diff --git a/src/libexpr/get-drvs.cc b/src/libexpr/get-drvs.cc
index 6670d0636a1..f3381aa75ea 100644
--- a/src/libexpr/get-drvs.cc
+++ b/src/libexpr/get-drvs.cc
@@ -6,6 +6,29 @@
 namespace nix {
 
 
+string DrvInfo::queryName(EvalState & state) const
+{
+    if (name == "" && attrs) {
+        Bindings::iterator i = attrs->find(state.sName);
+        (string &) name = state.forceStringNoCtx(*i->value);
+    }
+    return name;
+}
+
+
+string DrvInfo::querySystem(EvalState & state) const
+{
+    if (system == "" && attrs) {
+        Bindings::iterator i = attrs->find(state.sSystem);
+        if (i == attrs->end())
+            (string &) system = "unknown";
+        else
+            (string &) system = state.forceStringNoCtx(*i->value);
+    }
+    return system;
+}
+
+
 string DrvInfo::queryDrvPath(EvalState & state) const
 {
     if (drvPath == "" && attrs) {
@@ -27,12 +50,35 @@ string DrvInfo::queryOutPath(EvalState & state) const
     return outPath;
 }
 
+static MetaValue createMetaValue(EvalState & state, Value & v)
+{
+    MetaValue value;
+    try {
+        state.forceValue(v);
+        if (v.type == tString) {
+            value.type = MetaValue::tpString;
+            value.stringValue = v.string.s;
+            } else if (v.type == tInt) {
+                value.type = MetaValue::tpInt;
+                value.intValue = v.integer;
+            } else if (v.type == tList) {
+                value.type = MetaValue::tpStrings;
+                for (unsigned int j = 0; j < v.list.length; ++j)
+                    value.stringValues.push_back(state.forceStringNoCtx(*v.list.elems[j]));
+            } else
+                value.type = MetaValue::tpNone;
+    } catch (ImportReadOnlyError & e) {
+        value.type = MetaValue::tpNone;
+    }
+    return value;
+}
 
 MetaInfo DrvInfo::queryMetaInfo(EvalState & state) const
 {
     if (metaInfoRead) return meta;
     
     (bool &) metaInfoRead = true;
+    ((MetaInfo &) meta).clear();
     
     Bindings::iterator a = attrs->find(state.sMeta);
     if (a == attrs->end()) return meta; /* fine, empty meta information */
@@ -40,20 +86,8 @@ MetaInfo DrvInfo::queryMetaInfo(EvalState & state) const
     state.forceAttrs(*a->value);
 
     foreach (Bindings::iterator, i, *a->value->attrs) {
-        MetaValue value;
-        state.forceValue(*i->value);
-        if (i->value->type == tString) {
-            value.type = MetaValue::tpString;
-            value.stringValue = i->value->string.s;
-        } else if (i->value->type == tInt) {
-            value.type = MetaValue::tpInt;
-            value.intValue = i->value->integer;
-        } else if (i->value->type == tList) {
-            value.type = MetaValue::tpStrings;
-            for (unsigned int j = 0; j < i->value->list.length; ++j)
-                value.stringValues.push_back(state.forceStringNoCtx(*i->value->list.elems[j]));
-        } else continue;
-        ((MetaInfo &) meta)[i->name] = value;
+        MetaValue value = createMetaValue(state, *i->value);
+        if (value.type != MetaValue::tpNone) ((MetaInfo &) meta)[i->name] = value;
     }
 
     return meta;
@@ -62,8 +96,19 @@ MetaInfo DrvInfo::queryMetaInfo(EvalState & state) const
 
 MetaValue DrvInfo::queryMetaInfo(EvalState & state, const string & name) const
 {
-    /* !!! evaluates all meta attributes => inefficient */
-    return queryMetaInfo(state)[name];
+    if (metaInfoRead) return ((MetaInfo &)meta)[name];
+    if (meta.count(name)) return ((MetaInfo &)meta)[name];
+
+    Bindings::iterator m = attrs->find(state.sMeta);
+    if (m == attrs->end()) return ((MetaInfo &)meta)[name];
+
+    state.forceAttrs(*m->value);
+    Bindings::iterator i = m->value->attrs->find(state.symbols.create(name));
+    if (i == m->value->attrs->end()) return ((MetaInfo &)meta)[name];
+    MetaValue value = createMetaValue(state, *i->value);
+    if (value.type != MetaValue::tpNone) ((MetaInfo &) meta)[name] = value;
+
+    return ((MetaInfo &)meta)[name];
 }
 
