 Sentences can be analyzed into hierarchies of constituents. This unit discusses the historical development of phrase structure systems from 1957 until today. Well, why 1957? Well, that was the year when Chomsky published syntactic structures, his first major influential work. Well, and today is influenced by his minimalist program and the discussion and alternations of what he published in 1997. The method of representing syntactic structure visually by the use of tree diagrams, also referred to as phrase markers, has a long tradition with a number of significant milestones. So as already mentioned, the first milestone, and we will illustrate this on the basis of one sentence. The first milestone was the year 1957, when Noam Chomsky introduced the first version of a phrase structure rule system as you can see here. It was neither strictly binary as it is today, nor did it use intermediate category levels such as bar levels we know from modern systems. Before 1957, American structuralists such as Leonard Bloomfield or Zellick Harris suggested preliminary versions of hierarchical structures in linguistic analysis, thus predecessors of modern phrase structure systems. Let's look at the central properties of the 1957 system. Well, S, which stands for sentence, is the highest category. Inconsist, it consists of two central categories, the noun phrase and the verb phrase. The verb phrase itself consists of the verbal complex, so this would be the verb itself, well an all optional and obligatory elements that are associated with it. So there is no distinction drawn between optionality and obligatory. So there is no distinction drawn between optional and obligatory elements such as adjuncts and compliments. The auxiliary part in this model exhibits all grammatical aspects, so here it is. Well, this is not too remote from what we have today. It exhibits all grammatical aspects associated with the verb, tense, aspect, modality, etc. Let's look at the successor from 1965. Now, this version was published in Chomsky's influential book Aspects of a Theory of Syntax and it was at a time referred to as the Standard Theory. Today, of course, it's no longer the Standard Theory, but in the 1970s, 1980s it was referred to as such. In the Standard Theory, two major changes were introduced to the phrase structure rule system of 1957. First of all, we find the predicate now, or predicate phrase. Now, this is a new node. It consists of the auxiliary complex and the verb phrase. And the second very interesting new node was the operator node. Now, the operator contains a symbol for the sentence type. So the idea was that prior to generating the syntactic structure of a sentence, we have to determine what type of sentence it is that we want to generate. A declarative sentence, an interrogative sentence, an imperative sentence, a declarative sentence in the passive, a negative declarative sentence, and so on and so forth. So this operator node is, well, if you wish, an early realization of the space comp node in modern theories. Well, the next major step was published in Reflections on Language in 1976. However, one of Chomsky's disciple Ray Jackendorf was also very influential in the development of this first version of what they referred to as X-bar syntax. The idea goes back to Chomsky and Jackendorf, as I said, and a discussion of the representation of nominals. The intermediate categories, so we have something like a system like X double-bar, X-bar and X, so this would be the intermediate category, this would stand for the highest category, Xp, so that is the idea. The intermediate categories between Xp and X, for example, between noun, phrase and noun, so here we have such an intermediate category. Here is another one, here is one, and here is one, verb bar. These intermediate categories are represented either by means of a real bar on top or for reasons of simplicity, especially if you want to write these symbols by means of an apostrophe. They filled the gap between phrasal and lexical categories. The resulting phrase structure system has been called X-bar syntax, henceforth. Now, what was new in this system apart from this intermediate level? Well, we have a new node called complementizer, a node for all those elements that can be moved into sentence initial position, for example, WH elements like which and who, that, conjunctions, etc. Well, and we have, well, similar to the 1957 system, we have an inflection node infill, which is filled with the inflectional properties of the verb. In English, these are all parts of the verb group except the main verb itself. Well, as we move on in time, in 1986, Chomsky published a book called Barriers. Now, moving on, the new system exhibits now strict binary branching and a change of the former top level node S-bar into CP, complementizer phrase. So this is the complementizer phrase. Now, we have strict binary branching and intermediate categories in all sorts of nodes. For example, new was the P-bar node, which now filled the gap. It was simply forgotten in versions prior to that. Now, also we have C-bar, which is the equivalent of former S. So here, this well is former S-bar. We have IP, the inflectional phrase that is the projection of infill, inflectional phrase. This is the, by the way, I forgot the bar here. This is the projection of infill. The verb phrase now contains just verb bar and an optional specifier which has been dropped here. So in items, in constructions like have just gone, just would be the specifier of verb. Propositional phrase have the typical S-bar structure and infill is filled with the inflectional properties of the verb. Now, today's system is generally associated with S-bar syntax. No serious syntactic representation in generative grammar does not use S-bar syntax. However, we have now two different types of phrase. You can see them here. Type 1 and type 2. As a consequence of this, now phrases can now be reanalyzed either as simple phrases, which would be here. So you have just the head in the specifier. Or as complex phrases, which would be here. So this would be number 2 and this would be number 1. Now note that the term noun phrase has been replaced by determiner phrase as a consequence of having complex determiners like a lot of etc. A simple determiner phrase with a simple determiner and a noun would be number 1. And a complex determiner phrase with a noun phrase structure inside would be determiner phrase 2. So here we have the old noun phrase structure. Further changes concern the introduction of a general functional category and an extended daughter structure of I-bar. So extended daughter structure would be here and I-bar. To account for the morphological features of tense and aspect. So something like this. Now several interacting arguments lend support to the postulation of the phrasal categories and the branching as presented here. These arguments can be subdivided into non-syntactic evidence, distributional evidence and other syntactic evidence. The e-lecture phrase structure testing illustrates these arguments on the basis of various phrase structure rules.