Technical Glossary

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  • Apache (Server):

The Apache HTTP Server, commonly referred to simply as Apache, is primarily used to serve both static content and dynamic Web pages on the World Wide Web. Many web applications are designed expecting the environment and features that Apache provides.

  • API:

An application programming interface (API) is a source code interface that a computer application, operating system or library provides to support requests for services to be made of it by a computer program.

  • Client:

A client is an application that connects to a (remote) service on another network by some form of computer network. The term was first applied to devices that were not capable of running their own stand-alone programs, but could interact with remote computers via a network.

The client-server model is still used today on the Internet, where a user may connect to a service operating on a remote system through the internet protocol suite. Web browsers are clients that connect to web servers and retrieve web pages for display. Most people use e-mail clients to retrieve their e-mail from their internet service provider's mail storage servers. Online chat uses a variety of clients, which vary depending on the chat protocol being used.

Increasingly, existing large client applications are being switched to websites, making the browser a sort of universal client. This avoids the hassle of downloading a large piece of software onto any computer you want to use the application on. An example of this is the rise of webmail. (See: Server, Thin Client and Fat Client)

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  • Domain Name:

A name that identifies a computer or computers on the internet. These names appear as a component of a Web site's URL, e.g. wikipedia.org. This type of domain name is also called a hostname.

  • Fat Client:

A fat client (see: Client) is a client that performs the bulk of any data processing operations itself, and does not necessarily rely on the server. The fat client is most common in the form of a personal computer, as the personal computers or laptops can operate independently. Programming environments for rich clients include Curl, Delphi, Droplets, Java, win32 and X11.

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g h i

  • GET:

See HTTP

  • GML:

The Geography Markup Language (GML) is the XML grammar defined by the Open Geospatial Consortium (OGC) to express geographical features. GML serves as a modeling language for geographic systems as well as an open interchange format for geographic transactions on the Internet.

Example of Polygon definition: 

<gml:Polygon>
        <gml:outerBoundaryIs>
             <gml:LinearRing>
                <gml:coordinates>0,0 100,0 100,100 0,100 0,0</gml:coordinates>
             </gml:LinearRing>
       </gml:outerBoundaryIs>
</gml:Polygon>
  • GUI:

A graphical user interface (GUI) is a type of user interface which allows people to interact with a computer and computer-controlled devices which employ graphical icons, visual indicators or special graphical elements called "widgets", along with text, labels or text navigation to represent the information and actions available to a user. The actions are usually performed through direct manipulation of the graphical elements.

  • GPL:

The GNU General Public License (GNU GPL or simply GPL) is a widely used free software license, originally written by Richard Stallman for the GNU project. It is the license used by the Linux kernel. The GPL is the most popular and well known example of the type of strong copyleft license that requires derived works to be available under the same copyleft. Under this philosophy, the GPL is said to grant the recipients of a computer program the rights of the free software definition and uses copyleft to ensure the freedoms are preserved, even when the work is changed or added to.

  • HTTP:

Hypertext Transfer Protocol (HTTP) is a communications protocol used to transfer or convey information on the World Wide Web. HTTP is a request/response protocol between clients and servers. The client making an HTTP request - such as a web browser, spider, or other end-user tool - is referred to as the user agent. The responding server - which stores or creates resources such as HTML files and images - is called the origin server. In between the user agent and origin server may be several intermediaries, such as proxies, gateways, and tunnels. It is useful to remember that HTTP does not need to use TCP/IP or its supporting layers. Indeed HTTP can be "implemented on top of any other protocol on the Internet, or on other networks. HTTP only presumes a reliable transport; any protocol that provides such guarantees can be used."

HTTP defines eight methods (sometimes referred to as "verbs") indicating the desired action to be performed on the identified resource. But GET and POST are the most currently used.

GET -- Requests a representation of the specified resource. By far the most common method used on the Web today. Should not be used for operations that cause side-effects (using it for actions in web applications is a common misuse).