 
@@ -100,13 +145,6 @@ static bool getDerivation(EvalState & state, Value & v,
         Bindings::iterator i = v.attrs->find(state.sName);
         /* !!! We really would like to have a decent back trace here. */
         if (i == v.attrs->end()) throw TypeError("derivation name missing");
-        drv.name = state.forceStringNoCtx(*i->value);
-
-        Bindings::iterator i2 = v.attrs->find(state.sSystem);
-        if (i2 == v.attrs->end())
-            drv.system = "unknown";
-        else
-            drv.system = state.forceStringNoCtx(*i2->value);
 
         drv.attrs = v.attrs;
 
@@ -117,6 +155,8 @@ static bool getDerivation(EvalState & state, Value & v,
     
     } catch (AssertionError & e) {
         return false;
+    } catch (ImportReadOnlyError & e) {
+        return false;
     }
 }
 
diff --git a/src/libexpr/get-drvs.hh b/src/libexpr/get-drvs.hh
index 25d8baa559b..b0176d958ee 100644
--- a/src/libexpr/get-drvs.hh
+++ b/src/libexpr/get-drvs.hh
@@ -26,6 +26,8 @@ typedef std::map<string, MetaValue> MetaInfo;
 struct DrvInfo
 {
 private:
+    string name;
+    string system;
     string drvPath;
     string outPath;
 
@@ -35,20 +37,30 @@ private:
     bool failed; // set if we get an AssertionError
     
 public:
-    string name;
     string attrPath; /* path towards the derivation */
-    string system;
 
     /* !!! make this private */
     Bindings * attrs;
 
     DrvInfo() : metaInfoRead(false), failed(false), attrs(0) { };
 
+    string queryName(EvalState & state) const;
+    string querySystem(EvalState & state) const;
     string queryDrvPath(EvalState & state) const;
     string queryOutPath(EvalState & state) const;
     MetaInfo queryMetaInfo(EvalState & state) const;
     MetaValue queryMetaInfo(EvalState & state, const string & name) const;
 
+    void setName(const string & s)
+    {
+        name = s;
+    }
+
+    void setSystem(const string & s)
+    {
+        system = s;
+    }
+
     void setDrvPath(const string & s)
     {
         drvPath = s;
diff --git a/src/libexpr/nixexpr.hh b/src/libexpr/nixexpr.hh
index bc6c3287c79..0eac3d69d88 100644
--- a/src/libexpr/nixexpr.hh
+++ b/src/libexpr/nixexpr.hh
@@ -16,6 +16,7 @@ MakeError(ThrownError, AssertionError)
 MakeError(Abort, EvalError)
 MakeError(TypeError, EvalError)
 MakeError(ImportError, EvalError) // error building an imported derivation
+MakeError(ImportReadOnlyError, EvalError) // error when trying to import a derivation in read-only mode
 
 
 /* Position objects. */
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index d3809e6984a..7189465af93 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -45,24 +45,41 @@ static void prim_import(EvalState & state, Value * * args, Value & v)
 
