Metadata for digital collections is usually stored in two places: either within the digital file itself; or within a database (or less usually a spreadsheet). Neither option is mutually exclusive and it is increasingly common to use both methods concurrently.
Storing metadata within the digital file
As the earlier discussion of file-stored metadata indicated, there is already a certain amount of, usually technical, metadata held within a digital file. Modern file-formats (such as JPEG2000 and MPEG4, for example) have increased support for metadata storage. And there are many software applications that can be used to view, edit and export this metadata.
Some of this might be extracted for use outside of the digital asset. In addition to extracting metadata, it is possible to embed some metadata within the digital asset. Those embedding metadata into still image files can make use of the well-supported IPTC standard (originally developed to enable photojournalists to 'wire' their images) or the eXstensible Metadata Platform (XMP) standard.
An advantage of storing metadata within the digital file itself is that it always remains with the file, even when it is removed from its original context.
Storing metadata within a database
Most developers of digital collections will make use of a database to hold their metadata. Usually the database will store the metadata separately from the file itself and link or make reference to it. There are a wealth of database software and content and asset management systems available for the purposes of storing and managing metadata.
A system could be as simple as creating a small database with fields for the required elements of descriptive information and the location of a digital file on an internal hard drive. Such simple systems allow for infinite customisation and are usually relatively straight forward to develop. But for collections that perhaps require a more complex set of metadata, an asset management system may be required. Dedicated management systems allow for more advanced operations and often support at least some standard metadata schemas.
A further point to note is that the choice of system can also be affected by local considerations such as the available staff skills and the technical infrastructure of the institution. Therefore it may be worthwhile consulting with the IT department to ascertain which database software and systems can be supported.