World Meteorological Organizations WMO Observing and Information Systems

World Meteorological Organizations (WMO) Observing and Information Systems Department WMO Information System (WIS) Interoperability Standards at Levels of Syntax and Semantics Presented by Eliot Christian <echristian@wmo. int> at the First Meeting of WMO / CBS / ISS / ET-ADRS (Expert Team On Assessment Of Data Representation Systems) in Silver Spring, MD, USA on 23 - 25 April 2008 Interoperability Standards at Levels of Syntax and Semantics

Syntax and Semantics Ø Semantics deals with the meaning of a symbol in some language Ø Syntax deals with handling of symbols independent of their meaning, e. g. , ² ASN. 1 (Abstract Syntax Notation) ² XML (e. Xtensible Markup Language) Interoperability Standards at Levels of Syntax and Semantics 2

Standards-based Interoperability at the Level of Syntax Ø Structure Types, e. g. , ² sub-element is part of element ² record is part of file ² table has three dimensions Ø Data Types, e. g. , ² integers or decimal numbers. . . ² dates, times, coordinates. . . ² text, images, sound. . . Ø Indicating structure in an instance, e. g. , ² start-position, length ² mark-up with start-end tagging Interoperability Standards at Levels of Syntax and Semantics 3

ASN. 1 Snippet PDU : : = CHOICE{ search. Request [22] IMPLICIT Search. Request, search. Response [23] IMPLICIT Search. Response, Search. Request : : = SEQUENCE{ result. Set. Name [17] IMPLICIT International. String, database. Names [18] IMPLICIT SEQUENCE OF Database. Name, query [21] Query Search. Response : : = SEQUENCE{ result. Count [23] IMPLICIT INTEGER, number. Of. Records. Returned [24] IMPLICIT INTEGER, next. Result. Set. Position [25] IMPLICIT INTEGER, search. Status [22] IMPLICIT BOOLEAN, result. Set. Status [26] IMPLICIT INTEGER, records Records OPTIONAL, Interoperability Standards at Levels of Syntax and Semantics 4

Comparing ASN. 1 and XML Syntactic Mechanisms ASN. 1 syntax description XML specification schema structure mechanism start-position and length mark-up with start-end tags atomic element character bit encoding mechanism encoding rules Unicode filter (basic, packed. . . ) (ISO 8859 -1, UTF-8. . . Interoperability Standards at Levels of Syntax and Semantics 5

ASN. 1 and Encoding Rules In ASN. 1, concrete syntax ("on-the-wire encoding") is handled separately from the abstract syntax: ASN. 1 "Encoding Rules" are applied to make actual messages in compliance with an ASN. 1 specification ü Basic Encoding Rules (BER): represent each byte present, as defined in the specification ü Packed Encoding Rules (PER): group repeated bytes ü Distinguished Encoding Rules (DER): represent only bytes that change, on a message to message basis ü XML Encoding Rules (XER): translate between ASN. 1 elements and their XML equivalents Interoperability Standards at Levels of Syntax and Semantics 6

ASN. 1 and XML Interoperability using XML Encoding Rules Ø An XML Encoding Rules (XER) tool can generate, automatically and losslessly: ² an XML schema from an ASN. 1 specification OR ² an ASN. 1 specification from an XML schema Ø In addition, XER can be applied at the instance level rather than the schema level, i. e. , XER converters inserted at both ends of a communications link will enhance transmission efficiency "on-the-fly" Interoperability Standards at Levels of Syntax and Semantics 7

Example: Common Alerting Protocol Uses XER to Bridge ASN. 1 and XML Ø Common Alerting Protocol (CAP) standardizes all-hazards, all-media public warning messages Ø Message formats in the CAP standard were originally defined using XML Schema Ø XER was used to create an ASN. 1 specification for CAP messages, required for ITU adoption Ø International Telecommunication Union (ITU) adopted CAP as ITU Recommendation X. 1303 Interoperability Standards at Levels of Syntax and Semantics 8

Standards-based Interoperability at the Level of Semantics Interoperability Standards at Levels of Syntax and Semantics 9

Standards-based Interoperability at the Level of Semantics Ø Semantic interoperability is often constrained in practice by a lack of available data definitions Ø It is risky to integrate or transform any data or information element without its explicit definition Ø ISO/IEC 11179, Metadata Registries, provides useful guidance for documenting the meanings of data or information elements Ø The objective is to have good definitions for data and information elements, not to fully automate inferencing (sometimes called "Semantic Web") Interoperability Standards at Levels of Syntax and Semantics 10

