diff --git a/app/corpora/cqi/api/client.py b/app/corpora/cqi/api/client.py
index 30896494..6a9460db 100644
--- a/app/corpora/cqi/api/client.py
+++ b/app/corpora/cqi/api/client.py
@@ -421,13 +421,8 @@ class APIClient:
         self.port = port
         self.socket = socket.socket()
 
-    def setup(self):
-        self.socket.connect((self.host, self.port))
-
-    def teardown(self):
-        self.socket.close()
-
     def ctrl_connect(self, username, password):
+        self.socket.connect((self.host, self.port))
         # INPUT: (STRING username, STRING password)
         # OUTPUT: CQI_STATUS_CONNECT_OK, CQI_ERROR_CONNECT_REFUSED
         self.__send_WORD(CTRL_CONNECT)
@@ -439,7 +434,9 @@ class APIClient:
         # INPUT: ()
         # OUTPUT: CQI_STATUS_BYE_OK
         self.__send_WORD(CTRL_BYE)
-        return self.__recv_response()
+        response = self.__recv_response()
+        self.socket.close()
+        return response
 
     def ctrl_user_abort(self):
         # INPUT: ()
@@ -575,7 +572,7 @@ class APIClient:
         # INPUT: (STRING attribute)
         # OUTPUT: CQI_STATUS_OK
         # unload attribute from memory
-        self.__send_WORD(CL_LEXICON_SIZE)
+        self.__send_WORD(CL_DROP_ATTRIBUTE)
         self.__send_STRING(attribute)
         return self.__recv_response()
 
@@ -589,7 +586,7 @@ class APIClient:
         # OUTPUT: CQI_DATA_INT_LIST
         # returns -1 for every string in <strings> that is not found in the
         # lexicon
-        self.__send_WORD(CL_LEXICON_SIZE)
+        self.__send_WORD(CL_STR2ID)
         self.__send_STRING(attribute)
         self.__send_STRING_LIST(strings)
         return self.__recv_response()
diff --git a/app/corpora/cqi/client.py b/app/corpora/cqi/client.py
index 5917f2fa..50de46b4 100644
--- a/app/corpora/cqi/client.py
+++ b/app/corpora/cqi/client.py
@@ -1,31 +1,15 @@
 from .api import APIClient
-from .constants import MAJOR_VERSION, MINOR_VERSION
 from .models.corpora import CorpusCollection
 
 
-class CQiClient(APIClient):
+class CQiClient:
     def __init__(self, host, port=4877):
-        super(CQiClient, self).__init__(host, port=port)
+        self.api = APIClient(host, port=port)
 
     def connect(self, username='anonymous', password=''):
-        super(CQiClient, self).setup()
-        self.ctrl_connect(username, password)
-        self.__load()
+        self.api.ctrl_connect(username, password)
+        self.corpora = CorpusCollection(self)
 
