Talk:Dependency grammar

message: The sections on "Implementations" and "External Links" primarily seem to be a billboard promoting random scientific work stemming from both the computational and linguistic realms. Essentially everything under implementations appears to be data-driven parser generators that are completely agnostic to underlying grammar formalisms. External links mostly hold links to randomly chosen treebanks (UD being an exception, and most likely deserving its own section in the article). imo they should all be truncated and, where it make sense, be incorporated into sections of the overall DG article that motivate the links.79.204.248.31 (talk) 00:43, 27 February 2016 (UTC)
thread_title: Random Billboard

message: Is there a reason Ddxc removed the LG demo link?  –jonsafari (talk) 04:00, 14 January 2008 (UTC)
thread_title: LG demo removal

message: This article has been completely replaced by text that has been obviously copied from somewhere else (note the missing inline images and the textual references to these!).  The text was added at the very end of August 2009 by User:Tjo3ya. I am slightly concerned about WP:COPYVIO.  I would like to know who the original author of the text is!  linas (talk) 04:14, 9 September 2009 (UTC)
replies: text: Yeah, the references to images and their relative position to text is a tell tale sign of copyright infringement. I'm not able to find the text in Google books though. But many books are yet not indexed there. I think this article should be reverted to the stub version of June 11. Pcap ping 11:33, 11 September 2009 (UTC)
thread_title:  New article is a copy from ... ? 

message: Thank-you for the reply.  But I really am not following your line of reasoning here.
(a) why do you conclude the analysis is semantic?  The labels on that diagram identify syntactic roles, not semantic content.  Which words belong to which syntactic roles isn't a semantic issue either.  A combination of phonetic properties, sub-morphemes, and part of speech tagging can be used to combine words into phrases and to define the role of each phrase in the sentence -- as amply demonstrated by our ability to comprehend the nonsense poem "The Jaberwocky".
(b) Any diagram that could be transformed algorithmically to create those four sentences would count as a head by the standard you just presented.  With two small modifications to my diagram and no change in head word, it would be trivial to construct an algorithm to make those four sentences using "understand" as a head word.  All you have to do is move the parenthesized labels an add an "aux verb" label to the word "are"
  (head)
    |
understand -----------------------------
  |             |                      |
(subject)  (time/aspect)          (verbal     )
  |        (signifier  )          (complement )
  |             |                      | 
  we       --------------           sentence   
           |             |             |
         (aux verb)  (w/o aux verb)   the
           |             | 
           are         trying
                         |
                        to 
With those small changes your four sentences become simple substitutions:
   (i) Topicalization: and [time aspect signifier minus aux verb] [head] [verbal complement], [subject] [aux verb]
   (ii) Pseudoclefting:  What we are [time aspect signifier] do is [head] [verbal complement]
   (iii) Proform substitution:  [subject] [aux verb] doing that.
   (iv) Answer fragment: What are you doing?  [time aspect signifier minus aux verb ] [head] [verbal complement]
(c) Isn't your choice of transformational tests assuming a priori that this sentence as a copula with "trying" acting as a modifier?  In that case all time/aspect/mood alterations only involve the verb "to be".  However, there is another reading: that of progressive present.  
English is inherently ambiguous about whether an "ing" word is acting as an adjective or the second half of a progressive present verb.  Whatever head we chose therefore has to be associated with an algorithm/parse tree that works with both readings.  If we view this as a progressive present verb then we also need to be able to support transformations of mood/aspect/timeframe on the verb "try" and not just the verb "are".  Many of these transformations cause the verb "are" to go away but they never cause the verb "try" to disappear.  On the other hand, if we view this as a copula these transformations both "are" and "try" are persistent.  Therefore the phrase "try to understand" as the head is compatible with both readings but "are" as the head word is not.
For example, to change this sentence to an optative mood we'd get "We {would like|want|wish} to try to understand the sentence".  The word "are" disappears completely from the sentence and is replaced by "would like to".  Change it to simple past you get "We tried to understand the sentence".  "are" also disappears, but this time it isn't even replaced by anything.  Instead we get an inflected form of "tried".
(d) It was my understanding that one of the goals of dependency grammar was to adapt the insights of functional grammar to the more structured needs of computational linguistics.  Languages have such a wide variety of ways of representing the notions of timeframe/aspect/mood.  If you have any intention of using your parse tree as the basis for automated translation, it is a dangerous strategy to make standalone words that set timeframe/aspect/mood into top nodes in your tree. You end up with source languages missing nodes that the target language needs or target languages needing to insert null nodes for the nodes that simply aren't relevant to their particular combination of syntax/morphology just to avoid losing a whole branch of the tree.
Some languages use auxiliary verbs and some don't. If you make an auxiliary verb the head simply because it is the carrier of the subject inflection, you will end up with different heads when you useo a language that doesn't use auxilary verbs as the starting point for your parse tree.  "am walking" in English is one word in Latin (ambulo), German (laufe or gehe depending on dialect) and one word in Hebrew (holekh or holekhet depending on the gender of the speaker).  Swahili also uses one word "ninakwenda".   In Hebrew, Latin, German, and Swahili, "are" would never appear as the head because it doesn't exist in the sentence.  
If you try to claim "well, I can still parse out morphemes" that are equivalent to "am" and get the head that way.  I'd say sometimes yes, sometimes no. German uses a single verb form for both simple present and present progressive.  If you really want to stress that you mean the progressive sense you use an adverb like "jetzt".  Sure there is a second word, but it isn't the one that carries the subject inflection the way "am" does.  Hebrew also uses a single verb form for the simple present and present progressive.  But when it wants to clarify it means ongoing action it uses a very different strategy : it converts walk to an infinitive and makes it the complement of an inflected verb. "holekh" means either "I walk" or "I am walking".  To stress that walking is ongoing you say "Mamshikh=continue lalekehet=to walk".  Mamshikh is no more the head word than "jetzt" is even though it is clearly the inflected word.  It is a modifier on the lemma for "walk".
Or consider the conversion of an intransitive verb to a transitive verb with a third party actor.  In English we convert a verb to its causitive sense by prefixing it with the inflected word "made" ( He ate --->  I made him eat ).  In Hebrew you quite often modify the word stem and convert the verb from a Qal/Piel stem to a Hifil stem by adding the prefix "ha" and making certain internal vowel changes.
 