Example: CAP Data Dictionary Element Name Context. Class. Attribute. Representation Definition and (Optionality) Notes or Value Domain alert cap. alert. group The container for all component parts of the alert message (REQUIRED) (1) Surrounds CAP alert message sub-elements. (2) MUST include the xmlns attribute referencing the CAP URI as the namespace, e. g. : <cap: alert xmlns: cap="urn: oasis: names: tc: emergency: cap: 1. 1"> [sub-elements] </cap: alert> (3) In addition to the specified sub-elements, MAY contain one or more <info> blocks. identifier cap. alert. identifier The identifier of the alert message (REQUIRED) (1) A number or string uniquely identifying this message, assigned by the sender (2) MUST NOT include spaces, commas, or restricted characters (< and &) sender cap. alert. sender. identifier The identifier of the sender of the alert message (REQUIRED) (1) Identifies the originator of this alert. Guaranteed by assigner to be unique globally; e. g. , may be based on an Internet domain name (2) MUST NOT include spaces, commas, or restricted characters (< and &) sent cap. alert. sent. time The time and date of the origination of the alert message (REQUIRED) The date and time is represented in [date. Time] format (e. g. , "2002 -05 -24 T 16: 49: 0007: 00" for 24 May 2002 at 16: 49 PDT). status cap. alert. status. code The code denoting the appropriate handling of the alert message (REQUIRED) Code Values: “Actual" Actionable by all targeted recipients “Exercise" Actionable only by designated exercise participants; exercise identifier should appear in <note> “System" For messages that support alert network internal functions. “Test" Technical testing only, all recipients disregard Interoperability Standards at Levels of Syntax and Semantics 11

Actions Proposed Ø Syntactic interoperability should be achieved using automated transformations, based on standardized syntax description languages Ø Syntactic interoperability cannot assure that information is meaningful--precise definitions of data and information elements are necessary Ø ISO/IEC 11179, Metadata Registries, provides useful guidance for defining elements, within and among data dictionaries Ø A policy promoting use of ISO/IEC 11179 would complement broader use of ISO 191 xx series of standards, especially ISO 19115 Interoperability Standards at Levels of Syntax and Semantics 12

References: GEOSS (Global Earth Observation System of Systems) 10 Year Implementation Plan and Reference Document http: //earthobservations. org/ ISO/IEC 11179 Metadata Registries http: //standards. iso. org/ittf/Publicly. Available. Standards/ c 035343_ISO_IEC_11179 -1_2004(E). zip Questions? Interoperability Standards at Levels of Syntax and Semantics 13

Using Registries to Manage Data / Metadata Syntax and Semantics Interoperability Standards at Levels of Syntax and Semantics 14

Registries are Tools for Data Management, Information Management, Knowledge Management Ø Several types of “registries” commonly used Ø The types of registries have related content, but extended and utilized in different ways Ø The registries vary according to: ² intended purpose ² granularity of contents ² the level of semantics management Interoperability Standards at Levels of Syntax and Semantics 15

Types of Registries ISO 11179 Registries Database Catalogs UDDI Registries Common Content OASIS/eb. XML Registries CASE Tool Repositories Common Content Software Component Registries Common Content Ontological Registries Common Content Interoperability Standards at Levels of Syntax and Semantics 16

Example using "Country Name" as Common Content across Registry Types Database Catalogs ISO 11179 Registries Common Content OASIS/eb. XML Registries Common Content Software Component Registries Common Content UDDI Registries Country Name CASE Tool Repositories Common Content Ontological Registries Common Content Interoperability Standards at Levels of Syntax and Semantics 17

"Country Name" in a 11179 Registry Data Element Concept Name: Country Identifiers Context: Definition: Unique ID: 5769 Conceptual Domain: Maintenance Org. : Steward: Classification: Registration Authority: Others Algeria Belgium China Denmark Egypt France. . . Zimbabwe Data Elements ISO 3166 French Name ISO 3166 2 -Alpha Code ISO 3166 3 -Numeric Code Algeria L`Algérie DZ DZA 012 Belgium Belgique BE BEL 056 China Chine CN CHN 156 Denmark Danemark DK DNK 208 Egypte EG EGY 818 France La France FR FRA 250 . . . . Zimbabwe ZW ZWE 716 ISO 3166 English Name: Context: Definition: Unique ID: 4572 Value Domain: Maintenance Org. Steward: Classification: Registration Authority: Others Interoperability Standards at Levels of Syntax and Semantics 18

Registries Address Different Needs Example using "Country Name" as Common Content Database Catalogs Common Content ISO 11179 Registries Common Content OASIS/eb. XML Registries Data Element XML Tag Common Content Software Component Registries Common Content Table Column UDDI Registries Common Content Business Specification Country Name Attribute Term Hierarchy Business Object CASE Tool Repositories Common Content Ontological Registries Common Content Interoperability Standards at Levels of Syntax and Semantics 19

