WIS in a Nutshell

Version 0.99, 2012-03-11, original English version.

1. Introduction to WIS in a Nutshell

1.1. About this document

This document is written by representatives of Members of the WMO RA-VI in collaboration with the WMO Secretariat. The need for an introductory document on the WMO Information System (WIS), and how to implement WIS, arose during the RA-VI Workshop on the Implementation of the WIS in Sofia, 1-3 November 2011. The RA-VI Task Team on WIS agreed to this task, with volunteers from RA-VI and the WIS Branch in the Observing and Information Systems Department of the WMO Secretariat.

The target audiences of this document are:

• Executives responsible for decisions related to the implementation or use of WIS
• Managers and technical personnel responsible for implementing WIS in their organizations
• Users of WIS

No prior knowledge of WIS is required to read this document, but familiarity with the WMO Global Telecommunications system (GTS) will be an advantage.

The aim of this document is to provide an easily readable overview of what WIS is, what are its benefits and how it can be conceptually implemented. The document will discuss at high level all relevant aspects of WIS and build a bridge towards the formal WIS publications. Furthermore it can be used as a good basis for discussions in organizations planning to join WIS.

WIS in a Nutshell is approved by the RA VI Management Group. It is however not a mandatory publication of WMO, and in case of any conflict, the regulatory material on WIS takes precedence. The regulatory material is in No. 1060 Manual on WMO Information System and No. 1061 Guide to WMO Information System.

This document is written in English and the English version will be maintained by the WMO Secretariat. The most recent version of the document will be available on the WIS Wiki pages, and to avoid confusion between versions, this is the only place the document will be published by WMO.

WMO Members are welcome to translate the document into other languages. These translations will also be available from the WIS Wiki, and they will include a line stating "Translated by <‹name of organization(s) / WMO member(s)>>". The translated versions will contain information on which version of the English document was used for the translation.

1.2. Structure of this document

Section 2 gives an overview of the WIS, especially how it can be used, and how it relates to existing WMO programmes and the GTS. This section also outlines the benefits of WIS.

Section 3 describes the high level structure of the WIS, including the relationship between the GTS and the WIS. It is intended for users wanting to know about the components of WIS and for existing users of GTS who would like obtain a better understanding of how the GTS remain a part of WIS and will be further developed within WIS, making it more available to all WMO programmes.

Section 4 details how data can be found and retrieved through the WIS, as well as how data, and metadata, can be published in the WIS.

Section 5 is concerned with the important concepts of catalogues and discovery metadata - data describing the data and products in WIS. Understanding the catalogue entries and discovery metadata is essential for all use of WIS, and the quality and availability of the discovery metadata is a vital factor in making WIS a successful data management system. This section should therefore be of interest to all readers.

Section 6 outlines the functionality of the three types of WIS centres: National Centre (NC), Data Collection and Production Centre (DCPC) and Global Information System Centre (GISC).

Sections 7 and 8 cover details of the implementation of WIS in an organization, including how to implement an NC and a DCPC, an introduction to the full WIS documentation and formal administrative procedures for becoming a WIS centre. The main audience for these sections are managers and technical personnel responsible for implementing WIS in their organizations.

2. What is WIS?

The WMO Information System (WIS) is our global infrastructure for managing and making available weather, climate and water information. WIS meets the requirements for routine collection and automated dissemination of observed data and products, as well as data discovery, access and retrieval services for all weather, climate, water and related data and products provided by centres and Member countries in the framework of all WMO Programmes.

2.1. WIS Services

While WIS is builds on and extends the World Weather Watch Global Telecommunication System (GTS), it is also a new approach to data discovery and data provision in the meteorological community. WIS goes far beyond providing a telecommunication services, and offers new and modern data management services to its users. These are essentially the possibility to discover all data and products of the wider WMO community, as well as the means and information on how to obtain the data. It is assumed that, with the combination of utilizing the GTS and the Internet, WIS will have sufficient bandwidth/link capacity available to fulfil future user needs. To this end, WIS provides three types of services.

