Ask HN: Why GraphQL APIs but no Datalog APIs?

https://news.ycombinator.com/item?id=21738331

by networked • 7 years ago

162 107 7 years ago

news.ycombinator.com

Why doesn't anyone use Datalog (or another limited-by-design logic programming language) as the query language in a public Web API? The adoption of GraphQL suggests demand for letting the API user write more sophisticated queries even at a performance cost per query. Datalog would let the user do more, likely saving many HTTP round-trips. A lot more research exists on optimizing Datalog than GraphQL. It is unclear that the total impact on performance would be significantly negative compared to the typical GraphQL API. If this line of thinking is valid, where are the Datalog API experiments?

triska3• 7 years ago

That's a very justified question!

In my opinion, Datalog or — more generally — Prolog is where many querying APIs will eventually arrive, because this syntax has many nice advantages: It is very convenient, expressive and readable, programs and queries can be easily parsed and analyzed with Prolog's built-in mechanisms, there is an ISO standard for it etc.

When semantic web formalisms were discussed, Prolog was sometimes mentioned. However, it is so far not very widely used as a querying or modeling language even for semantic web applications. Recent advances in Prolog implementations may increase the uptake of this syntax.

Also, public perception of Datalog and Prolog lags somewhat behind recent developments in these areas and what these technologies can actually do or what they even are. For example, here on HN, many posted articles that claim to be about Datalog often show snippets and examples that use completely different notations which are no longer a subset of ISO Prolog and therefore also not Datalog. Thus, they also do not immediately benefit from recent advances in Prolog systems in that they cannot directly be parsed and interpreted by them. It may take some time to advertise these improvements, and increase interest in these formalisms.

patrickmn• 7 years ago

What's the best example of modern Datalog?

thom3• 7 years ago

Datomic. Also interesting:

https://github.com/sixthnormal/clj-3df

triska3• 7 years ago

A good way to try Datalog is to use a state-of-the-art Prolog system that supports SLG resolution (tabling).

SLG resolution is an evaluation strategy of Prolog programs that provides favourable termination properties compared to SLDNF resolution which is Prolog's default execution strategy.

A great example for this is XSB Prolog, since it has pioneered and refined many of these techniques and serves as an example and benchmark for many other Prolog systems in this area:

https://xsb.com/xsb-prolog

The nice thing is that this approach allows you to use Datalog, and at the same time gives you a Turing-complete programming language that is comparatively easy to grasp once you understand Datalog, while sharing many of the same advantages and being syntactically only a slight extension of it.

muydeemer• 7 years ago

You might want to check out Grakn (https://github.com/graknlabs/grakn/) - its query language is an implementation of recursive datalog with negation and comes with lazy execution. I am one of its developers.

lordgrenville• 7 years ago

Certainly not the best, but worth mentioning the Python implementation pydatalog.

https://sites.google.com/site/pydatalog/home

zdragnar• 7 years ago

My last and only experience with Datalog (or a variation thereof) was (I believe) Logicblox, which (at least at the time) had zero support for pagination. In spite of all the supposed benefits of the system, that makes it fundamentally unsuitable imho.

Karrot_Kream• 7 years ago

This was (is?) what the semantic web dream was all about, and I find it funny that it took a corporation (FB) developing a clone before others discovered the concept. Semantic web data would be published as RDF data and clients would consume this data using a SPARQL query engine to get whichever shape of data that they desired.

triska3• 7 years ago

To clarify: I mean that Prolog was under consideration to be used for what SPARQL was then developed, as a more readable and simpler query and also modeling language.

Several researchers working in this area considered the development of SPARQL to be a missed opportunity for better formalisms, since Prolog could have been used instead.

And, yes, to many who have worked with RDF, SPARQL and the various notations that have been developed for semantic web technologies, Prolog seems like a dream that shows what these technologies could have been, and can become in the future, i.e., easily processable, with a uniform and simple syntax that already has an ISO standard, and amenable to formal reasoning based on well-known logical rules.

j-pb5• 7 years ago

notations which are no longer a subset of ISO Prolog and therefore also not Datalog.

This is false. Datalog is not (or no longer) about prolog like syntax, Datalog as used nowadays in research, describes the semantics for a logic which includes conjunctive queries and recursion, often denoted as an abstract syntax consisting of rules with a body and head, no ascii syntax attached.

Thus, they also do not immediately benefit from recent advances in Prolog systems in that they cannot directly be parsed and interpreted by them.

