| .. This work is licensed under a Creative Commons Attribution 4.0 International License. |
| .. http://creativecommons.org/licenses/by/4.0 |
| .. Copyright (C) 2021 Nordix Foundation |
| |
| .. DO NOT CHANGE THIS LABEL FOR RELEASE NOTES - EVEN THOUGH IT GIVES A WARNING |
| .. _design: |
| |
| |
| CPS Path |
| ######## |
| |
| .. warning:: draft |
| |
| .. toctree:: |
| :maxdepth: 1 |
| |
| Introduction |
| ============ |
| |
| Several CPS APIs use the CPS path (or cpsPath in Java API) parameter. |
| The CPS path parameter is used for querying xpaths. CPS path is inspired by the `XML Path Language (XPath) 3.1. <https://www.w3.org/TR/2017/REC-xpath-31-20170321/>`_ |
| |
| This section describes the functionality currently supported by CPS Path. |
| |
| Sample Data |
| =========== |
| |
| The xml below describes some basic data to be used to illustrate the CPS Path functionality. |
| |
| .. code-block:: xml |
| |
| <shops> |
| <bookstore name="Chapters"> |
| <bookstore-name>Chapters</bookstore-name> |
| <categories code="1" name="SciFi" numberOfBooks="2"> |
| <books> |
| <book title="2001: A Space Odyssey" price="5"> |
| <label>sale</label> |
| <label>classic</label> |
| <edition>1968</edition> |
| <edition>2018</edition> |
| </book> |
| <book title="Dune" price="5"> |
| <label>classic</label> |
| <edition>1965</edition> |
| </book> |
| </books> |
| </categories> |
| <categories code="2" name="Kids" numberOfBooks="1"> |
| <books> |
| <book title="Matilda" /> |
| </books> |
| </categories> |
| </bookstore> |
| </shops> |
| |
| **Note.** 'categories' is a Yang List and 'code' is its key leaf. All other data nodes are Yang Containers. 'label' and 'edition' are both leaf-lists. |
| |
| General Notes |
| ============= |
| |
| - String values must be wrapped in quotation marks ``"`` (U+0022) or apostrophes ``'`` (U+0027). |
| - String comparisons are case sensitive. |
| - List key-fields containing ``\`` or ``@[`` will not be processed correctly when being referenced with such key values in absolute or descendant paths. This means such entries will be omitted from any query result. See `CPS-500 <https://jira.onap.org/browse/CPS-500>`_ Special Character Limitations of cpsPath Queries |
| |
| Query Syntax |
| ============ |
| |
| ``( <absolute-path> | <descendant-path> ) [ <leaf-conditions> ] [ <text()-condition> ] [ <ancestor-axis> ]`` |
| |
| Each CPS path expression need to start with an 'absolute' or 'descendant' xpath. |
| |
| absolute-path |
| ------------- |
| |
| **Syntax**: ``'/' <container-name> ( '[' <list-key> ']' )? ( '/' <containerName> ( '[' <list-key> ']' )? )*`` |
| |
| - ``container name``: Any yang container or list. |
| - ``list-key``: One or more key-value pairs, each preceded by the ``@`` symbol, combined using the ``and`` keyword. |
| - The above van repeated any number of times. |
| |
| **Examples** |
| - ``/shops/bookstore`` |
| - ``/shops/bookstore/categories[@code=1]`` |
| - ``/shops/bookstore/categories[@code=1]/book`` |
| |
| **Limitations** |
| - Absolute paths must start with the top element (data node) as per the model tree. |
| - Each list reference must include a valid instance reference to the key for that list. Except when it is the last element. |
| |
| descendant-path |
| --------------- |
| |
| **Syntax**: ``'//' <container-name> ( '[' <list-key> ']' )? ( '/' <containerName> ( '[' <list-key> ']' )? )*`` |
| |
| - The syntax of a descendant path is identical to a absolute path except that it is preceded by a double slash ``//``. |
| |
| **Examples** |
| - ``//bookstore`` |
| - ``//categories[@code=1]/book`` |
| - ``//bookstore/categories`` |
| |
| **Limitations** |
| - Each list reference must include a valid instance reference to the key for that list. Except when it is the last element. |
| |
| leaf-conditions |
| --------------- |
| |
| **Syntax**: ``<xpath> '[' @<leaf-name1> '=' <leaf-value1> ( ' and ' @<leaf-name> '=' <leaf-value> )* ']'`` |
| - ``xpath``: Absolute or descendant or xpath to the (list) node which elements will be queried. |
| - ``leaf-name``: The name of the leaf which value needs to be compared. |
| - ``leaf-value``: The required value of the leaf. |
| |
| **Examples** |
| - ``/shops/bookstore/categories[@numberOfBooks=1]`` |
| - ``//categories[@name="Kids"]`` |
| - ``//categories[@name='Kids']`` |
| - ``//categories[@code=1]/book[@title='Dune' and price=5]`` |
| |
| **Limitations** |
| - Only the last list or container can be queried leaf values. Any ancestor list will have to be referenced by its key name-value pair(s). |
| - Multiple attributes can only be combined using ``and``. ``or`` and bracketing is not supported. |
| - Only leaves can be used, leaf-list are not supported. |
| - Only string and integer values are supported, boolean and float values are not supported. |
| |
| **Notes** |
| - For performance reasons it does not make sense to query using key leaf as attribute. If the key value is known it is better to execute a get request with the complete xpath. |
| |
| text()-condition |
| ---------------- |
| |
| The text()-condition can be added to any CPS path query. |
| |
| **Syntax**: ``<cps-path> ( '/' <leaf-name> '[text()=' <string-value> ']' )?`` |
| - ``cps-path``: Any CPS path query. |
| - ``leaf-name``: The name of the leaf or leaf-list which value needs to be compared. |
| - ``string-value``: The required value of the leaf or leaf-list element as a string wrapped in quotation marks (U+0022) or apostrophes (U+0027). This wil still match integer values. |
| |
| **Examples** |
| - ``//book/label[text()="classic"]`` |
| - ``//book/edition[text()="1965"]`` |
| |
| **Limitations** |
| - Only the last list or container can be queried for leaf values with a text() condition. Any ancestor list will have to be referenced by its key name-value pair(s). |
| - Only one leaf or leaf-list can be tested. |
| - Only string and integer values are supported, boolean and float values are not supported. |
| - Since CPS cannot return individual leaves it will always return the container with all its leaves. Ancestor-axis can be used to specify a parent higher up the tree. |
| - When querying a leaf value (instead of leaf-list) it is better, more performant to use a text value condition use @<leaf-name> as described above. |
| |
| ancestor-axis |
| ------------- |
| |
| The ancestor axis can be added to any CPS path query but has to be the last part. |
| |
| **Syntax**: ``<cps-path> ( '/ancestor::' <ancestor-path> )?`` |
| - ``cps-path``: Any CPS path query. |
| - ``ancestor-path``: Partial path to ancestors of the target node. This can contain one or more ancestor nodes separated by a ``/``. |
| |
| **Examples** |
| - ``//book/ancestor::categories`` |
| - ``//categories[@genre="SciFi"]/book/ancestor::bookstore`` |
| - ``book/ancestor::categories[@code=1]/books`` |
| - ``//book/label[text()="classic"]/ancestor::shop`` |
| |
| **Limitations** |
| - Ancestor list elements can only be addressed using the list key leaf. |
| - List elements with compound keys are not supported. |