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

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

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

Interoperability Standards at Levels of Syntax and Semantics 4 ASN.1 Snippet PDU ::= CHOICE{ searchRequest [22] IMPLICIT SearchRequest, searchResponse [23] IMPLICIT SearchResponse, SearchRequest ::= SEQUENCE{ resultSetName [17] IMPLICIT InternationalString, databaseNames [18] IMPLICIT SEQUENCE OF DatabaseName, query [21] Query SearchResponse ::= SEQUENCE{ resultCount [23] IMPLICIT INTEGER, numberOfRecordsReturned [24] IMPLICIT INTEGER, nextResultSetPosition [25] IMPLICIT INTEGER, searchStatus [22] IMPLICIT BOOLEAN, resultSetStatus [26] IMPLICIT INTEGER, records Records OPTIONAL,

Interoperability Standards at Levels of Syntax and Semantics 5 Comparing ASN.1 and XML Syntactic Mechanisms ASN.1XML syntax descriptionspecificationschema structure mechanismstart-position and length mark-up with start-end tags atomic elementbitcharacter encoding mechanismencoding rules (basic, packed...) Unicode filter (ISO , UTF-8...

Interoperability Standards at Levels of Syntax and Semantics 6 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 Basic Encoding Rules (BER): represent each byte present, as defined in the specification Packed Encoding Rules (PER): group repeated bytes Distinguished Encoding Rules (DER): represent only bytes that change, on a message to message basis XML Encoding Rules (XER): translate between ASN.1 elements and their XML equivalents

Interoperability Standards at Levels of Syntax and Semantics 7 ASN.1 and XML Interoperability using XML Encoding Rules  An XML Encoding Rules (XER) tool can generate, automatically and losslessly:  an XML schema from an ASN.1 specification OR  an ASN.1 specification from an XML schema  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 8 Example: Common Alerting Protocol Uses XER to Bridge ASN.1 and XML  Common Alerting Protocol (CAP) standardizes all-hazards, all-media public warning messages  Message formats in the CAP standard were originally defined using XML Schema  XER was used to create an ASN.1 specification for CAP messages, required for ITU adoption  International Telecommunication Union (ITU) adopted CAP as ITU Recommendation X.1303

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

Interoperability Standards at Levels of Syntax and Semantics 10 Standards-based Interoperability at the Level of Semantics  Semantic interoperability is often constrained in practice by a lack of available data definitions  It is risky to integrate or transform any data or information element without its explicit definition  ISO/IEC 11179, Metadata Registries, provides useful guidance for documenting the meanings of data or information elements  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 11 Example: CAP Data Dictionary Element Name Context. Class. Attribute. Represent- ation Definition and (Optionality)Notes or Value Domain alertcap. 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.: [sub-elements] (3) In addition to the specified sub-elements, MAY contain one or more blocks. identifiercap. 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 &) sendercap. 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 &) sentcap. alert. sent. time The time and date of the origination of the alert message (REQUIRED) The date and time is represented in [dateTime] format (e.g., " T16:49:00- 07:00" for 24 May 2002 at 16: 49 PDT). statuscap. 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 “System" For messages that support alert network internal functions. “Test" Technical testing only, all recipients disregard

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

Interoperability Standards at Levels of Syntax and Semantics 13 Questions? References: GEOSS (Global Earth Observation System of Systems) 10 Year Implementation Plan and Reference Document ISO/IEC Metadata Registries c035343_ISO_IEC_ _2004(E).zip

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

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

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

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

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

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

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

Interoperability Standards at Levels of Syntax and Semantics 21 Database Catalog

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

Interoperability Standards at Levels of Syntax and Semantics 23 UDDI Registry Alice Wilson 161 North Street Happy Valley MO USA Business-to-Business

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

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

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

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

Interoperability Standards at Levels of Syntax and Semantics 28 Types of Registries: Software Component Registries  Registers reusable software components built on specific vendor platforms such as EJB, COM, CORBA IDL etc.  Includes basic common elementary objects and object patterns  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 29 An Example of Software Component Registry

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

Interoperability Standards at Levels of Syntax and Semantics 31 OASIS/ebXML XML Registry JPN Repository VI304 ListPrice Currency Dollars XML Instance UnitPrice XML Instance JPN Collaboration Partner #1 X12 EDIFACT DISA DISA Schema or Template DISA DISA Schema or Template Collaboration Partner #2 Alice Wilson 161 North Street Happy Valley MO USA

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

Interoperability Standards at Levels of Syntax and Semantics 33 Data Element List – Address Group Alice Wilson 161 North Street Happy Valley MO USA ISO Registry 33c Name Street Address City, State Postal Code Country