POST -- Submits data to be processed (e.g. from an HTML form) to the identified resource. The data is included in the body of the request. This may result in the creation of a new resource or the updates of existing resources or both.

  • IIS:

Microsoft's Internet Information Services (IIS, formerly called Internet Information Server) is a set of Internet-based services for servers using Microsoft Windows.

  • IP:

An IP address (Internet Protocol address) is a unique address that certain electronic devices use in order to identify and communicate with each other on a computer network utilizing the Internet Protocol standard (IP)—in simpler terms, is a computer address Example: 127.0.0.1 or 132.72.132.23

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  • JAVA:

Java is a programming language originally developed by Sun Microsystems and released in 1995 as a core component of Sun's Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities. Java applications are typically compiled to bytecode which can run on any Java virtual machine (JVM) regardless of computer architecture.

  • KVP: A Key-Value-Pair is a set of data items that contain a key, such as an account number or part number, associated to a value. Key-value pairs are widely used in tables, configuration files, databases or HTTP request. Examples of KVP: version=0.1 or Request=DescribeCapabilities.
  • Linux:

Is a Unix-like computer operating system. Linux is one of the most prominent examples of free software and open source development; its underlying source code can be freely modified, used, and redistributed by anyone.

  • Linux distribution:

A Linux distribution, often simply distribution or distro, is a member of the Linux family of Unix-like operating systems comprising the Linux kernel, the non-kernel parts of the GNU operating system, and assorted other software. Because most (if not all) of the kernel and software packages are free and open source, Linux distributions have taken a wide variety of forms — from fully-featured desktop and server operating systems to minimal environments (typically for use in embedded systems, or for booting from a floppy). Aside from certain custom software (such as installers and configuration tools) a "distro" simply refers to a particular assortment of applications married with a particularly compiled kernel, such that its "out-of-the-box" capabilities meets most of the needs of its particular end-user base.

There are currently over three hundred Linux distribution projects in active development, constantly revising and improving their respective distributions. One can distinguish between commercially-backed distributions, such as Fedora (Red Hat), SUSE Linux (Novell), Ubuntu (Canonical Ltd.) and Mandriva Linux and community distributions such as Debian and Gentoo.

  • LGPL:

The GNU Lesser General Public License (formerly the GNU Library General Public License) or LGPL is a free software license published by the Free Software Foundation. It was designed as a compromise between the strong-copyleft GNU General Public License and permissive licenses such as the BSD licenses and the MIT License.

The main difference between the GPL and the LGPL is that the latter can be linked to (in the case of a library, 'used by') a non-(L)GPLed program, which may be free software or proprietary software.

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  • MONO:

The Mono project provides the necessary software to develop and run .NET client and server applications on Linux, Solaris, Mac OS X, Windows, and Unix.

  • .NET:

The Microsoft .NET Framework is a software component that can be added to or is included with Microsoft Windows operating system. It provides a large body of pre-coded solutions to common program requirements, and manages the execution of programs written specifically for the framework. The .NET Framework is a key Microsoft offering, and is intended to be used by most new applications created for the Windows platform.

The pre-coded solutions that form the framework's class library cover a large range of programming needs in areas including: user interface, data access, database connectivity, cryptography, web application development, numeric algorithms, and network communications. The functions of the class library are used by programmers who combine them with their own code to produce applications.

  • OGC:

The Open Geospatial Consortium (OGC) is an international voluntary consensus standards organization. In the OGC, more than 330 commercial, governmental, nonprofit and research organizations worldwide collaborate in an open consensus process encouraging development and implementation of standards for geospatial content and services, GIS data processing and exchange. It was previously known as Open GIS Consortium.

  • OM:

Obervation & Measurements, is a general model and XML encodings for observations and measurements, including but not restricted to those using sensors.

  • Open Source:

Open source is a set of principles and practices that promote access to the design and production of goods and knowledge. The term is most commonly applied to the source code of software that is available to the general public with relaxed or non-existent intellectual property restrictions. This allows users to create software content through incremental individual effort or through collaboration.

