Meetings

TERMS OF REFERENCE

Co-Chairs: Ammatzia Peled (Israel) & Antony Cooper (South Africa)

Introduction

At the 19^th International Cartographic Conference and 11^th General Assembly of the International Cartographic Association (ICA), held in Ottawa, Canada, from 15 to 21 August 1999, the ICA established a new Working Group on Incremental Updating and Versioning. The reasons for establishing the Working Group are:

There are many spatial data sets supplied by many producers that provide users with the framework for their spatial data bases (ie: base data sets) and upon which they build their value-added data sets and topology;
There should be no need to redistribute an entire data set to its users to propagate changes that are only minor or few in number;
It will be more efficient to disseminate only the changed or updated data (ie: patches to the data set);
There is a need for secure algorithms and procedures for updating incrementally a base data set, to minimise the impact of the changes on the users’ value-added data sets and topology;
It will be more efficient and effective to automate the update process, to avoid error-prone, labour-intensive work to introduce the changes to one’s existing data bases;
Data producers run out of budget, resulting in inconsistent updating of base data sets, not according to plan; and
There is a need to keep track of different versions of a data set, for legal reasons, time-series analysis, historical research and planning.

Terms of reference

Against this background, the following are the terms of reference for the ICA’s Working Group on Incremental Updating and Versioning, for the 1999 to 2003 cycle of work:

1. To serve as a focal point for research into the incremental updating and versioning of digital spatial data bases and the implementation of solutions. Research issues include: bi-directional, multi-level, historical and temporal updating, planning for future changes, data base maintenance, feature identifiers, modularity (dimension, context, layer, theme and size), inconsistent updating and simultaneous updating by field teams;

2. To identify those individuals and organisations interested in the problems of incremental updating and versioning who are willing to contribute, and to support networking between them;

3. To foster inter-society cooperation on incremental updating and versioning;

4. To conduct a literature study and publish an overview of the current state of the art of the incremental updating and versioning of digital spatial data bases, especially for protecting the integrity and spatial referencing of value-added data and topology;

5. To organise seminars and/or workshops in conjunction with International Cartographic Conferences and other events, leading to:

(a) A conceptual model of incremental updating and versioning of digital spatial data bases; and

(b) In the longer term, the publication of a reference manual (cookbook) focussing on the definition of the problem, the setting of further research goals and efforts, and identifying best practices;

6. To define algorithms for modular and/or application-oriented incremental updating and versioning;

7. To establish and maintain a Web site for the Working Group on Incremental Updating and Versioning; and

8. To organise regular business meetings.

Much of the work of the proposed Working Group will take place on-line, though meetings will also be held. It will be crucial to the success of the Working Group and the rapid dissemination of results that the workload of the Working Group be shared between its members. Responsibilities for individual terms of reference will be assigned to different members of the Working Group.

For more information, please see the Working Group’s Web site: http://geo.haifa.ac.il/~icaupd

Background

The following is a brief introduction to the problems to be addressed by this Working Group.

Spatial data bases are already serving as the platform for cartographic production. In the analogue era, the hard-copy maps themselves served also as the data bases for spatial data. Hence, updating the map also meant updating the spatial data set.

In the digital era, the maps should be updated by updating the data base and them producing the new maps. Updating can take place periodically (eg: daily, monthly, annually, etc), as part of a planned updating cycle (with each subset of the data base or each map sheet being updated in rotation), when the amount of change crosses a threshhold, by special request for a specific need (such as an election or census), or other reasons.

There is rapid change taking place all over the world, especially to the types of physical features recorded in spatial data bases. In addition, more and more data are captured for these and other features, as the number of spatial data users, applications and sensors grow.

Thus, there is a need to speed up the frequency of updates and to automate the update processes. To facilitate this, one needs a formalised, continuous and incremental updating process for the digital spatial data bases, and some method of keeping track of the different versions of individual data sets or features. Typically, the updated versions of the data set are then disseminated to the end users by sending them the whole, updated version of the data set or a subset (eg: tiles or layers). Examples of this process are NIMA's Digital Chart of the World (DCW) and road atlases for in-car navigation.

End users tend to use data sets obtained from several different sources, which they often have to integrate themselves, and upon which they build their own value-added data sets. Ultimately, the end user is more concerned about maintaining the integrity, quality and spatial-referencing of their value-added data and topology, in which they have invested much time and money, rather than the external data sets. Yet, these external data sets provide a crucial framework for their value-added data sets.

Hence, when a user receives one of these bulk updates today, they are faced with the dilemma of either ignoring the update (if it is not significant enough) or accepting the update, but with the need to then rebuild their value-added data on top of the updated data set. This rebuilding process involves checking to see if any of the features they have used for geocoding their non-spatial data bases have been changed, aggregated, sub-divided or deleted, and then making the appropriate changes (which can be complex). The update might also result in the loss or change of unique identifiers. It might also be necessary for the user to rebuild the topology of their data base.

Some work has been done on the incremental updating of events, though this is done only to data sets where the users do not add any significant amounts of value-added data, for example, the Electronic Nautical Charts (ENC) of the International Hydrographic Organisation. The Working Group will also consider the work of CERCO, ISO/TC 211, NOTAM (Notice to Airmen), the Open GSI Consortium (OGC) and the European Union Commission V. These types of projects will be used as a starting point for the work of the Working Group.

It is the intention of the proposed Working Group ultimately to take the problem of the incremental updating and versioning of spatial data sets from conception to implementation.