Inventories of lasting value may be built on the results coming from detailed individual building research projects. Preliminary inventories may be carried out from the front seats of automobiles, or on foot, using pre-printed forms to simplify and regularize responses. Once the reports have been completed, the data-forms collected, the as-found records and archaeological finds collated and catalogued, it is important to assemble the information in a manner which facilitates access, use and understanding.

Computers have been used in some areas for over two decades now to assist with data collection and management. A national computerized inventory system developed by the Canadian Parks Service 20 years ago revolutionized data collection in this area. Imitated many times since, the original Canadian Inventory of Historic Buildings (C.I.H.B.) system still provides an excellent model for those in need of a reliable, low-tech, low-budget approach, and has been adapted in many jurisdictions.

Most World Heritage towns and cities, however, have not found the resources or means to systematically incorporate site research reports within an overall system which links them to other relevant research, and which ensures easy access. While most are able to maintain files for properties within their boundaries, the knowledge base within the files is inconsistent, and dependent to a great extent on past interest or urgency attached to specific projects.

Cities that have begun to systematically implement documentation management systems are not only able to manage their assets more efficiently and carefully, but are in a position to improve understanding of their own development through the thematic patterns that emerge from a research base of consistent depth and focus. In Rome for example, the development of a computerized data base linking building use, configuration and condition data with cadastral and aerial photogrammetric plans permits planning officials to quickly explore the ramifications of proposed developments.



The criteria used to judge the suitability of actions proposed for the enhancement or protection of urban ensembles will come from two major sources - from the intrinsic values of the sites themselves, and from the body of accepted wisdom defining appropriate means to respect defined values. These latter are generally described as principles; translated into specific and measurable targets, they are described as standards.

It is useful to look at the body of doctrine developed to deal with urban historic quarters in three areas:
1. the global principles of urban conservation, as they may have evolved with time and been incorporated into governing charters;
2. the principles pertinent to existing sites, as embodied in guidelines to constrain and channel change in appropriate directions;
3. the principles pertinent to new construction, usually expressed in the form of guidelines intended to guide infill projects to respect context.



The growth of interest in the development and application of conservation principles to urban ensembles has been described in great detail in section B of this guide. The international charters provide general guidance with respect to the key issues in dealing with important sites, urban or otherwise. Each is, to some extent, limited in its usefulness by the context of the specific time and circumstances within which it was developed.

To bring the principles of conservation to bear with force on any particular urban setting, it may be useful for each civic jurisdiction to develop a charter of its own - a clear statement of principles of most relevance in the local situation, adapted in language and tone to its own exigencies.

There is perhaps only one conservation principle of universal applicability in almost all circumstances, that of ensuring that conservation decisions are shared with more than the single expert. Meeting that principle should be a key consideration in urban conservation programmes for historic towns of great worth.



Many historic quarters have developed sets of design/conservation guidelines intended to provide practical advice in the face of proposed changes. These guidelines are usually meant to link the principles of urban conservation and the particular characteristics of sites, in down-to-earth, accessible language and concepts.

Guidelines come in many forms. Some are heavily illustrated; some rely entirely on words. Some are "prescriptive", defining desired results in precise terms; others are "interpretive", establishing a range within which acceptable solutions may be found. Whatever the choice of methods, formats or presentations, the keys to development and application of guideliness best suited to success in a community are the following:
- the clear expression of the qualities the guidelines are meant to protect;
- the development of a vocabulary adequate to describe these qualities;
- the involvement of a diverse group of individuals representing professional and public interests in their development and management;
- their built-in capacity to be reviewed and modified regularly in the light of experience.



One of the most frequently encountered design problems in historic ensembles is the insertion of new structures into empty spaces. The international charters and principles espouse honesty - a general preference for contemporary approaches over imitative reconstructions. At the same time, the design challenge is one of the most difficult a contemporary architect can confront : too avant-garde in style or composition, too modern in materials or arrangement and a jarring note will be struck; equally, too much obeisance to the usual precepts of fidelity to adjacent structures in texture, form, proportions, material and scale, and unconvincing two-dimensional pastiches may result.

Architects, designers or planners confronted with this design challenge might use the following checklist to advantage in assessing "infill" problems :
- allusions to adjacent traditional forms need not literally echo precedent; the goal is to reflect the spirit of a place or street, not just its literal forms;
- a preference for contemporary design does not require the architect to replace traditional materials with plastic or anodized metal; it merely suggests modern approaches to fenestration, layout and manipulation of forms; moreover, almost all traditional materials are still in use and may therefore be regarded as modern materials;
- an imitative approach may be quite legitimate if the adjacent context is overwhelmingly homogeneous; any other approach might be unduly self-conscious;
- the conservation principle of legibility may be satisfactorily achieved in very modest ways, and need not mar or affect overall aesthetic coherence in strongly visible fashion.