Even though "try" is the word that gets inflected in the simple past in English and all tenses in Hebrew, I suggested "try" was a modifier on "understand" because its role is to frame the core activity/state discussed by the sentence.  A few weeks before I read this Wikipedia article, I ran across an article on a tribal language in the Americas that used word stem to indicate effort in a manner that looked a lot like the causative inflections that I just mentioned in Hebrew. So it is possible that one language's "trying + infinitive" is captured in another language with a single lemma (root + "trying" morpheme).
(e) You seem to be defining finite verb in a manner that is language dependent and then trying to claim cross linguistic significance.
If by finite verb we mean the lemma that identifies state/action discussed by the sentence once we have factored out all syntactic/morphological elements meant to communicate mood/timeframe/aspect in a pro-forma fashion, then I would agree the evidence weights strongly in favor of this lemma controlling the sentence structure.  The number of complements, particular combination of case markings, prepositions, post-positions, affixes, word order and other sorts of noun phrase role markers typically is determined by this lemma.
This lemma and the structure it creates is also permissive of a great many transformations. Most languages  support a fairly standardized set of transformations between different timeframe/mood/aspect.  You may need to know the morphological class of a word, to effect these transformations but you don't need to know the meaning.  Throughout all these changes the selection of noun phrases, role markers, and verb lemma will stay the same even when the syntax and number of morphemes related to timeframe/mood/aspect varies wildly.  
But if you are equating "are" with the finite verb then that is clearly NOT what you mean. Instead you seem to mean the word with subject inflections.
But if I may step back a bit, how would that work cross linguistically?  If you are parsing a sentence how do you identify the subject?  In ergative languages, there is a nominative case, but stative verbs agree with a word that has accusative case markings.  In Swahili a verb can agree with the location where action takes place and not just the actor or the things affected.  Most English speakers would not consider a location (adverb) a valid verbal subject and have trouble even conceiving of how that would work in Swahili.
Many languages inflect adjectives as well as verbs.  These can agree with the same word as the verb.  How do you tell which is verb and which is adjective?  Is it really just inflection?  Hebrew words acting as present tense verbs, adjectives, and animate nouns all use the same inflectional endings an all agree solely with the number and gender of the subject - NOT person.  You have to use position and other syntactical clues, not subject-word agreement to pick out the verb in the sentence.
What about sentences where there is NO agreement at all?  There's no subject inflection on any word in an English sentence that uses a modal, e.g. "I could run".  What word would you then chose?  Modern Swahili copulas have a variety of particles they use in place of the English "am/are/is". But they aren't inflected.  No subject markers, no tense markers. Nada.   
And what if a non-inflected or less inflected word controls the form of an inflected word?  Consider French: in the compound past (aux verb + participle) the auxiliary verb agrees with person and number whereas the participle agrees only with gender.  Since both agree with the subject, which do you chose? Maybe you should chose the auxiliary verb, since the auxiliary verb contains person as well as gender?  But wait.  You can't know what the auxiliary verb is without knowing the participles.   In French the participle determines the choice of auxiliary verb (avoir, etre).  Furthermore since both auxiliary verbs are irregular, you can't even guess what morphemes to use to represent person/number inflections on the auxiliary verb without the help of the participle.  So now which is head and which is dependent?
It seems to me that equating finite verb with some sort of purely morphological criteria, does not survive well cross-linguistically.  What works in one language is either too specific or too general to work in another language or simply irrelevant.  It doesn't even work consistently within a language.  Some English sentences have subject inflections and some don't.  You need a higher level functional definition that is then operationalized in different ways. In one language it could be as simple as looking for a word with certain morphemes or submorphemes.  In another language it might involve a multistage analysis that first uses various sorts of markers that classify sentence types and then uses other sentence type dependent clues to identify the word or words that compose the sentence's finite verb.
 