     def disconnect(self):
-        self.ctrl_bye()
-        super(CQiClient, self).teardown()
-
-    def __load(self):
-        self.corpora = CorpusCollection(self)
-        self.info = {'version': '{}.{}'.format(MAJOR_VERSION, MINOR_VERSION)}
-
-    def features(self):
-        features = []
-        if self.ask_feature_cqi_1_0():
-            features.append('cqi_1_0')
-        if self.ask_feature_cl_2_3():
-            features.append('cl_2_3')
-        if self.ask_feature_cqp_2_3():
-            features.append('cqp_2_3')
-        return features
+        del self.corpora
+        self.api.ctrl_bye()
diff --git a/app/corpora/cqi/models/attributes.py b/app/corpora/cqi/models/attributes.py
new file mode 100644
index 00000000..8c8e0a72
--- /dev/null
+++ b/app/corpora/cqi/models/attributes.py
@@ -0,0 +1,139 @@
+class AttributeCollection:
+    def __init__(self, client, corpus):
+        self.client = client
+        self.corpus = corpus
+        self.alignment = AlignmentAttributeCollection(client, corpus)
+        self.positional = PositionalAttributeCollection(client, corpus)
+        self.structural = StructuralAttributeCollection(client, corpus)
+
+
+class Attribute:
+    def __init__(self, client, corpus, name):
+        self.client = client
+        self.corpus = corpus
+        self.name = name
+        self._name = '{}.{}'.format(corpus.name, name)
+        self.size = client.api.cl_attribute_size(self._name)
+
+    def drop(self):
+        return self.client.api.cl_drop_attribute(self._name)
+
+
+class AlignmentAttributeCollection:
+    def __init__(self, client, corpus):
+        self.client = client
+        self.corpus = corpus
+
+    def get(self, name):
+        return AlignmentAttribute(self.client, self.corpus, name)
+
+    def list(self):
+        return [AlignmentAttribute(self.client, self.corpus, attr) for attr in
+                self.client.api.corpus_alignment_attributes(self.corpus.name)]
+
+
+class AlignmentAttribute(Attribute):
+    def cpos_by_ids(self, id_list):
+        return self.client.api.cl_alg2cpos(self._name, id_list)
+
+    def ids_by_cpos(self, cpos_list):
+        return self.client.api.cl_cpos2alg(self._name, cpos_list)
+
+
+class PositionalAttributeCollection:
+    def __init__(self, client, corpus):
+        self.client = client
+        self.corpus = corpus
+
+    def get(self, name):
+        return PositionalAttribute(self.client, self.corpus, name)
+
+    def list(self):
+        return [PositionalAttribute(self.client, self.corpus, attr) for attr in
+                self.client.api.corpus_positional_attributes(self.corpus.name)]
+
+
+class PositionalAttribute(Attribute):
+    def __init__(self, client, corpus, name):
+        super(PositionalAttribute, self).__init__(client, corpus, name)
+        self.lexicon_size = client.api.cl_lexicon_size(self._name)
+
+    def cpos_by_id(self, id):
+        return self.client.api.cl_id2cpos(self._name, id)
+
+    def cpos_by_ids(self, id_list):
+        return self.client.api.cl_idlist2cpos(self._name, id_list)
+
+    def freqs_by_ids(self, id_list):
+        return self.client.api.cl_id2freq(self._name, id_list)
+
+    def ids_by_cpos(self, cpos_list):
+        return self.client.api.cl_cpos2id(self._name, cpos_list)
+
+    def ids_by_regex(self, regex):
+        return self.client.api.cl_regex2id(self._name, regex)
+
+    def ids_by_values(self, value_list):
+        return self.client.api.cl_str2id(self._name, value_list)
+
+    def values_by_cpos(self, cpos_list):
+        return self.client.api.cl_cpos2str(self._name, cpos_list)
+
+    def values_by_ids(self, id_list):
+        return self.client.api.cl_id2str(self._name, id_list)
+
+
+class StructuralAttributeCollection:
+    def __init__(self, client, corpus):
+        self.client = client
+        self.corpus = corpus
+
+    def get(self, name):
+        return StructuralAttribute(self.client, self.corpus, name)
+
+    def list(self, filters={}):
+        attrs = [StructuralAttribute(self.client, self.corpus, attr) for attr
+                 in self.client.api.corpus_structural_attributes(
+                    self.corpus.name)]
+        for k, v in filters.items():
+            if k == 'part_of':
+                attrs = list(filter(lambda x: x.name.startswith(v.name + '_'),
+                                    attrs))
+        return attrs
+
+
+class StructuralAttribute(Attribute):
+    def __init__(self, client, corpus, name):
+        super(StructuralAttribute, self).__init__(client, corpus, name)
+        self.has_values = client.api.corpus_structural_attribute_has_values(
+            self._name
+        )
+
+    def cpos_by_id(self, id):
+        return self.client.api.cl_struc2cpos(self._name, id)
+
+    def ids_by_cpos(self, cpos_list):
+        return self.client.api.cl_cpos2struc(self._name, cpos_list)
+
+    def lbound_by_cpos(self, cpos_list):
+        return self.client.api.cl_cpos2lbound(self._name, cpos_list)
+
+    def rbound_by_cpos(self, cpos_list):
+        return self.client.api.cl_cpos2rbound(self._name, cpos_list)
+
+    def values_by_ids(self, id_list):
+        return self.client.api.cl_struc2str(self._name, id_list)
+
+    def lrcontext_by_cpos(self, cpos_first, cpos_last=None, context=3):
+        if cpos_last is None:
+            cpos_last = cpos_first
+        id_l, id_r = self.ids_by_cpos([cpos_first, cpos_last])
+        id_lc = max(0, id_l - context)
+        id_rc = min(id_r + context, self.size - 1)
+        ids = {id: list(range(*self.cpos_by_id(id))) for id
+               in range(id_lc, id_rc)}
+        cpos_list = [cpos for cpos_list in ids.values() for cpos in cpos_list]
+        lookups = self.corpus.lookups_by_cpos(cpos_list)
+        return {'ids': ids,
+                'match_cpos_list': list(range(cpos_first, cpos_last)),
+                **lookups}
diff --git a/app/corpora/cqi/models/corpora.py b/app/corpora/cqi/models/corpora.py
index 4d25318d..f9537a9c 100644
--- a/app/corpora/cqi/models/corpora.py
+++ b/app/corpora/cqi/models/corpora.py
@@ -1,3 +1,4 @@
+from .attributes import AttributeCollection
 from .subcorpora import SubcorpusCollection
 
