public interface ModelInterpolator {

    /**
     * Interpolates expressions in the specified model. Note that implementations are free to either interpolate the
     * provided model directly or to create a clone of the model and interpolate the clone. Callers should always use
     * the returned model and must not rely on the input model being updated.
     *
     * @param model The model to interpolate, must not be {@code null}.

            }
        });

        interpolator.addValueSource(new MapBasedValueSource(context.getProjectProperties()));
        interpolator.addValueSource(new MapBasedValueSource(context.getUserProperties()));
        interpolator.addValueSource(new MapBasedValueSource(context.getSystemProperties()));

        String absolutePath = interpolator.interpolate(path, "");

        }

        toolchains = interpolate(toolchains, request, problems);

        return toolchains;
    }

    private PersistedToolchains interpolate(
            PersistedToolchains toolchains, ToolchainsBuilderRequest request, List<BuilderProblem> problems) {

        RegexBasedInterpolator interpolator = new RegexBasedInterpolator();

        return settings;
    }

    private Settings interpolate(Settings settings, SettingsBuilderRequest request, List<BuilderProblem> problems) {

        RegexBasedInterpolator interpolator = new RegexBasedInterpolator();

        interpolator.addValueSource(new MapBasedValueSource(request.getSession().getUserProperties()));

        interpolator.addValueSource(new MapBasedValueSource(request.getSession().getSystemProperties()));

        }

        try {
            path = profileActivationFilePathInterpolator.interpolate(path, context);
        } catch (InterpolationException e) {
            problems.add(
                    BuilderProblem.Severity.ERROR,
                    ModelProblem.Version.BASE,
                    "Failed to interpolate file location " + path + " for profile " + profile.getId() + ": "
                            + e.getMessage(),

        StringSearchInterpolator interpolator = new StringSearchInterpolator();
        interpolator.setCacheAnswers(true);
        for (ValueSource vs : valueSources) {
            interpolator.addValueSource(vs);
        }
        for (InterpolationPostProcessor postProcessor : postProcessors) {
            interpolator.addPostProcessor(postProcessor);
        }

            }
        }

        Model tmpModel = lineage.get(0);

        // inject interpolated activations
        List<Profile> interpolated = interpolateActivations(tmpModel.getProfiles(), profileActivationContext, problems);
        if (interpolated != tmpModel.getProfiles()) {
            tmpModel = tmpModel.withProfiles(interpolated);
        }

        // inject external profile into current model

RegexBasedInterpolat { private java.util.List valueSources; public void RegexBasedInterpolat(); public void RegexBasedInterpolat(java.util.List); public void addValueSource(ValueSource); public void removeValuesSource(ValueSource); public String interpolate(String, String); } org/codehaus/plexus/util/interpolation/ValueSource.class package org.codehaus.plexus.util.interpolation; public abstract interface ValueSource { public abstract Object getValue(String); } org/codehaus/plexus/util/InterpolationFilterR.class...

                            Severity.WARNING,
                            Version.V30,
                            prefix + path,
                            null,
                            "Failed to interpolate profile activation property " + s + ": " + propertyName
                                    + " expressions are not supported during profile activation.",
                            locationSupplier.get());
                }

 have properties file (something I would like to avoid) say they don't
 contribute in any meaningful way to information in the POM. For example a
 properties file could be used the specify $ so it can be interpolated in
 <developerConnection/> but you couldn't use a properties file to specify the
 version of your project say. Anyway, food for thought to begin with.

 - elements that are critical for pom dissemination