access to high quality resources and tools that support innovations in teaching and learning at all levels of science, technology, engineering, and mathematics education" . The NSDL is not a single entity, but a collection of many educational digital libraries which are connected together through a centralised portal using Open Archive Initiative (OAI) services. The GROW digital library focuses on three areas: Civil Engineering, Rock and Water resources, with the intention to extend to other engineering fields. At the University of Arizona the project team is comprised of faculty and staff members from Civil Engineering, Mining and Geological Engineering, Agriculture and BioSystems Engineering, the Learning Technologies Center and the University Library. The team members have considerable experience in metadata, digital library system design and analysis, subject expertise, teaching, and instructional design. The diverse backgrounds of the team members promise a strong combination of skills to carry out this project.
The mission of GROW is 'to encourage and promote interest, exploration and learning in Civil Engineering through the development, collection, and dissemination of reviewed and ranked interactive learning resources continuously enhanced by new technological innovations.' There are two significant factors that distinguish GROW from other Civil Engineering digital libraries. Firstly, GROW's resources are high-quality materials, peer-reviewed by Engineering Faculty members, catalogued with a controlled vocabulary, and ranked by users. These resources are harvested from the Internet or recommended by users. Secondly, GROW has a collection of over 200 interactive learning objects created by the team. These learning objects are interactive, multimedia, and educational resources which place a strong emphasis on the active learning experience.
A learning object is defined as 'any digital resource that can be reused to support learning' . GROW learning objects are arranged in a hierarchical structure, containing four classes (element, learning unit, module and theme) that are in a sub-class and super-class relationship. An element, the lowest granularity, is a base piece that may consist of an image, some text or a data file. A learning unit, consisting of elements, is the smallest self-contained learning lesson and which provides at least one learning outcome. Interactive multimedia technology such as Macromedia Flash has been used. A module, consisting of learning units, has one or more learning outcomes. The learning units can be sequenced to accomplish different learning outcomes. These modules adopt multimedia media types, including interactive animation, video, sound, images and text. These steps in the module bring to users virtual experiments as if they were in a real laboratory. Finally, a theme, a collection of modules, can address a global topic. For example, a theme called "Effects of Water on Soils" can have modules that provide a series of learning experiences in topics on the effects of water on soils for a variety of users, such as K-12  and undergraduates .
Most of the learning objects are created using Macromedia Flash technology and require the Flash player to view them. This sometimes creates accessibility problems for users who do not have that player. Nonetheless these innovative, interactive learning objects actively support the aims of the library to encourage active learning and exploration on the part of its users. The following figure is an example of learning objects which dynamically demonstrate the danger of flowing water.
This learning object allows users to examine the effects of rising flowing water on three different sizes of vehicles (a pickup, a full-size car and a small car). The three vehicles are in the centre of a flood-stream and the flowing water is just starting to rise. The water rises gradually. The water streams past the vehicles at about 4 mph. As the water begins to rise around each vehicle, each one experiences a buoyancy force as it begins to displace water. The frictional force between the tyres and the road is what keeps the vehicles from being swept away down-stream. However when the force of the stream pushing on the cars exceeds that of the friction force, the vehicles lose contact with the road surface and are swept away.
Learning objects in GROW provide an interactive learning experience with multimedia components, to provide an alternative approach to traditional teaching and learning. This approach emphasises active learning, allows learners to learn at their own pace, and provides immediate feedback when needed. The collection of learning objects can meet the needs of users from K-12 students, to undergraduates, to professionals looking for continuing education.
GROW is also a Civil Engineering Web portal like Yahoo Civil Engineering directory . Users can suggest Web sites and Web resources for GROW's focused subjects. The GROW system has a built-in workflow that notifies reviewers for new resources, allows reviewers to examine these resources at their own pace, and helps them to release qualified resources which meet the required standards. At the same time, metadata is assigned by the reviewers based on a pre-defined template and a controlled vocabulary set. Figure 2 shows a screen capture of the GROW home page.
Metadata was one of the prime areas in which the GROW team reached a high level of efficiency and quality. GROW was one of eight projects that achieved a successful metadata harvesting from NSDL on the first attempt. GROW uses the recommended metadata elements from NSDL, basic elements from Dublin Core (DC), plus three IEEE elements recommended by the DC Education Working Group .The standard metadata allows GROW to contribute easily to the NSDL and to ensure its compatibility and interoperability within the NSDL. The primary method for contributing GROW's metadata to the NSDL is currently through OAI protocols.
GROW uses authority control, such as controlled vocabularies, to make quality metadata. The team evaluated multiple thesauri, taxonomies and controlled vocabularies based on the nature of GROW and its intended users. The American Society of Civil Engineers (ASCE) Subject Heading List  was selected as the controlled vocabulary for DC element subject.
The success of the project is reflected in several awards, users' responses, and encouraging site statistics. GROW has received awards from a number of organisations, including the prestigious Macromedia 2003 MAX award in the Educational category, Emerald Abstract's Civil Engineering Coolsite and Geotechnical Coolsite in 2003, and Best Learning Object/Instructional Module (University of Arizona Multimedia Users Group Festival 2003). In addition, the team has received very positive responses from a variety of users such as middle school teachers, engineers, undergraduate students and faculty members. Statistics show that there are many users from across the world. After the United States, Canada, United Kingdom and Australia are the top three in terms of site traffic. The learning objects collection contributes to over 50% of the site's hits. With awards and many other collaborative and outreach efforts, the site has seen a 200% increase in traffic since August 2003.
The GROW digital library not only provides its unique collection of interactive digital learning objects, but also works as a gateway to peer-reviewed high-quality civil engineering resources. The learning objects provide an interactive learning experience for a variety of users employing multimedia types. This new model of teaching and learning uses digital resources and multimedia technology to enhance learners' experience and improve knowledge retention. As the transition from traditional teaching to a hybrid traditional-digital method approaches, extensive research and evaluation will be necessary to consolidate and develop this new area of learning.
GROW is funded by a National Science Foundation (NSF) grant #DUE-0121691, and some of GROW resources were developed under NSF grant #DUE-9950906. The help of Dr. Lee Zia, Lead Program Director for the NSF National Science, Mathematics, Engineering, and Technology Education Digital Library (NSDL) Program, is greatly appreciated.