This is like saying, that Javascript can benefit from updates to the Java virtual machine. Prolog and Datalog require radically different evaluation strategies and implementations.

Etheryte• 7 years ago

For context, I'm a frontend development lead who oversees a number of projects of different shape and size. My personal and very subjective opinion is it's simply hype. If you say "Datalog" to a frontend developer, they will either hear "obsolete" or just not know what you mean. If you say "GraphQL", they hear "+5 CV points". Obviously that is slightly tongue in cheek, but the marketing side of it is a very real factor.

Facebook currently holds one of the largest levers in frontend development — React. If they say the officially recommended way to do X with React is Y, you can be sure that Y will get at least moderate traction.

I'm sure they exist out in the wild, but personally I haven't seen a project where GraphQL really shines through. In my experience, HTTP2 and reasonably well designed RESTful endpoints are the right default to go with. There is the argument that building good APIs is hard, but I believe someone who has reasonable experience with a stable technology will outperform someone using a new tool for the job. If you're not familiar with it, you won't know what to look out for.

shantly4• 7 years ago

I'm sure they exist out in the wild, but personally I haven't seen a project where GraphQL really shines through. In my experience, HTTP2 and reasonably well designed RESTful endpoints are the right default to go with. There is the argument that building good APIs is hard, but I believe someone who has reasonable experience with a stable technology will outperform someone using a new tool for the job. If you're not familiar with it, you won't know what to look out for.

GraphQL doesn't make a ton of sense to me, unless you're expecting many clients with significantly different query pattern requirements and prefer to take on performance and (maybe) security uncertainty & complexity to accommodate that more easily.

If you only expect one client (or a few very similar ones) and you want GraphQL-like division of labor just have your frontend and backend folks actually talk to each other and maybe have the backend folks also write a client library for their services (my preference, most of the time).

[EDIT] but you bet your ass I'm not putting up much of a fight against it if I'm in anything lower than a development lead or architect position—no use fighting that fight from poor footing when, as you mention, it's +5 CV points anyway, so who cares if it's maybe not the best solution :-)

eurasiantiger• 7 years ago

GraphQL makes a ton of sense when your queries use data from multiple different and possibly interdependent source APIs. It allows you to hide all manners of ugly hacks behind a single, neat, cacheable endpoint that can even act as a normalisation layer.

zo12• 7 years ago

"GraphQL doesn't make a ton of sense to me, unless you're expecting many clients with significantly different query pattern requirements and prefer to take on performance and (maybe) security uncertainty & complexity to accommodate that more easily."

My impression of it is that it's an "API" that's masquerading as a dumb relay, essentially giving almost datastore-level access to the frontend client (even though they don't market it that way). And this is done so that "Frontend devs" can just do "Frontend" things with access to all the data they might end up using. A bit snarky, but I do see it as a way to just "offload" the problem down the line, instead of thinking about the API-usage and what it means for potential frontend clients. That's the "old way" of doing things of course.

It fits in to the rest of the "movement" or trend currently happening: Thick (web) clients that do everything and the kitchen sink (including auth. See JWT in arb HTTP headers instead of cookies), SPAs so that there is no server side page rendering (this must all be done in the thick web client you see), document databases instead of SQL so the "frontend" devs don't have to worry about schemas, SPAs so that we break half the bloody internet because we now need to retrofit browser navigation using hashtags, everything has to be an "API" now because we can't convey data using server-rendering, etc.

Honestly, just that navigation thing alone is nuts and I can't believe we ever allowed it to be imposed on us. At this point, I'm afraid to touch those buttons on a new website without first trying them to learn their specific behavior on that site.

kumarvvr4• 7 years ago

A few weeks ago, I was pondering over the pain involved in designing and implementing a REST api, for an simple backend.

After much deliberation, it was clear to me that I dont understand the HATEOS part of REST and that I have been using the url as a filter and get or post parameters as variables for calling some functions on the backend server. And often, for an SPA, I would have to do multiple queeies in quick succession.

Then I realised, why cant I simply group those multiple query calls into one giant post request, with custom codes for querying or mutation, send a post request with a body that is a DSL i have thought of, and let my backend decode that DSL and send the replies. No longer would I be limited by URL structure, no longer would I have to make multiple query calls for getting a complex nested entity.

The only downside is that I have to docume t it more thoroughly and that my api does not have easy discoverability.

But since I have only one client, my frontend that I program,this is not an issue.