Beth 87.68.215.176 (talk) 18:24, 1 August 2012 (UTC)
thread_title:  Thank you for your reply 

message: Hello Beth,
Your message is long, too long, I think. It is difficult to see how to craft an appropriate response to the tremendous content. Let me summarize where I think the disagreement lies between our views. It boils down to this: I think you are failing to distinguish between semantic, syntactic, and morphological dependencies. For me, the following summaries hold:
*1. Semantic dependencies: determined by predicate-argument structures, the arguments of a predicate depend semantically on the predicate
*2. Syntactic dependencies: determined by distribution, the root word/morph of a given syntactic unit determines the distribution of that unit
*3. Morphological dependencies: when one word or part of a word influences the morphological form of another word, the latter depends morphologically on the former.
These dependency types can coincide, run opposite to each other, or be independent of each other entirely. If one fails to distinguish between them, unending confusion can be the result. Igor Mel'cuk's works have been insightful for establishing the necessity that one distinguish between these three types of dependencies. And again, most work in modern dependency grammars focuses primarily on syntactic dependencies.  
There are relatively easy answers to some of your counterarguments. In particular, the string are trying to does qualify as a concrete unit of dependency syntax. It is a catena. By acknowledging catenae, I think one gains the ability to acknowledge as concrete syntactic units many of the word combinations you point to.
Your reluctance to position the auxiliary verb are as the root of all clause structure in your example runs counter to almost all work in modern syntax. This fact is true regardless of whether one chooses a dependency grammar or a constituency grammar. 
Finally, my points here can be illustrated with examples from English or other languages, but these matters should be limited to a discussion of one or two examples at a time. --Tjo3ya (talk) 20:01, 1 August 2012 (UTC)
thread_title: Three types of dependencies

