diff --git a/+file/fillClass.m b/+file/fillClass.m
index 9006a0ad..0bfc1773 100644
--- a/+file/fillClass.m
+++ b/+file/fillClass.m
@@ -11,6 +11,7 @@
 optional = {};
 readonly = {};
 defaults = {};
+dependent = {};
 %separate into readonly, required, and optional properties
 for i=1:length(allprops)
     pnm = allprops{i};
@@ -22,12 +23,23 @@
         optional = [optional {pnm}];
     end
     
-    if isa(prop, 'file.Attribute') && prop.readonly
-        readonly = [readonly {pnm}];
-    end
-    
-    if isa(prop, 'file.Attribute') && ~isempty(prop.value)
-        defaults = [defaults {pnm}];
+    if isa(prop, 'file.Attribute')
+        if prop.readonly
+            readonly = [readonly {pnm}];
+        end
+        
+        if ~isempty(prop.value)
+            defaults = [defaults {pnm}];
+        end
+       
+        if ~isempty(prop.dependent)
+            %extract prefix
+            parentname = strrep(pnm, ['_' prop.name], '');
+            parent = classprops.named(parentname);
+            if ~parent.required
+                dependent = [dependent {pnm}];
+            end
+        end
     end
 end
 non_inherited = setdiff(allprops, inherited);
@@ -50,8 +62,8 @@
     '% ' name ' ' class.doc]; %name, docstr
 propgroups = {...
     @()file.fillProps(classprops.named, ro_unique, 'SetAccess=protected')...
-    @()file.fillProps(classprops.named, req_unique)...
-    @()file.fillProps(classprops.named, opt_unique)...
+    @()file.fillProps(classprops.named, setdiff(req_unique, ro_unique))...
+    @()file.fillProps(classprops.named, setdiff(opt_unique, ro_unique))...
     };
 docsep = {...
     '% READONLY'...
@@ -70,6 +82,7 @@
 constructorBody = file.fillConstructor(name,...
     depnm,...
     defaults,... %all defaults, regardless of inheritance
+    dependent,...
     req_unique,...
     opt_unique,...
     classprops);
diff --git a/+file/fillConstructor.m b/+file/fillConstructor.m
index b6d10585..e4580063 100644
--- a/+file/fillConstructor.m
+++ b/+file/fillConstructor.m
@@ -1,12 +1,12 @@
-function fcstr = fillConstructor(name, parentname, defaults, required, optional, props)
+function fcstr = fillConstructor(name, parentname, defaults, dependent, required, optional, props)
 caps = upper(name);
 fcnbody = strjoin({['% ' caps ' Constructor for ' name]...
     ['%     obj = ' caps '(parentname1,parentvalue1,..,parentvalueN,parentargN,name1,value1,...,nameN,valueN)']...
     }, newline);
 fcns = {...
-    @()fillParamDocs('REQUIRED', required, props.named)...
-    @()fillParamDocs('OPTIONAL', optional, props.named)...
-    @()fillBody(parentname, defaults, required, optional, props)...
+    @()fillParamDocs('REQUIRED', setdiff(required, dependent), props.named)...
+    @()fillParamDocs('OPTIONAL', setdiff(optional, dependent), props.named)...
+    @()fillBody(parentname, defaults, dependent, required, optional, props)...
     };
 for i=1:length(fcns)
     fcn = fcns{i};
@@ -74,7 +74,7 @@
 end
 end
 