1. Routine collection and dissemination service for time-critical and operation-critical data and products: This service is an extension of the current GTS. It is based on subscription to real-time “push and forward” distribution systems, including multicast and broadcast, and implemented mostly through dedicated telecommunication means providing a guaranteed quality of service. An important component of this service will be the “all hazards warning network” facilitating warnings to be distributed from one point in WIS to all other points within 2 minutes.
2. Service for the timely delivery of non time-critical, operationally critical or voluminous data and products: This is a new service which allows users to subscribe to data that would not otherwise have been available through the GTS because it is too voluminous or because the delivery is not so critically time or operationally dependent so does not need to use up the valuable capacity of the GTS. It is also ideal for those users not connected to the GTS. The service is focused on a “push” mechanism and implemented mostly via public data-communication networks, such as the Internet. As with the time and operationally critical service (1), users may use the discovery Service (3) in order to search for the information they would like to subscribe to.
3. Data Discovery, Access and Retrieval (DAR) service: This is a new service where the user can use a variety of discovery services to search for data, products or other information registered within the WIS. Depending on the access policy for the data, the user may also access and download the data. The service is based on a request/reply “pull” mechanism and is to be implemented mainly through the Internet, but may also subscribe to receive the data or products via the GTS or any other delivery mechanism available between the information provider (for example via e-mail, sms, facsimile, courier or postal services) and user. In this way, WIS users can potentially discover and access all WMO data and products without having to have an extensive knowledge of the information practices and procedures of the WMO Programme responsible for the data or product. Note that if a user has an account at a GISC, then, depending on the data policy, this may be able to access information directly from the GISC all of which hold information that is available for global exchange for 24 hours.

As illustrations of how services 2 and 3 work, consider the following examples:

• A scientist at a university in Chile is studying the climate in Antarctica. Through a web browser, over the Internet, she accesses the GISC Melbourne portal at the Australian Bureau of Meteorology. Here, she searches for data marked "climate" and south of latitude 60°S. She obtains a list of datasets from organizations all over the world. Some of the data she can access and download interactively. Other data have access restrictions, and for these data she gets the contact information.
• A programme at the Food and Agriculture Organization of the United Nations is monitoring the availability of water for agriculture in Africa. Through the GISC Pretoria portal of the South African Weather Service, the programme searches for and subscribes to all Resolution 40 Essential Data (data that WMO Members have agreed to share with each other), from the NMHSs in Africa, and receives these daily through email.
• An NMHS manages the list of bulletins needed for their forecast through the subscription interface of its associated GISC. The search functionality of the GISC allows the NMHS to quickly discover what data and products are available elsewhere, and the online subscription interface allows the NMHS to subscribe to new data channels in a matter of minutes.

2.2. Benefits of WIS

WIS is open to all authorized users and will therefore be of value to all people, projects, programmes and organizations disseminating or requesting weather, climate and water information. In particular, the following groups will benefit from WIS.

National Meteorological and Hydrological Services

• WIS will offer an enhanced GTS that addresses its previous shortcomings relating to the difficulties in knowing what information is available and subscribing to it.
• WIS will provide easier access to operational data as well as data and products available via channels.
• NMHSs will be able to interactively change their operational data provisions.
• WIS will provide mechanisms that detect inconsistencies in the lists of data and products, such as non-existing bulletins and bulletins intended for bilateral exchange listed as essential.
• NMHSs will be able to publish discovery metadata for their national data and products and allow their users to use the GISC DAR facilities to discover relevant national and international data and products.
• NMHSs in countries where EU regulation applies will benefit from WIS when implementing the INSPIRE directive, as the WIS metadata is INSPIRE compliant.

WMO programmes

• WIS will provide flexible and modern services for the implementation of data exchange tasks.
• WIS will provide shared infrastructure and data management that will reduce cost and shorten implementation time.
• WIS will facilitate the cross programme sharing of information through the publishing of discovery metadata in WIS for programme specific data and products.
• WIS will provide greater visibility of all of WMO Programmes and data in the rest of the world.

Individual users, either a person or an organization

• WIS will provide a single entry point for any data request, either routinely for user defined information sets or on an ad-hoc basis for special data sets.
• WIS will provide a 24 hour cache of data that are exchanged globally as routine, thus simplifying data collections for users collecting global data on a routinely basis, such as thematic data centres.

The specifications of WIS are fully open and based on standards that may be adopted by other organizations to provide interoperability across information systems. In this way, any intergovernmental organization or international programme can benefit from WIS as demonstrated by the Global Earth Observation System of Systems (GEOSS) that harvests WIS discovery metadata and publishes it alongside that from other contributing systems.

3. The structure of WIS

The WIS services described above are realized by WMO Members and associated centres by implementing three types of WIS centres as well as the WIS data communication network. The concept of interoperability guarantees that the overall functionality of WIS is realized by each WIS centre only implementing the specifications required of this type of centre.
These four core components are listed below. The official list of designated WIS centres is in Appendix B of the [http://www.wmo.int/pages/prog/www/WIS/documents/Manual-on-WIS-en.pdf |Manual on WIS. These and other potential WIS centres and their designation status can be found on the WMO WIS Centres Database page

• National Centres (NCs)
• Data Collection or Production Centres (DCPCs)
• Global Information System Centres (GISCs)
• Data networks

3.1. WIS Centres

The functionality of WIS is realized by the WMO Members implementing three types of WIS centres, as said earlier. Here only a short overview of the centres is given. Please see section 6 for a more detailed description of the centres' roles.