message: Tjo3ya writes --- Your message is long, too long...  ---  
So I will simplify:
a) I see you defending a diagram of limited utility against a diagram with greater utility.
b) It appears to you feel compelled to do this because of a fixed notion of what should be the head. This forces you to unnaturally separate an auxiliary verb from its participle and treat it as if it were no more part of the verb than "red" is part of the verb in the sentence "The ball is red with polka dots".   The difference though is there is NO valid transformation along the lines of "The ball is red" to "The ball redded ...".  but there is a valid transformation of "I am trying to ..." to "I tried to...".  "is-red" and "is-trying" do not have the same behavior yet you insist it is valid to draw them as if they were identical. 
Personally, I think showing a less powerful diagram at the top of the article doesn't do much at all to suggest to readers what dependency theory is capable of.
Tjo3ya writes --- Your reluctance to position the auxiliary verb are as the root of all clause structure in your example runs counter to almost all work in modern syntax. ---  
Not that I see.  What I see is variety:
* Rambow et al. "A Dependency Treebank for English".  Discusses dependency grammar research at U. Penn.  Please note that all the diagrams treat auxiliaries and modals as child nodes. (ftp://ling.upenn.edu/studentpapers/creswell/rambow-et-al.pdf ) 
* Case and Gender: Concept Formation Betweeen Morphology and Syntax - http://books.google.co.il/books?id=5XaeNozadRMC )  :  Van Helden, p. 593 claims Tensier himself treated auxiliary verbs and prepositions as part of other nodes.
According to Van Helden ( pp. 675-676 ) the Russian school of dependency analysis has gone through various stages, first putting the subject at the head, then the whole verb phrase and then finally just the tense bearing portion at the head (Mel'cuk).  But if you read on, it turns out that Van Helden's main point is simply that there are a lot of disputes about what should be the head.  
This article, based on the work of Mel'cuk, also puts the aux at the head.  http://acl.ldc.upenn.edu/P/P01/P01-1029.pdf . If you look at this article and the Rambow article you will see that (a) both are recent and both come out of one institution. If Upenn can tolerate two different views of what counts as the head of a dependency diagram, shouldn't Wikipedia articles represent the full range of viewpoints?  Seems to me that the article ought to at least be discussing the fact that different theoreticians have different ideas about what should be the head.
Tjo3ya writes:  --- The string are trying to does qualify as a concrete unit of dependency syntax. It is a catena.---
Agreed its a catena.  But the diagram in the article does not indicate that. Graphically a catena is a subtree, not some arbitrary portion of a long chain of connected words.  It has to be a subtree because otherwise there is no way to identify a unit to extract and transform.
Drawing the diagram as I did, with the string elements situated in a labeled subtree made it very easy to extract the phrase and manipulate it. The diagram supports all of the copula transformation, all of the tense/mood/aspect transformations for "is trying to", translations to several other languages that are structured in very different ways from Western European languages, and several other transformations as well: "I am trying to understand..." to "I do understand..." or "If only I understood".
By contrast the diagram in the article only supports transformations for a copula.   There is no way to do the other transformations because the diagram has a single long line "am ..... the".  There is no tagging or any other information that would allow a software program to isolate "am trying to" as a transformable element nor even "understand the sentence".  Without that, there is no way to do any transformation other than the four copula transformations.You lose the ability to support the  full range of transformations of which an actual human speaker would be capable.
Tjo3ya writes:  --- I think you are failing to distinguish between semantic, syntactic, and morphological dependencies. --
Recognizing  a distinction between dependency types won't solve the problem.  All it does is allow you to let the morphological relationship between the French auxiliary and participle go one direction and the syntactic relationship go the other. The only thing that will solve the problem is a subtree that allows the extraction of "is trying to" as a unit.
Without that ability to extract a subtree you are limited in the kind of transformations you can do.  In French you need to treat the aux + participle as a unit if you want to do the full range of tense transformations: simple present, simple past,  future all use a single word in place of the two word combination "aux + participle".  They may be written as two separate words, but they function as one.
The failure to couple the French auxiliary and participle also would result in incorrect translations between Hebrew and French. The Hebrew equivalent to "avoir/etre + participle" is a single word marked for person, number, and gender.   The French auxiliary verb is only marked for person and number.  The French participle is only marked for number and gender.  But together they are marked for person, number, and gender just as the Hebrew verb.  You can have an accurate translation from French to Hebrew and back again only if you take  aux verb + participle as a unit even though it is written as two words.
Beth 87.68.215.176 (talk) 16:26, 6 August 2012 (UTC)
thread_title:  Reply 