-function bodystr = fillBody(pname, defaults, required, optional, props)
+function bodystr = fillBody(pname, defaults, dependent, required, optional, props)
 if isempty(defaults)
     bodystr = '';
 else
@@ -97,15 +97,46 @@
     var = params{i};
     bodystr = [bodystr newline 'addParameter(p, ''' var ''', []);'];
 end
-req_unset = setdiff(required, defaults); %check required values that don't have a set value
-req_body = strjoin({...
-    'parse(p, varargin{:});'...
-    ['required = ' util.cellPrettyPrint(req_unset) ';']...
-    'missing = intersect(p.UsingDefaults, required);'...
-    'if ~isempty(missing)'...
-    '    error(''Missing Required Argument(s) { %s }'', strjoin(missing, '', ''));'...
-    'end'}, newline);
-bodystr = [bodystr newline req_body];
+
+bodystr = [bodystr newline 'parse(p, varargin{:});'];
+
+%check required values that don't have a set value and are independent
+req_unset = setdiff(required, [defaults dependent]);
+if ~isempty(req_unset)
+    req_body = strjoin({...
+        ['required = ' util.cellPrettyPrint(req_unset) ';']...
+        'missing = intersect(p.UsingDefaults, required);'...
+        'if ~isempty(missing)'...
+        '    error(''Missing Required Argument(s) { %s }'', strjoin(missing, '', ''));'...
+        'end'}, newline);
+    bodystr = [bodystr newline req_body];
+end
+
+%construct parent->dependent structure
+dep_parents = struct();
+for i=1:length(dependent)
+    dep = dependent{i};
+    dep_p = props.named(dep);
+    parent = dep_p.dependent;
+    if ~startsWith(dep, parent)
+        parent = strrep(dep, ['_' dep_p.name], '');
+    end
+    if isfield(dep_parents, parent)
+        deps = dep_parents.(parent);
+        dep_parents.(parent) = [deps {dep}];
+    else
+        dep_parents.(parent) = {dep};
+    end
+end
+
+%check each optional parent if they exist, then check their required dependents
+dep_p_list = fieldnames(dep_parents);
+for i=1:length(dep_p_list)
+    parent = dep_p_list{i};
+    children = util.cellPrettyPrint(dep_parents.(parent));
+    bodystr = [bodystr newline 'types.util.checkDependent(''' parent ''', ' children ', p.UsingDefaults);'];
+end
+
 for i=1:length(params)
     var = params{i};
     bodystr = [bodystr newline 'obj.' var ' = p.Results.' var ';'];
diff --git a/+file/fillValidators.m b/+file/fillValidators.m
index c724cae5..8ae1a5b1 100644
--- a/+file/fillValidators.m
+++ b/+file/fillValidators.m
@@ -39,26 +39,28 @@
         constr = {};
         for i=1:length(prop.datasets)
             ds = prop.datasets(i);
+            if isempty(ds.type)
+                type = ds.dtype;
+            else
+                ds_namespace = namespacereg.getNamespace(ds.type).name;
+                type = ['types.' ds_namespace '.' ds.type];
+            end
+            
             if isempty(ds.name)
-                if isempty(ds.type)
-                    typespec = ds.dtype;
-                else
-                    typespec = ds.type;
-                end
-                constr = [constr {typespec}];
-            elseif isempty(ds.type)
-                namedprops.(ds.name) = ds.dtype;
+                constr = [constr {type}];
             else
-                namedprops.(ds.name) = ds.type;
+                namedprops.(ds.name) = type;
             end
         end
         
         for i=1:length(prop.subgroups)
             sg = prop.subgroups(i);
+            sg_namespace = namespacereg.getNamespace(sg.type).name;
+            sgfullname = ['types.' sg_namespace '.' sg.type];
             if isempty(sg.name)
-                constr = [constr sg.type];
+                constr = [constr {sgfullname}];
             else
-                namedprops.(sg.name) = sg.type;
+                namedprops.(sg.name) = sgfullname;
             end
         end
         
