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• (PoC) Store and validate a set of modules (a model file)
• (Full project) Load a model instance and validate it given a model set reference.(using a separate SPI)

1.2   Anchor

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persistence

1.2.1       Anchor

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persistence/retrieval

A system or human user should be able to create an anchor point . This serves the purpose of providing a name (or ID) for the model data and a root for the structure (together with the odd case of floating leaves at the top of a module).  

As a user of CPS I want to be able to: 

• Create an anchor point given a name and a dataspace 
• Retrieve an anchor point and the associated attributes given a name and a dataspace
• List the anchor points anchors in the system given a dataspace
• Delete an anchor point anchors given a name and a dataspace 

An anchor point name shall be unique within a dataspace. Duplicates shall be rejected. If a dataspace is not defined in the system, it shall be created upon anchor point creation. 

1.2.2       Anchor

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models set association

A system or human user should be able to associate an anchor point to a model set. 

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• Associate an anchor point to a module set given an anchor point and a module set reference. (upon creation)Retrieve a model set reference, given an anchor point 

1.3       Fragment (Node) Persistence

1.3.1       Fragment (Node) persistence

A system or human user should be able to persist and retrieve a model data fragment ie. Node under a parent fragment. A fragment is considered an anchor point, a container or a list element, the xpath identifying the fragment together with the leaf and leaf-list attributes.
As a user of CPS I want to be able to:

• Persist a fragment given an
  • Anchor point
• Retrieve a fragment given a
  • anchor pointAnchor
  • Xpath expression (limited to path and key equality, e.g. /A/B/C will grab a container while /A/B/C/ L[@key1='a key'][@key2='another key'] will grab a keyed list element)

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As a user of CPS I want to be able to:

• Retrieve the anchor point Anchor of a fragment Node given an
  • A fragmentNode

1.4.3       Containment Query

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• Retrieve all the relevant fragments (nodes) given an
  • Schema node identifier  

2        Database backend

2.

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Old draft from early ENM study:

Image Removed

1 A Few considerations

• If we can ignore mutability of key attributes the schema largely holds, an XPATH can be used as unique key for each data element (fragment) 
• We should stick to an XPATH with equality operators on key attributes only (e.g. no access by list index).
• 255 characters may not be enough for an XPATH.
• Conditions on multiple key attributes in the XPATH will have to be ordered to work as a single string.
• 'MO type' will require another definition since it is path dependent in Yang. Schema node identifier is as close as it gets.
• Given the work done in Neo4J to flatten attributes the use of a JSON format (possibly binary) in another DB technology makes sense – it will be easier to store and retrieve (no need to flatten the whole structure).

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• An anchor is a fragment, as such it can have properties
• The first element of the xpath array is the name of the anchor. All the children append elements to that.
• All the fragments have a reference to the anchor point.
• The full xpath is stored as text
• The parent ID column in the fragment table is there for transactional integrity. It references the id column to prevent creating orphan records under concurrency. It also serves lookup performance for parent/children.
• A schema node identifier can be inferred from the xpath (in fact, for containers it is the xpath bar the first element). There is no need to link it to a model set.
• The link between anchor points and module sets is purely for storing the association. The DB SPI has no notion of the model semantics.

The proposed DB for this schema is Postgres (as it uses some Postgres specific datatypes)

Note the 1. The module_set table above will not be used like this in the PoC instead we will start with a ‘modules’ table which will contain the complete source for each module. Including colums for namespace and revision.

Note 2. The latest DB Schema (as implemented) is documented on CPS Internal Relation DB Schema

2.2.1       Schema Code

CREATE TABLE RELATION_TYPE 
( 
    RELATION_TYPE TEXT NOT NULL, 
    ID SERIAL PRIMARY KEY 
); 
 
CREATE TABLE DATASPACE 
( 
    ID SERIAL PRIMARY KEY, 
    NAME TEXT NOT NULL, 
    CONSTRAINT "UQ_NAME" UNIQUE (NAME) 
); 
 
CREATE TABLE SCHEMA_NODE 
( 
    SCHEMA_NODE_IDENTIFIER TEXT NOT NULL, 
    ID SERIAL PRIMARY KEY 
); 
 
CREATE TABLE MODULE_SET 
( 
    MODULE_SET_REFERENCE TEXT NOT NULL, 
    ID SERIAL PRIMARY KEY 
); 
 
CREATE TABLE FRAGMENT 
( 
    ID BIGSERIAL PRIMARY KEY, 
    XPATH TEXT NOT NULL, 
    DATASPACE_ID INTEGER NOT NULL REFERENCES DATASPACE(ID), 
    ATTRIBUTES JSONB, 
    ANCHOR_ID BIGINT REFERENCES FRAGMENT(ID), 
    PARENT_ID BIGINT REFERENCES FRAGMENT(ID), 
    MODULE_SET_ID INTEGER REFERENCES MODULE_SET(ID), 
    SCHEMA_NODE_ID INTEGER REFERENCES SCHEMA_NODE(ID) 
); 
 
CREATE TABLE RELATION 
( 
    FROM_FRAGMENT_ID BIGINT NOT NULL REFERENCES FRAGMENT(ID), 
    TO_FRAGMENT_ID   BIGINT NOT NULL REFERENCES FRAGMENT(ID), 
    RELATION_TYPE_ID  INTEGER NOT NULL REFERENCES RELATION_TYPE(ID), 
    FROM_REL_XPATH TEXT NOT NULL, 
    TO_REL_XPATH TEXT NOT NULL, 
    CONSTRAINT RELATION_PKEY PRIMARY KEY (TO_FRAGMENT_ID, FROM_FRAGMENT_ID, RELATION_TYPE_ID) 
); 
 
CREATE INDEX "FKI_FRAGMENT_DATASPACE_ID_FK"         ON FRAGMENT USING BTREE(DATASPACE_ID) ; 
CREATE INDEX "FKI_FRAGMENT_MODULE_SET_ID_FK"         ON FRAGMENT USING BTREE(MODULE_SET_ID) ; 
CREATE INDEX "FKI_FRAGMENT_PARENT_ID_FK"         ON FRAGMENT USING BTREE(PARENT_ID) ; 
CREATE INDEX "FKI_FRAGMENT_ANCHOR_ID_FK"         ON FRAGMENT USING BTREE(ANCHOR_ID) ; 
CREATE INDEX "PERF_SCHEMA_NODE_SCHEMA_NODE_ID"    ON SCHEMA_NODE USING BTREE(SCHEMA_NODE_IDENTIFIER) ; 
CREATE INDEX "FKI_SCHEMA_NODE_ID_TO_ID"    ON FRAGMENT USING BTREE(SCHEMA_NODE_ID) ; 
CREATE INDEX "FKI_RELATION_TYPE_ID_FK"        ON RELATION USING BTREE(RELATION_TYPE_ID); 
CREATE INDEX "FKI_RELATIONS_FROM_ID_FK"       ON RELATION USING BTREE(FROM_FRAGMENT_ID); 
CREATE INDEX "FKI_RELATIONS_TO_ID_FK"         ON RELATION USING BTREE(TO_FRAGMENT_ID); 
CREATE INDEX "PERF_MODULE_SET_MODULE_SET_REFERENCE" ON MODULE_SET USING BTREE(MODULE_SET_REFERENCE) ; 
CREATE UNIQUE INDEX "UQ_FRAGMENT_XPATH"ON FRAGMENT USING btree(xpath COLLATE pg_catalog."default" text_pattern_ops, dataspace_id); 

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