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  • Port(s):

In the TCP and UDP protocols used in computer networking, a port is a special number present in the header of a data packet. Ports are typically used to map data to a particular process running on a computer.

Ports can be readily explained with an analogy: think of IP addresses as the street address of an apartment building, and the port number as the number of a particular apartment within that building. If a letter (a data packet) is sent to the apartment (IP) without an apartment number (port number) on it, then nobody knows who it is for (which service it is for). In order for the delivery to work, the sender needs to include an apartment number along with the address to ensure the letter gets to the right domicile.

Port numbers can occasionally be seen in the URLs of websites. By default, HTTP uses port 80 and HTTPS uses port 443, but a URL like http://www.example.com:8000/blah/ would try to connect to an HTTP server on port 8000 instead.

  • POST:

See HTTP

  • Python:

Python is a high-level programming language first released by Guido van Rossum in 1991. Python is designed around a philosophy which emphasizes readability and the importance of programmer effort over computer effort. Python core syntax and semantics are minimalist, while the standard library is large and comprehensive. Community practices in Python programming have led to the recognition of a Python philosophy.

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  • SAS:

Sensor Alert Service is a standard web service interface for publishing and subscribing to alerts to sensors.

  • Schema (XML):

XML Schema is a set of rules to which an XML document must conform in order to be considered 'valid' according to that schema. However, unlike most other schema languages, XML Schema was also designed with the intent of validation resulting in a collection of information adhering to specific datatypes, which can be useful in the development of XML document processing software,

An example of a very simple XML Schema Definition to describe a country is given below. 

<xs:schema
  xmlns:xs="http://www.w3.org/2001/XMLSchema">
    <xs:element name="country" type="Country"/>
    <xs:complexType name="Country">
        <xs:sequence>
            <xs:element name="name" type="xs:string"/>
            <xs:element name="population" type="xs:decimal"/>
        </xs:sequence>
    </xs:complexType>
</xs:schema>

An example of an XML document that conforms to this schema is given below (assuming the schema file name is "country.xsd"). 

<country
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:noNamespaceSchemaLocation="country.xsd">
    <name>France</name>
    <population>59.7</population>
</country>
  • SensorML:

SensorML is an Open Geospatial Consortium standard markup language (using XML schema) for providing descriptions of sensor systems. By design it supports a wide range of sensors, including both dynamic and stationary platforms and both in-situ and remote sensors.

Functions supported include: 

   - sensor discovery
   - sensor geolocation
   - processing of sensor observations
   - a sensor programming mechanism
   - subscription to sensor alerts
  • Server:

Is an application or device that performs services for connected clients as part of a client-server architecture. Any computer or device serving out applications or services can technically be called a server. (See Apache).

  • SOAP:

SOAP is a protocol for exchanging XML-based messages over computer networks, normally using HTTP/HTTPS.

  • SOS:

Sensor Observation Service has the goal of providing access to observations from sensors and sensor systems in a standard way that is consistent for all sensor systems including remote, in-site, fixed and mobile sensors. An SOS organizes collections of related sensor systems as constellations (Observation Offering).

  • SPS:

Sensor Planning Service is a standard web service interface for requesting filtering user-driven acquisitions and observations. This is the intermediary between a client and a sensor collection management environment.

  • SWE:

Sensor Web Enablement is an overview and high level architecure of a computer accessible network of spatially distribuited sensors that monitor several/(or a) conditions. SWE can be considered an "umbrella" architecture and XML scheme of Observation & Measurements Schema (OM), Sensor model Language (SensorML), Transducer Markup Language (TransducerML ot TML), Sensor Observation Service (SOS), Sensor Planning Service (SPS), Sensor Alert Service (SAS) and Web Notification Services (WMS).