     foreach (PathSet::iterator, i, context) {
         Path ctx = decodeContext(*i).first;
+        string outputName = decodeContext(*i).second;
         assert(isStorePath(ctx));
-        if (!store->isValidPath(ctx))
-            throw EvalError(format("cannot import `%1%', since path `%2%' is not valid")
-                % path % ctx);
-        if (isDerivation(ctx))
-            try {
-                /* For performance, prefetch all substitute info. */
-                PathSet willBuild, willSubstitute, unknown;
-                unsigned long long downloadSize, narSize;
-                queryMissing(*store, singleton<PathSet>(ctx),
-                    willBuild, willSubstitute, unknown, downloadSize, narSize);
+        if (!store->isValidPath(ctx)) {
+            if (outputName.empty())
+                throw EvalError(format("cannot import `%1%', since path `%2%' is not valid")
+                    % path % ctx);
+            else
+                throw ImportReadOnlyError(format("cannot import `%1%', since path `%2%' cannot be written to the store in read-only mode")
+                    % path % ctx);
+        }
+        if (isDerivation(ctx)) {
+            Derivation drv = derivationFromPath(*store, ctx);
+
+            if (outputName.empty() ||
+                    !store->isValidPath(drv.outputs[outputName].path)) {
+                if (settings.readOnlyMode)
+                    foreach (DerivationOutputs::iterator, j, drv.outputs)
+                        if (!store->isValidPath(j->second.path))
+                            throw ImportReadOnlyError(format("cannot import `%1%', since derivation `%2%' cannot be realised in read-only mode")
+                                % path % ctx);
+                try {
+                    /* For performance, prefetch all substitute info. */
+                    PathSet willBuild, willSubstitute, unknown;
+                    unsigned long long downloadSize, narSize;
+                    queryMissing(*store, singleton<PathSet>(ctx),
+                        willBuild, willSubstitute, unknown, downloadSize, narSize);
                   
-                /* !!! If using a substitute, we only need to fetch
-                   the selected output of this derivation. */
-                store->buildPaths(singleton<PathSet>(ctx));
-            } catch (Error & e) {
-                throw ImportError(e.msg());
+                    /* !!! If using a substitute, we only need to fetch
+                       the selected output of this derivation. */
+                    store->buildPaths(singleton<PathSet>(ctx));
+                } catch (Error & e) {
+                    throw ImportError(e.msg());
+                }
             }
+        }
     }
 
     if (isStorePath(path) && store->isValidPath(path) && isDerivation(path)) {
diff --git a/src/nix-env/nix-env.cc b/src/nix-env/nix-env.cc
index 5174daf90d8..218a646bee2 100644
--- a/src/nix-env/nix-env.cc
+++ b/src/nix-env/nix-env.cc
@@ -173,7 +173,7 @@ static void loadDerivations(EvalState & state, Path nixExprPath,
        system. */
     for (DrvInfos::iterator i = elems.begin(), j; i != elems.end(); i = j) {
         j = i; j++;
-        if (systemFilter != "*" && i->system != systemFilter)
+        if (systemFilter != "*" && i->querySystem(state) != systemFilter)
             elems.erase(i);
     }
 }
@@ -217,9 +217,13 @@ static bool isPrebuilt(EvalState & state, const DrvInfo & elem)
 {
     assert(false);
 #if 0
-    return
-        store->isValidPath(elem.queryOutPath(state)) ||
-        store->hasSubstitutes(elem.queryOutPath(state));
+    try {
+        return
+            store->isValidPath(elem.queryOutPath(state)) ||
+            store->hasSubstitutes(elem.queryOutPath(state));
+    } catch (ImportReadOnlyError & e) {
+        return false;
+    }
 #endif
 }
 
@@ -241,7 +245,7 @@ static DrvInfos filterBySelector(EvalState & state, const DrvInfos & allElems,
         for (DrvInfos::const_iterator j = allElems.begin();
              j != allElems.end(); ++j, ++n)
         {
-            DrvName drvName(j->name);
+            DrvName drvName(j->queryName(state));
             if (i->matches(drvName)) {
                 i->hits++;
                 matches.push_back(std::pair<DrvInfo, unsigned int>(*j, n));
@@ -263,35 +267,35 @@ static DrvInfos filterBySelector(EvalState & state, const DrvInfos & allElems,
             StringSet multiple;
 
             for (Matches::iterator j = matches.begin(); j != matches.end(); ++j) {
-                DrvName drvName(j->first.name);
+                DrvName drvName(j->first.queryName(state));
                 int d = 1;
 
