"A standard for a markup language, similar to HTML, that allows tags to be defined to describe any kind of data you have, making it very popular as a format for data feeds." (Mike Moran & Bill Hunt , "Search Engine Marketing, Inc", 2005)
"Facilitates the assignment of meaningful structures and definitions of data and services for use by multiple systems. XML simplifies the ability to transmit and share data." (Jill Dyché & Evan Levy, "Customer Data Integration: Reaching a Single Version of the Truth", 2006)
"Simple and flexible text format used to represent data. XML was designed by the World Wide Web Consortium (W3C)." (Sara Morganand & Tobias Thernstrom , "MCITP Self-Paced Training Kit : Designing and Optimizing Data Access by Using Microsoft SQL Server 2005 - Exam 70-442", 2007)
"separates content from format, thus letting the browser decide how and where content gets displayed. XML is not a language, but a system for defining other languages so that they understand their vocabulary." (Craig F Smith & H Peter Alesso, "Thinking on the Web: Berners-Lee, Gödel and Turing", 2008)
"A platform-independent markup language for specifying the structure of data in a text document used for both data storage and the transfer of data." (Jan L Harrington, "Relational Database Design and Implementation" 3rd Ed., 2009)
"A way of representing data and data relationships in text files, typically for data exchange between software of different types." (Jan L Harrington, "SQL Clearly Explained" 3rd Ed. , 2010)
"A metalanguage used to represent and manipulate data elements. Unlike other markup languages, XML permits the manipulation of a document’s data elements. XML is designed to facilitate the exchange of structured documents such as orders and invoices over the Internet." (Carlos Coronel et al, "Database Systems: Design, Implementation, and Management" 9th Ed., 2011)
"A specification for creating text files that contain hierarchical data." (Rod Stephens, "Start Here!™ Fundamentals of Microsoft® .NET Programming", 2011)
"Has been created to overcome some difficulties proper to HTML (Hypertext Markup Language) that – developed as a means for instructing the Web browsers how to display a given Web page – is a ‘presentation-oriented’ markup tool. XML is called ‘extensible’ because, at the difference of HTML, is not characterized by a fixed format, but it lets the user design its own customized markup languages (using, e.g., a specific DTD, Document Type Description) for limitless different types of documents; XML is then a ‘content-oriented’ markup tool." (Gian P Zarri, "RDF and OWL for Knowledge Management", 2011)
"A set of rules for encoding documents electronically. XML was chosen as the standard message format because of its widespread use and open source development efforts." (Mike Harwood, "Internet Security: How to Defend Against Attackers on the Web" 2nd Ed., 2015)
"A standard metalanguage for defining markup languages that is based on Standard Generalized Markup Language (SGML)." (Sybase, "Open Server Server-Library/C Reference Manual", 2019)
"Extensible markup language (XML) is a simple, very flexible text format derived from SGML (standard generalized markup language). While XML was originally designed to meet the challenges of large-scale electronic publishing, it plays an increasingly significant role in the exchange of a wide variety of data on the web." (Kamalendu Pal, "Integrating Heterogeneous Enterprise Data Using Ontology in Supply Chain Management", 2019)
"A universal markup language for text and data, using nested tags to add structure and meta-information to the content." (Daniel Leuck et al, "Learning Java" 5th Ed., 2020)
"A 'best practices' subset of SGML that has been designed by the Worldwide Web Consortium (W3C) for use on the Internet." (Microfocus)
"A notation in which you describe the structure of information in a text document by enclosing information in user-defined tags that define the syntactic elements. A flexible way to create common information formats and share both the format and the data on the World Wide Web, intranets, and elsewhere. J2EE deployment descriptors are expressed in XML." (Microfocus)