  • TCP:

The Transmission Control Protocol (TCP) is one of the core protocols of the Internet protocol suite. TCP provides reliable, in-order delivery of a stream of bytes, making it suitable for applications like file transfer and e-mail. It is so important in the Internet protocol suite that sometimes the entire suite is referred to as "the TCP/IP protocol suite."

  • Thin Client:

A thin client is a minimal sort of client. Thin clients use the resources of the host computer. A thin client's job is generally just to graphically display pictures provided by an application server, which performs the bulk of any required data processing. Programming environments for thin clients include JavaScript/AJAX (client side automation), ASP, JSP, Ruby on Rails, Python's Django, PHP and other (depends on server-side backend and uses HTML pages or rich media like Flash, Flex or Silverlight on client).

  • TransducerML:

TransducerML (Transducer Markup Language) or TML is an Open Geospatial Consortium candidate standard developed to describe any transducer (sensor or transmitter) in terms of a common model, including characterizing not only the data but XML formed metadata describing the system producing that data.

  • URL:

Abbreviation of Uniform Resource Locator, the global address of documents and other resources on the World Wide Web.

The first part of the address indicates what protocol to use, and the second part specifies the IP address or the domain name where the resource is located.

For example, the two URLs below point to two different files at the domain pcwebopedia.com. The first specifies an executable file that should be fetched using the FTP protocol; the second specifies a Web page that should be fetched using the HTTP protocol:

  1. ftp://www.pcwebopedia.com/stuff.exe
  2. http://www.pcwebopedia.com/index.html
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  • W3C:

The World Wide Web Consortium (W3C) is the main international standards organization for the World Wide Web (W3). It is arranged as a consortium where member organizations maintain full-time staff for the purpose of working together in the development of standards for the W3


  • WCS:

The Web Coverage Service is an Open Geospatial Consortium standard web service for exchanging geospatial data. Coverage refers to continuous spatial data, such as aerial photography, land cover, and elevation data. WCS allows remote users access to coverage data without the need to manage the dataset themselves.

WCS provides available data together with their detailed descriptions; allows complex queries against these data; and returns data with its original semantics (instead of pictures) which can be interpreted, extrapolated, etc. -- and not just portrayed. This is in contrast to a Web Feature Service (WFS), which returns actual vector data, and a Web Map Service (WMS) which produces a digital image file.

WCS provides three operations:

    • GetCapabilities: The GetCapabilities operation returns an XML document describing the service and brief descriptions of the data collections from which clients may request coverages. Clients would generally run the GetCapabilities operation and cache its result for use throughout a session, or reuse it for multiple sessions. If GetCapabilities cannot return descriptions of its available data, information from a separate image catalog source is used.
    • GetCoverage: The GetCoverage operation of WCS is normally run after GetCapabilities and DescribeCoverage replies have shown what requests are allowed and what data are available. The GetCoverage operation returns a coverage (that is, values or properties of a set of geographic locations), bundled in a well-known coverage format. Its syntax and semantics bear some resemblance to the WMS GetMap and WFS GetFeature requests, but several extensions support the retrieval of coverages rather than static maps or discrete features.
    • DescribeCoverage: The DescribeCoverage operation lets clients request a full description of one or more coverages served by a particular WCS server. The server responds with an XML document that fully describes the identified coverages.

These three operations provide enough functionality to retrieve, process and/or view coverage data.

  • Web Service:

The W3C defines a Web service (many sources also capitalize the second word, as in Web Services) as "a software system designed to support interoperable Machine to Machine interaction over a network." Web services are accessed over a network, such as the Internet, and executed on a remote system hosting (server) as requested services. The specifications that define Web services are intentionally modular, and as a result there is no one document that contains them all. Additionally, there is neither a single, nor a stable set of specifications. There are a few "core" specifications that are supplemented by others as the circumstances and choice of technology dictate, Like:SOAP or WSDL.