                 Newest::iterator k = newest.find(drvName.name);
                 
                 if (k != newest.end()) {
-                    d = j->first.system == k->second.first.system ? 0 :
-                        j->first.system == settings.thisSystem ? 1 :
-                        k->second.first.system == settings.thisSystem ? -1 : 0;
+                    d = j->first.querySystem(state) == k->second.first.querySystem(state) ? 0 :
+                        j->first.querySystem(state) == settings.thisSystem ? 1 :
+                        k->second.first.querySystem(state) == settings.thisSystem ? -1 : 0;
                     if (d == 0)
                         d = comparePriorities(state, j->first, k->second.first);
                     if (d == 0)
-                        d = compareVersions(drvName.version, DrvName(k->second.first.name).version);
+                        d = compareVersions(drvName.version, DrvName(k->second.first.queryName(state)).version);
                 }
 
                 if (d > 0) {
                     newest[drvName.name] = *j;
-                    multiple.erase(j->first.name);
+                    multiple.erase(j->first.queryName(state));
                 } else if (d == 0) {
-                    multiple.insert(j->first.name);
+                    multiple.insert(j->first.queryName(state));
                 }
             }
 
             matches.clear();
             for (Newest::iterator j = newest.begin(); j != newest.end(); ++j) {
-                if (multiple.find(j->second.first.name) != multiple.end())
+                if (multiple.find(j->second.first.queryName(state)) != multiple.end())
                     printMsg(lvlInfo,
                         format("warning: there are multiple derivations named `%1%'; using the first one")
-                        % j->second.first.name);
+                        % j->second.first.queryName(state));
                 matches.push_back(j->second);
             }
         }
@@ -395,7 +399,7 @@ static void queryInstSources(EvalState & state,
                 }
                 else elem.setOutPath(path);
 
-                elem.name = name;
+                elem.setName(name);
 
                 elems.push_back(elem);
             }
@@ -469,8 +473,8 @@ static void installDerivations(Globals & globals,
            path is not the one we want (e.g., `java-front' versus
            `java-front-0.9pre15899'). */
         if (globals.forceName != "")
-            i->name = globals.forceName;
-        newNames.insert(DrvName(i->name).name);
+            i->setName(globals.forceName);
+        newNames.insert(DrvName(i->queryName(globals.state)).name);
     }
 
     /* Add in the already installed derivations, unless they have the
@@ -483,19 +487,19 @@ static void installDerivations(Globals & globals,
         
         DrvInfos allElems(newElems);
         foreach (DrvInfos::iterator, i, installedElems) {
-            DrvName drvName(i->name);
+            DrvName drvName(i->queryName(globals.state));
             MetaInfo meta = i->queryMetaInfo(globals.state);
             if (!globals.preserveInstalled &&
                 newNames.find(drvName.name) != newNames.end() &&
                 !keep(meta))
                 printMsg(lvlInfo,
-                    format("replacing old `%1%'") % i->name);
+                    format("replacing old `%1%'") % i->queryName(globals.state));
             else
                 allElems.push_back(*i);
         }
 
         foreach (DrvInfos::iterator, i, newElems)
-            printMsg(lvlInfo, format("installing `%1%'") % i->name);
+            printMsg(lvlInfo, format("installing `%1%'") % i->queryName(globals.state));
     
         printMissing(globals.state, newElems);
     
@@ -547,7 +551,7 @@ static void upgradeDerivations(Globals & globals,
         /* Go through all installed derivations. */
         DrvInfos newElems;
         foreach (DrvInfos::iterator, i, installedElems) {
-            DrvName drvName(i->name);
+            DrvName drvName(i->queryName(globals.state));
 
             try {
 
@@ -566,7 +570,7 @@ static void upgradeDerivations(Globals & globals,
                 DrvInfos::iterator bestElem = availElems.end();
                 DrvName bestName;
                 foreach (DrvInfos::iterator, j, availElems) {
-                    DrvName newName(j->name);
+                    DrvName newName(j->queryName(globals.state));
                     if (newName.name == drvName.name) {
                         int d = comparePriorities(globals.state, *i, *j);
                         if (d == 0) d = compareVersions(drvName.version, newName.version);
@@ -594,12 +598,12 @@ static void upgradeDerivations(Globals & globals,
                 {
                     printMsg(lvlInfo,
                         format("upgrading `%1%' to `%2%'")
-                        % i->name % bestElem->name);
+                        % i->queryName(globals.state) % bestElem->queryName(globals.state));
                     newElems.push_back(*bestElem);
                 } else newElems.push_back(*i);
 