@@ -81,7 +83,8 @@
 elseif isa(prop, 'file.Attribute')
     fuvstr = fillDtypeValidation(name, prop.dtype, namespacereg);
 else %Link
-    fuvstr = fillDtypeValidation(name, prop.type, namespacereg);
+    namespace = namespacereg.getNamespace(prop.type).name;
+    fuvstr = fillDtypeValidation(name, ['types.' namespace '.' prop.type], namespacereg);
 end
 end
 
diff --git a/+io/parseDataset.m b/+io/parseDataset.m
index cde9468d..fbca61db 100644
--- a/+io/parseDataset.m
+++ b/+io/parseDataset.m
@@ -36,33 +36,46 @@
 
 datatype = info.Datatype;
 if strcmp(datatype.Class, 'H5T_REFERENCE')
-    reftype = datatype.Type;
-    path = H5R.get_name(did, reftype, data);
-    props('ref') = [];
-    if strcmp(reftype, 'H5R_DATASET_REGION')
-        sid = H5R.get_region(did, reftype, data);
-        [start, finish] = H5S.get_select_bounds(sid);
-        H5S.close(sid);
-        reg = [start finish];
-    else
-        reg = [];
-    end
+    [path, reg] = parseReference(did, datatype.Type, data);
     refs([fullpath '/ref']) = struct('path', path, 'region', reg);
+    props('ref') = [];
 elseif strcmp(datatype.Class, 'H5T_COMPOUND')
     t = table;
     compound = datatype.Type.Member;
-    isref = logical(size(compound));
     for j=1:length(compound)
         comp = compound(j);
         if strcmp(comp.Datatype.Class, 'H5T_REFERENCE')
-            isref(j) = true;
+            refnames = data.(comp.Name);
+            reflist = repmat(struct('path', [], 'region', []), size(refnames));
+            for k=1:size(refnames,2)
+                r = refnames(:,k);
+                [path, reg] = parseReference(did, comp.Datatype.Type, r);
+                reflist(k).path = path;
+                reflist(k).region = reg;
+            end
+            refs([fullpath '/' info.Name '.' comp.Name]) = reflist;
+            %for some reason, raw references are stored transposed.
+            data.(comp.Name) = cell(size(refnames, 2), 1);
         end
     end
+    props('table') = struct2table(data);
 else
+    keyboard;
 end
 kwargs = io.map2kwargs(props);
 parsed = eval([typename '(kwargs{:})']);
 
 H5D.close(did);
 H5F.close(fid);
-end
\ No newline at end of file
+end
+
+function [target, region] = parseReference(did, type, data)
+target = H5R.get_name(did, type, data);
+region = [];
+if strcmp(type, 'H5R_DATASET_REGION')
+    sid = H5R.get_region(did, type, data);
+    [start, finish] = H5S.get_select_bounds(sid);
+    H5S.close(sid);
+    region = [start finish];
+end
+end
diff --git a/+io/parseGroup.m b/+io/parseGroup.m
index 9f1486a0..84fb588e 100644
--- a/+io/parseGroup.m
+++ b/+io/parseGroup.m
@@ -2,10 +2,11 @@
 % NOTE, group name is in path format so we need to parse that out.
 % parsed is either a containers.Map containing properties mapped to values OR a
 % typed value
-links = [];
+links = containers.Map;
 refs = containers.Map;
 [~, root] = io.pathParts(info.Name);
 [props, typename] = io.parseAttributes(info.Attributes);
+hasTypes = false;
 
 %parse datasets
 for i=1:length(info.Datasets)
@@ -16,37 +17,65 @@
         props = [props; ds];
     else
         props(ds_info.Name) = ds;
+        hasTypes = true;
     end
     
     refs = [refs; dsrefs];
 end
 
-%parse links if present
-for i=1:length(info.Links)
-    links = [links io.parseLink(info.Links)];
-end
-
 %parse subgroups
 for i=1:length(info.Groups)
     g_info = info.Groups(i);
     [~, gname] = io.pathParts(g_info.Name);
     [subg, glinks, grefs] = io.parseGroup(filename, g_info);
-    props(gname) = subg;
-    links = [links glinks];
+    if isa(subg, 'containers.Map')
+        props = [props; subg];
+    else
+        props(gname) = subg;
+        hasTypes = true;
+    end
+    
+    links = [links; glinks];
     refs = [refs; grefs];
 end
 