  • WFS:

The WFS (Web Feature Service) is an OGC specification that defines interfaces for describing data manipulation operations of geographic features. Data manipulation operations include the ability to: 

   * Create a new feature instance
   * Delete a feature instance
   * Update a feature instance
   * Get or Query features based on spatial and non-spatial constraints

The basic Web Feature Service allows querying and retrieval of features. A transactional Web Feature Service (WFS-T) allows creation, deletion, and updating of features.

A WFS describes discovery, query, or data transformation operations. The client generates the request and posts it to a web feature server using HTTP. The web feature server then executes the request. The WFS specification uses HTTP as the distributed computing platform, although this is not a hard requirement.

There are two encodings defined for WFS operations: 

   - XML (amenable to HTTP POST/SOAP)
   - Keyword-Value pairs (amenable to HTTP GET/Remote procedure call)


When writing a WFS , the following operations should be used: 

   - GetCapabilities - this queries the WFS service to determine available options.
   - DescribeFeatureType - this retrieves the XML schema to allow the WFS client to parse the resultsets.
   - GetFeature - this performs the actual query - parameters such as bounding box and any other filters should be passed in, as appropriate, and the WFS service then returns a GML resultset containing full geometry and feature attributes.

The Geography Markup Language (GML) passes data back and forth between a Web Feature Server and a client. GML normally communicates geospatial data, but also supports other types of data.

  • WMS:

An OGC Web Map Service (WMS) produces maps of spatially referenced data dynamically from geographic information. This international standard defines a "map" to be a portrayal of geographic information as a digital image file suitable for display on a computer screen. A map is not the data itself. WMS-produced maps are generally rendered in a pictorial format such as PNG, GIF or JPEG, or occasionally as vector-based graphical elements in Scalable Vector Graphics (SVG) or Web Computer Graphics Metafile (WebCGM) formats.

Web Map Service operations can be invoked using a standard web browser by submitting requests in the form of Uniform Resource Locators (URLs).


  • WPS:

An OGC Web Processing Service (WPS) is a Web Service that takes a defined set of inputs, applies a calculation, and produces a defined set of outputs. WPS is designed to work with spatially referenced data but can be used with other kinds of data. WPS is a generic Web Service in that the specific processes provided by a WPS implementation are defined by the owner of that implementation.

  • WPS makes it possible to create, publish, find, and bind to web services. Theoretically it is transport/platform neutral (like SOAP), but in practice is tied to HTTP.

WPS defines three operations: 

  - GetCapabilities returns service-level metadata
  - DescribeProcess returns a description of a "process" including its inputs and outputs
  - Execute returns the output of a "process"

WPS operations can be invoked using a standard web browser by submitting requests in the form of Uniform Resource Locators (URLs) via HTTP GET, or XML documents via HTTP POST. The content of such URLs or XML documents depends on which operation is requested

  • WSDL:

The Web Services Description Language is an XML-based language that provides a model for describing Web services.

  • XML:

The Extensible Markup Language (XML) is a general-purpose markup language. It is classified as an extensible language because it allows its users to define their own tags. Its primary purpose is to facilitate the sharing of structured data across different information systems, particularly via the Internet. General Example of XML: 

<recipe name="bread" prep_time="5 mins" cook_time="3 hours">
   <title>Basic bread</title>
   <ingredient amount="3" unit="cups">Flour</ingredient>
   <ingredient amount="0.25" unit="ounce">Yeast</ingredient>
   <ingredient amount="1.5" unit="cups" state="warm">Water</ingredient>
   <ingredient amount="1" unit="teaspoon">Salt</ingredient>
   <instructions>
     <step>Mix all ingredients together.</step>
     <step>Knead thoroughly.</step>
     <step>Cover with a cloth, and leave for one hour in warm room.</step>
     <step>Knead again.</step>
     <step>Place in a bread baking tin.</step>
     <step>Cover with a cloth, and leave for one hour in warm room.</step>
     <step>Bake in the oven at 350° for 30 minutes.</step>
   </instructions>
</recipe>
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