GISCs are a specialist WIS centre in much the same way that RTHs are in the GTS: They have specific functions essential for WIS to work. They collect and distribute information for routine global dissemination, such as GTS data. They serve as collection and distribution centres in their areas of responsibility and they provide access points for any request for data held within the WIS. A WIS user accessing the web portal of any GISC will be able to browse the data catalogue of information available in WIS.

DCPCs are centres that operate under a WMO or related international programme and/or a Regional Association. They may have a national role but they are primarily focused on international or global activities. They are connected to the GISCs and are responsible for the collection or generation of sets of data, forecast products, processed or value-added information, and/or for providing archiving services.

NCs, like DCPCs, are also a categorization of existing centres within WMO or national programmes. Although they may have some international role, their focus is primarily on national activities. This includes collection and distribution of data and creation of products and services on a national basis, NCs also coordinate or authorize the use of the WIS by national users, under the authority of the respective Permanent Representative with WMO.

The terms NC, DCPC and GISC are used for describing the necessary functions, not actual organizational entities. There may be organizations, such as NMHSs, which combine all three functions within their structure.

As well as providing for the information exchange needs of NMHSs, the WIS will also connect other national centres, research facilities, and international programme centres. There may be several NCs and DCPCs in any one country, and some DCPCs will be hosted by international organizations.

3.2. Mapping between WWW centres and WIS centres

Existing centres within WMO Member States that comply with the required WIS functions and technical specifications will be designated as one of the three types of WIS centre. While Members can chose to apply for a type of centre matching their level of responsibilities and commitment, the expected mapping of current WWW centres into WIS centres is:

WWW Centre	WIS Centre
NMC	NC
RSMC	DCPC
WMC	DCPC and/or GISC
RTH	DCPC
RTH on MTN	DCPC and/or GISC
Others	NC and/or DCPC

For example, a Regional Telecommunications Hub (RTH), that collects and disseminates regional data, might apply for a DCPC role in the WIS. Centres such as ECMWF and ACMAD, or other climate research centres or specialized agricultural forecast centres which produce regional forecasts, also qualify for this role. Generally, the NMHS of a country is an NC, with the added roles of DCPCs, when the NMS has additional responsibilities in the region.

The RTH roles and the mapping of RTHs to WIS centres needs special attention. 'RTH' is a function whereas 'DCPC' is a categorization. RTH roles include activities such as maintenance of station lists (Vol. A), which will continue. RTHs may ensure WIS compliance by delegating the required new functionality to another centre, (e.g. their GISC), but the communications in their region will define if they must continue as a part of the GTS communications chain. Some RTHs have also taken on the role of a GISC.

3.3. WIS data networks

The WIS network structure consists of a WIS Core Network connecting all GISCs and several Area Meteorological Data Communication Networks (AMDCNs) connecting NCs and DCPCs to their principal and backup GISCs. This is illustrated in Figure 2. An NC or DCPC may be in multiple AMDCNs. The AMDCNs incorporate GTS infrastructure and may involve single, partial or multiple regional meteorological telecommunication networks (RMTNs).

The data communication networks that can be used in WIS include:

• The Main Telecommunication Network (MTN) of the GTS forms the WIS Core Network.
• GISCs are also connected by the Internet, which presently is being used for metadata synchronisation.
• The GTS (MTN and RMTN) provides the dedicated network component of the AMDCNs, especially for meeting real-time exchange requirements and the all hazards network. Note that the GTS includes extensive use of Internet through Virtual Private Networks (VPN) in many areas.
• Satellite distribution systems such as those described by the Integrated Global Data Dissemination Service (IGDDS) form an essential part of the GTS and therefore the WIS, especially for the support of remote areas where terrestrial communication systems do not effectively meet the need. This is includes data collections systems for remote platforms as well as for distribution of data and products related to the WMO Space Programme
• Terrestrial links or managed data network services
• The Internet, either open or utilising VPN, which will be used in the AMDCNs to increase bandwidth capacity to many centres as well as providing connectivity for non-GTS centres and for individual users accessing WIS.

3.4. GTS and WIS

The role of the GTS in WIS merits a special mention.