+%parse links and add to map of links
+for i=1:length(info.Links)
+    l = info.Links(i);
+    fpname = [info.Name '/' l.Name];
+    props(l.Name) = [];
+    links([info.Name '/' l.Name]) = l;
+    hasTypes = true;
+end
+
 if isempty(typename)
-    parsed = containers.Map;
-    keyboard;
+    %immediately elide prefix all property names with this but only if there are
+    %no typed objects in it.
+    propnames = keys(props);
+    if hasTypes
+        parsed = containers.Map({root}, {props});
+    else
+        parsed = containers.Map;
+        for i=1:length(propnames)
+            pnm = propnames{i};
+            p = props(pnm);
+            parsed([root '_' pnm]) = p;
+        end
+    end
+    
+    if isempty(parsed)
+        %special case where a directory is simply empty.  Return itself but
+        %empty
+        parsed(root) = [];
+    end
 else
     %construct as kwargs and instantiate object
+    kwargs = io.map2kwargs(props);
     if isempty(root)
         %we are root
-        parsed = types.core.NWBFile;
+        parsed = types.core.NWBFile(kwargs{:});
         return;
     end
-    kwargs = io.map2kwargs(props);
     parsed = eval([typename '(kwargs{:})']);
 end
 end
\ No newline at end of file
diff --git a/+io/parseLink.m b/+io/parseLink.m
deleted file mode 100644
index 63af4918..00000000
--- a/+io/parseLink.m
+++ /dev/null
@@ -1,4 +0,0 @@
-function link = parseLink(info)
-% just return a link
-link = [];
-end
\ No newline at end of file
diff --git a/+types/+util/checkConstrained.m b/+types/+util/checkConstrained.m
index c413d0eb..6f8acf40 100644
--- a/+types/+util/checkConstrained.m
+++ b/+types/+util/checkConstrained.m
@@ -1,4 +1,7 @@
 function checkConstrained(name, namedprops, constrained, val)
+if isempty(val)
+    return;
+end
 if ~isa(val, 'containers.Map')
     error('Property `%s` must be a containers.Map.', name);
 end
diff --git a/+types/+util/checkDependent.m b/+types/+util/checkDependent.m
new file mode 100644
index 00000000..8de45586
--- /dev/null
+++ b/+types/+util/checkDependent.m
@@ -0,0 +1,10 @@
+function checkDependent(parent, children, unconstructed)
+    if ~any(strcmp(parent, unconstructed))
+        for i=1:length(children)
+            child = children{i};
+            if any(strcmp(child, unconstructed))
+                error('Dependent type `%s` is required for parent property `%s`', child, parent);
+            end
+        end
+    end
+end
\ No newline at end of file
diff --git a/+types/+util/checkDims.m b/+types/+util/checkDims.m
index 4f6e2411..deb385c1 100644
--- a/+types/+util/checkDims.m
+++ b/+types/+util/checkDims.m
@@ -1,8 +1,13 @@
 function checkDims(valsize, validSizes)
+    if any(valsize == 0)
+        return; %ignore empty arrays
+    end
     validSizesStrings = cell(size(validSizes));
     for i=1:length(validSizes)
         vs = validSizes{i};
-        if length(valsize) ~= length(vs)
+        
+        if (length(vs) == 1 && (length(valsize) > 2 || ~any(valsize == 1))) ||...
+            (length(vs) > 1 && length(valsize) ~= length(vs))
             continue;
         end
         
diff --git a/+types/+util/checkDtype.m b/+types/+util/checkDtype.m
index ae2fb694..93a145cf 100644
--- a/+types/+util/checkDtype.m
+++ b/+types/+util/checkDtype.m
@@ -15,11 +15,11 @@ function checkDtype(name, type, val)
             error(errmsg);
         end
         