message: Hello Beth,
Thanks for your interesting message. I appreciate the sources you have given to illustrate your point.
Rambow et al.'s analysis of dependency structure is challenged in major ways. The biggest difficulty for me with those structures is that the constituents (= complete subtrees) shown are NOT identified as constituents by a large majority of constituency tests. Take the example sentence The flight will have been booked from Figure 2. The tree shows each of the auxiliaries as a constituent, but let's focus on the finite auxiliary verb will.
::The flight will have been booked.
:::a. *Will the flight have been booked. - Topicalization (unacceptable as a statement)
:::b. *It is will that the flight have been booked. - Clefting
:::c. *what the flight have been booked is will. - Pseudoclefting
:::d. *The flight does have been booked. - Proform substitution
:::e. What about the flight being booked? - *Will. - Answer fragment
:::f. *The flight have been booked. - Omission
The tests deliver consistent results. Based on these data, we can conclude that will is NOT a constituent. The exercise can be extended to the other two auxiliary verbs. Each of the auxiliaries alone is NOT identified as a constituent by the constituency tests, yet Rambow et al.'s analysis takes each of these words alone to be a constituent. Please note that these considerations are empirical. That is, I have produced an argument that is backed by empiricism. What empirical considerations can be produced to illustrate that we should view will and each off the other auxiliary verbs as constituents. If Rambow et al.'s analysis is to receive empirical support, concrete illustrations like this are needed, not vague claims about the ease of automatic tagging and translation in terms of transformations.
Concerning transformations, you seem to take it for granted that transformations occur. I think a majority of dependency grammars reject the concept of transformation as it is understood in derivational systems (e.g. TG, GB, MP). My particular stance is that a construction-based theory of syntax is the better approach.   
A catena is any subtree, any subtree at all!. A complete subtree (= constituent) is a particular type of catena. See the article on catenae again. Every constituent is a catena, but there are many catenae that are not constituents. The point you make concerning simple vs. periphrastic forms is nicely accommodated in terms of catenae. The word combinations associated with periphrasis are catenae. See the article on periphrasis. While there may not at present be any software designed to acknowledge and manipulate catenae, it must be possible to produce applications that would do so. That can't be that difficult of a task for those who have the necessary programming knowledge. 
Yes, Wikipedia should accommodate the minority stance. But let me emphasize in this regard that what you are arguing for is represented by a very small minority in theoretical linguistics. Almost all work in GB and MP positions auxiliary verbs above the main verb. Most dependency grammars do this as well - I'm thinking here in particular of the German schools such as Heringer (1996) and Eroms (2000). Word Grammar does it too, as does MTT, as you point out. 
If you want to add a section to the article that points to the alternative analysis you propose, I will likely not attempt to remove it. I will, however, strive to include statements in the section to the effect that the analysis is not supported by empirical considerations such as the results of constituency tests. Furthermore, the section should include a tree illustrating the analysis. 
Finally, I can point you to an interesting debate about the importance of constituency tests for our understanding of syntactic structure. See the at times heated exchange between me and Rjanag and Taivo here. --Tjo3ya (talk) 19:44, 6 August 2012 (UTC)
replies: text: I need to qualify something I wrote yesterday. If you add a section demonstrating the analysis you prefer, I would not attempt to remove it assuming that it is supported by at least one or two prominent sources. The paper by Rambow et al. that you included above does not seem to appear in a peer-reviewed journal. Prominent sources are necessary to justify the presence of a section presenting the alternative analysis of sentence structure. If these sources exist, then I am actually in favor of including such a section, although again, I will likely strive to point out that the analysis is not supported by constituency tests. --Tjo3ya (talk) 19:57, 7 August 2012 (UTC)
thread_title: Constituency tests