Being an integrated part of WIS, the aim of the GTS is to ensure delivery of time-critical and operation-critical data, products, and services including warnings to NMHSs. GTS realizes in this essentially the "Routine collection and dissemination service for time-critical and operation-critical data and products", mentioned above.

The GTS will continue to develop and incorporate new technology, linking all WMO Members with a dedicated, secure network. This network will continue to be supported by advanced satellite distribution systems. In addition, the GTS will also be able to supplement the private networks and make better use of public communications such as the Internet.

The GTS data management framework will include the development of data representations, including fast and efficient coding practices that allow voluminous data streams to reach countries with less advanced or low capacity communication systems.

New functionality for GTS users will include:

• Online discovery of which data and products are available on the GTS by interactively accessing a GISC portal;
• Download or reruns of GTS data and products published during the past 24 hours. This is of interest for users that have missed data because of a failure of IT systems, equipment or networks;
• Updating of GTS routeing based on online subscription services rather than service messages requesting the GTS Point of Contacts to change the routeing. An NMHS may configure its own routeing information. Thus a centre need only deal with its associated GISC for changing subscription and publishing schedules:
• Configure upload of data to the GTS. Rather than requesting the GTS Point of Contact and WMO to change information about the data that is uploaded to the GTS, the NMHS may do the configuration.

Note that even if centres create new GTS links to their GISC, RTHs will continue to be responsible for other World Weather Watch activities such as maintenance of WMO No 9. Vol A.

4. WIS Discovery, Access and Retrieval

The WIS Discovery, Access and Retrieval (DAR) service makes it easier to find and access WMO data and products. Since information about all WMO data and products is available in the GISCs in the form of catalogue entries of discovery metadata provided by NCs and DCPCs, all WMO data and products can be found in the search portals of the GISCs. The WIS DAR, thus implements the discovery service, described in section 2.1.

4.1. Different ways of finding information

There are different search methods that allow both humans and computers to find information in the WIS.
The WIS GISC portals offer a full-text search form to discover all the products containing the keywords typed by the user. If necessary, an advanced search mode also offers a search form with different input fields to search text fields such as the abstract, title or author.
Apart from text-based fields, the information in WIS can also be searched geographically or by time. The geospatial search allows the retrieval of products from a specific country, region or user-defined bounding box, while the temporal search allows the discovery of data covering a certain time period, such as a time series.

Browsing is an alternative to searching where the data and products in the portal have been categorized, and the user can search these categories without prior knowledge.

The information in WIS can also be searched automatically. Search and Retrieval by URL (SRU) is an interface that enables remote searching. For example, an NMHS website could have a search box that allows their users to search WMO information by sending the search terms to a GISC and retrieving a result-set from it, which can then be displayed on the portal in the NMHS's corporate style.
Making information in WIS available via a standardized search-interface and standardized discovery metadata, makes it possible for WMO information to be used outside the WMO community, as well as including information from outside, hence increasing WMO's relevance in a broader domain.

4.2. Data access

Once a data or product has been found, depending on its status, it can be directly obtained from the GISC, or be obtained directly from the data custodian.

If the data or product is globally available, it can be directly downloaded from the GISC's cache, which stores at least 24 hours of globally available data and products. Depending on whether the data is Resolution 40 Essential or Additional Data, the data can be downloaded without or with logging into the GISC.

On the other hand, if the data or product is not globally available, it can be obtained directly from the data custodian, usually an NC or DCPC. The discovery metadata contains a web link that points to a web page of the custodian, where more information about how to obtain the data or product can be found.

This data or product could be downloaded directly, by logging into a system for authorization and/or payment, or by other means, such as satellite broadcast, e-mail or delivery by post. Thus the data owner does not lose control of the data or product, and at the same time, uses the WIS to make information about the data or product more visible.

4.3. Publishing information in the WIS

So that information about a centre's data or products can be found, the centre must publish discovery metadata in the WIS as follows. Firstly, the centre generates a discovery metadata record for the data or product in question. This metadata record contains a web link pointing to a website with more information about how to obtain the data. This discovery metadata is then made available to the GISC associated with the centre. The method to share these metadata records is agreed bilaterally between the centre and the GISC, but is usually by file transfer or the OAI-PMH protocol.

Smaller WIS centres could use a web interface provided by the GISC, to create, update and delete the discovery metadata records for its own products directly in the GISC discovery metadata catalogue.

The way data and products (described by the discovery metadata) of the WIS centre are distributed depends on their status. In the case of GTS data, the data are simply input into the GTS, either by transferring them directly to the associated GISC, or via an intermediary RTH.