After pondering over the DSL a bit, I realised I am actually conceptualizing GraphQL.

hamandcheese• 7 years ago

The big win of using GraphQL, at least for me, is not the performance, but the developer experience. I can craft a query in Graphiql, paste it into my application, and from there generate Flow types for the query response. Make a breaking change to my graphql API? Flow types will fail CI tests until I fix any dependent client code. All of this works pretty nicely out of the box, and it’s leaps and bounds better than my past experience with homegrown rest APIs.

ng12• 7 years ago

Many years ago I worked at a company that had built a janky version of GraphQL in-house. The model fit our use case perfectly: our customers were dealing with a complicated ontology of objects and it allowed us to build new UIs on top of that data without implementing new REST apis. Of course our implementation wasn't the best but for a certain class of applications the graph-query model is a godsend.

watwut• 7 years ago

If you only expect one client (or a few very similar ones) and you want GraphQL-like division of labor just have your frontend and backend folks actually talk to each other and maybe have the backend folks also write a client library for their services (my preference, most of the time).

Yeah, but same result is much easier faster with graphql. When frontend developer can in most cases just slightly tweak the query, then it takes less time then having to talk to backend developer and wait till backend developer even starts working on it.(I am assuming that backend developer is normally occupied and is not sitting around bored until frontend developer needs query.)

And also, it avoids friction when backend developer is one of those superstars who are difficult to talk with.

jcadam• 7 years ago

I sort of agree. GraphQL just seems like a solution for a small set of niche problems that's being promoted as a general REST replacement for any and all web APIs.

Seems like we (as in, our industry) went through this before with everyone ditching relational databases and glomming onto NoSQL (particularly MongoDB) - only to realize later it was a mistake.

TheCoelacanth• 7 years ago

GraphQL turns a social problem (getting your frontend and backend folks to coordinate with each other) into a technical problem that someone else already solved 75% of for you. That's a big win.

GraphQL doesn't do anything that you can't do with sufficient coordination, but coordination is actually one of the hardest parts of getting things done at a large company.

thom3• 7 years ago

For what it's worth, if I saw Datalog on a CV I would think "has studied the ways of the old masters" and when I see GraphQL I think "blub". But I don't claim to be good at hiring.

Aeolun• 7 years ago

If you are trying to attach a lot of different API’s together in a consistent way, a graphQL API may be what you need.

JMTQp8lwXL3• 7 years ago

This assumes the backend teams are even ready to offer HTTP/2 for us. For some reason or another, we're stuck at HTTP/1.1 since we are fronted by a certain CDN provider and our process for change management in that tool is skittish, since the rules grew organically and making changes is now tough.

vnorilo• 7 years ago

Github's api [1] makes sense to me - there are lots and lots of query patterns and the previous Rest api results in quite a bit of link chasing and bandwidth burning.

It would actually be interesting to see if someone could design a very good Rest api for gh-like usage.

1: https://developer.github.com/v4/

reinhardt1053• 7 years ago

8 closed brackets in their first example query.

query { repository(owner:"octocat", name:"Hello-World") { issues(last:20, states:CLOSED) { edges { node { title url labels(first:5) { edges { node { name

}

https://developer.github.com/v4/guides/forming-calls/

tiborsaas• 7 years ago

Kinda unfair since it's 1000x easier to get started with GraphQL than Datalog.

I'm sure they exist out in the wild, but personally I haven't seen a project where GraphQL really shines through.

Look into how Gatsby.js uses GraphQL. You can query data from markdown files, configuration files (JSON) and resize images by specifying it in a query.

JoelMcCracken• 7 years ago

You are asking for a rational explanation for why something better is less popular than something that is worse. The answer almost certainly is "just because", and more specifically "because Facebook made GraphQL, not Datalog".

Graphql had a lot of hype around it when it was first announced. It so happens that I had just learned Prolog at the time and was personally bemoaning why SQL was so popular when a Prolog-like solution would be so much better. A month or so later comes all the podcasts and articles on HN from Facebook devs about GraphQL.

Datalog is a really great technology, and the idea that you can guarantee that each statement terminates is very powerful.

GraphQL seems to be a great technology when you have an extremely specific requirements. I personally would certainly use it if i had those requirements, but IMO it seems totally unjustified for your average tech company.

andrewingram2• 7 years ago

Ultimately GraphQL is popular because the query ergonomics fit well with the component architecture everyone is using these days, and once you're familiar with it you can be extremely productive.

dominotw• 7 years ago

sorry not a frontend dev, where can i get basic info about 'component architecture'

hawkice• 7 years ago

He's talking about the recommended use of things like React or Elm. React will probably have the basic info that ties it to GraphQL the closest, given the creators.

hmcdona1• 7 years ago

Modern SPA frameworks are usually built on components. You can combine components to define a tree of elements that represents your UI. This pattern is also often referred to as a Declarative UI pattern.