 
@@ -9,94 +10,59 @@ class CorpusCollection:
         return Corpus(self.client, name)
 
     def list(self):
-        return [Corpus(self.client, corpus) for corpus
-                in self.client.corpus_list_coprora()]
+        return [Corpus(self.client, corpus) for corpus in
+                self.client.api.corpus_list_coprora()]
 
 
 class Corpus:
     def __init__(self, client, name):
         self.client = client
         self.name = name
-        self.__load()
+        self.size = client.api.cl_attribute_size('{}.word'.format(name))
+        # self.info = client.api.corpus_info(name)
+        self.charset = client.api.corpus_charset(name)
+        # self.full_name = client.api.corpus_full_name(name)
+        self.properties = client.api.corpus_properties(name)
+        self.attributes = AttributeCollection(client, self)
+        self.subcorpora = SubcorpusCollection(client, self)
 
-    def __load(self):
-        self.size = self.client.cl_attribute_size('{}.word'.format(self.name))
-        # self.info = client.corpus_info(self.name)
-        self.charset = self.client.corpus_charset(self.name)
-        # self.full_name = self.client.corpus_full_name(self.name)
-        self.properties = self.client.corpus_properties(self.name)
-        self.alignment_attributes = \
-            self.client.corpus_alignment_attributes(self.name)
-        self.structural_attributes = \
-            self.client.corpus_structural_attributes(self.name)
-        self.positional_attributes = \
-            self.client.corpus_positional_attributes(self.name)
-        self.subcorpora = SubcorpusCollection(self.client, self)
-
-    def alg2cpos(self, attribute, alg):
-        __attribute = '{}.{}'.format(self.name, attribute)
-        return self.client.cl_alg2cpos(__attribute, alg)
-
-    def cpos2alg(self, attribute, cpos_list):
-        __attribute = '{}.{}'.format(self.name, attribute)
-        return self.client.cl_cpos2alg(__attribute, cpos_list)
-
-    def cpos2id(self, attribute, cpos_list):
-        __attribute = '{}.{}'.format(self.name, attribute)
-        return self.client.cl_cpos2id(__attribute, cpos_list)
-
-    def cpos2lbound(self, attribute, cpos_list):
-        __attribute = '{}.{}'.format(self.name, attribute)
-        return self.client.cl_cpos2lbound(__attribute, cpos_list)
-
-    def cpos2rbound(self, attribute, cpos_list):
-        __attribute = '{}.{}'.format(self.name, attribute)
-        return self.client.cl_cpos2rbound(__attribute, cpos_list)
-
-    def cpos2str(self, attribute, cpos_list):
-        __attribute = '{}.{}'.format(self.name, attribute)
-        return self.client.cl_cpos2str(__attribute, cpos_list)
-
-    def cpos2struc(self, attribute, cpos_list):
-        __attribute = '{}.{}'.format(self.name, attribute)
-        return self.client.cl_cpos2struc(__attribute, cpos_list)
-
-    def id2cpos(self, attribute, id):
-        __attribute = '{}.{}'.format(self.name, attribute)
-        return self.client.cl_id2cpos(__attribute, id)
-
-    def idlist2cpos(self, attribute, ids):
-        __attribute = '{}.{}'.format(self.name, attribute)
-        return self.client.cl_idlist2cpos(__attribute, ids)
-
-    def id2freq(self, attribute, ids):
-        __attribute = '{}.{}'.format(self.name, attribute)
