return (T) computeIfAbsent(new GavCacheKey(groupId, artifactId, version, tag), data);
    }

    @Override
    @SuppressWarnings({"unchecked"})
    public <T> T computeIfAbsent(Source path, String tag, Supplier<T> data) {
        return (T) computeIfAbsent(new SourceCacheKey(path, tag), data);
    }

 * identity of a model. The tag allows for further classification of the associated data on the sole discretion of the
 * model builder.
 *
 */
public interface ModelCache {

    <T> T computeIfAbsent(String groupId, String artifactId, String version, String tag, Supplier<T> data);

    <T> T computeIfAbsent(Source path, String tag, Supplier<T> data);

        }
    }

    @Override
    public Optional<String> getString(URI relativeSource, Charset charset) {
        requireNonNull(charset, "charset is null");
        Optional<byte[]> data = getBytes(relativeSource);
        return data.map(bytes -> new String(bytes, charset));
    }

    @Override
    public void put(Path source, URI relativeTarget) {
        requireNonNull(source, "source is null");