-        if strcmp(types, 'uint64') && val < 0
+        if strcmp(type, 'uint64') && val < 0
             error('Property `%s` must be greater than zero.', name);
         end
     case 'char'
-        if ~ischar(val)
+        if ~ischar(val) && ~iscellstr(val)
             error(errmsg);
         end
     otherwise %class or ref to class
@@ -28,6 +28,9 @@ function checkDtype(name, type, val)
         end
         for i=1:length(val)
             subval = val{i};
+            if isempty(subval)
+                continue;
+            end
             if ~isa(subval, type)
                 error(errmsg);
             end
diff --git a/nwbRead.m b/nwbRead.m
index 42aa1b22..50f73976 100644
--- a/nwbRead.m
+++ b/nwbRead.m
@@ -25,18 +25,8 @@
 else
   ff = fullfile(pwd, filename);
 end
-[fp, ~, ~] = fileparts(ff); %complete filepath
-
-for lref = linkRefs
-  lr = lref{1};
-  if isempty(lr.filename)
-    lr.ref = nwb(lr.path);
-  else
-    % we assume the external reference is to a dataset.
-    if ~java.io.File(lr.filename).isAbsolute
-      lr.filename = fullfile(fp, lr.filename);
-    end
-    lr.ref = h5read(lr.filename, lr.path);
-  end
-end
+keyboard;
+%process refs
+%process links
+[fp, ~, ~] = fileparts(ff);
 end
\ No newline at end of file
diff --git a/nwbfile.m b/nwbfile.m
index fc2eae87..474f60b0 100644
--- a/nwbfile.m
+++ b/nwbfile.m
@@ -1,30 +1,46 @@
-classdef nwbfile < handle
-  % nwbfile Root object representing data read from an NWB file.
-  %
-  % Requires that core and extension NWB types have been generated
-  % and reside in a 'types' package on the matlab path.
-  %
-  % Example. Construct an object from scratch for export:
-  %    nwb = nwbfile;
-  %    nwb.epochs = types.untyped.Group;
-  %    nwb.epochs.stim = types.Epoch;
-  %    nwbExport(nwb, 'epoch.nwb');
-  %
-  % See also NWBREAD, GENERATECORE, GENERATEEXTENSIONS
-  methods
-    function obj = nwbfile(varargin)
-      obj = obj@types.core.NWBFile(varargin{:});
+classdef nwbfile < types.core.NWBFile
+    % nwbfile Root object representing data read from an NWB file.
+    %
+    % Requires that core and extension NWB types have been generated
+    % and reside in a 'types' package on the matlab path.
+    %
+    % Example. Construct an object from scratch for export:
+    %    nwb = nwbfile;
+    %    nwb.epochs = types.untyped.Group;
+    %    nwb.epochs.stim = types.Epoch;
+    %    nwbExport(nwb, 'epoch.nwb');
+    %
+    % See also NWBREAD, GENERATECORE, GENERATEEXTENSIONS
+    methods
+        function obj = nwbfile(varargin)
+            p = inputParser;
+            p.KeepUnmatched = true;
+            p.PartialMatching = false;
+            p.StructExpand = false;
+            addParameter(p, 'nwb_version', []);
+            addParameter(p, 'file_create_date', []);
+            parse(p, varargin{:});
+            if any(strcmp('nwb_version', p.UsingDefaults))
+                varargin = [{'nwb_version'} {'1.0.2'}];
+            end
+            if any(strcmp('file_create_date', p.UsingDefaults))
+                varargin = [{'file_create_date'} {''}];
+            end
+            obj = obj@types.core.NWBFile(varargin{:});
+        end
+        
+        function export(obj, filename)
+            if exist(filename, 'file')
+                warning('Overwriting %s', filename);
+                delete(filename);
+            end
+            fid = H5F.create(filename);
+            export@types.core.NWBFile(obj, fid);
+            H5F.close(fid);
+            
+            if isempty(obj.file_create_date)
+                h5write(filename, '/file_create_date', datestr(datetime, 30));
+            end
+        end
     end
-    
-    function export(obj, filename)
-      validateattributes(filename, {'string', 'char'}, {'scalartext'});
-      if exist(filename, 'file')
-        warning('Overwriting %s', filename);
-        delete(filename);
-      end
-      fid = H5F.create(filename);
-      export@types.NWBFile(obj, fid);
-      H5F.close(fid);
-    end
-  end
 end
\ No newline at end of file