-        return self.client.cl_id2freq(__attribute, ids)
-
-    def id2str(self, attribute, ids):
-        __attribute = '{}.{}'.format(self.name, attribute)
-        return self.client.cl_id2str(__attribute, ids)
+    def lookups_by_cpos(self, cpos_list):
+        cpos_list = list(set(cpos_list))
+        lookups = {}
+        if cpos_list:
+            lookups['cpos_lookup'] = {}
+        for cpos in cpos_list:
+            lookups['cpos_lookup'][cpos] = {}
+        for attr in self.attributes.positional.list():
+            cpos_attr_values = attr.values_by_cpos(cpos_list)
+            for i, cpos in enumerate(cpos_list):
+                lookups['cpos_lookup'][cpos][attr.name] = cpos_attr_values[i]
+        for attr in self.attributes.structural.list():
+            if attr.has_values:
+                continue
+            cpos_attr_ids = attr.ids_by_cpos(cpos_list)
+            for i, cpos in enumerate(cpos_list):
+                if cpos_attr_ids[i] != -1:
+                    lookups['cpos_lookup'][cpos][attr.name] = cpos_attr_ids[i]
+            occured_attr_ids = list(filter(lambda x: x != -1,
+                                           set(cpos_attr_ids)))
+            if not occured_attr_ids:
+                continue
+            subattrs = self.attributes.structural.list(
+                filters={'part_of': attr})
+            if not subattrs:
+                continue
+            lookup_name = '{}_lookup'.format(attr.name)
+            lookups[lookup_name] = {}
+            for attr_id in occured_attr_ids:
+                lookups[lookup_name][attr_id] = {}
+            for subattr in subattrs:
+                subattr_values = subattr.values_by_ids(occured_attr_ids)
+                for i, subattr_value in enumerate(subattr_values):
+                    lookups[lookup_name][occured_attr_ids[i]][subattr.name] = \
+                        subattr_value
+        return lookups
 
     def query(self, query, subcorpus_name='Results'):
-        self.client.cqp_query(self.name, subcorpus_name, query)
+        self.client.api.cqp_query(self.name, subcorpus_name, query)
         return self.subcorpora.get('Results')
-
-    def regex2id(self, attribute, regex):
-        __attribute = '{}.{}'.format(self.name, attribute)
-        return self.client.cl_regex2id(__attribute, regex)
-
-    def structural_attribute_has_values(self, attribute):
-        __attribute = '{}.{}'.format(self.name, attribute)
-        return self.client.corpus_structural_attribute_has_values(__attribute)
-
-    def str2id(self, attribute, strings):
-        __attribute = '{}.{}'.format(self.name, attribute)
-        return self.client.cl_str2id(__attribute, strings)
-
-    def struc2cpos(self, attribute, struc):
-        __attribute = '{}.{}'.format(self.name, attribute)
-        return self.client.cl_struc2cpos(__attribute, struc)
-
-    def struc2str(self, attribute, strucs):
-        __attribute = '{}.{}'.format(self.name, attribute)
-        return self.client.cl_struc2str(__attribute, strucs)
diff --git a/app/corpora/cqi/models/subcorpora.py b/app/corpora/cqi/models/subcorpora.py
index 6606639b..38ba3957 100644
--- a/app/corpora/cqi/models/subcorpora.py
+++ b/app/corpora/cqi/models/subcorpora.py
@@ -3,47 +3,42 @@ from ..constants import (CONST_FIELD_KEYWORD, CONST_FIELD_MATCH,
 