GraphQL works well with declarative UIs, because you can define fragments and combine them to create queries that best match the data the current set of components you are loading require. In this way, it's flexible in a way REST isn't (at least typically) and syncs well with Declarative UIs.

I can't speak to datalog though.

rhizome• 7 years ago

GraphQL is popular because the query ergonomics fit well with the component architecture everyone is using these days

Were they using that architecture prior to moving to GraphQL, or did the tail wag the dog in most cases?

andrewingram2• 7 years ago

I can't speak for everyone, but in my case it's "yes". I'd also be fairly comfortable claiming that there are a lot more people using component architectures (React, Vue, Elm, Ember and Angular) than are using GraphQL.

fulafel• 7 years ago

Do you feel GraphQL is better than Datalog here?

JMTQp8lwXL3• 7 years ago

jQuery, for its time, fit well its architecture and those familiar with it were extremely productive. Doesn't necessarily mean something is a great paradigm.

dzonga• 7 years ago

I will say something that is commonly known. a lot of frontend software dev revolves around hype. if React is the in thing and fb dev's are promoting Graphql, then everyone will go towards that. I don't know much about Datalog, but JSonAPiSpec meets most of things that people tout Graphql for. + if you're a person trying to keep employed then you've to follow the trends .

JMTQp8lwXL3• 7 years ago

React came out in 2013. That's six years and counting of "hype".

dreamcompiler• 7 years ago

Prolog (Datalog) has always been the gold standard for query languages. GraphQL is merely the latest attempt to reinvent it by people who obviously don't know what came before (or don't care). This might be because CS programs are no longer teaching Prolog, but I think it's more likely because one doesn't get career advancement points for using something "old" unless one reinvents it and renames it so it seems "new."

erik_seaberg• 7 years ago

I know Prolog (from college) and SPARQL (from hobbyist dinking around with SemWeb). I love DSLs and weird languages. I should be almost the ideal Datalog user, so how did it stay completely off my radar until this post?

OJFord• 7 years ago

Because it's a niche tangent of an already niche language.

I'm only aware of it because a databases course taught it (relational algebra to datalog to SQL) and I thought it was superb, and a couple of times since I've tried to find if I can use it, but it seems to suffer from the combination of age + academia + proprietariness that makes such things hard to discover and use. (Compared to graphql and plethora of open source libs on Github, etc.)

dustingetz• 7 years ago

Hyperfiddle (my startup) is a datalog API experiment, wrapped up in a low-code tool. We vertically integrate Datomic, a datalog database for AWS. Can you imagine GraphQL ever being low-code?

http://www.hyperfiddle.net/

https://gist.github.com/dustingetz/654e502340070280ab9744723...

leetrout• 7 years ago

That is really cool. I’ll have to check this out this week.

FYI Your HTTPS cert is tied to cloudfront and not configured correctly.

qeternity• 7 years ago

As a company that runs both Django Rest Framework and GraphQL backends, there is one phenomenal argument in favor of GQL: Apollo Client. When you just want a simple, normalized reactive data store it’s really amazing (even though the Apollo kids seem to break it with every minor release). Loads of redux boilerplate go right out the window.

acemarke2• 7 years ago

Per the last comment, please check out our new official Redux Toolkit package. It includes utilities to simplify several common Redux use cases, including store setup, defining reducers, immutable update logic, and even creating entire "slices" of state at once without writing any action creators or action types by hand:

https://redux-toolkit.js.org

Not saying it's a replacement for Apollo (since Redux itself doesn't provide anything around data fetching), but we specifically created RTK to eliminate the concerns around "Redux boilerplate".

damidekronik• 7 years ago

Still requires boilerplate for thunks, which in my case is most redux actions. Also I think you still don't support for specifying same reducer for many actions (for example as an array - https://github.com/piotrwitek/typesafe-actions). The immutable update logic however is amazing and I am glad I got introduced to it by you!

imtringued2• 7 years ago

How do I implement Datalog in my application? Crickets...

vchak1• 7 years ago

Depending on the stack, you can use some open source libraries. Datascript is quite robust, and useable from javascript/clojurescript. https://github.com/tonsky/datascript

tveita• 7 years ago

"An immutable in-memory database and Datalog query engine"

Most uses of GraphQL is to expose existing data from a relational database through an API, so although this looks like an interesting project, is doesn't look like it would be a contender against any GraphQL implementation.