Types of Registries: Database Catalogs/Data Dictionaries/ Repositories Database Catalogs Common Content Ø Registers schema, integrity & operational information Ø Includes all elements of database schemas: data elements, relations, integrity constraints Ø Emphasis on information required to make database systems work for queries, etc. , not semantic management Interoperability Standards at Levels of Syntax and Semantics 20

Database Catalog Interoperability Standards at Levels of Syntax and Semantics 21

Types of Registries: Universal Description, Discovery, and Integration (UDDI) Registries Ø Registers Web-based Business Services Ø A White page directory of the business activities of firms Ø Emphasis on interface specifications UDDI Registries Common Content Interoperability Standards at Levels of Syntax and Semantics 22

UDDI Registry Business-to-Business <? xml version="1. 0"? > <ship. To> <name>Alice Wilson</name> <street>161 North Street</street> <city>Happy Valley</city> <state>MO</state> <zip>63105</zip> <country code>USA</country code> </ship. To> Interoperability Standards at Levels of Syntax and Semantics 23

Types of Registries: Case Tool (Encyclopedias/Repositories) Ø Registers data models and application program logic Ø Includes information needed to create a database and potentially the program code for a system, including database schemas CASE Tool Repositories Common Content Ø Emphasis not on semantic management Interoperability Standards at Levels of Syntax and Semantics 24

Case Tool Repository Interoperability Standards at Levels of Syntax and Semantics 25

Types of Registries: Ontological Registries Ø Registers Concept Structures Ø Includes relations among concepts (subsumption, inheritance, …) and axioms for inference among concepts, e. g. , temporal/spatial reasoning, etc. Ø Emphasis is on semantics Ontological Registries Common Content Interoperability Standards at Levels of Syntax and Semantics 26

Ontological Registry Concept Geographic Area Geographic Sub-Area Country Identifier Country Name Short Name Mailing Address Country Name Long Name Distributor Country Name Country Code ISO 3166 2 -Character Code ISO 3166 3 -Numeric Code Interoperability Standards at Levels of Syntax and Semantics ISO 3166 3 - Character Code FIPS Code 27

Types of Registries: Software Component Registries Ø Registers reusable software components built on specific vendor platforms such as EJB, COM, CORBA IDL etc. Ø Includes basic common elementary objects and object patterns Ø Emphasis on reusability of software component to build flexible and standardized business systems. Software Component Registries Common Content Interoperability Standards at Levels of Syntax and Semantics 28

An Example of Software Component Registry Interoperability Standards at Levels of Syntax and Semantics 29

Types of Registries: OASIS/eb. XML Registries Ø Registers XML Artifacts OASIS/eb. XML Registries Common Content Ø Includes schemas and DTDs (XML schemata typically relate to a paper form, EDI document, or reporting requirement) Ø Emphasis on syntactic (structure) information Interoperability Standards at Levels of Syntax and Semantics 30

OASIS/eb. XML Registry <? xml version="1. 0"? > <ship. To > <name>Alice Wilson</name> <street>161 North Street</street> <city>Happy Valley</city> <state>MO</state> <zip>63105</zip> <country code>USA</country code> Repository VI 304 Dollars X 12 EDIFACT List. Price Currency </ship. To> Unit. Price Collaboration Partner #1 Schema or Template Collaboration Partner #2 Schema or Template <Rep href= “http: //www. disa. mil”>DISA</Rep> <ELEMENT rep= ‘DISA’ name=‘Country’ Biz =‘VI 304’ > <ELEMENT rep= ‘DISA’ name=‘Cntry. Code’ Biz =‘VI 304’ > XML Instance <Country>JPN</Country> <Cntry. Code>JPN</Cntry. Code> Interoperability Standards at Levels of Syntax and Semantics 31

Types of Registries: ISO 11179 Metadata Registries ISO 11179 Registries Common Content Ø Registers Data Elements, components of data elements and groups of data elements (e. g. , country codes for customer place of residence) Ø Includes data element concepts, data elements (including representation), value domains, and (multiple) taxonomies Ø Emphasis on semantic information such as definitions of data elements and value meanings, and stewardship responsibilities Interoperability Standards at Levels of Syntax and Semantics 32

ISO 11179 Registry Data Element List – Address Group 33 c Name Street Address City, State Postal Code Country <? xml version="1. 0"? > <ship. To > <name>Alice Wilson</name> <street>161 North Street</street> <city>Happy Valley</city> <state>MO</state> <zip>63105</zip> <country code>USA</country code> </ship. To> Interoperability Standards at Levels of Syntax and Semantics 33