The Bluffers Guide to…Metadata!
In my past few posts I have referred constantly to Metadata, but what is it? And how can you use it?
Metadata in its most trivial form is data about other data. If you know that one line you know everything there is to know about metadata, all we need to do now is elaborate…
Metadata can classified in terms of content, mutability and logical function, I can’t describe this in any better terms than Wikipedia already has so:
- Content. Metadata can either describe the resource itself (for example, name and size of a file) or the content of the resource (for example, “This video shows a boy playing football”).
- Mutability. With respect to the whole resource, metadata can be either immutable (for example, the “Title” of a video does not change as the video itself is being played) or mutable (the “Scene description” does change).
- Logical function. There are three layers of logical function: at the bottom the subsymbolic layer that contains the raw data itself, then the symbolic layer with metadata describing the raw data, and on the top the logical layer containing metadata that allows logical reasoning using the symbolic layer.
Metadata Lifecycles and Storage
Metadata usually lasts as long as the resource it is describing lasts, this is not always ideal however. What happens when two resources merge or the resource changes in some other way, what happens to the metadata? Sometimes it is useful to keep old metadata e.g. to keep an archive of the resource as it changes. When two resources merge e.g. text documents, the metadata from each is usually discarded and fresh metadata is generated, this is something which should change if we really want an accurate version history of our documents, images and music.
Metadata is usually stored within a resource, usually in the header part of a file format, there are occasions when metadata exists outside a resource, e.g. An XML file describing a photo album might be located somewhere and the photos that make up the album may be stored somewhere completely different. Where to put metadata and how to store it is becoming a major issue, do we increase the size of the file? Or do we store it externally and risk it being separated? Should it be plain text and human readable, or should be store it as binary to decrease the storage space needed to hold it?
Metacrap?
Those who oppose metadata, or so called metacrap, are against metadata for a number of reasons, mainly they say it clogs up file formats for no particular reason, another argument is that metadata is subjective and as so there is no real objective need to have it.
My response? Their wrong. Metadata is continually being used everyday, ever tag your blog entry? What about your friends pictures on facebook? What about the author of a word document? The truth is that metadata is an essential part of digitial life, it allows us to add meaning and context to the 1’s and 0’s. Only when metadata is used incorrectly does it start becoming useless.