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1++++
2+title = "Graph Store"
3+weight = 3
4+template = "doc.html"
5++++
6+
7+# What is Graph Store?
8+
9+Graph store is a gall implementation of a tree-based database that has an affordance for cyclic structures by allowing nodes to reference other nodes. It is most comparable to modern NoSQL databases in structure, though it allows for schemas to be written in the form of marks. It is used as the backend for an increasing number of Landscape applications, and is considered to be best used for social data.
10+
11+## Data types
12+
13+`graphs` is a map of `resource` to `marked-graph`
14+
15+`resource` is a pair of ship and term which is where the graph is hosted and the name of the resource. Every graph is it's own resource.
16+
17+`marked-graph` is a pair of `graph` and `(unit mark)`. The semantics of a graph are defined by the mark. This is just for validating the structure of the graph.
18+
19+`graph` is a `mop`, a mold builder for order map, of an atom and a `node`.
20+
21+`node` is a pair of `post` and `children`.
22+
23+`post` is defined in `sur/post`. It contains:
24+
25+`author=ship`
26+`index`
27+`time-sent=time`
28+`contents=(list content)`
29+`hash=(unit hash)`
30+`signatures`
31+
32+Most of these elements are self explanatory.
33+
34+`contents` is a `list` of `content` where `content` is a tagged union of text, url, code, or reference. This is where the contents of a publish post or an entry from links would be stored.
35+
36+`hash` is a `sham` hash of `validated-portion` which includes the parent hash, author, time sent, and contents.
37+
38+`signatures` is a set of `signature` which is used to cryptographically sign graph-store messages.
39+
40+When interacting with `graph-store` you will need to create an `update`
41+
42+`update` is a tagged union that currently only has one option
43+
44+`[%0 p=time q=update-0]`
45+
46+The reason this is a union is to serve as future proofing for version changes.
47+
48+An `update-0` can either be logged in the case of adding and removing nodes or signatures or non logged as in the case of adding or removing a graph. This logging refers to if this action adds an entry to the update log that is used to synchronize state between ships.
49+
50+Below is an excerpt or `sur/graph-store.hoon` at the time of writing showing the definition of `logged-update-0` and `update-0` which should now be readable.
51+
52+```
53++$ logged-update-0
54+ $% [%add-nodes =resource nodes=(map index node)]
55+ [%remove-nodes =resource indices=(set index)]
56+ [%add-signatures =uid =signatures]
57+ [%remove-signatures =uid =signatures]
58+ ==
59+::
60++$ update-0
61+ $% logged-update-0
62+ [%add-graph =resource =graph mark=(unit mark)]
63+ [%remove-graph =resource]
64+ ::
65+ [%add-tag =term =resource]
66+ [%remove-tag =term =resource]
67+ ::
68+ [%archive-graph =resource]
69+ [%unarchive-graph =resource]
70+ [%run-updates =resource =update-log]
71+ ::
72+ :: NOTE: cannot be sent as pokes
73+ ::
74+ [%keys =resources]
75+ [%tags tags=(set term)]
76+ [%tag-queries =tag-queries]
77+ ==
78+```
79+
80+
81+## Pokes
82+
83+Graph store can be poked with a `graph-update` which can:
84+ - add and remove a graph
85+
86+ `[%add-graph =resource =graph mark=(unit mark)]`
87+
88+ `[%remove-graph =resource]`
89+
90+ - add and remove a node to a graph
91+
92+ `[%add-nodes =resource nodes=(map index node)]`
93+
94+ `[%remove-nodes =resource indices=(set index)]`
95+
96+ - add and remove signatures
97+
98+ `[%add-signatures =uid =signatures]`
99+
100+ `[%remove-signatures =uid =signatures]`
101+
102+ - add and remove tags
103+
104+ `[%add-tag =term =resource]`
105+
106+ `[%remove-tag =term =resource]`
107+
108+ - archive and unarchive a graph
109+
110+ `[%archive-graph =resource]`
111+
112+ `[%unarchive-graph =resource]`
113+
114+## Scrys
115+
116+What follows is a summary of the scrys available in graph-store
117+
118+- Fetch keys
119+ `[%x %keys ~]`
120+
121+- Fetch tags
122+ `[%x %tags ~]`
123+
124+- Fetch tag queries
125+ `[%x %tag-queries ~]`
126+
127+- Fetch a specific graph by resource
128+ `[%x %graph @ @ ~]`
129+
130+- Archive a specific graph by resource
131+ `[%x %archive @ @ ~]`
132+
133+- Fetch a subset of the graph by resource and start and end indices
134+ `[%x %graph-subset @ @ @ @ ~]`
135+
136+- Select a node from a graph by resource and index
137+ `[%x %node @ @ @ *]`
138+
139+- Fetch a subset of the children of a node by resource, index, and start and end indices
140+ `[%x %node-children-subset @ @ @ @ @ *]`
141+
142+- Fetch a subset of the update log by resource and start and end indices
143+ `[%x %update-log-subset @ @ @ @ ~]`
144+
145+- Fetch the update log by resource
146+ `[%x %update-log @ @ ~]`
147+
148+- Fetch the time of the last entry of the update log
149+ `[%x %peek-update-log @ @ ~]`
150+
151+## Marks
152+
153+There are marks in `mar/graph/validator` that are worth review. They are each short enough to read quickly. They are used to validate the shapes of various nouns to be stored in the graph-store.