If the data are not GTS data, the NC or DCPC uses other means for distribution, such as download from the web page, Internet subscription or satellite dissemination, according to its programme responsibilities. In this case, none of the data is uploaded to the WIS, and it is exclusively available from the data provider or its custodians.

5. Discovery Metadata

5.1. What is Discovery Metadata ?

To describe a product by listing its characteristics is a very old principle. Anyone who goes into a library and searches for information about a specific topic, experiences the use of discovery metadata. Simply, discovery metadata provides descriptive information about a particular object or resource. Discovery metadata is usually used to organise collections of information in order to allow grouping and searches of data in a structured way.

In the library example, the library catalogue cards are book metadata information and the books themselves also contain individual metadata information on their covers.

The metadata information can be basic or very detailed, layered and complex depending on need. A book front and spine typically declares the author and the book title. The back cover often describes in more detail a summary of the book content, the publisher and also technical information such as the book unique identifier (ISBN).

5.2. Discovery Metadata in the WIS context

One of the goals of the WIS is to provide discovery services to allow users to easily find meteorological datasets. A discovery metadata description of the actual data is the essential element of such discovery services.

To create catalogues of weather and climate products for WIS users, catalogue implementers need to index information describing all existing products. To facilitate the creation of those product catalogues, the discovery information for each of these products has to be expressed in an agreed common standard: the WIS discovery metadata. The WIS discovery metadata contains all the information necessary to provide search results that are useful to the WIS user.

Similar to finding literature in a library on a special topic, the discovery metadata descriptions are grouped around standard key questions such as:

• What: Product, Dataset name
• Summary: Product description
• Who: Data producer contact details
• When: Production date and for meteorological datasets: computation date, forecast date and more
• Where: Geographical area covered by the product
• How:
  • How to access the datasets? Using FTP, HTTP, the GTS
  • Who can access the data ? Licensing issues and data policies

Just as there is a diversity of data formats in the meteorological community, such as the traditional ASCII files and the Table Driven Formats, there are numerous formats and notations for the metadata. Some can be plain text, as in the example of the book. However, in most cases, and the WIS in particular, computers are used to read and use metadata and therefore XML (eXtended Markup Language) notation has been chosen. This allows encoding of hierarchically structured information, is easy to use in IT and is also widely supported.

5.3. WIS discovery metadata standards

Adherence to standards is the key to interoperability. To make the WIS infrastructure accessible and to allow other scientific communities to use and cross reference products made available by the WIS, WMO has chosen a standard metadata format, the ISO and OGC metadata standard ISO19115. It permits the description of complex geospatial information and can be understood and ingested by many existing software components, thus helping communities across traditional boundaries.

For example, a forestry scientist could, via the WIS, discover meteorological products correlating the growth of certain tree species with some particular meteorological weather conditions. Similarly meteorologists could discover forestry products describing the different forest types and derive a “forest” density index affecting the weather conditions and use it in numerical weather prediction (NWP) models.

ISO19115 is a conceptual model, independent of technology, for describing geospatial information and it can be expressed in XML following the encoding rules defined in ISO19139. That is, the ISO19115 says what should be recorded in the metadata and ISO19139 tells how it should be described using XML. Both these standards are far richer in content and diversity than needed to create WIS discovery metadata and their scope can be reduced by creating a Profile which defines a subset of objects that will be used in a specific domain such as meteorology. In the context of the WIS, a profile called WMO Core Profile has been defined. The WMO Core Profile narrows down the ISO19115 model content that can be used to define WIS metadata discovery records and also specifies how to describe different specificities of meteorological data such as time dimensions and vertical coordinates.



Even with these simplifications and restrictions, defining XML metadata records in the WMO Core Profile dialect can be a daunting tedious technical task and it is better to create discovery metadata using a tool, such as the GISC metadata maintenance portal to be insulated from the technical details of ISO metadata records. GISCs provide metadata editing services through which users only enter the required fields to create the ISO 19139 XML representation. The discovery metadata records are then automatically created and published in the GISC discovery catalogue.

5.4. Day to day process for creating and editing discovery metadata records

To make the management of discovery metadata convenient for data producers as well as data users, some tools and services have been developed within WIS.

• For centres with few records: edit metadata using a web form to generate the metadata record.
• For centres with thousand of records: create templates and add the individual information for each record automatically.
• Send the metadata to the associated GISCs for synchronisation purposes.
• Create individual procedures to update own or others metadata records (provided the editor has the permission of the data custodian).

