From Wiki:Metadata is loosely defined as data about data. Though this definition is easy to remember, it is not very precise. The strength of this definition is in recognizing that metadata is data. As such, metadata can be stored and managed in a database, often called a registry or repository. However, it is impossible to identify metadata just by looking at it. We don't know when data is metadata or just data. Metadata is a concept that applies mainly to electronically archived data and is used to describe thedefinitionstructureadministrationof data files with all contents in context to ease the use of the captured and archived data for further use. Web pages often include metadata in the form of meta tags. Description and keywords meta tags are commonly used to describe the Web page's content. Most search engines use this data when adding pages to their search index.
From Wiki: For example: The purpose of a digital image created may include metadata that describes how large the picture is, the color depth, the image resolution, when the image was created, and 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, and a short summary of the document.In various form metadata has been used in so far as a means of cataloging information archived. An example of an earlier form of metadata is the Dewy Decimal System employed by libraries to index books. In this system, the data found on small 3x5 inch (A7) sized cards with the name of the book, its author, subject matter, a brief synopsis and typically an abbreviated alpha- numeric system indicating the location of the book on particular shelves. Such data helps classify, aggregate and identify the book(s) in question to find quickly. Another form of older metadata collection is the use by US Census Bureau in what is known as the “Long Form”. The Long Form asks questions that are used to create demographic data to create patters and to find patterns of distribution.  The term was coined in 1968 by Philip Bagley, one of the pioneers of computerized document retrieval. Since then the fields of information management, information science, information technology, librarianship and GIS have widely adopted the term. In these fields the word metadata is defined as “data about data”. While this is the generally accepted definition, various disciplines have adopted their own more specific explanation and uses of the term.For the purposes of this article, an "object" refers to any of the following:a physical item such as a book, CD, DVD, map, chair, table, flower pot, etcan electronic file such as a digital image, digital photo, document, program file, database table etcPhotographic Metadata Definition: Useful information written into your photo file that will identify who owns it, what camera took it along with exposure information and keywords describing the photo making it searchable. Some is written by the camera and some is input by the photographer after downloading to a computer.
From Wiki: As the metadata application is manifold covering a large variety of fields of application there are nothing but specialised and well accepted models to specify types of metadata. Bretheron & Singley (1994) distinguish between two distinct classes: structural/control metadata and guide metadata.Structural metadata is used to describe the structure of computer systems such as tables, columns and indexes. Guide metadata is used to help humans find specific items and is usually expressed as a set of keywords in a natural language. According to Ralph Kimball metadata can be divided into 2 similar categories - Technical metadata and Business metadata. Technical metadata correspond to internal metadata, business metadata to external metadata. Kimball adds a third category named Process metadata. On the other hand, NISO distinguishes between three types of metadata: descriptive, structural and administrative. Descriptive metadata is the information used to search and locate an object such as title, author, subjects, keywords, publisher; structural metadata gives a description of how the components of the object are organised; and administrative metadata refers to the technical information including file type. Two sub-types of administrative metadata are rights management metadata and preservation metadata.metadata is an data abonut data
From Wiki: International standards apply to metadata. Much work is being accomplished in the national and international standards communities, especially ANSI (American National Standards Institute) and ISO (International Organization for Standardization) to reach consensus on standardizing metadata and registries.The core standard is ISO/IEC 11179-1:2004  and subsequent standards (see ISO/IEC_11179). All yet published registrations according to this standard cover just the definition of metadata and do not serve the structuring of metadata storage or retrieval neither any administrative standardisation.
