Metadata is "data that provides information about other data". Many distinct types of metadata exist, among these descriptive metadata, structural metadata, administrative metadata, reference metadata and statistical metadata. Descriptive metadata describes a resource for purposes such as identification, it can include elements such as title, abstract and keywords. Structural metadata is metadata about containers of data and indicates how compound objects are put together, for example, how pages are ordered to form chapters, it describes the types, versions and other characteristics of digital materials. Administrative metadata provides information to help manage a resource, such as when and how it was created, file type and other technical information, who can access it. Reference metadata describes the contents and quality of statistical data Statistical metadata may describe processes that collect, process, or produce statistical data. Metadata was traditionally used in the card catalogs of libraries until the 1980s, when libraries converted their catalog data to digital databases.
In the 2000s, as digital formats were becoming the prevalent way of storing data and information, metadata was used to describe digital data using metadata standards. The first description of "meta data" for computer systems is purportedly noted by MIT's Center for International Studies experts David Griffel and Stuart McIntosh in 1967: "In summary we have statements in an object language about subject descriptions of data and token codes for the data. We have statements in a meta language describing the data relationships and transformations, ought/is relations between norm and data."There are different metadata standards for each different discipline. Describing the contents and context of data or data files increases its usefulness. For example, a web page may include metadata specifying what software language the page is written in, what tools were used to create it, what subjects the page is about, where to find more information about the subject; this metadata can automatically improve the reader's experience and make it easier for users to find the web page online.
A CD may include metadata providing information about the musicians and songwriters whose work appears on the disc. A principal purpose of metadata is to help users discover resources. Metadata helps to organize electronic resources, provide digital identification, support the archiving and preservation of resources. Metadata assists users in resource discovery by "allowing resources to be found by relevant criteria, identifying resources, bringing similar resources together, distinguishing dissimilar resources, giving location information." Metadata of telecommunication activities including Internet traffic is widely collected by various national governmental organizations. This data can be used for mass surveillance. In many countries, the metadata relating to emails, telephone calls, web pages, video traffic, IP connections and cell phone locations are stored by government organizations. Metadata means "data about data". Although the "meta" prefix means "after" or "beyond", it is used to mean "about" in epistemology.
Metadata is defined as the data providing information about one or more aspects of the data. Some examples include:Means of creation of the data Purpose of the data Time and date of creation Creator or author of the data Location on a computer network where the data was created Standards used File size Data quality Source of the data Process used to create the dataFor example, a digital image may include metadata that describes how large the picture is, the color depth, the image resolution, when the image was created, the shutter speed, other data. A text document's metadata may contain information about how long the document is, who the author is, when the document was written, a short summary of the document. Metadata within web pages can contain descriptions of page content, as well as key words linked to the content; these links are called "Metatags", which were used as the primary factor in determining order for a web search until the late 1990s. The reliance of metatags in web searches was decreased in the late 1990s because of "keyword stuffing".
Metatags were being misused to trick search engines into thinking some websites had more relevance in the search than they did. Metadata can be stored and managed in a database called a metadata registry or metadata repository. However, without context and a point of reference, it might be impossible to identify metadata just by looking at it. For example: by itself, a database containing several numbers, all 13 digits long could be the results of calculations or a list of numbers to plug into an equation - without any other context, the numbers themselves can be perceived as the data, but if given the context that this database is a log of a book collection, those 13-digit numbers may now be identified as ISBNs - information that refers to the book, but is not itself the information within the book. The term "metadata" was coined in 1968 by Philip Bagley, in his book "Extension of Programming Language Concepts" where it is clear that he uses the term in the ISO 11179 "traditional" sense, "structural metadata" i.e. "data about the containers of data".
WinFS was the code name for a canceled data storage and management system project based on relational databases, developed by Microsoft and first demonstrated in 2003 as an advanced storage subsystem for the Microsoft Windows operating system, designed for persistence and management of structured, semi-structured and unstructured data. WinFS includes a relational database for storage of information, allows any type of information to be stored in it, provided there is a well defined schema for the type. Individual data items could be related together by relationships, which are either inferred by the system based on certain attributes or explicitly stated by the user; as the data has a well defined schema, any application can reuse the data. Because the system knows the structure and intent of the information, it can be used to make complex queries that enable advanced searching through the data and aggregating various data items by exploiting the relationships between them. While WinFS and its shared type schema make it possible for an application to recognize the different data types, the application still has to be coded to render the different data types.
It would not allow development of a single application that can view or edit all data types. When WinFS was introduced at the 2003 Professional Developers Conference, Microsoft released a video presentation, named IWish, showing mockup interfaces that showed how applications would expose interfaces that take advantage of a unified type system; the concepts shown in the video ranged from applications using the relationships of items to dynamically offer filtering options to applications grouping multiple related data types and rendering them in a unified presentation. WinFS was billed as one of the pillars of the "Longhorn" wave of technologies, would ship as part of the next version of Windows, it was subsequently decided that WinFS would ship after the release of Windows Vista, but those plans were shelved in June 2006, with some of its component technologies being integrated into ADO. NET and Microsoft SQL Server. Many filesystems found on common operating systems, including the NTFS filesystem, used in modern versions of Microsoft Windows, store files and other objects only as a stream of bytes, have little or no information about the data stored in the files.
Such file systems provide only a single way of organizing the files, namely via directories and file names. Because a file system has no knowledge about the data it stores, applications tend to use their own proprietary, file formats; this hampers sharing of data between multiple applications. It becomes difficult to create an application which processes information from multiple file types, because the programmers have to understand the structure and semantics of all the files. Using common file formats is a workaround to this problem but not a universal solution. Data with standardized schema, such as XML documents and relational data fare better, as they have a standardized structure and run-time requirements. A traditional file system can retrieve and search data based only on the filename, because the only knowledge it has about the data is the name of the files that store the data. A better solution is to tag files with attributes. Attributes are metadata about the files such as the type of file.
This allows files to be searched for by their attributes, in ways not possible using a folder hierarchy, such as finding "pictures which have person X". The attributes can be recognizable via some extension. Desktop search applications take this concept a step further, they extract data, including attributes, from files and index it. To extract the data, they use a filter for each file format; this allows for the data in it. However, this still does not help in managing related data, as disparate items do not have any relationships defined. For example, it is impossible to search for "the phone numbers of all persons who live in Acapulco and each have more than 100 appearances in my photo collection and with whom I have had e-mail within last month"; such a search could not be done unless it is based on a data model which has both the semantics as well as relationships of data defined. WinFS aims to provide such a data model and the runtime infrastructure that can be used to store the data, as well as the relationships between data items according to the data model, doing so at a satisfactory level of performance.
WinFS natively recognizes different types of data, such as picture, e-mail, audio, calendar, rather than just leaving them as raw unanalyzed bytestreams. Data stored and managed by the system are instances of the data type recognized by the WinFS runtime; the data are structured by means of properties. For example, an instance of a résumé type will surface the data by exposing properties, such as Name, Educational Qualification, Experience; each property may be complex types. Different data types expose different properties. Besides that, WinFS allows different data instances to be related together. Relationships are exposed as properties.