users and data providers. The data on PASDA is provided by federal, state, local and regional government agencies, non-profit organizations, and academic institutions throughout the region. Data updates to existing datasets come to PASDA at different intervals and are based on the update frequency of our data partners. Monthly, quarterly, and annual updates are the norm and include PennDOT, PA Department of Environmental Protection, PA Fish and Boat Commission, PA Department of Health, PA Department of Conservation and Natural Resources, Chester County, Allegheny County, Lancaster County, City of Philadelphia, Southeast PA Transportation Authority, Delaware Valley Regional Planning Commission, PA DCNR Rivers Conservation Program, and the Natural Lands Trust. The development of metadata on PASDA is one of the most important functions. The background of PASDA's metadata development has its origins in the development of the ANSI Z39.50 standard (also known as the ISO 23950 Search and Retrieval Protocol.) This protocol was originally designed for libraries to search and retrieve records from remote library catalogs. PASDA's goal is not only to meet the existing metadata standards but also to create metadata in a format that supports easy search and retrieval of data. In the early stages of PASDA's development the metadata was either in HTML or text format and was subsequently parsed with a metadata parser. PASDA was one of the first clearinghouses to implement the use of extensible markup language. Services & Applications PASDA provides direct access to download data via FTP. Currently, PASDA has approximately 60 terabytes of data for download including vector data, imagery, elevation and lidar. In addition to direct download, PASDA has developed multiple ways to access data. In 2000, PASDA was one of the first clearinghouses to address issues related to what is known as "clip, ship, and reproject"—a process by which large data sets can be clipped to a user specified geography, reprojected, and zipped for quick download. Subsequent advances, in particular the development of Internet Map Services, have, in part, eliminated the need for these specialized services. One of the most important developments in GIS in the past decade has been the ability to create Internet Map Services—also known simply as map services. Map services allow users to consume or pull in data to their GIS software without actually having to download it thereby saving download time and storage space. Map services have been some of the most heavily used features on PASDA