5.5. Getting started with metadata

WIS discovery metadata is the basis of the information and data management of WIS and WIS centres manage their metadata through their principal GISC.

To get started with metadata, a WIS centre has several options.

Start-up metadata has been generated by Météo France for data exchanged on the Global Telecommunications System (GTS). WIS uses the start-up metadata if centres have not provided their own metadata for the GTS traffic. WIS centres can either download their start-up metadata from any operational GISC, edit it locally and them make it available to their principal GISC, or manage the metadata directly through their principal GISC.

When wanting to create a metadata record for a new product, WIS centres can also search in WIS for a similar product, and use it as a template.

WMO Communities might also supply templates that can be used by Members for the creation of metadata records.

Initially not all WIS centres will have access to their principal GISC, since not all GISCs will be operational at the start up of WIS. To ensure all centres can manage their discovery metadata immediately, some GISCs are offering an interim metadata management service. A centre can chose which GISC's interim metadata management service it prefers. Once the centre’s principal GISC becomes operational, the centre will manage its metadata through the principal GISC.
This link contains more information about the Start-up metadata.

6. Roles and responsibilities of WIS centres

6.1. NC National Centre

The NCs are responsible for collecting and providing observational data and products intended for global or regional distribution to their responsible GISC or DCPC, and distributing data on a national basis. The NCs coordinate or authorise the use of the WIS by eligible national users. Depending on the national policy, more than one NC could exist in a country. Normally the Permanent Representative (PR) of the country establishes the national policy and practice and coordinates the various users. The typical NC in a country is the NMHS but other organizations can also become NCs. An NC's role can be summarised as follows:

• Collect observational data from within their country
• Collect, generate and disseminate products for national use
• Authorise their national users to access WIS, including allowing them to register with a GISC, as required (if the PR is the head of the NC or the NC is delegated this role from the PR)
• Provide observations and products intended for global or regional dissemination to their responsible GISC (possibly via a DCPC with RTH function)
• Provide observations and products intended for regional or specialized distribution to the responsible DCPC
• Maintain catalogue entries/metadata records for their data and products
• Participate in monitoring the performance of the system

Note that an NC can delegate its WIS requirements onto another centre, such as its principal GISC or RTH DCPC. The key is that a national centre must take responsibility for complying with WIS.

6.2. DCPC Data Collection or Production Centre

DCPCs are centres that fulfil an international responsibility within specific WMO Programmes for the generation and provision for international distribution of data, forecast products, processed or value-added information, and/or for providing archiving services. DCPCs may also provide basic WIS functions such as metadata catalogues, Internet portals and data access management. Examples of DCPCs are the Regional Specialized Meteorological Centres (RSMC) with activity specialization or geographic specialization, as well as the Regional Climate Centres. DCPC roles, where applicable, can be summarised as follows:

• Collect information intended for dissemination to NCs and DCPCs within its area of responsibility (i.e. regional collections)
• Collect special programme-related data and products;
• Produce regional or specialized data and products;
• Provide information intended for global exchange to their associated GISC;
• Disseminate information not intended for global exchange;
• Support access to their products via WMO request/reply (”Pull”) mechanisms in an appropriate manner;
• Describe their products according to an agreed WMO standard and provide access to this discovery metadata catalogue of products and provide this information as appropriate to other centres, in particular a GISC;
• Ensure that they have procedures and arrangements in place to provide appropriate recovery or backup of their essential services in the event of an outage (for example, because of fire or natural disaster);
• Participate in monitoring the performance of the system.

6.3. GISC Global Information System Centre

Global Information System Centres (GISCs) are operated by WMO Members as a major component of the WMO Information System (WIS) infrastructure. A GISC’s primary role is to collect from and disseminate information to WIS centres in its area of responsibility and with the global WMO community. GISCs also provide search portals through which information from WMO and other interoperable systems can be discovered and accessed.

7. How to implement a WIS centre

This section describes the differences between NCs and DCPCs, and gives guidance on how to implement them. The section is divided into administrative and technical implementation sections.

7.1. Administrative steps

When implementing the WIS in a country, a list of potential WIS centres should be made, and their roles understood. In WIS, NMHSs are NCs, but might also have the role of a DCPC, depending on its responsibilities. An NMHS might even operate several different types of WIS centres.

Each Member has at least one NC which by default is the centre at which it is connected to the GTS. This is the WMO Member’s prime NC which must implement compliance with WIS, either through proxy of another centre or within its own facilities. A DCPC has a regional or a WMO programme role, such as collecting or disseminating data regionally, or producing data of regional interest. See section 3 and 6 for an overview of the different WIS centres.