 
 class SubcorpusCollection:
-    def __init__(self, client, parent_corpus):
+    def __init__(self, client, corpus):
         self.client = client
-        self.parent_corpus = parent_corpus
+        self.corpus = corpus
 
     def get(self, name):
-        return Subcorpus(self.client, self.parent_corpus, name)
+        return Subcorpus(self.client, self.corpus, name)
 
     def list(self):
-        return [Subcorpus(self.client, self.parent_corpus, subcorpus)
-                for subcorpus
-                in self.client.cqp_list_subcorpora(self.parent_corpus.name)]
+        return [Subcorpus(self.client, self.corpus, subcorpus) for subcorpus in
+                self.client.api.cqp_list_subcorpora(self.corpus.name)]
 
 
 class Subcorpus:
-    def __init__(self, client, parent_corpus, name):
+    def __init__(self, client, corpus, name):
         self.client = client
-        self.parent_corpus = parent_corpus
+        self.corpus = corpus
         self.name = name
-        self.__name = '{}:{}'.format(parent_corpus.name, name)
-        self.__load()
-
-    def __load(self):
+        self._name = '{}:{}'.format(corpus.name, name)
         self.fields = {}
-        if self.client.cqp_subcorpus_has_field(self.__name, CONST_FIELD_MATCH):
+        if client.api.cqp_subcorpus_has_field(self._name, CONST_FIELD_MATCH):
             self.fields['match'] = CONST_FIELD_MATCH
-        if self.client.cqp_subcorpus_has_field(self.__name,
-                                               CONST_FIELD_MATCHEND):
+        if client.api.cqp_subcorpus_has_field(self._name,
+                                              CONST_FIELD_MATCHEND):
             self.fields['matchend'] = CONST_FIELD_MATCHEND
-        if self.client.cqp_subcorpus_has_field(self.__name,
-                                               CONST_FIELD_TARGET):
+        if client.api.cqp_subcorpus_has_field(self._name, CONST_FIELD_TARGET):
             self.fields['target'] = CONST_FIELD_TARGET
-        if self.client.cqp_subcorpus_has_field(self.__name,
-                                               CONST_FIELD_KEYWORD):
+        if client.api.cqp_subcorpus_has_field(self._name, CONST_FIELD_KEYWORD):
             self.fields['keyword'] = CONST_FIELD_KEYWORD
-        self.size = self.client.cqp_subcorpus_size(self.__name)
+        self.size = client.api.cqp_subcorpus_size(self._name)
 
     def drop(self):
-        return self.client.cqp_drop_subcorpus(self.__name)
+        return self.client.api.cqp_drop_subcorpus(self._name)
 
     def dump(self, field, first, last):
-        return self.client.cqp_dump_subcorpus(self.__name, field, first, last)
+        return self.client.api.cqp_dump_subcorpus(self._name, field, first,
+                                                  last)
 