             } catch (Error & e) {
-                e.addPrefix(format("while trying to find an upgrade for `%1%':\n") % i->name);
+                e.addPrefix(format("while trying to find an upgrade for `%1%':\n") % i->queryName(globals.state));
                 throw;
             }
         }
@@ -664,11 +668,11 @@ static void opSetFlag(Globals & globals,
 
         /* Update all matching derivations. */
         foreach (DrvInfos::iterator, i, installedElems) {
-            DrvName drvName(i->name);
+            DrvName drvName(i->queryName(globals.state));
             foreach (DrvNames::iterator, j, selectors)
                 if (j->matches(drvName)) {
                     printMsg(lvlInfo,
-                        format("setting flag on `%1%'") % i->name);
+                        format("setting flag on `%1%'") % i->queryName(globals.state));
                     setMetaFlag(globals.state, *i, flagName, flagValue);
                     break;
                 }
@@ -726,7 +730,7 @@ static void uninstallDerivations(Globals & globals, Strings & selectors,
         DrvInfos newElems;
 
         foreach (DrvInfos::iterator, i, installedElems) {
-            DrvName drvName(i->name);
+            DrvName drvName(i->queryName(globals.state));
             bool found = false;
             foreach (Strings::iterator, j, selectors)
                 /* !!! the repeated calls to followLinksToStorePath()
@@ -734,7 +738,7 @@ static void uninstallDerivations(Globals & globals, Strings & selectors,
                 if ((isPath(*j) && i->queryOutPath(globals.state) == followLinksToStorePath(*j))
                     || DrvName(*j).matches(drvName))
                 {
-                    printMsg(lvlInfo, format("uninstalling `%1%'") % i->name);
+                    printMsg(lvlInfo, format("uninstalling `%1%'") % i->queryName(globals.state));
                     found = true;
                     break;
                 }
@@ -764,12 +768,19 @@ static bool cmpChars(char a, char b)
 }
 
 
-static bool cmpElemByName(const DrvInfo & a, const DrvInfo & b)
+class cmpElemByName
 {
-    return lexicographical_compare(
-        a.name.begin(), a.name.end(),
-        b.name.begin(), b.name.end(), cmpChars);
-}
+    public:
+        cmpElemByName(EvalState & state) : _state(state) { }
+        bool operator()(const DrvInfo & a, const DrvInfo & b)
+        {
+            return lexicographical_compare(
+                a.queryName(_state).begin(), a.queryName(_state).end(),
+                b.queryName(_state).begin(), b.queryName(_state).end(), cmpChars);
+        }
+    private:
+        EvalState & _state;
+};
 
 
 typedef list<Strings> Table;
@@ -814,16 +825,16 @@ void printTable(Table & table)
 
 typedef enum { cvLess, cvEqual, cvGreater, cvUnavail } VersionDiff;
 
-static VersionDiff compareVersionAgainstSet(
+static VersionDiff compareVersionAgainstSet(EvalState & state,
     const DrvInfo & elem, const DrvInfos & elems, string & version)
 {
-    DrvName name(elem.name);
+    DrvName name(elem.queryName(state));
     
     VersionDiff diff = cvUnavail;
     version = "?";
     
     for (DrvInfos::const_iterator i = elems.begin(); i != elems.end(); ++i) {
-        DrvName name2(i->name);
+        DrvName name2(i->queryName(state));
         if (name.name == name2.name) {
             int d = compareVersions(name.version, name2.version);
             if (d < 0) {
@@ -921,9 +932,10 @@ static void opQuery(Globals & globals,
     /* Sort them by name. */
     /* !!! */
     vector<DrvInfo> elems2;
+    cmpElemByName nameComparer(globals.state);
     for (DrvInfos::iterator i = elems.begin(); i != elems.end(); ++i)
         elems2.push_back(*i);
-    sort(elems2.begin(), elems2.end(), cmpElemByName);
+    sort(elems2.begin(), elems2.end(), nameComparer);
 