I'd argue there are two faulty assumptions in the OP: 1. "GraphQL serves the same use case as Datalog.", and 2. "Datalog is better at that use case."

GraphQL is not a general purpose query language! There are practically no query operations at all built into the specification - it's all about field selection and parameter passing. At heart it's more like a RPC protocol geared towards requesting tree-like data. You would evaluate GraphQL against options like plain REST, OpenAPI, gRPC, not against Datatalog.

A more relevant question to ask is why Datalog never took over for SQL, but it would be harder to pretend that SQLs dominance is due to it being the current passing fad.

nickik2• 7 years ago

Crickets...

Why? There are libraries that you can use in most programming languages.

namelosw• 7 years ago

It is unclear that the total impact on performance would be significantly negative compared to the typical GraphQL API. Some of the problems also apply to GraphQL, people just need to constrain the query complexity in the end.

But yeah, it would bite Datalog more if not designed well enough, and it's harder to tackle Datalog than to GraphQL.

Other thoughts on this topic:

I love GraphQL but I would love Datalog more if the toolchain is as good as GraphQL.

There's a spectrum on API of simplicity and power -- on the left, there is HTTP/REST which could be seen as a primitive/naive way of describing API it's not consumer-driven at all. On the right there's Datalog which is a powerful way of describing API, it can maximize the flexibility of both the server and the client.

Things like 'map' and 'filter' became well-known to average programmers not very long time ago, though the elite programmers already knew them well half a centry ago. Datalog is definitely a very good idea for API, but I'm afraid it wound't be as popular as GraphQL if Facebook chose this route instead.

That being said, the industry always adopts things in a very passive manner, usually because the current solution is too painful to use, or almost couldn't solve the problem on new problem scale. There's a documentary[0] for GraphQL, the creators had enough of REST, they ended up with inventing GraphQL. It originally was to solving their data fetching problems, in the meantime it would solve others too. Meanwhile, it pushed the common understanding of API for average programmer from left to right on the spectrum. If it's close enough to the right, more and more people would discover Datalog and buzz other people to use it.

Just like type system, it's hard to expect the industry have a deep understanding on the topic itself. Type systems similar to Java dominates the industry for a long time, though ML already existed almost half a centry. Recently, languages like TypeScript tookoff because people need to type existing JavaScript. Then people would discover that the type system they used to is far from enough to describe existing code design. It's like a pandora box, new type operator would came out every release, until people realize there's a spectrum of type system (Lambda Cube[1]), and Dependent T ype would be on the same spot as Datalog on the spectrum.

[0] https://youtu.be/783ccP__No8?t=645 [1] https://en.wikipedia.org/wiki/Lambda_cube

beders• 7 years ago

Well, there's EQL and various implementations that use datalog under the hood.

https://edn-query-language.org/eql/1.0.0/what-is-eql.html

myguidingstar2• 7 years ago

EQL is surely a great alternative to Graphql because of namespaced keywords and rich data structure (in contrast of Graphql's string base). It is also inspired by Datomic's Pull API. However, it's a specification and the most popular imlementation (Pathom) has nothing to do with Datalog.

ptttr• 7 years ago

The original question made this mistake probably because the poster didn't know it but Pathom is the actual alternative to GraphQL-based APIs. Datalog solves a subtly different problem of querying the data, while Pathom/GraphQL/REST is about exposing the data (interfacing?) as API.

It's more like:

Pathom vs GraphQL-based API (vs REST)

and

Datalog vs SQL (vs NoSQL)

The mainstream is in the process of migrating from REST to GraphQL, but I think Pathom could be the black horse in this race. Just watch the last part of Wilker Silva's The Maximal Graph talk to see the potential: https://youtu.be/IS3i3DTUnAI?t=2080

rklaehn• 7 years ago

We currently looking for a powerful query language for a distributed event sourcing system. It would have to be embeddable in rust.

Is there a site where I can see more complex datalog queries and how they compare to other query languages? All the examples I have found so far were relatively trivial and basically just assumed that you knew that datalog was super powerful.