NCs and DCPCs have to choose one GISC as their principal GISC for the purposes of uploading metadata into WIS. However, an NC or DCPC can have associations with multiple GISCs for the purposes of uploading and receiving data. The association (either principal or other) is a bilateral agreement between a centre and a GISC, often in consultation with the Regional Association. The choice of backup GISC is a trilateral agreement with the 3 centres involved (Associated GISC, centre and backup GISC). In practice most GISCs will determine which GISC will serve as backup for their AMDCN since they will prefer to minimise the number of GISCs they have to maintain backup procedures with.
The WMO Secretariat must be notified of the GISC NC/DCPC associations, as established by this circular letter.

A list of designated WIS centres is recorded in the Manual on WIS.Along with new centres awaiting designation by Congress or EC, the list of designated centres can also be found on the WMO WIS Centres Database page. The online table also shows the presumed or tentative associated GISCs and the selected interim metadata management system where appropriate.

7.1.1. Formal designation procedure for a NC

Each WMO Member shall notify WMO of the current name and location of each of its centres to be designated as an NC. The NC notifications shall be provided by the Permanent Representatives in each member country. Executive Council will review the candidate centre as a part of the review of the Manual on WIS and subject to its agreement, designate the centre as an NC to be included in the Manual on WIS.

As stated above, each NMHS is an NC. However, a WMO Member may also elect to designate other centres as NCs. For example, a WMO Member having both a National Meteorological Service and a National Hydrological Service may chose to designate both as NCs. Alternatively, one of them could be designated NC, and provide the data and products of both.

The Commission for Basic Systems, with the involvement of the relevant Regional Associations and with the assistance of the WMO Secretariat, shall review the Member designations, to ensure each NC is supported by a GISC, DCPC, or other NC.

7.1.2. Formal designation procedure for a DCPC

The process of becoming a DCPC is initiated by the hosting organization, but it must be supported by a WMO programme or constituent body such as EC Working Group, regional association or technical commission. The hosting organization should have an international responsibility for the generation and provision for international distribution of data, forecast products, processed or value-added information, and/or for providing archiving services. The organization should produce or collect regional or thematic data or products, and provide these to the international community.

7.1.2.1. Audit

Designation of a DCPC is done by WMO Congress or the Executive Council on recommendation of CBS after the candidate DCPC has gone through a three step procedure:

1. Submission of Technical Paper: The candidate completes an online questionnaire and conducts the necessary demonstration test.
2. Assessment, Validation and Audit: In this step, the CBS Expert Team on GISC-DCPC Demonstration Process (ET-GDDP) will assess the information received, ask for clarification, help the candidate in providing the relevant information and run tests. The ET-GDDP can delegate the assessment to a GISC the candidate DCPC will be associated with. The tests include the provision of metadata and coordination and synchronization functions with the associated GISC. The role of the candidate DCPC in this phase is to be available to the auditor and provide any information requested.
3. Findings: Depending of the outcome of the second step, the ET-GDDP endorses the DCPC candidate, in which case CBS recommend to Congress or the Executive Council to designate the DCPC. If the ET-GDDP does not fully endorse the DCPC candidate, CBS may ask for a demonstration at a CBS session prior to recommending designation of the DCPC, for it to gain CBS endorsement.

7.2. Technical implementation

Technically, an NC and a DCPC share some aspects. Both generate and maintain discovery metadata for their products. In the case of a DCPC, a suitable distribution mechanism, such as satellite distribution, Internet based subscription or others, has to be provided. The type of distribution mechanism is specific to the type of centre and is not mandated.

Implementing a WIS centre requires three elements; infrastructure, knowledge and software. Whereas the required infrastructure usually exists and knowledge can be acquired through this document and other WIS publications, several approaches are possible to implement the software that can perform the functions and services required by WIS:

• Use existing software: Several solutions are available, some developed by Members and some by companies providing GTS message switches. Some of the solutions include functionality that covers the requirements for NCs, DCPCs and GISCs. The licences for these solutions vary. Some are available under an Open Source licence with an optional support, other are available under standard industrial terms.
• Develop your own software: For NCs and DCPCs, most of the required functionality is available through open source components. This makes in-house developments and integration possible for organizations familiar with use of open source components and/or an existing data management system they would like to integrate with WIS.
• Re-use or customise industrial software: Organizations having a data management system they would like to use, as part of an NC or DCPC, may want to extend this software to comply with the WIS specifications. This can be done either through development or by integrating it with a customised version of the industrial WIS software.