     
     /* We only need to know the installed paths when we are querying
@@ -941,13 +953,18 @@ static void opQuery(Globals & globals,
     PathSet validPaths, substitutablePaths;
     if (printStatus) {
         PathSet paths;
-        foreach (vector<DrvInfo>::iterator, i, elems2)
+        foreach (vector<DrvInfo>::iterator, i, elems2) {
+            string name; 
             try {
+                name = i->queryName(globals.state);
                 paths.insert(i->queryOutPath(globals.state));
             } catch (AssertionError & e) {
-                printMsg(lvlTalkative, format("skipping derivation named `%1%' which gives an assertion failure") % i->name);
+                printMsg(lvlTalkative, format("skipping derivation named `%1%' which gives an assertion failure") % name);
                 i->setFailed();
+            } catch (ImportReadOnlyError & e) {
+                printMsg(lvlTalkative, format("skipping derivation named `%1%' which gives an ImportReadOnly failure") % name);
             }
+        }
         validPaths = store->queryValidPaths(paths);
         substitutablePaths = store->querySubstitutablePaths(paths);
     }
@@ -974,19 +991,23 @@ static void opQuery(Globals & globals,
             XMLAttrs attrs;
 
             if (printStatus) {
-                Path outPath = i->queryOutPath(globals.state);
-                bool hasSubs = substitutablePaths.find(outPath) != substitutablePaths.end();
-                bool isInstalled = installed.find(outPath) != installed.end();
-                bool isValid = validPaths.find(outPath) != validPaths.end();
-                if (xmlOutput) {
-                    attrs["installed"] = isInstalled ? "1" : "0";
-                    attrs["valid"] = isValid ? "1" : "0";
-                    attrs["substitutable"] = hasSubs ? "1" : "0";
-                } else
-                    columns.push_back(
-                        (string) (isInstalled ? "I" : "-")
-                        + (isValid ? "P" : "-")
-                        + (hasSubs ? "S" : "-"));
+                try {
+                    Path outPath = i->queryOutPath(globals.state);
+                    bool hasSubs = substitutablePaths.find(outPath) != substitutablePaths.end();
+                    bool isInstalled = installed.find(outPath) != installed.end();
+                    bool isValid = validPaths.find(outPath) != validPaths.end();
+                    if (xmlOutput) {
+                        attrs["installed"] = isInstalled ? "1" : "0";
+                        attrs["valid"] = isValid ? "1" : "0";
+                        attrs["substitutable"] = hasSubs ? "1" : "0";
+                    } else
+                        columns.push_back(
+                            (string) (isInstalled ? "I" : "-")
+                            + (isValid ? "P" : "-")
+                            + (hasSubs ? "S" : "-"));
+                } catch (ImportReadOnlyError & e) {
+                    if (!xmlOutput) columns.push_back("?");
+                }
             }
 
             if (xmlOutput)
@@ -995,9 +1016,9 @@ static void opQuery(Globals & globals,
                 columns.push_back(i->attrPath);
 
             if (xmlOutput)
-                attrs["name"] = i->name;
+                attrs["name"] = i->queryName(globals.state);
             else if (printName)
-                columns.push_back(i->name);
+                columns.push_back(i->queryName(globals.state));
 
             if (compareVersions) {
                 /* Compare this element against the versions of the
@@ -1005,7 +1026,7 @@ static void opQuery(Globals & globals,
                    elements, or the set of installed elements.  !!!
                    This is O(N * M), should be O(N * lg M). */
                 string version;
-                VersionDiff diff = compareVersionAgainstSet(*i, otherElems, version);
+                VersionDiff diff = compareVersionAgainstSet(globals.state, *i, otherElems, version);
 
                 char ch;
                 switch (diff) {
@@ -1029,62 +1050,75 @@ static void opQuery(Globals & globals,
             }
 