     def dump_values(self, context=25, first_result=0,
                     num_results=float('inf')):
@@ -58,57 +53,21 @@ class Subcorpus:
                                          last_result))
         for match_start, match_end in match_boundaries:
             left_start = max(0, match_start - context)
-            right_end = min(self.parent_corpus.size, (match_end + 1 + context))
+            right_end = min(self.corpus.size, (match_end + 1 + context))
             matches.append({'lc': list(range(left_start, match_start)),
                             'hit': list(range(match_start, match_end + 1)),
                             'rc': list(range(match_end + 1, right_end))})
         cpos_list = []
         for match in matches:
             cpos_list += match['lc'] + match['hit'] + match['rc']
-        cpos_list = list(set(cpos_list))
-        lookups = {}
-        if len(cpos_list) > 0:
-            lookups['cpos_lookup'] = {}
-        for cpos in cpos_list:
-            lookups['cpos_lookup'][cpos] = {}
-        for attr in self.parent_corpus.positional_attributes:
-            cpos_attr_values = self.parent_corpus.cpos2str(attr, cpos_list)
-            for i, cpos in enumerate(cpos_list):
-                lookups['cpos_lookup'][cpos][attr] = cpos_attr_values[i]
-        for attr in self.parent_corpus.structural_attributes:
-            if self.parent_corpus.structural_attribute_has_values(attr):
-                continue
-            cpos_attr_ids = self.parent_corpus.cpos2struc(attr, cpos_list)
-            for i, cpos in enumerate(cpos_list):
-                if cpos_attr_ids[i] != -1:
-                    lookups['cpos_lookup'][cpos][attr] = cpos_attr_ids[i]
-            occured_attr_ids = list(set(cpos_attr_ids))
-            occured_attr_ids = list(filter(lambda x: x != -1,
-                                           occured_attr_ids))
-            if len(occured_attr_ids) == 0:
-                continue
-            attr_subattrs = \
-                list(filter(lambda x: x.startswith(attr + '_'),
-                            self.parent_corpus.structural_attributes))
-            attr_subattrs = list(map(lambda x: x.split('_', 1)[1],
-                                     attr_subattrs))
-            if len(attr_subattrs) == 0:
-                continue
-            lookups[attr + '_lookup'] = {}
-            for attr_id in occured_attr_ids:
-                lookups[attr + '_lookup'][attr_id] = {}
-            for subattr in attr_subattrs:
-                __subattr = attr + '_' + subattr
-                subattr_values = \
-                    self.parent_corpus.struc2str(__subattr, occured_attr_ids)
-                for i, value in enumerate(subattr_values):
-                    lookups[attr + '_lookup'][occured_attr_ids[i]][subattr] = \
-                        value
+        lookups = self.corpus.lookups_by_cpos(cpos_list)
         return {'matches': matches, **lookups}
 
     def fdist_1(self, cutoff, field, attribute):
-        return self.client.cqp_fdist_1(self.__name, cutoff, field, attribute)
+        return self.client.api.cqp_fdist_1(self._name, cutoff, field,
+                                           attribute._name)
 
     def fdist_2(self, cutoff, field_1, attribute_1, field_2, attribute_2):
-        return self.client.cqp_fdist_2(self.__name, cutoff, field_1,
-                                       attribute_1, field_2, attribute_2)
+        return self.client.api.cqp_fdist_2(self._name, cutoff,
+                                           field_1, attribute_1._name,
+                                           field_2, attribute_2._name)
diff --git a/app/corpora/cqi/wrapper.py b/app/corpora/cqi/wrapper.py
index 0b970f11..3dcfc2d5 100644
--- a/app/corpora/cqi/wrapper.py
+++ b/app/corpora/cqi/wrapper.py
@@ -32,7 +32,6 @@ class CQiWrapper(APIClient):
         Connects via socket to the CQP server using the given username and
         password from class initiation.
         '''
-        super(CQiWrapper, self).setup()
         self.ctrl_connect(self.username, self.password)
 
     def __create_attribute_strings(self):
@@ -79,7 +78,6 @@ class CQiWrapper(APIClient):
         Disconnects from the CQP server. Closes used socket after disconnect.
         '''
         self.ctrl_bye()
-        super(CQiWrapper, self).teardown()
         print('Disconnected from cqp server.')
 
     def query_subcorpus(self, query, result_subcorpus_name='Query-results'):