A comparison of how to solve problem X, Y, Z in datalog, graphql and SQL would go a long way to convince people that it is a superior alternative.

acjohnson55• 7 years ago

It's not clear to me that GraphQL and Datalog solve the same problems. GraphQL, to me, is fundamentally about designing the interface between a client and server, decoupled from the logic that satisfies requests. I think it's actually not a query language at all, any more than HTTP is a query language. Datalog is very much a query engine. And it's not super clear to me that the services exposed by a server map cleanly to a logic model. GraphQL requires no such purity.

fmjrey• 7 years ago

That: GraphQL is a mechanism for clients to specify the data document they want, and for servers to specify the documents they can serve. Datalog, or SQL for that matter, is a mechanism to expose data within a database. The GraphQL data model must be geared towards the end client point of view, e.g. some internal IDs can be hidden. Datalog on the other hand exposes the internal model of a data store, which is domain driven not client driven. Also you do not want end client devices to have the full power of datalog or SQL on your database, or else be ready to always watch those crazy queries that bring your server down to a crawl. GraphQL at least provides an indirection point where you can apply some form of resource control.

j-pb5• 7 years ago

It's all about the data manipulation capabilities that our current programming languages and libraries provide. Datalog and GraphQL are both graph query languages, but they differ significantly in the datastructures they return.

GraphQL queries describe Tree unfoldings of graphs, and thus return trees.

Datalog describes recursive conjunctive queries on hypergraphs (relational model) without or limited negation, and thus return a set or bag of hypergraph edges.

The reason why GraphQL is so successful is that it fits well with Reacts data-model (trees) and the way it performs its efficient delta updates (tree walking). Furthermore its somewhat easier to implement (albeit not simpler). Consider that there are very few actual GraphQL query engines for actual data (e.g. DGraph DB), instead GraphQL backends implement resolver functions which compute the "graph"/tree on the fly, based on side effects. Resolvers are what you'd call a computable in prolog or datalog knowledge bases and even though I work full time on incremental query evaluation in said knowledge bases I don't have a clue on how to make those efficient without resorting to the Big Cannon of Differential Dataflow.

Datalog queries don't return trees, they return relations a.k.a. hypergraph edges, and that simply doesn't map well to the datastructures (maps/dicts and lists/vectors/arrays, JSON and other tree description formalisms) that we have in basically every mainstream programming language that isn't prolog or some variant on logic programming. So the query results are hard to work with, and you'd want a LINQ style embeddable datalog query engine in your language of choice to work with the returned data, which is a much bigger undertaking.

So to recap: Datalog is great if you have it everywhere and your language is build around it and hypergraphs, but alas most languages we use today are build around trees, and graphql is a tree language.

macca321• 7 years ago

I've got this idea that you can chuck JMESPath into the range header on a standard json endpoint for ghetto graphql

nickik2• 7 years ago

This is actually fairly common in Clojure annd Clojure script. Sometimes using the Datomic DB as a backend for it.

This is an older presentation but its all about doing Datalog from the client to the DB.

See: https://www.youtube.com/watch?v=aI0zVzzoK_E

But if you go threw the Clojure world, there is Datalog all over the place, both client and server. Check out Datascript:

https://github.com/tonsky/datascript

This full-stack framework: http://book.fulcrologic.com/

myguidingstar2• 7 years ago

This is actually fairly common in Clojure annd Clojure script. Sometimes using the Datomic DB as a backend for it. What do you mean by "this" which is fairly common? Datascript is a Datalog implementation, however you can't just bring your query from backend to frontend, not only for incompatiblity but also for security issues. And Datascript is not that popular among Clojurescript apps.

Fulcro is defintely the go to framework. It makes use of EQL, which is a superior alternate to Graphql, for server-client communication.

scotty79• 7 years ago

For me the most important thing about graphql is composability.

Child component can communicate their data requirements to the parent and parent can include them in the query and feed the data to the children as it arrives.

Don't know if Datalog has anything for that.

ggleason• 7 years ago

TerminusDB does use a Datalog-like language as the query language for its public web API. Datalog has long seemed to me to be the obvious "next step" for query languages as it enables richer manipulations than those provided by vanilla SQL-like languages in a clean fashion.

However, as j-pb noted in another comment:

"GraphQL queries describe Tree unfoldings of graphs, and thus return trees.

Datalog describes recursive conjunctive queries on hypergraphs (relational model) without or limited negation, and thus return a set or bag of hypergraph edges."

TerminusDB allows you to use both approaches. Due to the way we have designed our graphs, with a strongly typed schema langage, you can extract sub-graphs as unfolded trees using a special predicate exposed in our datalog language.

This approach (hopefully) gives the best of both worlds, allowing graph traversal and extraction of objects/documents in a single framework, all communicating information via JSON-LD.

cheukting• 7 years ago

Sounds reasonable to me :-)

Ask HN: Why GraphQL APIs but no Datalog APIs?

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