message: Thank you again for your comments. 
Tjo3ya says:  --- A catena is any subtree, any subtree at all!. --
Of course it is, BUT
Mathematically a subtree is node X and all of its child nodes.  Another equivalent way to state this is:   A subtree is Node X,  all of its leaf nodes, and all nodes that have to be traversed to reach the leaf nodes.   Thus in the article's graph of "I am trying to understand the sentence" we have the following subtrees:
* "am" = the entire tree
* "I" = just the node "I"  - it has no children
* "trying" = "trying to understand sentence the"
* "to" = "to understand sentence the"
* "understand" = "understand sentence the"
* "sentence" = "sentence the"
* "the" = "the" – it has no children
No where in that list is something that ends with "trying" or "to".  So how would you know to extract "am trying to" or even "am trying"? 
The requirement of "all of its descendents" is needed because it gives the sub graph (= any connected subset of nodes in a graph)  certain useful mathematical properties.  One of the most important of these is that for any node in a directed acyclic graph there is one and only one subgraph that includes "all of its descendents".  Thus the node's id is also the subgraph's id.  No additional information is needed to know what nodes to extract.
But let's suppose I agree with you and say a catena=subtree can be any subgraph and not just the one mathemeticians call a subtree.  Then you have another problem.  If you remove the "all of its descendents" criteria then there isn't a neat way to identify the subgraph.  Since you are allowing arbitrary exclusion of some descendent nodes but not others, you have to specify in your subgraph identifier not only the head node but a rule for including or excluding descendents.  You can say "node X plus all children one to three levels deep" or "node X plus all chilren of the edges labeled "foo" and "bar" ) .  There are as many rules as there are possibilities for selecting some children but not others.
The graph in the article does not provide any rationale for selecting some children of "am" and not others.  So by either definition of a subtree,  mathematical or otherwise, there is no basis for selecting out "am trying to" and treating it as a catena.
Tjo3ya says: --- The biggest difficulty for me with those structures is that the constituents (= complete subtrees) shown are NOT identified as constituents by a large majority of constituency tests. ---
The difficulty with Rambow's diagram has nothing to do with the choice of head, but rather his failure to give you enough information to isolate "will have been" and "will have" in subtrees.  Once that's been done it is quite easy to algorithmically generate sentences that will pass  Topicalization, Omission,  Passivation/Activation, and Answer Fragment tests.
booked
|--------------|
flight         |
|            been
the            | 
             will
               |
             have
Constituency tests for "will have been":
* Topicalization: It [subtree=been] done, [node=booked] [subtree=flight] that is. =>  It will have been done, booked the flight, that is.
* Passivation/Activation  They [subtree=will] [node=booked] [subtree=flight]  =>   They will have booked the flight.
* Answer fragment:  Has the flight been booked?  It [subtree=been] by Tuesday =>  It will have been by Tuesday.
* Omission:   This is tricky because you have to chose a mood that does not require a timeframe/aspect signifier.     One option is the command but passive verbs can't be turned into imperatives.  Turning the sentence into a subjunctive might do though:   Would that [subtree=flight] were [node=booked]!   =>  Would that the flight were booked.
Ultimately it boils down to this: a graph is only as useful as the information content it provides.  This includes the end as well as the start of a catena.  
No one is disputing the importance of constituency tests.  They are a useful tool for seeing whether or not something functions as a unit.  But they aren't always enough to see what is really going on in the language and how it functions.  Languages do more than move around verbal complements and the tests you are considering as sufficient really do nothing more than shuffle and replace complements.  Tense/state/mood conversions like "is trying" to "tried" or "will have been X" to "has been X" are just part of how we use English.  They appear in the normal back and forth between individuals:  Mom: "Will you clean your room?"  Kid: "Mom, I already cleaned my room."   Speech writers use them to retorical effect "I fought for lower taxes.  I will always fight for lower taxes!".  Therapists use them to build connections and create empathy, and so on.
Similarly, we can't just ignore cross-lingual issues.  Conversions between languages aren't just for software: any bilingual or plurilingual person does them, especially if three or more conversation participants all are most comfortable in different languages.  So do real time translators at meetings and at their leisure book translators. Models of language have to support these facts. This isn't a case of generative grammar vs. dependency grammar.  There are simply some linguistic realities that need to be accounted for by any model.  You don't have to be a nativist and assume some sort of internal neuronal transformation engine to acknowledge them as linguistic behavior.
As for the article itself: there are a lot more issues in my opinion than just one diagram.  I've read a number of dependency grammar theory review articles recently and several of them do a much better job than this article at outlining the shared elements of a dependency grammar theory, the key debates it has engendered, the problems with early forms of tranformational/generative grammar they were trying to solve,  the mathematical formalisms typically used and so on. When I have a bit more time, I'll be happy to put together a list of a few examples if you are interested.
Beth 77.124.109.209 (talk) 11:12, 9 August 2012 (UTC)
thread_title:  Reply 

message: Hi, looking at the nice graph comparing the two competing (and apparently at odds) theories, it looked to me as if the two were - well - identical? Obviously not with the number of nodes they have, but it seems as if the one (Dependency grammar) could be expanded into the other and the other (Phrase structure) folded into the one ? I mean by means of a simple rule to follow, ie without "human" intervention (rather by an ~ algorithm). 
I might look into this more myself still, but not just now :). In the meantime, if anyone can comment, I'd be interested, thanks! 37.209.42.230 (talk) 14:12, 13 August 2015 (UTC)
replies: text: Yes, dependency structures can be mechanically translated to constituency structures, and if constituency structures are entirely endocentric (i.e. headed), they can be mechanically converted to dependency structures. The difference, though, lies with the number of groupings (complete subtrees). Since constituency allows the number of nodes to exceed the number of words, the structures can be very tall, whereas the one-to-one restriction (words to nodes) on dependency structures forces one to assume relatively flat syntactic structures. This is a big difference. The constituency structures that result when one translates from dependency structures are flatter than most constituency grammars want to assume. Much of modern syntactic theory in the Chomskian tradition assumes strict binarity of branching, which results in very tall tree structures, with a lot of nodes. There is no way for dependency to acknowledge so many groupings. Further, all dependency structures are endocentric (i.e. headed), whereas constituency structures can also be exocentric. This is a further big difference. --Tjo3ya (talk) 15:59, 13 August 2015 (UTC)

text: Cool, thanks for the thorough answer! I don't think I've worked out / followed you on all the differences yet, but that's a great head start :). I'll have to see if I can put it to some use. Regards 37.209.42.230 (talk) 11:56, 17 August 2015 (UTC)
thread_title:  Identity of Phrase structure (at least some) and dependency grammar? (Asking more out of interest than anything else)