             if (xmlOutput) {
-                if (i->system != "") attrs["system"] = i->system;
+                if (i->querySystem(globals.state) != "") attrs["system"] = i->querySystem(globals.state);
             }
             else if (printSystem) 
-                columns.push_back(i->system);
+                columns.push_back(i->querySystem(globals.state));
 
             if (printDrvPath) {
-                string drvPath = i->queryDrvPath(globals.state);
-                if (xmlOutput) {
-                    if (drvPath != "") attrs["drvPath"] = drvPath;
-                } else
-                    columns.push_back(drvPath == "" ? "-" : drvPath);
+                try {
+                    string drvPath = i->queryDrvPath(globals.state);
+                    if (xmlOutput) {
+                        if (drvPath != "") attrs["drvPath"] = drvPath;
+                    } else
+                        columns.push_back(drvPath == "" ? "-" : drvPath);
+                } catch (ImportReadOnlyError & e) {
+                    if (!xmlOutput) columns.push_back("?");
+                }
             }
         
             if (printOutPath) {
-                string outPath = i->queryOutPath(globals.state);
-                if (xmlOutput) {
-                    if (outPath != "") attrs["outPath"] = outPath;
-                } else
-                    columns.push_back(outPath);
+                try {
+                    string outPath = i->queryOutPath(globals.state);
+                    if (xmlOutput) {
+                        if (outPath != "") attrs["outPath"] = outPath;
+                    } else
+                        columns.push_back(outPath);
+                } catch (ImportReadOnlyError & e) {
+                    if (!xmlOutput) columns.push_back("?");
+                }
             }
 
             if (printDescription) {
-                MetaInfo meta = i->queryMetaInfo(globals.state);
-                MetaValue value = meta["description"];
-                string descr = value.type == MetaValue::tpString ? value.stringValue : "";
-                if (xmlOutput) {
-                    if (descr != "") attrs["description"] = descr;
-                } else
-                    columns.push_back(descr);
+                try {
+                    MetaValue value = i->queryMetaInfo(globals.state, "description");
+                    string descr = value.type == MetaValue::tpString ? value.stringValue : "";
+                    if (xmlOutput) {
+                        if (descr != "") attrs["description"] = descr;
+                    } else
+                        columns.push_back(descr);
+                } catch (ImportReadOnlyError & e) {
+                    if (!xmlOutput) columns.push_back("?");
+                }
             }
 
             if (xmlOutput)
                 if (printMeta) {
                     XMLOpenElement item(xml, "item", attrs);
-                    MetaInfo meta = i->queryMetaInfo(globals.state);
-                    for (MetaInfo::iterator j = meta.begin(); j != meta.end(); ++j) {
-                        XMLAttrs attrs2;
-                        attrs2["name"] = j->first;
-                        if (j->second.type == MetaValue::tpString) {
-                            attrs2["type"] = "string";
-                            attrs2["value"] = j->second.stringValue;
-                            xml.writeEmptyElement("meta", attrs2);
-                        } else if (j->second.type == MetaValue::tpInt) {
-                            attrs2["type"] = "int";
-                            attrs2["value"] = (format("%1%") % j->second.intValue).str();
-                            xml.writeEmptyElement("meta", attrs2);
-                        } else if (j->second.type == MetaValue::tpStrings) {
-                            attrs2["type"] = "strings";
-                            XMLOpenElement m(xml, "meta", attrs2);
-                            foreach (Strings::iterator, k, j->second.stringValues) { 
-                                XMLAttrs attrs3;
-                                attrs3["value"] = *k;
-                                xml.writeEmptyElement("string", attrs3);
-                           }
+		    try {
+                        MetaInfo meta = i->queryMetaInfo(globals.state);
+                        for (MetaInfo::iterator j = meta.begin(); j != meta.end(); ++j) {
+                            XMLAttrs attrs2;
+                            attrs2["name"] = j->first;
+                            if (j->second.type == MetaValue::tpString) {
+                                attrs2["type"] = "string";
+                                attrs2["value"] = j->second.stringValue;
+                                xml.writeEmptyElement("meta", attrs2);
+                            } else if (j->second.type == MetaValue::tpInt) {
+                                attrs2["type"] = "int";
+                                attrs2["value"] = (format("%1%") % j->second.intValue).str();
+                                xml.writeEmptyElement("meta", attrs2);
+                            } else if (j->second.type == MetaValue::tpStrings) {
+                                attrs2["type"] = "strings";
+                                XMLOpenElement m(xml, "meta", attrs2);
+                                foreach (Strings::iterator, k, j->second.stringValues) { 
+                                    XMLAttrs attrs3;
+                                    attrs3["value"] = *k;
+                                    xml.writeEmptyElement("string", attrs3);
+                               }
+                            }
                         }
-                    }
+                    } catch (ImportReadOnlyError & e) { }
                 }
                 else
                     xml.writeEmptyElement("item", attrs);
@@ -1094,7 +1128,7 @@ static void opQuery(Globals & globals,
             cout.flush();
 