As an alternative to implementing the software itself, a centre may also delegate the role to another centre such as its GISC or RTH or use a remote client like the GISC metadata management interface to undertake this activity. How a centre achieves WIS compliance is not mandatory although achieving compliance is.

7.2.1. Technical implementation of an NC

The technical implementation of an NC implies the provision of data and discovery metadata to the associated GISC.

For NMHSs connected to the GTS, using a message switch system for data exchange, there is usually no need to change the method of data delivery to the GTS. The global GTS data is simply transferred directly to the associated GISC or to the RTH in between the NC and the GISC. Organizations that will become NCs and are currently not connected to
the GTS, need to be connected to the WIS either through NMHSs or by installing
their own WIS compatible system.

If additional, non-global, products are made available by the NC, these should be available on a website or similar so that once the products are discovered they can be downloaded. The access and protection of these products could be achieved, for example, by using WIS software.

The main new task for organizations about to become an NC is discovery metadata provision. The discovery metadata can either be generated and updated by the NC itself, or it can be maintained in the GISC or a DCPC (RTH). If an NC is willing to maintain its own discovery metadata, it could have its own system installed for metadata functions. If the metadata is maintained in the GISC or DCPC (RTH), this can be arranged by creating a user registration at the GISC or DCPC and by maintaining the NCs discovery metadata there.

7.2.2. Technical implementation of a DCPC

Implementing a DCPC involves:

• Choice of software or a proxy that provides the necessary WIS functions.
• Ability to fulfil functional requirements and technical specifications, see the Manual on WIS. Depending on the choice of software, many of the requirements will be handled by the software.
• Ability to generate and maintain discovery metadata. The WIS software may ease the process of discovery metadata handling, but there will still be a need for the organization to provide and manage the discovery metadata.
• Data ingestion and discovery metadata generation
• Exchange of discovery metadata with the associated GISC.
• Data policy and licensing issues.
• Consideration of the network connection for the DCPC (Internet, AMDCN, satellite broadcast)
• Technical infrastructure (server, databases, logical placement in the network). This is closely related to the choice of WIS software.
• Training of staff.
• Cost of setting up and operating the DCPC.

8. More detailed documentation on WIS

WIS is now formally part of the WMO Technical Regulations through the Manual on WIS. Together with the Guide to WIS, which has the status of a WMO Guide, the Manual on WIS forms the high-level documentation of WIS.
The Manual and the Guide introduce the three types of WIS centres and the Technical Specifications mandated on them. They also describe the nomination procedures for the different centres and the functional specifications.

The WIS manual and guide remain the authoritative sources for information on WIS but are still being updated with relevant details. More information can be obtained from the development documentation of WIS which exists in the form of various other guides.

• The WMO Core Profile Metadata Guidelines introduce discovery metadata, as well as explaining the various elements in the WMO Core Profile metadata.
• The WIS Centre Nomination Guidelines detail the procedures for the nomination of WIS DCPCs and GISCs and the usage of the ET-GDDP online questionnaire.
• The OAI-PMH Operating Guidelines regulate the details of the GISC to GISC metadata synchronization.
• The SRU Implementors Note details the search indices and response format of the SRU Search interface needed of some types of WIS centres.
• The WIS Technical Specifications have been replaced by the Manual on WIS, but are a useful document providing the detailed technical specifications introduced by the Manual and Guide to WIS, and provide Use Cases to ease their comprehension.
• WMO hosts and maintains a web site that contains links to software available for WIS. This list might not be complete and shall only represent a snapshot of the current situation. WEBPAGE TO BE DEFINED

Other background information is contained in

• WIS Project and Implementation Plan
• Manual on the GTS, Volume I

List of abbreviations

AMDCN	Area Meteorological Data Communication Network
CBS	Commission for Basic Systems
DAR	Discovery, Access and Retrieval
ET-GDDP	The CBS Expert Team on GISC-DCPC Demonstration Process
GTS	Global Telecommunication System
ISO 19115	ISO Standard on Geographic information — Metadata
ISO 19139	ISO Standard on Geographic information — Metadata — XML schema implementation
OAI-PMH	Open Archives Initiative — Protocol for Metadata Harvesting
NMC	National Meteorological Centre
MTN	Main Telecommunication Network
RSMC	Regional Specialized Meteorological Centre
RTH	Regional Telecommunication Hub
SRU	Search and Retrieval by URL
WMO Core Profile	WMO Profile of the standard ISO 19115:2003 - Geographic information - Metadata
WWW	World Weather Watch Programme
XML	Extensible Markup Language