Whether in the traditional context or in the Internet context, the key purpose of metadata is to facilitate and improve the retrieval of information. At library school, we learnt to measure information retrieval in terms of recall and precision. If we miss a lot of relevant information, we have poor recall. If we get flooded by a lot of irrelevant information, we have poor precision. In certain circumstances (such as searches for patents) very high recall is essential. However, in most circumstances, searchers would be content with a small number of relevant documents, and would be willing to scan through a few dozen citations to identify them. Recall and precision factors of 10-20% are often acceptable for most purposes.However, our own experiences with Web search engines frequently involve precision factors of much less than one percent. For example, a search of the World Wide Web using the search engine ANZWERS on the acronym "IETF" (which stands for Internet Engineering Task Force) retrieved 896,354 matches in early August 1997. Every Web page which mentioned the IETF in an incidental way was retrieved by this search.This example illustrates that search engines can return a lot of irrelevant information because they have no means (or very few means) of distinguishing between important and incidental words in document texts. If we could target our searches onto words which are used as significant terms, we could achieve an enormous improvement in precision. Metadata can be used to achieve this by identifying just the major concepts of the information resource.If we could target searches onto words or phrases that identify their correct role, we would also improve precision. For example, we could retrieve just those resources where "Green" is the name of the author, without retrieving resources about green peas or environmental issues. Metadata can be used to achieve this by identifying the different characteristics of the information resource: the author, subject, title, publisher and so on.There is also a need to improve search recall - that is, to retrieve information resources that would otherwise be missed. For example, relevant information can be missed because sites contain types of resource in addition to HTML text, such as images, databases, and PDF documents. Metadata can support retrieval of these resources by identifying them, thus ensuring they are not missed by harvesting engines.Recall can also be improved due to other factors. For example, it is known that most harvesting engines do not index every page on a site, but often only the top two or three hierarchical levels. Thus, these engines miss significant documents which, on larger and more complex sites, may be located in lower levels of the hierarchy. A better harvesting process would gather metadata from a repository created locally from a complete coverage of the local site. The data in this repository could then be gathered regularly by the harvesting engine.Some search (or harvesting) engines do now take account, to some extent, of metadata stored within HTML documents, within the META field. The Search Engine Watch site, (http://searchenginewatch.com/features.htm) maintained by Calafia Consulting, documents the behaviour of these search engines in this and other respects.
From Wiki: The HTML format used to define web pages allows for the inclusion of a variety of types of metadata, from basic descriptive text, dates and keywords to further advanced metadata schemes such as the Dublin Core, e-GMS, and AGLS standards. Pages can also be geotagged with coordinates. Metadata may be included in the page's header or in a separate file. Microformats allow metadata to be added to on-page data in a way that users don't see, but computers can readily access.Interestingly, many search engines are cautious about using metadata in their ranking algorithms due to exploitation of metadata and the practice of search engine optimization, SEO, to improve rankings, see Meta element article for further discussion. Geospatial MetadataMetadata that describe geographic objects (such as datasets, maps, features, or simply documents with a geospatial component) have a history going back to at least 1994 (refer MIT Library page on FGDC Metadata). This class of metadata is described more fully on the Geospatial metadata page.
Contents<br />What is Metadata?<br />Metadata Defeinition<br />Metadata Structures<br />Metadata Standarts<br />The purpose of Metadata<br />
What is Metadata?<br />An element of metadata describes an information resource, or helps provide access to an information resource. A collection of such metadata elements may describe one or many information resources.<br />
Metadata definition<br />Metadata definition provides information about the distinct items, such as:<br />means of creation,<br />purpose of the data,<br />time and date of creation,<br />creator or author of data,<br />placement on a network (electronic form) where the data was created,<br />what standards used<br />etc.<br />
Creation of Metadata<br />Metadata can be created either by automated information processing or by manual work.<br />Elementary metadata captured by computers can include information about when a file was created, who created it, when it was last updated, file size and file extension.<br />Metadata shall primarily created by humans to enhance access and usage of content and provide information that computers are not yet able to interpret including subject, keywords, abstract.<br />
Metadata Structures<br /> Metadata is typically structured according to a standardised concept using a well defined metadata scheme, including: metadata standards and metadata models. Tools such as controlled vocabularies, taxonomies, thesauri, data dictionaries and metadata registries can be used to apply further standardisation to the metadata.<br />
Metadata Syntax<br />Metadata syntax refers to the rules created to structure the fields or elements of metadata. A single metadata scheme may be expressed in a number of different markup or programming languages, each of which requires a different syntax. For example, Dublin Core may be expressed in plain text, HTML, XML and RDF.<br />
Metadata Types<br />Metadata can be divided into 2 similar categories - Technical metadata and Business metadata.<br />Technical metadata correspond to internal metadata, business metadata to external metadata<br />
Metadata Standards<br />International standards apply to metadata. Much work is being accomplished in the national and international standards communities, especially ANSI and ISO to reach consensus on standardizing metadata and registries.<br />The core standard is ISO/IEC 11179-1:2004  and subsequent standards (see ISO/IEC_11179). <br />
The purpose of Metadata<br />Whether in the traditional context or in the Internet context, the key purpose of metadata is to facilitate and improve the retrieval of information.<br />
Metadata on the Internet<br />The HTML format used to define web pages allows for the inclusion of a variety of types of metadata, from basic descriptive text, dates and keywords to further advanced metadata schemes such as the Dublin Core, e-GMS, and AGLS standards.<br />