         } catch (AssertionError & e) {
-            printMsg(lvlTalkative, format("skipping derivation named `%1%' which gives an assertion failure") % i->name);
+            printMsg(lvlTalkative, format("skipping derivation named `%1%' which gives an assertion failure") % i->queryName(globals.state));
         }
     }
 
diff --git a/src/nix-env/user-env.cc b/src/nix-env/user-env.cc
index 510c5ca3817..1cd82cbea7f 100644
--- a/src/nix-env/user-env.cc
+++ b/src/nix-env/user-env.cc
@@ -11,7 +11,7 @@
 namespace nix {
 
 
-static void readLegacyManifest(const Path & path, DrvInfos & elems);
+static void readLegacyManifest(EvalState & state, const Path & path, DrvInfos & elems);
 
 
 DrvInfos queryInstalled(EvalState & state, const Path & userEnv)
@@ -27,7 +27,7 @@ DrvInfos queryInstalled(EvalState & state, const Path & userEnv)
         Bindings bindings;
         getDerivations(state, v, "", bindings, elems);
     } else if (pathExists(oldManifestFile))
-        readLegacyManifest(oldManifestFile, elems);
+        readLegacyManifest(state, oldManifestFile, elems);
 
     return elems;
 }
@@ -63,8 +63,8 @@ bool createUserEnv(EvalState & state, DrvInfos & elems,
         state.mkAttrs(v, 8);
 
         mkString(*state.allocAttr(v, state.sType), "derivation");
-        mkString(*state.allocAttr(v, state.sName), i->name);
-        mkString(*state.allocAttr(v, state.sSystem), i->system);
+        mkString(*state.allocAttr(v, state.sName), i->queryName(state));
+        mkString(*state.allocAttr(v, state.sSystem), i->querySystem(state));
         mkString(*state.allocAttr(v, state.sOutPath), i->queryOutPath(state));
         if (drvPath != "")
             mkString(*state.allocAttr(v, state.sDrvPath), i->queryDrvPath(state));
@@ -214,7 +214,7 @@ static MetaInfo parseMeta(std::istream & str)
 }
 
 
-static void readLegacyManifest(const Path & path, DrvInfos & elems)
+static void readLegacyManifest(EvalState & state, const Path & path, DrvInfos & elems)
 {
     string manifest = readFile(path);
     std::istringstream str(manifest);
@@ -234,10 +234,10 @@ static void readLegacyManifest(const Path & path, DrvInfos & elems)
             if (name == "meta") elem.setMetaInfo(parseMeta(str));
             else {
                 string value = parseStr(str);
-                if (name == "name") elem.name = value;
+                if (name == "name") elem.setName(value);
                 else if (name == "outPath") elem.setOutPath(value);
                 else if (name == "drvPath") elem.setDrvPath(value);
-                else if (name == "system") elem.system = value;
+                else if (name == "system") elem.setSystem(value);
             }
 
             expect(str, ",NoPos)");
@@ -245,7 +245,7 @@ static void readLegacyManifest(const Path & path, DrvInfos & elems)
 
         expect(str, ")");
 
-        if (elem.name != "") {
+        if (elem.queryName(state) != "") {
             elem.attrPath = int2String(n++);
             elems.push_back(elem);
         }