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topics/data.md

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-# Data & Discovery
+# Data
 
-Data structures, data availability, persistence, and mutability in decentralized applications.
-Data portability
+### Data Models
 
-Decentralized systems do not have a single central system to coordinate updates.
+Shared data models enable interoperability.
 
-### Data availability
+Solid - Solid's data model is RDF. [RDF](https://www.w3.org/RDF/) uses URIs to name the relationship between things, allowing structured data to be shared across different applications. RDF could potentially [be a barrier to adoption](https://hal.inria.fr/hal-01966561/document), due to its complexity.
 
-No server has a unified global view of a decentralized network.
+Matrix - Matrix transports messages using JSON, and tracks conversation history through DAGs.
 
-Data is only available along user connections or the follow graph, whether that is determined by node or by server.
+Mastodon - ActivityPub uses streams of JSON-LD. Mastodon was formerly compatible with OStatus, which used RSS.
 
-Mastodon - No global search functionality
+IPFS - IPFS uses a custom data model, [IPLD](https://ipld.io/), designed to treat hash-linked data structures as subsets of a unified information space.
+
+Ssb - Ssb uses append-only logs of signed JSON.
 
 ### Mutability
 
+Federated applications allow users to edit and delete content, handled at the server level. Content may not be guaranteed to be deleted across the entire network in some cases - protocols should require applications to honor delete messages.
+
+P2p applications have more variance around mutability.
+
 Ssb & Hypercore - Messages added to the append-only log are immutable. Applications can choose not to display messages indicated as deleted, but the data cannot be overwritten.
 
 IPFS - Once added to a network, content is discoverable by its hash. If a copy remains stored on the network, it is re-discoverable by this reference.
-
-### Data structures
-
-JSON-LD
-
-RDF